Collection of practical works on engineering technology. Tests in the discipline of mechanical engineering technology. The set of sizes forming a closed loop and assigned to one part is called
Task 1.66 option 3.
Given: d (size of the base surface of the shaft) \u003d 80-0.039 mm,
? (accuracy of the processing method) \u003d 60 μm,
Tizn (permissible wear of the sleeve) \u003d 10 microns,
A2 \u003d 50 ± 0.080 mm.
Determine the executive size D of the centering sleeve, which provides the specified accuracy of the size A2 when milling the groove.
Decision.
Analysis of the installation diagram shows that the accuracy of the diameter of the hole of the centering sleeve D affects the accuracy of the execution of size A2, set from the axis of the workpiece to the workpiece. It can be seen from the installation diagram that the fixing error (? S) for size A2 is zero. Based on this, we accept as the initial one that the accuracy of performing size A2: TA2 \u003d? BA2 + Tiz. +?, where? bA2 \u003d TD + Smin + Td is the error of basing size A2. The components TD and Smin are unknown quantities.
Solving the equality with respect to these unknowns, we obtain:
(Smin + TD) \u003d TA2 - (Td + Tv. +?) \u003d 0.16 - (0.039 + 0.010 + 0.060) \u003d 0.051 mm.
From the tables GOST 25347-82, select the hole tolerance field so that the condition is met: Smin + TD? ES.
Comparing the calculated value (Smin + TD) \u003d 0.051 with the tabular value of the upper deviation of the hole (ES), I take the tolerance field G7 (), which can be taken as the executive dimensions of the sleeve:
D \u003d 80G7.
Task 1.67 option 3.
Given: mandrel material - steel 20X,
workpiece material - bronze,
E 1 (steel) \u003d 210 GPa
E 2 (bronze) \u003d 100 GPa,
? 1 (steel) \u003d 0.3
? 2 (bronze) \u003d 0.33
f steel bronzes \u003d 0.05
u? 1,2 (Rz1 + Rz2)
d \u003d 30 + 0.013mm
L \u003d 40 mm
d1 \u003d 70 mm
K \u003d 2.0
Rz (mandrels) - 1.6
Rz (blanks) - 3.2
Pz \u003d 240 H
T life \u003d 10 microns.
Decision.
The initial condition for performing the calculations is the condition KMrez \u003d Mtr,
where: Mrez \u003d Pz - cutting moment when turning the surface
Mtr \u003d lfp is the moment of friction of the contact surface of the workpiece with the mandrel.
p \u003d is the contact pressure on the interface.
Necessary smallest fit: Ncal. min \u003d
When using a solid mandrel: c1 \u003d 1-? 1\u003e c1 \u003d 1-0.3 \u003d 0.7
c2 \u003d +? 2\u003e + 0.33 \u003d 1.78
Calc. min \u003d \u003d \u003d 3,767
Taking into account the correction u to the height of the crushed wrinkles during pressing in, we find the value of the measured interference fit:
Nism. min \u003d Ncalc. min + u\u003e 3.767 + 1.2 (1.6 + 3.2) \u003d 3.767 + 5.76 \u003d 9.5 μm;
From the tables GOST 25347-82, select the shaft tolerance field so that
(Td + Nmeas. Min + T life.)? Ei, where T life is the permissible wear of the mandrel.
In our case (13 + 9.5 + Tiz)? Ei.
For my version, tolerance fields of the shaft (mandrel) can be accepted
p5 () or p6 () with a permissible mandrel wear of 3.5 μm.
Then the executive dimensions of the mandrel:
d \u003d 30p5 () mm or d \u003d 30p6 () mm.
The pressing force at the highest interference, taking into account the safety factor K \u003d 2: P \u003d Kfp? Dl,
p \u003d\u003e p \u003d \u003d \u003d 15,
P \u003d 2 · 0.05 · 15 · 3.14 · 30 · 40 \u003d 5652H.
Task 1.57 option 1.
Given:? B \u003d 0.05 mm,? S \u003d 0.01 mm,? Whisker \u003d 0.01 mm,? S \u003d 0.012 mm,
Ng \u003d 3000pcs.,
Procurement: material - non-quenched steel., Hardness - HB 160, base surface - cylindrical, Tl \u003d 0.2 mm.
Adaptation: prism, Steel 20, hardness - HV 650, F \u003d 36.1 mm2, Q \u003d 10000H, L \u003d 20 mm.
Processing method - cooling milling,? (accuracy of the processing method) \u003d 0.1 mm, tm \u003d 1.95 min.
Determine the overhaul period of the device.
Decision.
Determine the allowable value [? And] according to the equations:
? y \u003d +\u003e? y \u003d + \u003d
=0,051+
? y \u003d Tl -?,\u003e 0.051+ \u003d Tl -?,\u003e 0.051+ \u003d 0.2-0.1\u003e
\u003e \u003d 0.049\u003e [? And] \u003d \u003d 0.04644 mm \u003d 46.44 microns.
