Axis mechanical engineering. Classification of shafts and machine axles, their application. Shafts and axles

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Introduction

At this stage of development market economy great attention is paid to the technology of mechanical engineering.

Mechanical engineering technology is a science that systematizes a set of techniques and methods for processing raw materials, materials, appropriate tools of production in order to obtain finished products... The subject of study in mechanical engineering is the manufacture of products of a given quality with the installed release program at least cost materials, minimum cost and high labor productivity.

The technological process in mechanical engineering is characterized not only by the improvement of the design of machines, but also by the continuous improvement of the technology of their production.

Currently, due to the high level of development of electronics in mechanical engineering, CNC machines are widely introduced. The use of such equipment makes it possible to reduce: fitting and finishing work; preliminary markup; terms of preparation of production, etc.

Considering all this, I widely use CNC machines, and also in the diploma project, a number of tasks are considered necessary for completing the assignment for the diploma design.

These tasks include:

Raising the technical level of production;

Mechanization and automation of production;

Development of progressive technological process processing of the "Axis" part;

Development of measures to further increase the saving of fixed assets, product quality and reduce the cost of manufacturing a part.

The correct solution to all of the above tasks can be obtained:

Labor productivity growth;

Release of some of the workers;

Increase in the annual economic effect;

Reducing the payback period for additional costs.

1 . Technological part

1.1 Description of working conditions, service purpose of the part, analysis of manufacturabilitydetails and feasibility of transferring its processing to CNC machines

Detail: "Axis" no. 5750.0001

It is an integral part of the stabilizer drive mechanism. The rocking arm of the drive rotates on the axis, therefore HTV is applied on the surface of Ш40f7. 48-80, Ш24H9 hole for special fixing bolt V. 5750.0001. For fixing with a special fastening bolt, grooves 20H11 are made, as well as 3 holes Ш1.5 are made for locking (locking) 2.2 OST 139502.77, cotter pin 2.5x 32.029 GOST 397-79.

The manufacturability of the design of the part is assessed by qualitative parameters and quantitative indicators.

Qualitative assessment of the manufacturability of the structure

1 The "Axis" part has a regular geometric shape and represents a body of revolution.

2 The material of the part (steel 30HGSA GOST 4543-71) has good machinability by mechanical means.

3 Possibility of using a stamping blank, the geometric shape and dimensions of which provide small allowances for machining.

4 The presence of unified elements of the part confirms the manufacturability of its design.

5 The design of the part has sufficient rigidity, since the condition

6 The configuration, accuracy and roughness of the surfaces allow processing the part on standard equipment of normal accuracy and using a standard cutting tool.

Table 1.1 - Dimensional accuracy and surface roughness parameter of the part

Surface dimensions	Accuracy quality	Roughness parameter	Number of structural elements	Number of unified elements

Quantitative assessment of the manufacturability of the structure

1 Coefficient of unification:

where Que is the number of unified elements;

Qe - the number of structural elements.

2 Coefficient of accuracy of the surfaces of the part:

where Ti is the quality of the precision of the processed surfaces, respectively;

Tav. - the average value of these parameters;

ni - number of sizes or surfaces for each grade

3 Coefficient of roughness of surfaces of parts:

where Rai - respectively the values of the parameters of the roughness of the treated surfaces;

Raav. - the average value of these parameters;

ni is the number of dimensions or surfaces for each value of the roughness parameter.

Conclusion: from the above calculated coefficients, it can be seen that the numerical values of almost all manufacturability indicators are close to 1, i.e. the manufacturability of the design of the part meets the requirements for the product. Part "Axis" is advisable to process on machines with numerical control, since the part is well machined by cutting and is conveniently based.

1.2 Chemical composition andmechanical properties of the materialdetails

Part "Axis" is made of steel 30HGSA - structural alloy steel that can withstand significant deforming loads.

It is recommended to make 30HGSA steel: shafts, axles, gear wheels, flanges, casing housings, blades of compressor machines operating at temperatures up to 2000C, levers, pushers, responsible welded structures operating at alternating loads, fasteners operating at low temperatures.

Chemical composition data and mechanical properties We place the material in tables from the appropriate sources.

Table 1.2 - Chemical composition of steel

Table 1.3 - Mechanical properties of steel

	Section, mm

Technological properties

Weldability - limited weldability.

Welding methods: RDS; Submerged arc and gas shielded ADS, ArDS, EShS.

Machinability by cutting - in the hot-rolled state at HB 207ch217 and h = 710 MPa.

Flock sensitivity - sensitive.

Tendency to temper brittleness - prone.

1.3 Determination of the type of production

In mechanical engineering, the following types of production are distinguished:

Single;

Serial (small batch, medium batch, large batch);

Massive.

Each type of production is characterized by the coefficient of fixing the operation Kz.o.

Coefficient of fixing operations Кз.о. determined by the formula:

where Qop. - the number of different operations performed on the site;

Pm is the number of workplaces (machines) on which these operations are performed.

According to GOST 3.1108-74, the coefficient of fixing operations is taken equal to

Table 1.4 - The value of the coefficient of fixing operations

From the above calculated, it follows that serial production, you should determine the batch of starting parts. The approximate size of the batch can be calculated using the formula:

where N is the annual output, pcs;

The number of working days in a year (365-Th. - Tsev.), Days;

The required stock of parts in the warehouse in days, fluctuates within 3 hours 8 days

For single and small-scale production 3 to 4 days

For medium batch production 5h6 days

For large-scale and mass production 7h8 days

Serial production is characterized by a limited range of products manufactured or repaired in periodic batches, and relatively large production volumes.

In serial production, universal machines are widely used, as well as specialized and partially special machines.

The equipment is located not only by group, but also by flow.

Technological equipment is universal, as well as special and universal-prefabricated, which makes it possible to reduce the labor intensity and cost of manufacturing the product.

The workers specialize in performing only a few operations. The technological process is differentiated, i.e. divided into separate independent operations, transitions, techniques, movements.

The cost of the product is average.

1.4 Factory Process Analysis

Each part must be manufactured with minimal labor and material costs... These costs can be reduced to a large extent from the right choice options for the technological process, its equipment, mechanization and automation, the use of optimal processing modes and correct preparation production. The complexity of manufacturing a part is particularly influenced by its design and technical requirements for manufacturing.

In the factory technological process, the "Axle" part is processed as follows:

005 Control 065 Locksmith

010 Turning 070 Marking

015 Turning 075 Drilling

020 Turning 080 Flushing

025 Control 085 Magnetic

030 Thermal 090 Control

035 Sandblasting 095 Coating

040 Turning 100 Grinding

045 Grinding 105 Locksmith

050 Turning 110 Flushing

055 Marking 115 Magnetic

060 Milling 120 Preparatory

As can be seen from the above listed operations of the factory technological process, a large number of control, locksmith, marking operations are used here, and old-model universal machines with manual control are used.

I believe that in its version of the technological process of machining the "Axis" part, it is necessary to use high-performance CNC machines in some operations, which will allow:

Increase labor productivity;

Eliminate marking and locksmith operations;

Reduce the time for changeover of equipment, for the installation of blanks due to the use of universal assembly devices;

Reduce the number of operations;

Reduce the time and money spent on transportation and control of parts;

Reduce marriage;

Reduce the need for labor;

Reduce the number of machines;

Apply multi-station service;

In addition, for horizontal milling and vertical drilling operations, it is advisable to use special quick-change devices with pneumatic clamping, which ensure reliable fastening and accurate positioning of the part during processing, as well as allow:

Reduce the time for equipment changeover;

Provide a fixed and secure position of the workpiece in the fixture;

Releases from preliminary marking before this operation

The use of a special high-performance cutting tool ensures high precision and the required roughness of the machined surfaces.

1.5 Feasibility study of the choice of the method for obtaining the workpiece

The choice of the method of obtaining the workpiece is one of critical factors in the design and development of a technological process.

The type of workpiece and the method is largely determined by the material of the part, the type of production, as well as such technological properties as the design form and overall dimensions of the part.

In modern production, one of the main directions in the development of machining technology is the use of finished workpieces with economical constructive forms, i.e. it is recommended to shift most of the part shaping process to the blank stage and thereby reduce costs and material consumption during machining.

In my thesis for the "Axis" part, I use the method of obtaining a blank, hot stamping on crank presses.

With this method, the shape of the workpiece in terms of its dimensions is close to the dimensions of the part and thereby reduces the consumption of material and the time for manufacturing the "Axis" part, and also reduces the number of machining operations and, consequently, reduces the cost of this part.

1.6 Selection of technological bases

A base is a surface that replaces a set of surfaces, an axis, a point of a part with respect to which other parts processed in this operation are oriented.

To improve the accuracy of processing a part, it is necessary to observe the principle of alignment (unity) of bases, according to which, when assigning technological bases for precise processing of a workpiece, surfaces should be used as technological bases, which are simultaneously the design and measuring bases of the part.

And also the principle of the constancy of bases, which is that when developing a technological process, it is necessary to strive to use the same technological base, not allowing a change of technological bases unnecessarily.

The desire to carry out processing according to one technological base is explained by the fact that any change of bases increases the error in the relative position of the processed surfaces.

After analyzing all of the above, I conclude that for processing the "Axis" part, it is necessary to take as the base surfaces:

Operation 010 Turning CNC

Installation A: 61.8

Install B :? 40.3

: ?40,3

Operation 025 Cylindrical grinding: otv. W24H9

1.7 Designing a route technological process of a part: processing sequence; choice of equipment; selection of machine tools; selection of cutting tools; select op of auxiliary tools

When developing a technological process, they are guided by the following basic principles:

First of all, I process those surfaces that are basic for further processing;

After that, the surfaces with the largest allowances are processed;

Surfaces, the processing of which is due to the high accuracy of the relative position of the surfaces, must be processed from one setup;

When processing precise surfaces, one should strive to comply with two main allowances: the combination (unity) of the bases and the constancy of the bases

Processing sequence

Operation 005 Blank

Operation 010 Turning CNC

Installation A

Install, fix the workpiece

1 Sharpen the butt end "clean"

2 Sharpen a chamfer 1x450

3 Sharpen Ш40.4 mm at l = 63.5-0.2 mm, keeping R1

4 Sharpen a chamfer 1x450

5 Countersink chamfer 1x450

Installation B

Reinstall, fix the workpiece

1 Sharpen the butt end "cleanly" keeping l = 79.5-0.2 mm

2 Sharpen a chamfer 1x450

3 Sharpen Ш60 mm per pass

4 Countersink Ø 23.8 mm per passage

5 Countersink a 2.5x450 chamfer

6 Expand Ш24H9 (+0.052)

7 Control by the performer

Operation 015 Horizontal milling

Installation A

Install, fix the part

1 Mill the groove B = 20H11 (+0.13) at l = 9.5 mm, keeping R1

Installation B

Reinstall, secure part

1 Mill the groove B = 20H11 (+0.13) at l = 41 mm

2 Blunt sharp edges, saw off 2 chamfers 0.5x450; 2 chamfers 1x450

3 Control by the performer

Operation 020 Vertical drilling

Install, fix the part

1 Drill 3 holes Ш1,5 mm per passage, having sustained? 1200, l = 48 mm

2 Drill 3 chamfers 0.3x450

3 Control by the performer

Operation 025 Thermal

1 Heat 35.5 ... 40.5 HRC

Install, fix the part

1 Grind Ш40f) at l = 60 using the cross feed method

2 Control by the performer

Operation 035 Control

Equipment selection

When choosing equipment, the following factors are taken into account:

Production type;

Workpiece type;

Requirements for processing accuracy and surface roughness;

Required power;

Annual program.

Based on the above, I choose technological equipment.

Operation 010 CNC Turning

CNC screw-cutting lathe 16K20F3

The machine is designed for turning the outer and inner surfaces of parts with a stepped and curved profile in the axial section in a semi-automatic cycle, set by a program on punched tape.

Options	Numerical values
The largest diameter of the workpiece to be processed:
over bed
over support
The largest diameter of the bar passing through the spindle bore
The greatest length of the workpiece to be processed
Thread pitch:
Metric
Spindle speeds

Greatest movement of the caliper:
longitudinal
transverse
Caliper feed, mm / rev (mm / min):
longitudinal
transverse
Number of steps of giving
Rapid movement speed of the support, mm / min:
longitudinal and transverse
vertical
Main drive motor power, kW
Dimensions (without CNC):



weight, kg

Operation 015 Horizontal milling

Horizontal milling universal machine 6P81SH / 10 /

The machine is designed for various milling work, as well as drilling and simple boring work in workpieces made of cast iron, steel and non-ferrous metals. The machine can work in semi-automatic and automatic modes, which makes multi-station equipment possible.

Machine specifications

Options	Numerical values
Working surface dimensions (width x length), mm
The greatest movement of the table; mm:
longitudinal
transverse
vertical
Distance:
from the axis of the horizontal spindle axis to the table surface
from the vertical spindle axis to the bed guides
from the end of the vertical spindle to the table surface
The greatest movement of the sleeve of the vertical spindle, mm
Rotation angle of the vertical milling head, in a plane parallel to:
longitudinal table travel
transverse course of the table:
from the bed
to the bed
Internal spindle taper according to GOST 15945-82:
horizontal
vertical
Spindle speeds:
horizontal
vertical
Spindle speed, rpm:
horizontal
vertical
Number of working table feeds
Table feed, mm / min:
longitudinal
transverse
vertical
Speed of rapid movement of the table, mm / min:
longitudinal
transverse
vertical

Dimensions:



Weight (without external equipment), kg

Operation 020 Vertical drilling

Vertical drilling machine 2H125

The machine is designed for drilling, reaming, countersinking, reaming, tapping and cutting the ends with knives.

Options	Numerical values
The largest conditional drilling diameter, mm
Table top
The greatest distance from the end of the spindle to the working surface of the table
Spindle overhang
Spindle travel
Largest vertical displacement:
drill head

Spindle bore morse taper
Spindle speeds
Spindle speed, rpm	45; 63; 90; 125; 180; 250; 355; 500; 710; 1000; 1400; 2000
Number of spindle feeds
Spindle feed, mm / rev	0,1; 0,14; 0,2; 0,28; 0,4; 0,56; 0,8; 1,12; 1,6
Main drive motor power movement, kW
Machine efficiency
Overall dimensions, mm:



weight, kg

Operation 030 Cylindrical grinding

Semi-automatic cylindrical grinding machine for plunge-cut and longitudinal grinding, increased accuracy 3M151

The machine is designed for external grinding of cylindrical and shallow tapered surfaces.

Options	Numerical values
The largest dimensions of the workpiece to be installed:



Greatest length of grinding: external
Center height above table
The greatest longitudinal movement of the table
Rotation angle in about:
clockwise
counterclock-wise
Automatic table movement speed (stepless regulation), m / min
Workpiece spindle speed with stepless regulation, rpm
Morse taper of headstock spindle and tailstock quill
Largest grinding wheel dimensions:
outside diameter

Moving the grinding head:
the greatest
per division of the limb
in one turn of the jog handle
Grinding wheel spindle speed, rpm
when grinding external
Cut-in feed rate of the grinding head, mm / min
Main drive motor power, kW
Overall dimensions, mm:



weight, kg

Selection of machine tools

When developing a technological process for machining a part, it is necessary to choose the right device that should improve labor productivity, processing accuracy, improve working conditions, eliminate preliminary marking of the part and align it when installed on a machine.

Operation 010 Turning CNC

Device: three-jaw self-centering chuck

GOST 2675-80 is included in the set of the machine; revolving center

GOST 2675-80.

Operation 015 Horizontal milling

Attachment: A special tool for milling a workpiece with an integrated pneumatic cylinder.

Operation 020 Vertical drilling

Device: Universal dividing head GOST 8615-89;

hard cent GOST 13214-79.

Operation 030 Cylindrical grinding

Attachment: chuck for grinding work

GOST 13334-67 Drive clamp for grinding work

GOST 16488-70

Choosing a cutting tool

When choosing a cutting tool, it is necessary to strive to accept a standard tool, but sometimes it is advisable to accept a special, combined or shaped tool that allows you to combine the processing of several surfaces.

The correct choice of the cutting part of the tool is also of great importance for increasing labor productivity, increasing the accuracy and quality of the processed surface.

Operation 010 CNC Turning

Installation A

Transition 01, 02, 03, 04 Continuous thrust cutter with plates made of hard alloy T15K6, 16x25 GOST 18879-73 / 7 /

Installation B

Transition 01, 02, 03 Continuous bent bent cutter with carbide inserts T15K6, 16x25 GOST 18879-73

Technical characteristics of the cutter: H = 25 mm, B = 16 mm, L = 140 mm, n = 7 mm, l = 16 mm, r = 1.0 mm.

Transition 04 One-piece countersink Ш23.8 mm made of high-speed steel R6M5 with a tapered shank GOST 12489-71

Technical characteristics of the countersink: D = 23.8 mm, L = 185 mm, l = 86 mm.

Transition 05 Countersink? 450 from high-speed steel R6M5 with tapered shank OST-2

Countersink specifications: D = 32 mm, L = 145 mm, l = 56 mm.

Transition 06 Reamer made of high-speed steel one-piece Ш24H9 (+0,052) with a tapered shank GOST 1672-80

Sweep specification: D = 24 mm, L = 225 mm, l = 34 mm

Operation 015 Horizontal milling

Transition 01 Disk three-sided cutter Ш125 with plug-in knives equipped with hard alloy Т15К6, z = 8 GOST 5348-69

Technical characteristics of the cutter: D = 100 mm, B = 20 mm, d = 32 mm, z = 8 mm.

Transition 02 Flat file GOST 1513-77

Technical characteristics of the cutter: L = 130 mm.

Operation 020 Vertical drilling

Transition 01 Spiral drill? 1.5 mm made of high-speed steel R6M5 with a cylindrical shank GOST 10902-77

Drill specifications: d = 1.5 mm, L = 63 mm, l = 28 mm.

Transition 02 Spiral drill ø 6 mm made of high-speed steel R6M5 with a cylindrical shank GOST 10902-77

Drill specifications: d = 6 mm, L = 72 mm, l = 34 mm

Operation 030 Cylindrical grinding

Transition 01 Grinding wheel 300x63x76 PP 24A40NSM25K8

GOST 2424-83.

Technical characteristics of the circle: D = 300 mm, B = 63 mm, d = 76 mm.

1.7.5 Selecting auxiliary tool

When choosing auxiliary tools, they use the same principles as machine tools.

Based on the above, I make a selection of auxiliary tools.

On operation 010 CNC Turning:

Installation A

Transition 05 - I use an adapter sleeve GOST 13598-85

Installation B

Transition 04, 05, 06 - I use an adapter sleeve GOST 13598-85.

1.8 Determination of operating allowances, tolerances, interoperativedimensions and dimensions of the workpiece (for twosurfaces to producecalculation of allowances analytical method)

The selection of a blank for further machining and the establishment of the values of rational allowances and tolerances for processing is one of the most important stages in the design of the technological process of manufacturing a part. From the correct choice of the workpiece, i.e. establishing its shapes, sizes, machining allowances, dimensional accuracy and material hardness, the nature and number of operations or transitions, the complexity of manufacturing the part, the amount of material and tool consumption, and, as a result, the cost of manufacturing the part, depend to a greater extent.

Determination of allowances by the analytical method

The analytical method for determining allowances is based on the analysis of production errors that arise under specific conditions for processing a workpiece.

For the outer or inner surfaces of bodies of revolution, the operating allowances 2Zi min μm are determined by the formula:

where is the height of the surface microroughness;

Depth of the surface defect layer;

The total value of spatial geometric deviations;

Installation error

Determine intermediate allowances and intermediate dimensions when machining the hole surface? 24H9 (+0.052).

For clarity and simplicity of determining intermediate allowances and sizes, we draw up a table.

Table 1.5 - Calculations of allowances, tolerances and intermediate dimensions for a given surface

The surface of the part and the route of its processing	Dimensional tolerance, mm	Allowance elements,	Intermediate allowances, mm

Blank-stamping
Single boring
Threading

Check: Tdzag - Tdd =

1400 - 62 = (3758+352) - (2488 + 284)

1338 microns = 1338 microns

Rice. 1.1 - Layout of the fields of allowances and tolerances on the processed surface

Determine intermediate allowances and intermediate dimensions when processing the surface of the shaft? 40f7.

For clarity and simplicity of determining intermediate allowances, tolerances and sizes, we draw up a table / 10 /

Table 1.6 - Calculations of allowances, tolerances and intermediate dimensions for a given surface

Type of workpiece and technological operation	Precision of workpiece and work surface	Dimensional tolerance, mm	Allowance elements, μm	Intermediate dimensions of the workpiece, mm	Intermediate allowances, mm

Blank-stamping
Rough turning
Finish turning
Heat treatment grinding

Check: Tdzag - Tdd =

1400 - 25 = (2818+468+54) - (1668+257+40)

1375 microns = 1375 microns

Rice. 1.2 - Layout of the fields of allowances and tolerances on the processed surface

Calculation of allowances, tolerances, interoperational dimensions in a tabular way

On the rest of the surface of the workpiece, allowances, tolerances, interoperational dimensions are considered in a tabular way, I put the data obtained in a table

Table 1.7 - Calculation of allowances, tolerances and intermediate dimensions for other surfaces

Subsequence processing	Accuracy quality	Roughness	Tolerances mm	Stock size	Estimated size, mm	Limit size, mm	Limit allowance, mm

Blank-stamping Single semi-fine turning l = 79.5
Blank-stamping One-time semi-fine turning? 60

Table 1.8 - Interoperative dimensions of the workpiece surfaces

1.9 Determination of the normconsumption (calculate the utilization rate of the material and the utilization rate of the workpiece)

To determine the rate of consumption of material, it is necessary to determine the mass of the workpiece. The mass of the workpiece is calculated based on its volume and material density. It is necessary to strive to ensure that the shape and dimensions of the workpiece are close to the shape and dimensions of the finished part, which reduces the labor intensity of machining, reduces the consumption of material, cutting tools, electricity, etc.

The mass of the workpiece is calculated by the formula:

where is the density of the material, g / cm3

The total volume of the workpiece, cm3.

Usually, the complex figure of the workpiece must be broken down into elementary parts of the correct geometric shape and the volumes of these elementary parts must be determined. The sum of the elementary volumes will be the total volume of the workpiece.

The volume of a cylindrical pipe V, cm3 is calculated by the formula:

where is the outer diameter of a cylindrical pipe, cm

Internal diameter of a cylindrical pipe, cm

h is the height of the cylindrical pipe, cm.

The correct choice of the method for obtaining a workpiece is characterized by two factors:

Kim - material utilization factor

Kiz - the utilization rate of the workpiece

where is the mass of the part, g

where is the mass of metal losses (waste, flaking, per segment, etc.)

The utilization rate of the material varies within the following limits:

For casting 0.65 h 0.75 ... 0.8

For stamping 0.55 h 0.65 ... 0.75

For rent 0.3h 0.5

Having made calculations of the utilization factor of the material and the utilization factor of the workpiece, I conclude that these factors are within acceptable limits, therefore, the chosen method of obtaining the workpiece is correct.

1.10 Determination of cutting conditions, power for two

Determination of cutting conditions and power can be done in two ways:

Analytical (by empirical formulas);

Tabular

Calculation of cutting conditions for two different operations or transitions using empirical formulas

We calculate cutting conditions and power for various operations and transitions using empirical formulas

Operation 010 Turning CNC

Installation B

Transition 01 Sharpen the butt end "cleanly" keeping l = 79.5-0.2 mm

Cutting depth: t = 1.0 mm

Feed: S = 0.5 mm / rev / 10 /

Cutting speed V, m / min:

where Cv = 350; x = 0.15; y = 0.35; m = 0.2 / 7 /

T - tool life, min (T = 60 min)

Kv = Kmv Knv Kuv KTv KTc Kц Kr

where Kf is a coefficient characterizing a steel group in terms of machinability

Кnv - coefficient taking into account the influence of the state of the workpiece surface on the cutting speed (Кnv = 0.8) / 9 /

Kuv - coefficient taking into account the influence of the tool material on the cutting speed (Kuv = 1.15) / 9 /

KTv - coefficient taking into account the tool life depending on the number of simultaneously working tools (KTv = 1.0) / 9 /

КTс - coefficient taking into account tool life depending on the number of simultaneously servicing machines (КTс = 1.0)

Kts - coefficient taking into account the influence of the main angle in the plan q (Kts = 0.7)

Kr - coefficient taking into account the influence of the radius r at the tip of the cutter (Kr = 0.94) / 9 /

Kv = 0.56 0.8 1.15 1.0 1.0 0.7 0.94 0.34

Workpiece rotation frequency, n rpm:

where V - cutting speed, m / min

D - diameter of the treated surface, mm

According to the processing conditions, we accept:

npr = 359 rpm

Cutting force, PZ N:

PZ = 10 Cp tx Sy Vn Kp

where Cp = 300; x = 1.0; y = 0.75; n = -0.15 / 7 /

Кр - coefficient influencing the cutting force

Кр = Kmp · Kцp · Kp · Kp · Krp

where n is the exponent (n = 0.75) / 9 /

Kcr - coefficient taking into account the influence of the main angle in the plan

on the cutting force (Kcr = 0.89) / 9 /

Кр - coefficient taking into account the influence of the rake angle on the cutting force (Кр = 1.0) / 9 / Кр - coefficient taking into account the influence of the angle of inclination of the main blade on the cutting force (Кр = 1.0). Krp is a coefficient that takes into account the effect of the nose radius on the cutting force (Krp = 0.87).

Cr = 1.31 0.89 1.0 1.0 0.87? 1.01

Hence the cutting force PZ N:

PZ = 10 300 1.01.0 0.50.75 70-0.15 1.01? 947 N

Minute feed Sm, mm / min

where So is the feed per turn of the workpiece, mm / rev;

npr - adopted workpiece rotation speed rpm

Sm = 0.5 359 180 mm / min

Effective cutting power Ne, kW:

where is the cutting force, N

Cutting speed, m / min

The effective power is calculated correctly if the condition is met: 1.08 kW 10 0.75

1.08 kW 7.5 kW

Operation 015 Horizontal milling

Transition 01 Mill times to size 20H

Cutting depth: 9mm

Milling width B = 20 mm

Feed: Sz. = 0.06 mm / tooth / 10 /

Cutting speed V, m / min:

where Cv = 690; m = 0.35; x = 0.3; y = 0.4; u = 0.1; p = 0/5 /

T - cutter durability, min (T = 120 min); / 7 /

B - milling width, mm. B = 20 mm

Kv - coefficient influencing the cutting speed

Kv = Kmv Kuv Klv

where Kmv is a coefficient that takes into account the influence of the physical and mechanical properties of the processed material on the cutting speed

where Kf is a coefficient characterizing a group of steel in terms of machinability (Kf = 0.8)

nv - exponent (nv = 1.0)

Kuv - coefficient taking into account the influence of the tool material on the cutting speed (Kuv = 1.0)

Kv = 0.54 0.8 1.0? 0.5

Hence the cutting speed V, m / min:

Spindle speed, n rpm:

where the notation is the same

nд = 500 rpm

Actual cutting speed Vd, m / min:

where the notation is the same

Minute feed Sm, mm / min:

where the notation is the same

Sm = 0.06 8 500 = 240 mm / min

According to the processing conditions and the passport data of the machine, I accept:

Sm = Sv = 200 mm / min, then the actual feed per tooth of the cutter is:

Cutting force, Pz N:

where Cp = 261; x = 0.9; y = 0.8; u = 1.1; = 1.1; w = 0.1 / 7 /

where Kp is a coefficient affecting the cutting force

where Kmp is a coefficient that takes into account the influence of the quality of the processed material on the cutting force

where n is the exponent (n = 0.3) / 9 /

Kmp =? 1.12 Hence the cutting force, Pz N:

Cutting power Nres, kW:

where the notation is the same

We check if the drive power of the machine is sufficient

Power on the spindle of the machine N_ (shp,)

where the notation is the same

The effective cutting power is calculated correctly if the following condition is met:

3.56 kW 6 Therefore, processing is possible.

Calculation of cutting conditions and power for other operations and transitions according to the current standards For the convenience of further use of the calculated cutting conditions, we draw up a table

Table 1.9 - Calculation of cutting conditions for the operations of the technological process

Cutting depth t, mm	Feed S mm / rev SZ mm / tooth	Cutting speed V, mm / min	Rotation frequency n, rpm	Actual cutting speed Vph m / min	Minute feed Sm mm / min	Cutting power Nр, kW
Operation 010 Turning CNC Transition 01 Sharpen the butt "clean"

Transition 02 Sharpen a chamfer 1х450

Transition 03 Sharpen Ш40.4 mm to l = 63.5-0.2 mm, keeping R1

Transition 04 Sharpen a chamfer 1x45о

Transition 05 Countersink chamfer 1х45о

Set B Transition 02 Sharpen a chamfer 1х45о

Transition 03 Sharpening Ш60 mm per pass

Transition 04 Countersink Ø 23.8 mm per passage

Transition 05 Countersink a chamfer 2.5x450

Transition 06 Expand Ш24H9 (+0.052)

Operation 020 Vertical drilling Transition 01 Drill 3 holes Ш1,5 mm per passage, having sustained? 1200, l = 48 mm

Transition 02 Drill 3 chamfers 0.3x450

Operation 030 Cylindrical grinding Transition 01 Grind Ш40f) to l = 60 mm using the cross feed method

1.11 Determination of time norms for operations

The technical standard of time for processing a workpiece is the main parameter for calculating the cost of a manufactured part, the number of production equipment, wages and production planning. The technical standard of time is determined on the basis of the technical capabilities of technological equipment, cutting tools, machine tools and correct organization workplace.