The permissible number of installed blanks [N] to the maximum wear of the mounting elements of the device is found from the equation:
[N] \u003d, from the directory - we find m \u003d 1818, m1 \u003d 1014, m2 \u003d 1309, the wear criterion is P1 \u003d 1.03, and the correction factor taking into account the processing conditions is Ku \u003d 0.9.
[N] \u003d \u003d \u003d \u003d 21716 pcs.
The overhaul period that determines the need to replace or restore the installation elements of the device is found from the equation:
Pc \u003d \u003d \u003d 73.8 months.
Task 1.43
Given: D1 \u003d D2 \u003d 50 + 0.039 mm, dc \u003d dc \u003d 50f7 mm,
TL \u003d 0.1 mm? (accuracy of the processing method) \u003d 0.050 mm.
Determine the accuracy of the execution of size 70 of the connecting rod head and the possibility of processing the surface of the connecting rod with a set of cutters, observing the accuracy of the sizes 45 + 0.4 mm.
Decision.
Based on the installation scheme of the workpiece in the device basing error when performing size 70 is determined by the equation:
? b70 \u003d Smax \u003d TD + Smin + Td \u003d 0.039 + 0.025 + 0.025 \u003d 0.089 mm,
Since the condition of the problem does not say anything about the errors of fixing and the position of the workpiece, then? S \u003d? Pz \u003d 0. Then
T70 \u003d? B70 +? \u003d 0.089 + 0.05 \u003d 0.139 mm.
For size 45, a tolerance is added to the size between the axes of the holes (he would also be able to influence size 70 if the fingers did not have the same tolerance field):
? b45 \u003d Smax \u003d TD + Smin + Td + TL \u003d 0.039 + 0.025 + 0.025 + 0.1 \u003d 0.189 mm,
T45 \u003d? B45 +? \u003d 0.189 + 0.05 \u003d 0.239 mm.
As we see the calculated tolerance 0.239< 0,4 мм допуска заданного, следовательно, мы можем применить набор фрез для обработки головки шатуна.
Literature:
1. Machine tools. Directory. / Ed. B.N. Vardashkina et al. M., Mechanical Engineering, 1984.
2. Directory of metalworker. / Ed. M.P. Novikova / M., Mechanical Engineering, 1977.
Transcript
1 FEDERAL AGENCY FOR EDUCATION State educational institution of higher professional education "TOMSK POLYTECHNICAL UNIVERSITY" YURGINSKY TECHNOLOGICAL INSTITUTE A.A. Saprykin, V.L. Bibik COLLECTION OF PRACTICAL TASKS ON THE DISCIPLINE "MACHINERY TECHNOLOGY" Textbook Publishing House of the Tomsk Polytechnic University 2008
2 BBK 34.5 i 73 UDC (076) S 19 S 19 Saprykin A.A. A collection of practical tasks in the discipline "Engineering Technology": a training manual / A.A. Saprykin, V.L. Bibik. Tomsk: Publishing House of Tomsk Polytechnic University, p. The manual contains examples and problems with solutions. It will help to acquire skills in solving technological problems, determining the improvement of existing and developing new technological processes. Designed to perform practical work in the discipline "Engineering Technology" by university students majoring in "Engineering Technology". UDC (076) Reviewers Doctor of Technical Sciences, Professor TPU S.I. Petrushin Deputy Head of Workshop 23 LLC Yurginsky Machine-Building Plant P.N. Bespalov Yurginsky Technological Institute (branch) of Tomsk Polytechnic University, 2008 Design. Publishing House of Tomsk Polytechnic University,
3 CONTENTS CHAPTER 1. BASES OF DESIGNING TECHNOLOGICAL PROJECTS PRODUCTION AND TECHNOLOGICAL PROCESSES. 4 2. PRECISION OF MECHANICAL PROCESSING OF THE BASE AND PRINCIPLES OF BASING TECHNOLOGY OF DESIGN OF THE GRANT FOR MECHANICAL. OPERATING DIMENSIONS AND THEIR TOLERANCES PROCEDURE FOR DESIGNING TECHNOLOGICAL PROCESSES PRODUCT QUALITY CONTROL PRODUCT INSTALLATION METHODS. INSTALLATION ELEMENTS OF ADAPTION 57 CHAPTER 2. METHODS OF PROCESSING THE MAIN SURFACES OF BILLETS PROCESSING EXTERNAL SURFACES OF ROTATION BODIES ... 62 CHAPTER 3. TECHNOLOGY OF ASSEMBLY OF MACHINES DESIGN TECHNOLOGY ... 3 APPROXIMAL ... 3
4 CHAPTER 1. BASES OF DESIGNING TECHNOLOGICAL PROCESSES 1. PRODUCTION AND TECHNOLOGICAL PROCESSES When working on the design of a technological process and its implementation and when preparing technological documentation, it is important to be able to determine the structure of the technological process and correctly formulate the name and content of its elements. In this work, they are guided by GOST and an important step in the development of the technological process is also the determination of the type of production. Roughly, the type of production is set at the initial stage of design. The main criterion in this case is the coefficient of consolidation of operations. This is the ratio of the number of all technological operations carried out during a certain period, for example, a month, on a mechanical site (O), and to the number of jobs (P) of this site: K z \u003d O / P. (1.1) Types of engineering industries are characterized by the following values \u200b\u200bof the coefficient of consolidation of operations: To z.o<1 массовое производство; 1<К з.о 10 крупносерийное производство; 10<К з.о 20 среднесерийное производство; 20<К з.о 40 мелкосерийное производство; К з.о не регламентируется единичное производство. Формулирование наименования и содержания операции Пример 1.1. Деталь (втулку) изготовляют в условиях серийного производства и из горячекатаного проката, разрезанного на штучные заготовки. Все поверхности обрабатываются однократно. Токарная операция выполняется согласно двум операционным эскизам по установкам (рис.1.1). 4