Determination of the norms of time for an operation performed on a CNC machine

Operation 010 Turning CNC

1 Time of automatic operation of the machine Ta, min:

Ta = Toa + Twa

where Toa is the main time of automatic operation of the machine, min;

Tva - auxiliary operating time of the machine according to the program, min.

where l is the length of the treated surface in the direction of supply, mm;

l1 - penetration value, mm;

l2 - the amount of overrun, mm;

S - part feed per revolution, mm / rev;

i is the number of passes.

Toa = 0.06 + 0.03 + 0.25 + 0.03 + 0.02 + 0.03 + 0.12 + 0.41 + 0.71 + 0.03 = 1.69 min

Tva = Tvha + Toast

where Tvkha is the execution time of automatic auxiliary moves (approach of a part or a tool from the starting points to the processing zones and retraction, setting the tool to size), min;

where dxx is the length of the idle, mm;

Sxx - idle speed, m / min;

The number of technological sites.

Toast - time of technological pauses (stops, spindle rotation feed for checking dimensions, inspection or tool change), min

where a is the number of stops

2 Time of auxiliary manual work TV, min:

where a = 0.0760; x = 0.170; y = 0.15

Auxiliary time associated with the operation, min

where a = 0.36; b = 0.00125; c = 0.04; d = 0.022; = 0

Xо Yо Zо - zero coordinates;

k is the number of correctors in the setup;

lpl - the length of the punched tape, m (lpl = 0.5 m)

Auxiliary time overlapped for control measurements of the part, min

where k = 0.0187; z = 0.21; u = 0.330 / 11 /

D - measured diameter, mm

L - measured length, mm

TV = 0.25 + 0.58 + 0.16 = 0.99 min

3 Preparatory and final time Тпз, min:

Tpz = a + b nu + c Pp + d Pnn

where a = 11.3; b = 0.8; c = 0.5; d = 0.4

nu is the number of cutting tools;

Рр - the number of established initial operating modes of the machine (Рр = 2);

Рnn - the number of sizes selected by switches on the control panel (Рnn = 2 h 3)

T nz = 11.3 + 0.8 4 + 0.5 2 + 0.4 3 = 16.7 min

After determining the TV, it is adjusted depending on the serial production.

4 Seriality correction factor:

where a = 4.17; x = 0.216;

where npr is a production batch of parts, pcs. (section 1.4)

5 Piece time Tsht, min:

where (aorg + aotl) is the percentage of time spent on organizational and Maintenance workplace and rest (aorg + aotl) = 10% / 2 /

Processing time for a batch of parts:

where the notation is the same

T = 3.44 280 + 16.7 = 980 min

Determination of norms of time for operations performed on universal machines

Operation 015 Horizontal milling

Installation A

Transition 01

where L is the path traversed by the tool, mm:

where l is the length of the treated surface, mm;

l1 is the value of the tool penetration, mm;

l2 - the amount of overrun of the tool, mm;

n is the frequency of rotation of the part, rpm;

i is the number of passes.

where is the auxiliary time for the installation and removal of the part, min

Auxiliary time associated with the transition, min

Auxiliary time associated with control measurements, min

Installation B

Transition 01

1 The main operating time of the machine To, min:

Auxiliary time TV, min:

where the notation is the same

Toper = 0.48 + 1.0 = 1.48 min

Tobs = 3.5% of Topper

Totl = 4% of Toper

where K is the total percentage of time spent on servicing the workplace and time for rest and personal needs

where is the preparatory and final time for setting up the machine, tool and accessories, min

Preparatory and final time for additional receptions, min

Preparatory and final time for receiving tools and devices before the start and handing over them after the end of processing, min

Operation 020 Vertical drilling

Transition 01

1 The main operating time of the machine To, min:

2 Auxiliary time TV, min:

Transition 02

1 The main operating time of the machine To, min:

2 Auxiliary time TV, min:

3 Operative time Toper, min:

Toper = 0.93 + 0.79 = 1.72 min

4 Time to service the workplace Tobs, min:

Tobs = 4% of Topper

5 Time for rest and personal needs Total, min:

Totl = 4% of Toper

6 Norm of piece time Tsht, min:

7 Preparatory and final time Тпз, min:

8 Piece-calculation time Tshk, min:

Operation 030 Cylindrical grinding

Transition 01

1 The main operating time of the machine To, min:

where is the length of the table stroke, mm / dv. move

Side machining allowance, mm

Minute longitudinal feed, mm / min

Cross feed, mm / rev

2 Auxiliary time TV, min:

3 Operative time Toper, min:

Toper = 0.3+ 0.81 = 1.11 minutes

4 Time to service the workplace Tobs, min:

Tobs = 9% of Topper

5 Time for rest and personal needs Total, min:

Totl = 4% of Toper

6 Piece time Tsht, min:

7 Preparatory - final time Тпз, min:

8 Piece-calculation time Tshk, min:

For the convenience of further calculations, I put all the data obtained in a table.

Table 1.10 - Time rates for all operations of the technological process

Calculation and coding of programs for specified operations

Based on all the above calculations, I perform the calculation and coding of the control program for operation 010 CNC turning.

Table 1.11 - Tool path

Using the compiled tabular data, I code the program:

Installation A

Installation B

Program control

When preparing a program, as a rule, errors occur, which are corrected in the process of debugging and implementing the program.

Errors occur when specifying the initial data in the process of calculating and writing the UE to the software carrier. Accordingly, a distinction is made between geometric errors, technological errors, and perforation or tape recording errors.

Geometric errors appear when the dimensions of a part, workpiece, etc. are incorrect. To detect geometric errors, various types of graphic devices are used, for example, coordinate and graphic displays. Technological errors are associated with the continuous selection of the cutting tool, cutting conditions, the sequence of machining the part on the machine. Errors in writing a program to a program medium appear as a result of improper actions of technologists when filling in information or as a result of failures in the operation of the data preparation device. These errors appear in the process of controlling the control program of the coordinator or on CNC machines.

2 . Design part

2.1 Description of the design and calculation of the machine tool

Purpose of the device and the principle of operation of the designed device

The dividing head with collet chuck is designed for processing grooves on milling operation parts of the "Axis" type.

The principle of operation of the device is as follows: Compressed air from the network through the fitting (19) is supplied to the pneumatic cylinder (20) formed in the body of the device and acts on the piston (22). The resulting force is transmitted through the thrust ball bearing (37) to three pins (25), which lift the glass (4), which is placed in the guide steel sleeve (7).

As it rises, the glass squeezes the collet cone (5) with a tapered hole. The workpiece is fixed in this case.

When the air supply is turned off, the fingers (9), under the action of the spring (8), return the glass to its original position.

To move to the next position, the collet together with the workpiece is turned by the handle (29). For clockwise movement, the eccentric disc (27) pushes the retainer (14) out of the slot of the dividing disc (28), and the pawl (30), under the action of the spring (31), falls into its next slot.

At reverse movement of the handle (29), the pawl (30) turns the dividing disc (28) with the disc (3) and the collet (5) mounted on it with the workpiece until the latch (14) falls into the next slot of the dividing disc and thus will fix the rotation of the part at 900.

The cap (6) prevents chips from entering the collet slots during milling.

Calculation and accuracy

The positioning error is called the deviation of the actually reached position, it is defined as the limiting field of dispersion, the distance between the technological and measuring bases in the direction of the maintained size.

The total error in performing any machining operation consists of:

1 error in setting the workpiece;

2 machine setting error

3 processing error arising during the manufacture of a part. The value of the basing error is determined by the following calculations:

where is the error in setting the workpiece;

Machine setting error;

Processing error arising in the process of manufacturing a part;

d - size tolerance.

Installation error is one of the components of the total error of the performed size of the part. It arises when the workpiece is installed in the fixture and is made up of the positioning error, the fixing error and the position error of the workpiece, which depends on the accuracy of the fixture and is determined by errors in the manufacture and assembly of its installed elements and their wear during operation.

An error in the setting of the machine arises when the cutting tool is set to the size, as well as due to the inaccuracy of the copiers and stops for automatically obtaining the size on the part.

The processing error that occurs during the manufacture of a part on a machine is explained by:

1 Geometric inaccuracy of the machine;

2 Deformation technological system under the influence of cutting forces;

3 Inaccuracy of manufacture and wear of cutting tools and devices.

4 Thermal deformations of the technological system.

Ey = 0.02 + 0 + 0.03 = 0.05 mm

0.05 + 0.03 + 0.03? 0.13 mm

0.11 mm? 0.13 mm

Determination of the clamping force

To determine the clamping force, it is necessary to calculate the cutting force for the operation for which the fixture is designed.

The cutting force for this operation is calculated in paragraph 1.10, then I take all the data for the calculation from there.

To ensure the reliability of clamping the workpiece, it is necessary to determine the safety factor according to the formula:

where is the guaranteed safety factor

Factor that takes into account the increase in cutting forces due to random irregularities on the machined surfaces

Coefficient characterizing the increase in cutting forces due to bluntness of the cutting tool

Factor that takes into account the increase in cutting forces during interrupted cutting

Coefficient characterizing the holding forces in the clamping mechanism

Coefficient characterizing the economy of manual clamping mechanisms

Coefficient that takes into account the presence of moments tending to turn the workpiece set on a flat surface

Since we accept

The required clamping force is determined by the formula:

The area of the pneumatic cylinder piston is determined by the formula:

where is the pressure in the network = 0.38 MPa

The diameter of the pneumatic cylinder is determined by the formula:

I accept the standard diameter of the pneumatic cylinder

Determine the actual clamping force of the cylinder

Determine the cylinder response time

where is the stroke of the rod

Rod stroke speed, m / s

Payment economic feasibility fixtures

The calculation of the economic feasibility of using the designed device is based on a comparison of costs and economic feasibility.

where is the annual savings without taking into account the annual costs of the adaptation, rubles.

P - annual cost of fixtures

Annual savings are calculated using the formula

work-off time when machining a part without a tool = 1.52 min

Unit time for the operation after the introduction of the device

Hourly rate for the operation of the workplace for the type of production

25 rub / hour

N - annual release program

Annual costs are determined by the formula:

where is the cost of the device

A - depreciation coefficient

B-factor, taking into account the repair and storage of fixtures

P = 4500 (0.56 + 0.11) = 3015 rubles.

According to production calculations and the condition of expediency, in my case this condition is fulfilled.

From this I conclude that the use of the designed device is economically feasible.

2.2 Description of the design and calculation of the special cuttinginstrument

When designing a cutting tool, certain conditions must be met:

Find the most advantageous sharpening angles;

Determine the forces acting on the cutting parts;

Choose the most suitable material for the cutting part and the connecting part of the tool;

Set the permissible deviations for the dimensions of the working and connecting parts of the tool, depending on the working conditions and the required accuracy and quality of the processed surface;

To produce necessary calculations elements of the cutting tool and, if necessary, make calculations for strength and rigidity;

Develop a working drawing of a tool with the necessary technical requirements for operation and its manufacture;

Calculate the economic costs of instrumental materials.

Based on the above conditions, I calculate a three-sided disc cutter for milling grooves in size 20h11 at operation 015 Milling

Initial data for the calculation:

Workpiece material 30HGSA;

Machining allowance t = 9 mm

1.1. Description of the design and service purpose of the part.

This part "Axis", weighing 3.7 kg, is made of steel 45 GOST 1050-88.

The part belongs to the "shaft" class and has the shape of rotation. The part consists of 6 steps:

At the first stage, the thread is M20-69, with a roughness of Ra6.3, at a length of 21 mm.

The second cylindrical Ø20 h8mm, surface roughness Ra3.2, 18 mm long; The h8 tolerance is intended for a rigid fit of the abutting part.

The third step is made without machining, Ø25mm, 5mm long.

The fourth cylindrical step Ø20mm, 80mm long, on which grooves are made for the mating part and excluding the rotation of the mating part.

The fifth step is made Ø15f7 mm, 25 mm long, this tolerance indicates that the mating part is rigidly put on the axle.

The sixth stage has a M12-83 thread and a Ø3.2mm hole.

Part "Axle" is designed to transmit torque.

1.2. Technological control of the drawing of the part and analysis of the part for manufacturability

Chemical composition and mechanical properties of the material of the part

Steel 45 GOST 1050-88. Quality structural carbon steel.

Part chemical composition

WITH	Si	Mn	Ni	S	P	Cr	Cu	As	Fe
0.42 ÷ 0.5	0.17 ÷ 0.37	0.5 ÷ 0.8	up to 0.25	up to 0.04	up to 0.035	up to 0.25	up to 0.25	up to 0.08	ost.

Mechanical properties

The part is quite technologically advanced.The part does not need to simplify the design. The base of the part is the axis and ends. No artificial bases required.

Turning will be carried out in centers and in special devices. We perform milling using a round cutter, and drilling on a CNC drilling machine and using a special device. We will make thread cutting on lathe with CNC.

To measure the dimensions specified in the drawing, the following measuring tools should be used: staples, plugs, calipers, templates, indicators, screw plugs.

Qualitative analysis of the manufacturability of the design of the part.

The part should be manufactured with minimal labor and material costs. These costs can be reduced to a large extent as a result of the correct choice of the technological process option, its equipment, mechanization and automation, the use of optimal processing modes and the correct preparation of production. The complexity of manufacturing a part is particularly influenced by its design and technical requirements for manufacturing.

This item is by qualitative assessment is technologically advanced:

The design of the part consists of standard and unified structural elements; most of the processed surfaces of the part have the correct sizing, the optimal degree of accuracy and roughness;

The design of the part allows it to be made from a workpiece obtained in a rational way;

The design allows the use of typical and standard manufacturing processes.

All of the above allows us to conclude that the presented part is technological.

The machining accuracy coefficient is determined by the formula

(1)

where

where numbers denote dimensional accuracy qualifications.

n 1; n 2, etc. - the number of sizes of a given accuracy grade.

The roughness coefficient of processing is determined by the formula

(3)

where

where the numbers indicate the surface roughness classes.

At K TO ≤0.80, the part is considered labor-consuming to manufacture.

n 1; n 2, etc. - the number of surfaces of a given roughness class.

When K SHO ≤0.16, the part is considered labor-intensive in production.

Output: Kt = 0.99 Ksh = 0.91

0.99 ›0.8 0.91› 0.16

All of the above allows us to conclude that the presented part is technological.

2.Technological section

2.1. Characteristics of the medium-batch type of production

Description of the type of production.

Serial the type of production is characterized by a limited nomenclature of production, parts are manufactured in periodic batches. Labor intensity and cost are lower than in one-off production. Distinguish between small batch, medium batch and large batch types of production. Large-scale type of production is characterized by the use of specialized equipment located on the site along the technological process. A specialized cutting and measuring tool is used. The qualifications of the workers are low. The principle of incomplete interchangeability applies.

Table 3.

Tentative definition of the type of production

Type of production	Annual production volume
	Heavy	Middle	Lungs
	> 30 kg	8 - 30 kg	< 8 кг
Single	< 5	< 10	< 100
Small batch	5 – 100	10 – 200	100 - 500
Medium batch	100 – 300	200 – 500	500 - 5000
High-volume	300 – 1000	500 – 5000	5000 - 50000
Massive	> 1000	> 5000	> 50000

Roughly according to the table, we determine the type of production - medium batch.

More precisely, you can determine the type of production by the rate of consolidation of operations To z.o. ...

at K z.o. = 1 - mass production,

1 £ K z.o. £ 10 - large-scale,

£ 10 K z. £ 20 - medium batch,

£ 20 C z. £ 40 - small batch,

40 > To z.o. - one-off production.

The value of K z.o. at the stage of development of the process is calculated by the formula:

Where: S О - the number of operations performed on the site during the month,

Shafts and axles

P l a n l e c i

General information.

Materials and machining of shafts and axles.

Performance criteria and calculation of shafts and axles.

Calculations of shafts and axles.

General information

Shafts- these are parts that serve to transmit torque along their axis and hold other parts located on them (wheels, pulleys, sprockets and other rotating machine parts) and perceive the acting forces.

Axles- these are parts that only hold the parts installed on them and perceive the forces acting on these parts (the axis does not transmit useful torque).

Classification of shafts and axles

Kl a s i f and k and c and i v al about in groups the latter according to a number of signs: by purpose, by form cross section, according to the shape of the geometric axis, according to the outer outline of the cross-section, according to the relative speed of rotation and according to the location in the node .

They are distinguished by purpose:

gear shafts, on which wheels, pulleys, sprockets, couplings, bearings and other gear parts are installed. In fig. eleven, a the transmission shaft is shown, in fig. eleven, b- transmission shaft;

main shafts(Fig. 11.2 - machine spindle), on which not only gear parts are installed, but also the working parts of the machine (connecting rods, turbine discs, etc.).

According to the cross-sectional shape, they are made:

solid shafts;

hollow shafts provide a reduction in weight or placement within another part. In large-scale production, hollow welded shafts made of wound tape are used.

According to the shape of the geometric axis, they are produced:

straight shafts:

a) constant diameter(fig.11.3). Such shafts are less laborious to manufacture and create a lower stress concentration;

b) stepped(fig.11.4). Based on the strength condition, it is advisable to design shafts of variable cross-section, approaching in shape to bodies of equal resistance. The stepped shape is convenient for manufacturing and assembly, the ledges can perceive large axial forces;

v) with flanges. Long shafts are split, connected by flanges;

G) with chopped gears(pinion shaft);

crankshafts(Fig. 11.5) in crank gears are used to convert rotary motion into reciprocating or vice versa;

flexible shafts(Fig. 11.6), which are multi-threaded torsion springs twisted from wires, are used to transfer torque between machine units that change their relative position in operation (portable instrument, tachometer, dental drills, etc.).

According to the external outline of the cross-section, the shafts are:

smooth;

keyed;

splined;

profile;

eccentric.

According to the relative speed of rotation and according to the location in the node (gearbox), the shafts are produced:

high-speed and input (leading)(pos. 1 rice. 11.7);

medium speed and intermediate(pos. 2 rice. 11.7);

slow-moving and weekend (slave)(pos. 3 rice. 11.7).

Rice. 11.2 Fig. 11.3

Rice. 11.7 Fig. 11.8

CLASS The axles can be stationary (fig. 11.8) and rotating together with the parts mounted on them. Rotating axles provide Better conditions operation of bearings, stationary is cheaper, but requires the installation of bearings in rotating parts on the axes.

Shaft and axle designs. the most common is a stepped shaft. Parts are fixed on shafts most often with prismatic keys (GOST 23360-78, GOST 10748-79), straight-sided splines (GOST 1139-80) or involute (GOST 6033-80) or landings with guaranteed interference. The bearing parts of shafts and axles are called journals. Intermediate pins are called necks, end pins are called spikes. The bearing areas that perceive the axial load are called heels. The heels are supported by thrust bearings.

In fig. 11.9 shows the structural elements of the shafts, where 1 - prismatic key, 2 - slots, 3 - pin, 4 - heel, 5 - cylindrical surface, 6 - conical surface, 7 - ledge, 8 - shoulder, 9 - groove for stop ring, 10 - threaded section, 11 - fillet, 12 - groove, 13 - chamfer, 14 - center hole.

The journals of shafts and axles operating in rolling bearings are almost always cylindrical, and in sleeve bearings - cylindrical, tapered or spherical (Figure 11.10.)

The main application is cylindrical pins (Fig.11.10, a, b) as simpler ones. Tapered pins with small taper (fig.11.10, v) are used to adjust the clearance in bearings and sometimes for axial fixation of the shaft. Spherical pins (Fig.11.10, G) due to the difficulty of their manufacture, they are used when it is necessary to compensate for significant angular displacements of the shaft axis.

a B C D

Landing surfaces under the hubs of various parts (according to GOST 6536-69 from the normal row), fitted on the shaft, and the end sections of the shafts are cylindrical (pos. 5 rice. 11.9, GOST 12080-72) or tapered (pos. 6 rice. 1.9, GOST 12081–72). Conical surfaces are used to ensure quick release and a given interference, to improve the accuracy of centering of parts.

For axial fixation of parts and the shaft itself, use ledges(pos. 7 rice. 11.9) and shoulders shaft (pos. 8 rice. 11.9, GOST 20226-74), tapered sections of the shaft, retaining rings(pos. 9 rice. 11.9, GOST 13940–86, GOST 13942–86) and threaded sections (pos. 10 rice. 11.9) under nuts(GOST 11871–80).

Transitional areas from one section of the shaft to another and the ends of the shafts are performed with grooves(pos. 12 rice. 11.9, fig. 11.11, GOST 8820-69), chamfers(pos. 13 rice. 11.9, GOST 10948-65) and fillets... Radius R fillets of constant radius (Fig.11.11, a) choose less than the radius of curvature or the radial dimension of the chamfer of the parts to be fitted. It is desirable that the radius of curvature in highly stressed shafts be greater than or equal to 0.1 d... It is recommended to take the fillet radii as large as possible to reduce the concentration of the load. When the fillet radius is strongly limited by the radius of curvature of the edges of the parts to be fitted, spacer rings are placed. Fillets of a special elliptical shape and with an undercut or, more often, fillets, outlined by two radii of curvature (Fig.11.11, b), are used when the fillet passes into a step of a smaller diameter (it makes it possible to increase the radius in the transition zone).

The use of grooves (fig.11.11, v) can be recommended for non-critical parts, since they cause a significant concentration of stresses and reduce the strength of the shafts at alternating stresses. The grooves are used for the exit of grinding wheels (they significantly increase their durability during processing), as well as at the ends of the threaded sections for the exit of the threading tool. The grooves must have the largest possible radii.

a B C

The ends of the shafts, in order to avoid crushing and damage to the hands of workers, to facilitate the attachments of parts are performed with chamfers.

Shafts are machined in centers, therefore, center holes should be provided at the ends of the shafts (pos. 14 rice. 11.9, GOST 14034–74).

The length of the axles usually does not exceed 3 m, the length of solid shafts, according to the conditions of manufacture, transportation and installation, should not exceed 6 m.

1.1 Service purpose and technical characteristics of the part

To draw up a high-quality technological process for manufacturing a part, it is necessary to carefully study its design and purpose in the machine.

The part is a cylindrical axis. The highest requirements for shape and position accuracy, as well as roughness, are imposed on the surfaces of the axle journals intended for bearing seating. So the accuracy of the bearing journals must correspond to grade 7. The high requirements for the accuracy of the positioning of these journals relative to each other result from the operating conditions of the axle.

All axle journals are surfaces of revolution of relatively high precision. This determines the advisability of using turning operations only for their preliminary processing, and the final processing in order to ensure the specified dimensional accuracy and surface roughness should be carried out by grinding. To ensure high requirements for the accuracy of the position of the axle journals, their final processing must be carried out in one setup or, in extreme cases, on the same bases.

Axes of this design are widely used in mechanical engineering.

The axles are designed to transmit torques and mount various parts and mechanisms on them. They are a combination of smooth landing and non-landing surfaces, as well as transitional surfaces.

The technical requirements for the axles are characterized by the following data. The diametric dimensions of the landing journals are made according to IT7, IT6, and other journals according to IT10, IT11.

The axle design, its dimensions and rigidity, technical requirements, production program are the main factors that determine the manufacturing technology and the equipment used.

The part is a body of revolution and consists of simple structural elements presented in the form of bodies of revolution of a circular cross-section of various diameters and lengths. There is a thread on the axle. The axle length is 112 mm, the maximum diameter is 75 mm and the minimum diameter is 20 mm.

Based on the constructive purpose of the part in the machine, all surfaces of this part can be divided into 2 groups:

main or work surfaces;

free or non-working surfaces.

Almost all surfaces of the axle belong to the main ones, because they mate with the corresponding surfaces of other machine parts or directly participate in the working process of the machine. This explains the rather high requirements for the accuracy of processing the part and the degree of roughness indicated in the drawing.

It can be noted that the design of the part is fully consistent with its service purpose. But the principle of manufacturability of design is not only to meet the operational requirements, but also the requirements of the most rational and economical manufacture of the product.

The part has surfaces that are easily accessible for processing; sufficient rigidity of the part allows it to be processed on machines with the most productive cutting conditions. This part is technologically advanced, since it contains simple surface profiles, its processing does not require specially designed devices and machines. Axle surfaces are machined on a turning, drilling and grinding machine. The required dimensional accuracy and surface roughness are achieved with a relatively small set of simple operations, as well as a set of standard cutters and grinding wheels.

Manufacturing of a part is laborious, which is associated, first of all, with the provision of technical conditions for the work of the part, the required dimensional accuracy, and the roughness of the working surfaces.

So, the part is technologically advanced in terms of design and processing methods.

The axle material, steel 45, belongs to the group of medium-carbon structural steels. It is used for medium loaded parts operating at low speeds and medium specific pressures.

The chemical composition of this material is summarized in Table 1.1.

Table 1.1

7
WITH	Si	Mn	Cr	S	P	Cu	Ni	As
0,42-05	0,17-0,37	0,5-0,8	0,25	0,04	0,035	0,25	0,25	0,08

Let us dwell a little on the mechanical properties of rolled products and forgings required for further analysis, which we will also summarize in Table 1.2.

Table 1.2

Here are some of the technological properties.

The temperature of the beginning of forging is 1280 ° C, and the temperature of the end of forging is 750 ° C.

This steel has limited weldability

Workability by cutting - in the hot-rolled state at HB 144-156 and σ B = 510 MPa.

1.2 Determining the type of production and batch size of the part

In the assignment for the course project, the annual program for the release of the product in the amount of 7000 pieces is indicated. Using the source formula, we determine the annual program for the production of parts in pieces, taking into account spare parts and possible losses:

where P is the annual product release program, pcs;

P 1 - the annual program for the manufacture of parts, pcs. (we accept 8000 pcs.);

b - the number of additionally manufactured parts for spare parts and to compensate for possible losses, in percent. You can take b = 5-7;

m - the number of parts of this name in the product (we accept 1 piece).

PCS.

The size of the production program in physical quantitative terms determines the type of production and has a decisive influence on the nature of the construction of the technological process, on the choice of equipment and tooling, on the organization of production.

In mechanical engineering, there are three main types of production:

Single or individual production;

Mass production;

Mass production.

Based on the release program, we can come to the conclusion that in this case we have mass production. In serial production, the manufacture of products is carried out in batches, or in series, periodically repeated.

Depending on the size of batches or series, there are three types of batch production for medium-sized machines:

Small-scale production with the number of products in a series up to 25 pcs;

Medium batch production with the number of items in the series 25-200 pcs;

Large-scale production with more than 200 items in a batch;

A characteristic feature of batch production is that the production of products is carried out in batches. The number of parts in a batch for simultaneous launch can be determined using the following simplified formula:

where N is the number of blanks in the batch;

P is the annual program for the manufacture of parts, pcs.;

L is the number of days for which it is necessary to have a stock of parts in the warehouse to ensure assembly (we take L = 10);

F is the number of working days in a year. You can take F = 240.

PCS.

Knowing the annual volume of production of parts, we determine that this production belongs to large-scale production (5000 - 50,000 pcs.).

In serial production, each operation of the technological process is assigned to a specific workplace. In most workplaces, several operations are performed, periodically repeating.

1.3 Choosing a method of obtaining a workpiece

The method of obtaining the initial blanks of machine parts is determined by the design of the part, the volume of production and the production plan, as well as the economy of manufacture. Initially, from the whole variety of methods for obtaining initial blanks, several methods are selected that technologically provide the possibility of obtaining a blank of a given part and allow the configuration of the original blank to be as close as possible to the configuration of the finished part. To choose a workpiece means to choose a method of obtaining it, outline allowances for processing each surface, calculate dimensions and indicate tolerances for manufacturing inaccuracies.

The main thing when choosing a blank is to ensure the desired quality of the finished part at its minimum cost.

The correct solution to the question of the choice of blanks, if from the point of view technical requirements and their various types are applicable, can be obtained only as a result of technical and economic calculations by comparing the options for the cost of the finished part with one or another type of workpiece. Technological processes for obtaining blanks are determined by the technological properties of the material, structural shapes and sizes of parts and the release program. Preference should be given to a workpiece with better metal utilization and lower cost.

Let's take two methods of obtaining blanks and having analyzed each, we will choose the desired method for obtaining blanks:

1) obtaining a billet from rolled products

2) obtaining a blank by stamping.

You should choose the most "successful" method of obtaining a workpiece by analytical calculation. Let's compare the options for the minimum value of the reduced costs for the manufacture of a part.

If the billet is made from rolled stock, then the cost of the blank is determined by the weight of the rolled stock required to manufacture the part and the weight of the chips. The cost of the billet obtained by rolling is determined by the following formula:

where Q is the mass of the workpiece, kg;

S - price of 1 kg of workpiece material, rubles;

q is the mass of the finished part, kg;

Q = 3.78 kg; S = 115 rubles; q = 0.8 kg; S ex = 14.4 kg.

Let's substitute the initial data into the formula:

Consider the option of obtaining a blank by stamping on the GCM. The cost of the procurement is determined by the expression:

Where C i is the price of one ton of stampings, rubles;

К Т - coefficient depending on the stamping accuracy class;

К С - coefficient depending on the group of stamping complexity;

K B - coefficient depending on the mass of the forgings;

K M - coefficient depending on the brand of stamping material;

К П - coefficient depending on the annual program of stampings production;

Q is the mass of the workpiece, kg;

q is the mass of the finished part, kg;

S waste - the price of 1 ton of waste, rub.

With i = 315 rubles; Q = 1.25 kg; K T = 1; K C = 0.84; K B = 1; K M = 1; K P = 1;

q = 0.8 kg; S ex = 14.4 kg.

The economic effect for comparing the methods of obtaining workpieces, in which the technological process of machining does not change, can be calculated by the formula:

where S E1, S E2 - the cost of the compared workpieces, rubles;

N - annual program, pcs.

We define:

From the results obtained, it can be seen that the option of obtaining a blank by stamping is economically viable.

Manufacturing of a blank by stamping on different types equipment is a progressive method, since it significantly reduces the allowances for machining in comparison with obtaining a billet from rolled products, and is also characterized by a higher degree of accuracy and higher productivity. In the process of stamping, the material is also compacted and the direction of the fiber of the material along the contour of the part is created.

Having solved the problem of choosing a method for obtaining a workpiece, you can proceed to the following steps term paper, which will gradually lead us to the direct drawing up of the technological process of manufacturing a part, which is the main goal of the course work. The choice of the type of workpiece and the method for its production have the most direct and very significant effect on the nature of the construction of the technological process for manufacturing a part, since, depending on the selected method of obtaining a workpiece, the amount of allowance for processing a part can vary within significant limits and, therefore, the set of methods does not change, used for surface treatment.

1.4 Purpose of methods and stages of processing

The choice of processing method is influenced by the following factors that must be taken into account:

shape and size of the part;

precision of processing and cleanliness of surfaces of parts;

economic feasibility of the selected processing method.

Guided by the above points, we will begin to identify a set of processing methods for each surface of the part.

Figure 1.1 Sketch of the part with the designation of the layers removed during machining

All axle surfaces have fairly high roughness requirements. We divide the turning of surfaces A, B, C, D, D, E, Z, I, K into two operations: rough (preliminary) and finishing (final) turning. For rough turning, remove most of the allowance; machining is carried out with a large depth of cut and a high feed. The scheme that provides the shortest processing time is the most beneficial. When finishing turning, we remove a small part of the allowance, and the order of surface processing is preserved.

When machining on a lathe, it is necessary to pay attention to the firm fixing of the workpiece and the cutter.

To obtain the specified roughness and the required quality of surfaces G and I, it is necessary to apply finishing grinding, in which the accuracy of processing the outer cylindrical surfaces reaches the third class, and the surface roughness is 6-10 classes.

For greater clarity, we schematically write down the selected processing methods on each surface of the part:

A: rough turning, finishing turning;

B: rough turning, finishing turning, threading;

B: rough turning, finishing turning;

D: rough turning, finishing turning, finishing grinding;

D: rough turning, finishing turning;

E: rough turning, finishing turning;

W: drilling, countersinking, reaming;

З: rough turning, finishing turning;

And: rough turning, finishing turning, finishing grinding;

K: rough turning, finishing turning;

L: drilling, countersinking;

M: drilling, countersinking;

Now you can proceed to the next stage of the course work, associated with the choice of technical bases.

1.5 Selection of bases and sequence of processing

The blank part in the process of processing must take and maintain during the entire processing time a certain position relative to the parts of the machine or fixture. To do this, it is necessary to exclude the possibility of three rectilinear movements of the workpiece in the direction of the selected coordinate axes and three rotational movements around these or parallel axes (i.e. to deprive the workpiece of a part of six degrees of freedom).

To determine the position of a rigid workpiece, six reference points are required. To place them, three coordinate surfaces are required (or three combinations of coordinate surfaces replacing them), depending on the shape and size of the workpiece, these points can be located on the coordinate surface in different ways.

It is recommended to choose design bases as technological bases in order to avoid recalculation of operational dimensions. The axis is a cylindrical part, the design bases of which are end surfaces. In most operations, the basing of the part is carried out according to the following schemes.

Figure 1.2 Installation diagram of the workpiece in a three-jaw chuck

In this case, when installing the workpiece in the chuck: 1, 2, 3, 4 - a double guide base, which takes away four degrees of freedom - movement about the OX and OZ axis and rotation around the OX and OZ axes; 5 - the support base deprives the workpiece of one degree of freedom - movement along the OY axis;

6 - support base, depriving the workpiece of one degree of freedom, namely, rotation around the OY axis;

Figure 1.3 Installation diagram of the workpiece in a vice

Taking into account the shape and size of the part, as well as the processing accuracy and surface finish, a set of processing methods were selected for each shaft surface. We can define the sequence of surface treatments.

Figure 1.4 Sketch of the part with the designation of surfaces

1. Turning operation. The workpiece is set on a surface 4 in

self-centering 3-jaw chuck with an emphasis on the end face 5 for rough turning of the end face 9, surface 8, end face 7, surface 6.

2. Turning operation. We turn the workpiece over and install it in a self-centering 3-jaw chuck along surface 8 with an emphasis on end face 7 for rough turning of end face 1, surface 2, end face 3, surface 4, end face 5.

3. Turning operation. The workpiece is set on a surface 4 in

self-centering 3-jaw chuck with an end stop 5 for finishing turning of end face 9, surface 8, end face 7, surface 6, chamfer 16 and groove 19.

4. Turning operation. We turn the workpiece over and install it in a self-centering 3-jaw chuck along surface 8 with an emphasis on end face 7 for finishing turning of end face 1, surface 2, end face 3, surface 4, end face 5, chamfers 14, 15 and grooves 17, 18.

5. Turning operation. We install the workpiece in a self-centering 3-jaw chuck along surface 8 with an emphasis on the end face 7 for drilling and countersinking surface 10, cutting threads on surface 2.

6. Drilling operation. The part is installed in a vice on surface 6 with an emphasis on the end 9 for drilling, countersinking and reaming surface 11, drilling and countersinking surfaces 12 and 13.

7. Grinding operation. The part is installed along surface 4 into a self-centering 3-jaw chuck with an emphasis on the end 5 for grinding surface 8.

8. Grinding operation. The part is installed along surface 8 in a self-centering 3-jaw chuck with an emphasis on the end 7 for grinding surface 4.

9. Remove the part from the fixture and send it for inspection.

The workpiece surfaces are machined in the following sequence:

surface 9 - rough turning;

surface 8 - rough turning;

surface 7 - rough turning;

surface 6 - rough turning;

surface 1 - rough turning;

surface 2 - rough turning;

surface 3 - rough turning;

surface 4 - rough turning;

surface 5 - rough turning;

surface 9 - finishing turning;

surface 8 - finishing turning;

surface 7 - finishing turning;

surface 6 - finishing turning;

surface 16 - chamfer;

surface 19 - sharpen a groove;

surface 1 - finishing turning;

surface 2 - finishing turning;

surface 3 - finishing turning;

surface 4 - finishing turning;

surface 5 - finishing turning;

surface 14 - chamfer;

surface 15 - chamfer;

surface 17 - sharpen the groove;

surface 18 - sharpen the groove;

surface 10 - drilling, countersinking;

surface 2 - threading;

surface 11 - drilling, countersinking, reaming;

surface 12, 13 - drilling, countersinking;

surface 8 - fine grinding;

surface 4 - fine grinding;

As you can see, the surface treatment of the workpiece is carried out in order from coarser to more precise methods. The last processing method in terms of accuracy and quality must comply with the requirements of the drawing.

1.6 Development of route technological process

The part represents an axis and refers to bodies of revolution. We process the workpiece obtained by stamping. When processing, we use the following operations.

010. Turning.

1. grind surface 8, cut end face 9;

2.Charge surface 6, cut end face 7

Cutter material: CT25.

Coolant brand: 5% emulsion.

015. Turning.

Processing is carried out on a 1P365 turret lathe.

1. grind surface 2, cut end face 1;

2. grind surface 4, cut end face 3;

3.cut the butt 5.

Cutter material: CT25.

Coolant brand: 5% emulsion.

The part is based in a three-jaw chuck.

We use a bracket as a measuring tool.

020. Turning.

Processing is carried out on a 1P365 turret lathe.

1. grind surfaces 8, 19, cut end face 9;

2. grind the surfaces 6, cut the butt end 7;

3.Remove chamfer 16.

Cutter material: CT25.

Coolant brand: 5% emulsion.

The part is based in a three-jaw chuck.

We use a bracket as a measuring tool.

025. Turning.

Processing is carried out on a 1P365 turret lathe.

1. grind surfaces 2, 17, cut end face 1;

2. grind surfaces 4, 18, cut end face 3;

3. trim the butt end 5;

4.Remove chamfer 15.

Cutter material: CT25.

Coolant brand: 5% emulsion.

The part is based in a three-jaw chuck.

We use a bracket as a measuring tool.

030. Turning.

Processing is carried out on a 1P365 turret lathe.

1. drill, countersink hole - surface 10;

2. cut threads - surface 2;

Drill material: CT25.

Coolant brand: 5% emulsion.

The part is based in a three-jaw chuck.

035. Drilling

Processing is carried out on a coordinate drilling machine 2550F2.

1. Drill, countersink 4 stepped holes Ø9 - surface 12 and Ø14 - surface 13;

2. drilling, countersinking, reaming Ø8 hole - surface 11;

Drill material: R6M5.

Coolant brand: 5% emulsion.

The part is based in a vice.

We use the caliber as a measuring tool.

040. Grinding

1.Grind the surface 8.

The part is based in a three-jaw chuck.

We use a bracket as a measuring tool.

045. Grinding

Processing is carried out on a 3T160 cylindrical grinding machine.

1.Grind the surface 4.

For processing, select the grinding wheel

PP 600 × 80 × 305 24А 25 Н СМ1 7 К5А 35 m / s. GOST 2424-83.

The part is based in a three-jaw chuck.

We use a bracket as a measuring tool.

050. Vibro-abrasive

Processing is carried out in a vibro-abrasive machine.

1.Dull sharp edges, remove burrs.

055. Flushing

Washing is done in the bathroom.

060. Control

They control all dimensions, check the roughness of surfaces, the absence of nicks, dullness of sharp edges. The control table is used.

1.7 Selection of equipment, tooling, cutting and measuring tools

axis workpiece cutting machining

The choice of machine tools is one of the most important tasks in the development of a technological process for machining a workpiece. The productivity of manufacturing a part, the economic use of production areas, mechanization and automation depends on its correct choice. manual labor, electricity and, as a result, the cost of the product.

Depending on the volume of production, machines are chosen according to the degree of specialization and high productivity, as well as machines with numerical control (CNC).

When developing a technological process for machining a workpiece, it is necessary to choose the right devices that should contribute to increasing labor productivity, processing accuracy, improving working conditions, eliminating preliminary marking of the workpiece and aligning them when installed on a machine.

The use of machine tools and auxiliary tools when processing workpieces gives a number of advantages:

improves the quality and accuracy of parts processing;

reduces the complexity of processing workpieces due to a sharp decrease in the time spent on installation, alignment and fastening;

expands the technological capabilities of machine tools;

creates the possibility of simultaneous processing of several workpieces fixed in a common fixture.

When developing a technological process for machining a workpiece, the choice of a cutting tool, its type, design and size is largely predetermined by the processing methods, the properties of the material being processed, the required processing accuracy and the quality of the workpiece surface being processed.

When choosing a cutting tool, it is necessary to strive to accept a standard tool, but, when appropriate, a special, combined, shaped tool should be used, allowing the processing of several surfaces to be combined.

Choosing the right cutting edge is essential for increasing productivity and reducing your machining cost.

When designing a technological process for machining a workpiece for interoperative and final control of the machined surfaces, it is necessary to use a standard measuring tool, taking into account the type of production, but at the same time, when appropriate, a special measuring tool or measuring device should be used.

The control method should help to increase the productivity of the controller and machine operator, create conditions for improving the quality of products and reducing its cost. In single and serial production, a universal measuring tool is usually used (vernier caliper, depth gauge, micrometer, goniometer, indicator, etc.)

In mass and large-scale production, it is recommended to use limiting calibers (staples, plugs, templates, etc.) and active control methods, which are widespread in many branches of mechanical engineering.

1.8 Calculation of operating dimensions

The operational dimension is understood as the dimension indicated on the operational sketch and characterizing the size of the surface to be machined or the relative position of the machined surfaces, lines or points of the part. The calculation of operational dimensions is reduced to the task correct definition the size of the operating allowance and the size of the operating tolerance, taking into account the peculiarities of the developed technology.

Long operating dimensions are understood as dimensions that characterize the processing of surfaces with a one-sided arrangement of the allowance, as well as dimensions between axes and lines. Calculation of long operating dimensions is carried out in the following sequence:

1. Preparation of initial data (based on the working drawing and operational maps).

2. Drawing up a processing scheme based on the initial data.

3. Building a graph of dimensional chains to determine allowances, drawing and operational dimensions.

4. Drawing up a statement of calculation of operating sizes.

On the processing diagram (Figure 1.5), we place a sketch of the part indicating all surfaces of a given geometric structure that are encountered during processing from the workpiece to the finished part. In the upper part of the sketch, all long drawing dimensions are indicated, drawing dimensions with tolerances (C), and below all operating allowances (1z2, 2z3,…, 13z14). Under the sketch in the processing table, there are dimension lines that characterize all the dimensions of the workpiece, oriented by one-sided arrows, so that no arrow approaches one of the surfaces of the workpiece, and only one arrow approaches the rest of the surfaces. The dimension lines below indicate the dimensions of the machining. The operating dimensions are oriented in the direction of the machined surfaces.

Figure 1.5 Part processing scheme

On the graph of the initial structures connecting surfaces 1 and 2 with wavy edges, characterizing the size of the allowance 1z2, surfaces 3 and 4 with additional ribs characterizing the size of the allowance 3z4, etc. And we also draw thick edges of drawing dimensions 2c13, 4c6, etc.

Figure 1.6 Graph of initial structures

The top of the graph. Characterizes the surface of a part. The number in the circle indicates the number of the surface on the machining diagram.

The edge of the graph. It characterizes the type of connections between surfaces.

"z" - Corresponds to the size of the operating allowance, and "c" - to the drawing dimension.

On the basis of the developed processing scheme, a graph of arbitrary structures is constructed. The construction of the derived tree begins from the surface of the workpiece, to which no arrows are drawn in the processing diagram. In Figure 1.5, such a surface is indicated by the number "1". From this surface we draw those edges of the graph that touch it. At the end of these edges, we indicate the arrows and the numbers of those surfaces to which the indicated dimensions are drawn. Similarly, we complete the graph according to the processing scheme.

Figure 1.7 Graph of derived structures

The top of the graph. Characterizes the surface of a part.

The edge of the graph. The constituent link of the dimensional chain corresponds to the operating size or the size of the workpiece.

The edge of the graph. The closing link of the dimensional chain corresponds to the drawing dimension.

The edge of the graph. The closing link of the dimensional chain corresponds to the operating allowance.

On all edges of the graph we put a sign ("+" or "-"), guided by following rule: if an edge of the graph enters with its arrow into a vertex with a higher number, then on this edge we put a “+” sign, if an edge of the graph enters with its arrow into a vertex with a lower number, then on this edge we put a sign “-” (Figure 1.8). We take into account that we do not know the operating dimensions, and according to the processing scheme (Figure 1.5) we determine approximately the value of the operating size or the size of the workpiece, using for this purpose the drawing dimensions and the minimum operating allowances, which are the sum of the microroughness values (Rz), the depth of the deformation layer (T) and spatial deviation (Δпр), obtained in the previous operation.

Column 1. In random order, rewrite all drawing dimensions and allowances.

Column 2. We indicate the numbers of operations in the sequence of their execution according to route technology.

Column 3. We indicate the name of the operations.

Column 4. We indicate the type of machine and its model.

Column 5. We place simplified sketches in one unchanged position for each operation, indicating the surfaces to be processed according to the route technology. Surfaces are numbered in accordance with the processing scheme (Figure 1.5).

Column 6. For each surface processed in this operation, indicate the operating size.

Column 7. We do not heat treatment of the part in this operation, therefore we leave the column blank.

Column 8. Filled in in exceptional cases when the choice of the measuring base is limited by the convenience of monitoring the operational size. In our case, the graph remains free.

Column 9. We indicate possible options for surfaces that can be used as technological bases, taking into account the recommendations given in Art.

The choice of surfaces used as technological and measuring bases, we begin with the last operation in the reverse order of the technological process. We write down the equations of dimensional chains according to the graph of initial structures.

After the selection of bases and operating dimensions, we proceed to the calculation of nominal values and the selection of tolerances for operating dimensions.

The calculation of long operating dimensions is based on the results of work to optimize the structure of operating dimensions and is carried out in accordance with the sequence of works. The preparation of the initial data for calculating the operating sizes is done by filling in the columns

13-17 maps for choosing bases and calculating operational sizes.

Column 13. To close the links of dimensional chains, which are drawing dimensions, write down the minimum values of these dimensions. To close the links, which are operational allowances, we indicate the value of the minimum allowance, which is determined by the formula:

z min = Rz + T,

where Rz is the height of the irregularities obtained in the previous operation;

T is the depth of the defective layer formed in the previous operation.

The Rz and T values are determined from the tables.

Column 14. For the closing links of the dimensional chains, which are drawing dimensions, we write down the maximum values of these dimensions. We do not put down the maximum values of the allowances yet.

Columns 15, 16. If the tolerance for the required operational size has a "-" sign, then in column 15 we put the number 1, if "+", then in column 16 we put the number 2.

Column 17. We put down the approximate values of the determined operating dimensions, we use the equations of the dimensional chains from column 11.

1.9A8 = 8c9 = 12 mm;

2.9A5 = 3s9 - 3s5 = 88 - 15 = 73 mm;

3.9A3 = 3s9 = 88 mm;

4.7A9 = 7z8 + 9A8 = 0.2 + 12 = 12mm;

5.7A12 = 3c12 + 7A9 - 9A3 = 112 + 12 - 88 = 36 mm;

6.10A7 = 7A9 + 9z10 = 12 + 0.2 = 12 mm;

7.10A4 = 10A7 - 7A9 + 9A5 + 4z5 = 12 - 12 + 73 + 0.2 = 73 mm;

8.10A2 = 10A7 - 7A9 + 9A3 + 2z3 = 12 - 12 + 88 + 0.2 = 88 mm;

9.6A10 = 10A7 + 6z7 = 12 + 0.2 = 12 mm;

10.6A13 = 6A10 - 10A7 + 7A12 + 12z13 = 12 - 12 + 36 + 0.2 = 36 mm;

11.1A6 = 10A2 - 6A10 + 1z2 = 88 - 12 + 0.5 = 77 mm;

12.1A11 = 10z11 + 1A6 + 6A10 = 0.2 + 77 + 12 = 89 mm;

13.1A14 = 13z14 + 1A6 + 6A13 = 0.5 + 77 + 36 = 114 mm.

Column 18. We put down the values of tolerances for operating dimensions adopted according to accuracy table 7, taking into account the recommendations set out in Art. After setting the tolerances in column 18, you can determine the value of the maximum values of the allowances and put them in column 14.

The value of ∆z is determined from the equations in column 11 as the sum of the tolerances for the operating dimensions that make up the dimensional chain.

Column 19. In this column it is necessary to put down the nominal values of the operating dimensions.

The essence of the method for calculating the nominal values of the operating dimensions is reduced to solving the equations of dimensional chains written in column 11.

1.8s9 = 9A89A8 =

2.3s9 = 9A39A3 =

3.3s5 = 3s9 - 9A5

9A5 = 3s9 - 3s5 =

We accept: 9A5 = 73 -0.74

3s5 =

4.9z10 = 10A7 - 7A9

10A7 = 7A9 + 9z10 =

We accept: 10A7 = 13.5 -0.43 (correction + 0.17)

9z10 =

5.4z5 = 10A4 - 10A7 + 7A9 - 9A5

10A4 = 10A7 - 7A9 + 9A5 + 4z5 =

We accept: 10A4 = 76.2 -0.74 (correction + 0.17)

4z5 =

6.2z3 = 10A2 - 10A7 + 7A9 - 9A3

10A2 = 10A7 - 7A9 + 9A3 + 2z3 =

Accept: 10A2 = 91.2 -0.87 (adjustment + 0.04)

2z3 =

7. 7z8 = 7A9 - 9A8

7A9 = 7z8 + 9A8 =

Accept: 7A9 = 12.7 -0.43 (adjustment: + 0.07)

7z8 =

8.3c12 = 7A12 - 7A9 + 9A3

7A12 = 3s12 + 7A9 - 9A3 =

We accept: 7A12 = 36.7 -0.62

3s12 =

9.6z7 = 6A10 - 10A7

6A10 = 10A7 + 6z7 =

Accept: 6A10 = 14.5 -0.43 (correction + 0.07)

6z7 =

10.12z13 = 6A13 - 6A10 + 10A7– 7A12

6A13 = 6A10 - 10A7 + 7A12 + 12z13 =

Accept: 6A13 = 39.9 -0.62 (adjustment + 0.09)

12z13 =

11.1z2 = 6A10 - 10A2 + 1A6

1A6 = 10A2 - 6A10 + 1z2 =

Accept: 1A6 = 78.4 -0.74 (correction + 0.03)

1z2 =

12.13z14 = 1A14 - 1A6 - 6A13

1A14 = 13z14 + 1A6 + 6A13 =

Accept: 1A14 = 119.7 -0.87 (adjustment + 0.03)

13z14 =

13.10z11 = 1A11 - 1A6 - 6A10

1A11 = 10z11 + 1A6 + 6A10 =

Accept: 1A11 = 94.3 -0.87 (adjustment + 0.03)

10z11 =

After calculating the nominal sizes, we enter them into column 19 of the base selection card and, with a processing tolerance, write them down in the “note” column of the Processing Schemes (Figure 1.5).

After we fill in column 20 and the column "approx.", The obtained values of the operating dimensions with a tolerance are applied to the sketches of the route technological process. This completes the calculation of the nominal values of the long operating dimensions.

Map for choosing bases and calculating operating sizes

Closing links

Operation No.

the name of the operation

Model equipment

processing

Operating

Base

Dimensional chain equations

Closing links of dimensional chains

Operating dimensions

Surfaces to be treated

Thermocontrol depth layer

Selected from the conditions of convenience of measurement

Technol options. bases

Accepted tech-nol. and measure. base

Designation

Limit sizes

Tolerance mark and approx.

operating value

The magnitude

Nominal

meaning

min

max

magnitude

Prepare.

GCM

13z14 = 1A14-1A-6A13

10z11 = 1A11-1A6-6A10

1z2 = 6А10-10А2 + 1А6

Lathe

1P365

12z13 = 6A13–6A10 + 10A7–7A12

Figure 1.9 Map of base selection and calculation of operational dimensions

Calculation of operating dimensions with a two-sided arrangement of the allowance

When processing surfaces with a two-sided arrangement of the allowance, it is advisable to calculate the operating dimensions using a statistical method for determining the size of the operating allowance, depending on the selected processing method and on the dimensions of the surfaces.

To determine the size of the operating allowance by the static method, depending on the processing method, we will use the source tables.

To calculate the operating dimensions with a two-sided arrangement of the allowance, for such surfaces we draw up the following calculation scheme:

Figure 1.10 Layout of operating allowances

Drawing up a statement of calculating diametrical operating dimensions.

Column 1: Indicates the numbers of operations according to the developed technology in which this surface is processed.

Column 2: Indicate the processing method in accordance with the operational chart.

Columns 3 and 4: Indicate the designation and the value of the nominal diametrical operating allowance, taken from the tables in accordance with the processing method and dimensions of the workpiece.

Column 5: Indicate the designation of the operating size.

Column 6: According to the adopted processing scheme, equations are drawn up to calculate the operating dimensions.

Filling out the sheet begins with the final operation.

Column 7: Indicate the accepted operating size with a tolerance. The estimated value of the required operational size is determined by solving the equation from column 6.

List of calculation of operating dimensions when processing the outer diameter of the axis Ø20k6 (Ø20)

	Name operations	Operational allowance		Operating size
	Name operations	Designation	The magnitude	Designation	Calculation formulas	Approximate size
1	2	3	4	5	6	7
Zag	Stamping	Ø24
10	Turning (roughing)	D10	D10 = D20 + 2z20
20	Turning (finishing)	Z20	0,4	D20	D20 = D45 + 2z45
45	Grinding	Z45	0,06	D45	D45 = damn. rr

Statement of calculation of operating dimensions when processing the outer diameter of the axis Ø75 -0.12

1	2	3	4	5	6	7
Zag	Stamping	Ø79
10	Turning (roughing)	D10	D10 = D20 + 2z20	Ø75.8 -0.2
20	Turning (finishing)	Z20	0,4	D20	D20 = damn. rr

List of calculation of operating dimensions when processing the outer diameter of the axis Ø30k6 (Ø30)

List of calculation of operating dimensions when processing the outer diameter of the shaft Ø20h7 (Ø20 -0.021)

1	2	3	4	5	6	7
Zag	Stamping	Ø34
15	Turning (roughing)	D15	D15 = D25 + 2z25	Ø20.8 -0.2
25	Turning (finishing)	Z25	0,4	D25	D25 = damn. rr	Ø20 -0.021

Statement of calculation of operating dimensions when machining a hole Ø8H7 (Ø8 +0.015)

Statement of calculation of operating dimensions when machining a hole Ø12 +0.07

Statement of calculation of operating dimensions when machining a hole Ø14 +0.07

Statement of calculation of operating dimensions when machining a hole Ø9 +0.058

After calculating the diametrical operating dimensions, we will apply their values to the sketches of the corresponding operations of the route description of the technological process.

1.9 Calculation of cutting conditions

When assigning cutting modes, the nature of processing, the type and size of the tool, the material of its cutting part, the material and condition of the workpiece, the type and condition of the equipment are taken into account.

When calculating cutting conditions, the depth of cut, the minute feed, and the cutting speed are set. Let's give an example of calculating cutting conditions for two operations. For the rest of the operations, the cutting conditions are assigned according to, vol. 2, p. 265-303.

010. Rough turning (Ø24)

Mill model 1P365, processed material - steel 45, tool material CT 25.

The cutter is equipped with a ST 25 carbide insert (Al 2 O 3 + TiCN + T15K6 + TiN). The use of a carbide insert, which does not need regrinding, reduces the time required for tool change, in addition, the basis of this material is improved T15K6, which significantly increases the wear resistance and temperature resistance of ST 25.

Cutting geometry.

We select all the parameters of the cutting part from the Through cutter source: α = 8 °, γ = 10 °, β = + 3 °, f = 45 °, f 1 = 5 °.

2. Coolant brand: 5% emulsion.

3. The depth of cut corresponds to the size of the allowance, since the allowance is removed in one pass.

4. The estimated feed is determined based on the roughness requirements (, page 266) and is specified according to the machine passport.

S = 0.5 rpm.

5. Fortitude, p. 268.

6. The design cutting speed is determined from the specified tool life, feed and depth of cut from, page 265.

where C v, x, m, y - coefficients [5], p. 269;

T - tool life, min;

S - feed, rev / mm;

t is the depth of cut, mm;

K v is a coefficient that takes into account the influence of the workpiece material.

K v = K m v ∙ K p v ∙ K and v,

K m v - coefficient that takes into account the effect of the properties of the processed material on the cutting speed;

K p v = 0.8 is a coefficient that takes into account the effect of the state of the workpiece surface on the cutting speed;

K and v = 1 is a coefficient that takes into account the influence of the tool material on the cutting speed.

K m v = K g ∙,

where K g is a coefficient characterizing a group of steel in terms of machinability.

K m v = 1 ∙

K v = 1.25 ∙ 0.8 ∙ 1 = 1,

7. Estimated speed.

where D is the processed diameter of the part, mm;

V Р - design cutting speed, m / min.

According to the passport of the machine, we take n = 1500 rpm.

8. Actual cutting speed.

where D is the processed diameter of the part, mm;

n - rotation frequency, rpm.

9. The tangential component of the cutting force Pz, H is determined by the formula of the source, p.271.

Р Z = 10 ∙ С р ∙ t х ∙ S у ∙ V n ∙ К р,

where P Z - cutting force, N;

С р, х, у, n - coefficients, page 273;

S - feed, mm / rev;

t is the depth of cut, mm;

V - cutting speed, rpm;

К р - correction factor (К р = К мр ∙ К j р ∙ К g р ∙ К l р, - the numerical values of these coefficients from, pp. 264, 275).

K p = 0.846 ∙ 1 ∙ 1.1 ∙ 0.87 = 0.8096.

Р Z = 10 ∙ 300 ∙ 2.8 ∙ 0.5 0.75 ∙ 113 -0.15 ∙ 0.8096 = 1990 N.

10. Power from, p. 271.

where P Z - cutting force, N;

V - cutting speed, rpm.

The power of the electric motor of the 1P365 machine is 14 kW, so the drive power of the machine is sufficient:

N res.< N ст.

3.67 kW<14 кВт.

035. Drilling

Drilling a hole Ø8 mm.

Machine model 2550F2, processed material - steel 45, tool material P6M5. Processing is carried out in one pass.

1. Justification of the grade of material and geometry of the cutting part.

Material of the cutting part of the P6M5 tool.

Hardness 63 ... 65 HRCэ,

Ultimate bending strength s p = 3.0 GPa,

Tensile strength s in = 2.0 GPa,

Compressive strength s compress = 3.8 GPa,

Cutting part geometry: w = 10 ° - angle of inclination of the helical tooth;

f = 58 ° - entering angle,

a = 8 ° - back angle to be sharpened.

2. Depth of cut

t = 0.5 ∙ D = 0.5 ∙ 8 = 4 mm.

3. Estimated feed is determined based on the roughness requirements .s 266 and is specified according to the machine passport.

S = 0.15 rpm.

4. Persistence with. 270.

5. The design cutting speed is determined from the specified tool life, feed and depth of cut.

where C v, x, m, y are coefficients, p. 278.

T - tool life, min.

S - feed, rev / mm.

t - cutting depth, mm.

K V is a coefficient that takes into account the influence of the workpiece material, surface condition, tool material, etc.

6. Estimated speed.

where D is the workpiece diameter to be machined, mm.

V p - design cutting speed, m / min.

According to the passport of the machine, we take n = 1000 rpm.

7. Actual cutting speed.

where D is the processed diameter of the part, mm.

n- rotation frequency, rpm.

8. Torque

М cr = 10 ∙ С М ∙ D q ∙ S у ∙ К р.

S - feed, mm / rev.

D - drilling diameter, mm.

M cr = 10 ∙ 0.0345 ∙ 8 2 ∙ 0.15 0.8 ∙ 0.92 = 4.45 N ∙ m.

9. Axial force R about, N on, p. 277;

P about = 10 ∙ С Р · D q · S y · К Р,

where С Р, q, у, K р, - coefficients с.281.

P o = 10 ∙ 68 8 1 0.15 0.7 0.92 = 1326 N.

9. Cutting power.

where М cr - torque, N ∙ m.

V - cutting speed, rpm.

0.46 kW< 7 кВт. Мощность станка достаточна для заданных условий обработки.

040. Grinding

Machine model 3T160, processed material - steel 45, tool material - normal electrocorundum 14A.

Plunge grinding with the periphery of the wheel.

1. Grade of material, geometry of the cutting part.

Choosing a circle:

PP 600 × 80 × 305 24А 25 Н СМ1 7 К5А 35 m / s. GOST 2424-83.

2. Depth of cut

3. Radial feed S p, mm / rev is determined by the formula from the source, p. 301, tab. 55.

S P = 0.005 mm / rev.

4. The speed of the circle V K, m / s is determined by the formula from the source, p. 79:

where D K is the diameter of the circle, mm;

D K = 300 mm;

n К = 1250 rpm - rotation frequency of the grinding spindle.

5. The estimated frequency of rotation of the workpiece n z.r, rpm will be determined by the formula from the source, p.79.

where V З.Р - the selected workpiece speed, m / min;

V З.Р will be determined according to table. 55, p. 301. Let's take V З.Р = 40 m / min;

d З - workpiece diameter, mm;

6. The effective power N, kW is determined according to the recommendation in

source p. 300:

when plunge-cut grinding with the periphery of the wheel

where the coefficient C N and the exponents r, y, q, z are given in Table. 56, p. 302;

V З.Р - workpiece speed, m / min;

S P - radial feed, mm / rev;

d З - workpiece diameter, mm;

b - grinding width, mm is equal to the length of the workpiece to be ground;

The power of the electric motor of the 3T160 machine is 17 kW, so the drive power of the machine is sufficient:

N res< N шп

1.55 kW< 17 кВт.

1.10 Rationing of operations

Calculation and technological norms of time are determined by calculation.

There are the unit time rate T SHT and the calculation time rate. The calculation rate is determined by the formula on page 46:

where T pcs is the unit time rate, min;

T p.z. - preparatory and final time, min;

n is the number of parts in the batch, pcs.

T pc = t main + t pop + t service + t lane,

where t main is the main technological time, min;

t aux - auxiliary time, min;

t obsl - time of service of the workplace, min;

t lane - time of breaks and rest, min.

The main technological time for turning, drilling operations is determined by the formula on page 47,:

where L is the calculated processing length, mm;

Number of passes;

S min - minute tool feed;

a - the number of simultaneously processed parts.

The estimated processing length is determined by the formula:

L = L res + l 1 + l 2 + l 3.

where L cut - cutting length, mm;

l 1 is the length of the tool approach, mm;

l 2 is the cutting length of the tool, mm;

l 3 - tool overrun length, mm.

The service time of the workplace is determined by the formula:

t service = t technical service + t org.examination,

where t technical service - maintenance time, min;

t org.examination - organizational service time, min.

where is the coefficient determined according to the standards. We accept.

The time for a break and rest is determined by the formula:

where is the coefficient determined according to the standards. We accept.

Here is the calculation of the time norms for three different operations

010 Turning

Let's preliminarily determine the estimated length of processing. l 1, l 2, l 3 will be determined according to the data of Tables 3.31 and 3.32 on page 85.

L = 12 + 6 +2 = 20 mm.

Minute feed

S min = S about ∙ n, mm / min,

where S about - reverse feed, mm / about;

n is the number of revolutions, rpm.

S min = 0.5 ∙ 1500 = 750 mm / min.

min.

Auxiliary time consists of three components: for installation and removal of a part, for transition, for measurement. This time is determined by cards 51, 60, 64 on pages 132, 150, 160 by:

t mouth / removed = 1.2 min;

t transition = 0.03 min;

t meas = 0.12 min;

t flash = 1.2 + 0.03 + 0.12 = 1.35 min.

Maintenance time

min.

Organizational Service Time

min.

Break times

min.

Piece time per operation:

T pcs = 0.03 + 1.35 + 0.09 + 0.07 = 1.48 min.

035 Drilling

Drilling a hole Ø8 mm.

Determine the estimated processing length.

L = 12 + 10.5 + 5.5 = 28 mm.

Minute feed

S min = 0.15 ∙ 800 = 120 mm / min.

Main technological time:

min.

Processing is carried out on a CNC machine. The cycle time of automatic operation of the machine according to the program is determined by the formula:

T c.a = T o + T mv, min,

where T about - the main time of automatic operation of the machine, T about = t main;

T mv - machine-auxiliary time.

T mv = T mv.i + T mv.x, min,

where T mv.i - machine-auxiliary time for automatic tool change, min;

Т мв.х - machine-auxiliary time for the execution of automatic auxiliary moves, min.

T mv. And determined by Appendix 47,.

We accept T mv.x = T o / 20 = 0.0115 min.

T c.a = 0.23 + 0.05 + 0.0115 = 0.2915 min.

The piece time rate is determined by the formula:

where Т в - auxiliary time, min. Determined by card 7,;

and those, and org, and ex - time for service and rest, is determined by, card 16: and those + a org + a ex = 8%;

T in = 0.49 min.

040. Grinding

Determination of the main (technological) time:

where l is the length of the processed part;

l 1 - the value of the penetration and overrun of the tool on the card 43,;

i is the number of passes;

S - tool feed, mm.

min

For definition of auxiliary times see map 44,

T in = 0.14 + 0.1 + 0.06 + 0.03 = 0.33 min

Determination of time for maintenance of the workplace, rest and natural needs:

where a obs and a dep is the time for servicing the workplace, rest and natural needs as a percentage of the operational time according to the map 50,:

a obs = 2% and a obs = 4%.

Determination of the piece time norm:

T w = T about + T in + T obs + T dep = 3.52 + 0.33 + 0.231 = 4.081 min

1.11 Economic comparison of 2 options of operations

When developing a technological process for mechanical processing, the problem arises to choose from several processing options one that provides the most economical solution. Modern methods of mechanical processing and a wide variety of machine tools allow you to create various options for technology, ensuring the manufacture of products that fully meet all the requirements of the drawing.

In accordance with the provisions for assessing the economic efficiency of new technology, the most profitable is the option in which the sum of current and reduced capital costs per unit of production will be minimal. The number of addends of the sum of the reduced costs should include only those costs that change their value during the transition to a new version of the technological process.

The sum of these costs, referred to the hours of operation of the machine, can be called hourly adjusted costs.

Consider the following two options for performing a turning operation, in which processing is carried out on different machines:

1. according to the first option, rough turning of the outer surfaces of the part is carried out on a universal screw-cutting lathe model 1K62;

2. According to the second option, rough turning of the outer surfaces of the part is performed on a 1P365 turret lathe.

1. Operation 10 is performed on the 1K62 machine.

The value characterizes the efficiency of the equipment. A lower value for comparing machines with equal productivity indicates that the machine is more economical.

The value of the hourly reduced costs

where is the main and additional wages, as well as social insurance charges to the operator and the adjuster for the physical hour of operation of the serviced machines, kop / h;

The multi-station factor, taken according to the actual state in the considered section, is taken as M = 1;

Hourly costs for the operation of the workplace, cop / h;

Standard coefficient of economic efficiency of capital investments: for mechanical engineering = 2;

Specific hourly capital investments in the machine, cop / h;

Specific hourly capital investments in the building, cop / h.

The basic and additional wages, as well as social insurance contributions to the operator and the adjuster can be determined by the formula:

, cop / h,

where is the hourly wage rate of the machine operator of the corresponding category, cop / h;

1.53 is the total coefficient representing the product of the following partial coefficients:

1.3 - coefficient of compliance with the norms;

1.09 - the coefficient of additional wages;

1.077 - social insurance deduction ratio;

k - the coefficient taking into account the salary of the adjuster, we take k = 1.15.

The value of the hourly costs for the operation of the workplace in the event of a decrease

the load on the machine must be corrected by a factor if the machine cannot be reloaded. In this case, the adjusted hourly cost is:

, cop / h,

where are the hourly costs of operating the workplace, cop / h;

Correction factor:

The share of conditionally fixed costs in hourly costs at the workplace, we take;

Machine load factor.

where T SHT - piece time for the operation, T SHT = 2.54 min;

t B - release cycle, we take t B = 17.7 minutes;

m P - the accepted number of machines per operation, m P = 1.

;

where is the practical adjusted hourly costs at the base workplace, kopecks;

The machine factor, which shows how many times the costs associated with the operation of a given machine are greater than those of the base machine. We accept.

cop / h.

The capital investment in the machine and building can be determined by:

where C is the book value of the machine, we take C = 2200.

, cop / h,

Where F is the production area occupied by the machine, taking into account the passes:

where is the production area occupied by the machine, m 2;

Coefficient taking into account additional production area,.

cop / h.

The cost of machining for the operation under consideration:

, cop.

cop.

2. Operation 10 is performed on the 1P365 machine.

C = 3800 rubles.

T PC = 1.48 min.

cop / h.

cop.

Comparing the options for performing the turning operation on various machines, we come to the conclusion that turning the outer surfaces of the part should be carried out on a 1P365 turret lathe. Since the cost of machining a part is lower than if it is performed on a 1K62 machine.

2. Design of special machine tooling

2.1 Initial data for the design of machine tooling

In this course project, a machine tool has been developed for operation No. 35, in which drilling, countersinking and reaming of holes is performed using a CNC machine.

The type of production, the release program, as well as the time spent on the operation, which determine the level of speed of the device when installing and removing the part, influenced the decision to mechanize the device (the part is clamped in teaks due to the pneumatic cylinder).

The fixture is used to install only one part.

Consider the layout of the part in the fixture:

Figure 2.1 Installation diagram of a part in a vice

1, 2, 3 - installation base - deprives the workpiece of three degrees of freedom: movement along the OX axis and rotation around the OZ and OY axes; 4, 5 - double support base - deprives of two degrees of freedom: movement along the axes OY and OZ; 6 - support base - deprives rotation around the OX axis.

2.2 Schematic diagram of the machine tool

As a machine tool, we will use a machine vise equipped with a pneumatic drive. The pneumatic drive ensures the constant clamping force of the workpiece, as well as the quick fixing and detaching of the workpiece.

2.3 Description of design and principle of operation

Universal self-centering vice with two movable replaceable jaws is designed for fixing axle-type parts when drilling, countersinking and reaming holes. Consider the design and principle of operation of the device.

On the left end of the body 1 of the vice is fixed the adapter sleeve 2, and on it the pneumatic chamber 3. Between the two covers of the pneumatic chamber diaphragm 4 is clamped, which is rigidly fixed on the steel disk 5, in turn, fixed on the rod 6. The rod 6 of the pneumatic chamber 3 is connected through the rod 7 with a rolling pin 8, at the right end of which there is a rack 9. The rack 9 is in engagement with the gear wheel 10, and the gear wheel 10 - with the upper movable rack 11, on which the right movable jaw is installed and secured by means of two pins 23 and two bolts 17 12. The lower end of the pin 14 enters the circular groove on the left end of the rolling pin 8, its upper end is pressed into the hole of the left movable jaw 13. Replaceable clamping prisms 15 corresponding to the diameter of the axis to be machined are fixed with screws 19 on movable jaws 12 and 13. Pneumatic chamber 3 is attached to the adapter sleeve 2 using 4 bolts 18. In turn, the adapter sleeve 2 is attached to the body of the tool 1 using bolts 16.

When compressed air enters the left cavity of the pneumatic chamber 3, the diaphragm 4 bends and moves to the right the rod 6, the rod 7 and the rolling pin 8. The rolling pin 8 with the finger 14 moves the sponge 13 to the right, and with the left rack and pinion end, rotating the gear 10, moves the upper rack 11 with the sponge 12 to the left. Thus, the jaws 12 and 13, moving, clamp the workpiece. When compressed air enters the right cavity of the pneumatic chamber 3, the diaphragm 4 bends to the other side and the rod 6, the rod 7 and the rolling pin 8 are moved to the left; rolling pin 8 spreads jaws 12 and 13 with prisms 15.

2.4 Calculation of the machine tool

Force calculation of the device

Figure 2.2 Scheme for determining the clamping forces of the workpiece

To determine the clamping force, we will simplify the workpiece in the device and depict the moments from the cutting forces and the required required clamping force.

Figure 2.2:

M is the torque on the drill;

W is the required fastening force;

α is the angle of the prism.

The required clamping force of the workpiece is determined by the formula:

, H,

where M is the torque on the drill;

α is the angle of the prism, α = 90;

The coefficient of friction on the working surfaces of the prism, we take;

D is the diameter of the workpiece, D = 75 mm;

K is the safety factor.

K = k 0 ∙ k 1 ∙ k 2 ∙ k 3 ∙ k 4 ∙ k 5 ∙ k 6,

where k 0 is the guaranteed safety factor, for all cases of processing k 0 = 1.5

k 1 - coefficient taking into account the presence of random irregularities on the workpieces, which entails an increase in cutting forces, we take k 1 = 1;

k 2 - coefficient taking into account the increase in cutting forces from progressive bluntness of the cutting tool, k 2 = 1.2;

k 3 - coefficient taking into account the increase in cutting forces during interrupted cutting, k 3 = 1.1;

k 4 - coefficient taking into account the variability of the clamping force when using pneumatic lever systems, k 4 = 1;

k 5 - coefficient taking into account the ergonomics of hand clamping elements, we take k 5 = 1;

k 6 - coefficient taking into account the presence of moments tending to rotate the workpiece, we take k 6 = 1.

K = 1.5 ∙ 1 ∙ 1.2 ∙ 1.1 ∙ 1 ∙ 1 ∙ 1 = 1.98.

Torque

М = 10 ∙ С М ∙ D q ∙ S у ∙ К р.

where C M, q, y, K p, are the coefficients, p. 281.

S - feed, mm / rev.

D - drilling diameter, mm.

M = 10 ∙ 0.0345 ∙ 8 2 ∙ 0.15 0.8 ∙ 0.92 = 4.45 N ∙ m.

Determine the force Q on the rod of the diaphragm pneumatic chamber. The force on the rod changes as it moves, since the diaphragm begins to resist in a certain area of movement. The rational stroke length of the rod, at which there is no sharp change in the force Q, depends on the calculated diameter D, the thickness t, the material and design of the diaphragm, as well as on the diameter d of the supporting disk.

In our case, we take the diameter of the working part of the diaphragm D = 125 mm, the diameter of the supporting disk d = 0.7 ∙ D = 87.5 mm, the diaphragm is made of rubberized fabric, the thickness of the diaphragm is t = 3 mm.

Force in the initial position of the stem:

, H,

Where p is the pressure in the pneumatic chamber, we take p = 0.4 ∙ 10 6 Pa.

Rod force for 0.3D travel:

, N.

Calculation of the device for accuracy

Based on the accuracy of the maintained size of the workpiece, the following requirements are imposed on the corresponding dimensions of the fixture.

When calculating the accuracy of fixtures, the total error in processing the part should not exceed the tolerance value T of the size, i.e.

The total error of the device is calculated using the following formula:

where T is the tolerance of the size to be performed;

Positioning error, since in this case there is no deviation of the actually reached position of the part from the required one;

Fixing error,;

Installation error of the device on the machine,;

The error in the position of the part due to wear of the elements of the device;

The approximate wear of the installation elements can be determined by the formula:

where U 0 is the average wear of the mounting elements, U 0 = 115 microns;

k 1, k 2, k 3, k 4 are, respectively, coefficients that take into account the influence of the workpiece material, equipment, processing conditions and the number of workpiece installations.

k 1 = 0.97; k 2 = 1.25; k 3 = 0.94; k 4 = 1;

We accept microns;

Error from skewing or displacement of the tool, since there are no guiding elements in the fixture;

The coefficient taking into account the deviation of the scattering of the values of the constituent quantities from the law of normal distribution,

Coefficient that takes into account the reduction of the limiting value of the positioning error when working on tuned machines,

Coefficient that takes into account the share of processing error in the total error caused by factors that do not depend on the device,

Economic precision of processing, = 90 microns.

3. Design of special control equipment

3.1 Initial data for the design of the test fixture

Control and measuring devices are used to check the compliance of the parameters of the manufactured part with the requirements of the technological documentation. Preference is given to devices that allow you to determine the spatial deviation of some surfaces in relation to others. This device meets these requirements, because measures the radial runout. The device has a simple device, easy to operate and does not require high qualifications of the controller.

Parts of the axle type in most cases transmit significant torques to the mechanisms. In order for them to work reliably for a long time, high accuracy of the main working surfaces of the axis in terms of diametric dimensions is of great importance.

The inspection process predominantly provides for a complete check of the radial runout of the outer surfaces of the axle, which can be carried out on a multidimensional inspection device.

3.2 Schematic diagram of the machine tool

Figure 3.1 Schematic diagram of the test fixture

Figure 3.1 shows a schematic diagram of a device for monitoring the radial runout of the outer surfaces of the axle part. The diagram shows the main parts of the device:

1 - device body;

2 - headstock;

3 - tailstock;

4 - rack;

5 - indicator heads;

6 - controlled detail.

3.3 Description of design and principle of operation

On the body 1 with the help of screws 13 and washers 26, a headstock 2 with a mandrel 20 and a tailstock 3 with a fixed return center 23 are fixed, on which the tested axis is installed. The axial position of the axle is fixed by a fixed reverse center 23. The axle is pressed against the latter by a spring 21, which is located in the central axial hole of the quill 5 and acts on the adapter 6. The quill 5 is mounted in the headstock 2 with the possibility of rotation about the longitudinal axis thanks to the bushings 4. at the left end quill 5, a handwheel 19 with a handle 22 is installed, which is secured with a washer 8 and a pin 28, the torque from the handwheel 19 is transmitted to the quill 5 using the key 27. To the adapter 6, the rotational movement during measurement is transmitted through the pin 29, which is pressed into the quill 5. In addition , at the other end of the adapter 6, a mandrel 20 with a conical working surface is inserted for precise, backlash-free positioning of the axis, since the latter has a cylindrical axial hole with a diameter of 12 mm. The taper of the mandrel depends on the tolerance T and the diameter of the axle hole and is determined by the formula:

mm.

In two racks 7, attached to the housing 1 with screws 16 and washers 25, there is a shaft 9, along which the brackets 12 move and are fixed with screws 14. On the brackets 12, rolling pins 10 are installed using screws 14, on which screws 15, nuts 17 and washers 24 fixed by IG 30.

Two IG 30 serve to check the radial runout of the outer surfaces of the axle, which is given one or two revolutions and the maximum readings of the IG 30, which determine the runout, are counted. The device ensures high productivity of the control process.

3.4 Calculation of the test fixture

The most important condition, which must be satisfied by control devices, is to ensure the required measurement accuracy. Accuracy largely depends on the adopted measurement method, on the degree of perfection of the circuit diagram and design of the device, as well as on the accuracy of its manufacture. An equally important factor influencing the accuracy is the accuracy of the surface fabrication, which is used as a measuring base for the parts to be inspected.

where is the error in the manufacture of the installation elements and their location on the device body, we take mm;

The error caused by the inaccuracy of the manufacturing of the transfer elements is taken as mm;

The systematic error, taking into account the deviations of the installation dimensions from the nominal ones, is taken as mm;

Basis error, we accept;

The error of displacement of the measuring base of the part from the given position, we take mm;

Fixing error, take mm;

The error from the gaps between the axes of the levers, we accept;

The error in the deviation of the installation elements from the correct geometric shape, we accept;

The error of the measurement method, we take mm.

The total error can be up to 30% of the tolerance of the controlled parameter: 0.3 ∙ T = 0.3 ∙ 0.1 = 0.03 mm.

0.03 mm ≥ 0.0034 mm.

3.5 Development of a setup card for operation No. 30

The development of a setup card allows you to understand the essence of setting up a CNC machine when performing an operation with an automatic method of obtaining a given accuracy.

As the adjustment dimensions, we take the dimensions corresponding to the middle of the tolerance field of the operating dimension. The value of the tolerance for the setting size is taken

T n = 0.2 * T op.

where T n is the tolerance for the setting size.

T op - tolerance for the operating size.

For example, in this operation we sharpen the surface Ø 32.5 -0.08, then the adjustment size will be equal to

32.5 - 32.42 = 32.46 mm.

T n = 0.2 * (-0.08) = - 0.016 mm.

Adjustment dimension Ø 32.46 -0.016.

The calculation of the remaining sizes is carried out in the same way.

Conclusions on the project

According to the assignment for the course project, a technological process for manufacturing a shaft was designed. The technological process contains 65 operations, for each of which cutting conditions, time rates, equipment and tooling are indicated. For the drilling operation, a special machine tool has been designed, which allows to ensure the necessary precision in the manufacture of the part, as well as the required clamping force.

When designing a technological process for manufacturing a shaft, a setup card for a turning operation No. 30 was developed, which makes it possible to understand the essence of setting up a CNC machine when performing an operation with an automatic method of obtaining a given accuracy.

During the implementation of the project, a settlement and explanatory note was drawn up, which describes in detail all the necessary calculations. Also, the settlement and explanatory note contains applications that include operational cards, as well as drawings.

Bibliography

1. Handbook of a mechanical engineer. In 2 volumes / ed. A.G. Kosilova and R.K. Meshcheryakova.-4th ed., Revised. and add. - M .: Mechanical Engineering, 1986 - 496 p.

2. G.I. Granovsky, V.G. Granovsky Cutting metals: Textbook for machine building. and instrument specialist. universities. _ M .: Higher. shk., 1985 - 304 p.

3. Marasinov M.A. Guidelines for calculating operating sizes. - Rybinsk. RGATA, 1971.

4. Marasinov M.A. Design of technological processes in mechanical engineering: Textbook.- Yaroslavl. 1975.-196 p.

5. Mechanical engineering technology: a textbook for the implementation of a course project / V.F. Languageless, V.D. Korneev, Yu.P. Chistyakov, M.N. Averyanov.- Rybinsk: RGATA, 2001.- 72 p.

6. General machine-building standards for the auxiliary, for the maintenance of the workplace and the preparatory - final for the technical standardization of machine work. Mass production. M, Mechanical Engineering. 1964.

7. Anserov M.A. Accessories for metal-cutting machine tools. 4th edition, revised. and additional L., mechanical engineering, 1975

The axles serve to support various parts of machines and mechanisms rotating with them or on them. The rotation of the axle, together with the parts mounted on it, is carried out relative to its bearings, called bearings. An example of a non-rotating axle is the axle of a load-lifting machine block (Fig. 1, a), and a rotating axle is a carriage axle (Fig. 1, b). The axles take the load from the parts located on them and work in bending.

Rice. 1

Axle and shaft designs.

Shafts, unlike axes, are designed to transmit torques and, in most cases, to maintain various machine parts rotating with them relative to the bearings. The shafts carrying the parts through which the torque is transmitted receive loads from these parts and, therefore, work simultaneously in bending and torsion. When the parts mounted on the shafts (bevel gears, worm wheels, etc.) are subjected to axial loads, the shafts additionally work in tension or compression. Some shafts do not support rotating parts (cardan shafts in cars, coupling rolls of rolling mills, etc.), so these shafts are torsionally only. According to their purpose, gear shafts are distinguished, on which gear wheels, sprockets, couplings and other gear parts are installed, and main shafts, on which not only gear parts are installed, but also other parts, such as flywheels, cranks, etc.

The axes are straight rods(Figure 1, a, b), and the shafts are distinguished straight(Fig. 1, c, d), cranked(Fig. 1, e) and flexible(Fig. 1, f). Straight shafts are widespread. Crankshafts in crank gears are used to convert reciprocating motion into rotary motion or vice versa and are used in piston machines (engines, pumps). Flexible shafts, which are multi-threaded torsion springs twisted from wires, are used to transfer torque between machine units that change their relative position in operation (power tools, remote control and monitoring devices, dental drills, etc.). Crankshafts and flexible shafts are special parts and are studied in the corresponding special courses. Axles and shafts in most cases are of solid round, and sometimes of annular cross-section. Individual sections of the shafts have a solid round or annular section with a keyway (Fig. 1, c, d) or with splines, and sometimes a profile section. The cost of axles and shafts with an annular section is usually more than that of a solid section; they are used in cases where it is required to reduce the mass of a structure, for example, in airplanes (see also the axes of the planetary gear satellites in Fig. 4), or to place another part inside. Hollow welded axles and shafts made from tape located on a helical line allow for weight savings of up to 60%.

Axes of small length are made of the same diameter along the entire length (Fig. 1, a), and long and heavily loaded ones are shaped (Fig. 1, b). Straight shafts, depending on the purpose, are made either of a constant diameter along the entire length (transmission shafts, Fig. 1, c), or stepped (Fig. 1, d), i.e. of different diameters in certain areas. The most common are stepped shafts, since their shape is convenient for installing parts on them, each of which must pass freely to its place (for gear shafts, see the article "Gear reducers" Fig. 2; 3; and "Worm gear" Fig. 2 ; 3). Sometimes shafts are made together with gears (see Fig. 2) or worms (see Fig. 2; 3).

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The sections of the axles and shafts with which they rest on the bearings are called trunnions when radial loads are perceived, heels when axial loads are perceived. End journals running in plain bearings are called thorns(Fig. 2, a), and the trunnions located at some distance from the ends of the axes and shafts - necks(Fig. 2, b). The journals of axles and shafts operating in plain bearings are cylindrical (Fig. 2, a), conical(Fig. 2, c) and spherical(Fig. 2, d). The most common are cylindrical boards, since they are the simplest, most convenient and cheapest to manufacture, install and operate. Tapered and spherical pins are used relatively rarely, for example, for adjusting the clearance in bearings of precision machines by moving the shaft or bearing shell, and sometimes for axial fixation of an axis or shaft. Spherical pins are used when the shaft, in addition to rotational movement, must perform angular movement in the axial plane. Cylindrical trunnions operating in plain bearings are usually made somewhat smaller in diameter compared to the adjacent section of the axis or shaft, so that, thanks to the shoulders and shoulders (Fig. 2, b), the axes and shafts can be fixed against axial displacements. The journals of axles and shafts for rolling bearings are almost always cylindrical (Fig. 3, a, b). Tapered pins with a small taper angle are relatively rarely used to regulate the clearances in rolling bearings by elastic deformation of the rings. On some axes and shafts, for fixing rolling bearings near the trunnions, a thread for nuts (Fig. 3, b;) or annular grooves for retaining spring rings is provided.

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The feet, working in plain bearings, called thrust bearings, are usually made annular (Fig. 4, a), and in some cases - comb (Fig. 4, b). Comb heels are used when large axial loads are applied to shafts; they are rare in modern mechanical engineering.

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The seating surfaces of the axles and shafts, on which the rotating parts of machines and mechanisms are installed, are cylindrical and much less often conical. The latter are used, for example, to facilitate the installation and removal of heavy parts from the shaft with increased accuracy of centering of parts.

The surface of a smooth transition from one stage of an axis or shaft to another is called a fillet (see Fig. 2, a, b). The transition from steps of a smaller diameter to a step of a larger diameter is performed with a rounded groove for the exit of the grinding wheel (see Fig. 3). To reduce the stress concentration, the radii of fillets and grooves are taken as large as possible, and the depth of the grooves - smaller (GOST 10948-64 and 8820-69).

The difference between the diameters of adjacent stages of axes and shafts to reduce the stress concentration should be minimal. The ends of the axles and shafts to facilitate the installation of rotating machine parts on them and the prejudice of injury to the hands are made with chamfers, that is, they are slightly grinded onto a cone (see Fig. 1 ... 3). Fillet radii and chamfer sizes are normalized by GOST 10948-64.

The length of the axles usually does not exceed 2 ... 3 m, the shafts can be longer. According to the conditions of manufacture, transportation and installation, the length of solid shafts should not exceed 6 ... 7 m. Longer shafts are made integral and separate parts are connected with couplings or using flanges. The diameters of the seats of the axles and shafts, on which the rotating parts of machines and mechanisms are installed, must be consistent with GOST 6636-69 (ST SEV 514-77).

Axle and shaft materials.

Axles and shafts are made of carbon and alloy structural steels, as they have high strength, surface and volumetric hardening, ease of rolling cylindrical blanks and good machinability on machine tools. For axles and shafts without heat treatment, carbon steels St3, St4, St5, 25, 30, 35, 40 and 45 are used. improvement of 35, 40, 40X, 40HX, etc. To increase the wear resistance of the shaft journals rotating in plain bearings, the shafts are made of steel 20, 20X, 12XNZA and others, followed by carburizing and quenching of the journals. Responsible heavy-loaded shafts are made of alloy steels 40ХН, 40ХНМА, 30ХГТ, etc. Heavy-loaded shafts of complex shape, for example, engine crankshafts, are also made of modified or high-strength cast iron.

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Axis mechanical engineering. Classification of shafts and machine axles, their application. Shafts and axles

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Work description

The work contains 1 file

1.General section

1.1. Description of the design and service purpose of the part.

1.2. Technological control of the drawing of the part and analysis of the part for manufacturability

2.Technological section

2.1. Characteristics of the medium-batch type of production

1.1 Service purpose and technical characteristics of the part

1.2 Determining the type of production and batch size of the part

1.3 Choosing a method of obtaining a workpiece

1.4 Purpose of methods and stages of processing

1.7 Selection of equipment, tooling, cutting and measuring tools

1.8 Calculation of operating dimensions

1.9 Calculation of cutting conditions

1.10 Rationing of operations

1.11 Economic comparison of 2 options of operations

2. Design of special machine tooling

3.5 Development of a setup card for operation No. 30

Conclusions on the project

Axle and shaft designs.

Axle and shaft materials.