5 3 Ó ñ ò ò â Ç Ç Ç Ç 0 9 0 * Ç 8 0 5 5 6 5 6 ð * * ç à ç Рис ì Рис Рис Рис Рис Рис Рис Рис Fig Operating sketches Required: to analyze operational sketches and other source data; establish the content of the operation and formulate its name and content; establish the sequence of processing the workpiece in this operation; Describe the contents of the conversion operation. Decision. 1. Analyzing the initial data, we establish that in the operation under consideration, consisting of two plants, nine surfaces of the workpiece are processed, for which it will be necessary to perform nine technological transitions in series. 2. To perform the operation, a turning or screw-cutting machine will be used, and the name of the operation will be “Turning” or “Turning and screw-cutting” (GOST). According to the same GOST, we determine the number of the operation group (14) and the operation number (63). To record the contents of the operation in the presence of operational sketches, an abbreviated recording form can be applied: “Cut three ends”, “Drill and drill a hole”, “Bore one and sharpen two chamfers”. 3. We establish a rational sequence of technological transitions in installations, guided by operational sketches. In the first installation, you need to trim 5
6 end 4, sharpen surface 2 with the formation of end 1, sharpen chamfer 3, drill a hole 6 and bore chamfer 5. In the second installation, you need to trim end 9, sharpen surface 7 and chamfer 8. Table 1.1 Initial data View Contents of transition transition 1 PV Install and fix the workpiece 2 PT Cut end 4 Sharpen surface 2 with the formation of the end 1 3 PT (when turning 2, 2 working strokes are made) 4 PT Grind the bevel 3 5 PT Drill a hole 6 6 PT Bore the bevel 5 7 PV Reset the workpiece 8 PT Cut end face 9 9 PT Sharpen the surface 7 10 PT Sharpen the chamfer 8 11 PV Inspect the dimensions of the parts 12 PV Remove the part and put it in a container 4. The contents of the operation in the technological documentation are recorded for transitions: technological (PT) and auxiliary (PV). When formulating the content of transitions, an abbreviated record is used according to GOST. Table 1.1 shows the records of the considered example. Task 1.1. For a turning operation, an operational sketch was developed and executive dimensions were set with tolerances and requirements for the roughness of the machined surfaces (Fig. 1.2). Each surface is treated once. 6
7 3 I, VIR a Å Ç 2 5 H 1 2 II, VII 2 45 Å 3 2 ô Ç Ç 9 4, 5 h 1 4 Ç 9 5 h 1 4 Ç 8 0 hjshhh 1 4 III, VIIIR a VI, IXR a 2 0 Ç 6 0 h 1 1 Ç 5 0 h 1 1 Ç 4 5 H 1 2 Ç 6 5 H 1 2 Ç H * 2 5 * * ð à ç å ð ä ï à â ê ê 4 5 ± 0, ± 0, 3 3 V, XR a 1 0 Ç, 5 Ç 5 5 H 1 2 Ç hh ± 0, 5 Fig. Operational sketches 7
8 Required: set the type of machine; determine the configuration and dimensions of the workpiece; establish a baseline; number on the sketch all the machined surfaces; to formulate for the record in technological documents the name and content of the operation; write down the contents of all technological transitions in the technological sequence in full and abbreviated forms. Establishing the name and structure of the operation and recording its contents in the technological documentation Example 1.2. In Fig. 1.3, which is a fragment of the working drawing of the part, the structural element of the part to be processed in serial production is highlighted. R a 20 Ç 18 H 12 6 ò â. Ç ± 0, 2 8 Ç * * ð ç ì Рис Рис Рис Рис Рис Рис Рис Рис Fig. Working drawing Required: to analyze the source data; choose a method of processing a constructive type of production; choose the type of metal cutting machine; set the name of the operation; write down the contents of the operation in full form; formulate a record of the contents of the operation on technological transitions. Decision. 1. We establish that six holes in the housing flange are to be machined, evenly spaced on a circumference of Ø 280 mm. 2. The holes in the solid material are made by drilling. 3. For processing, choose a radial drilling machine. 4. The name of the operation (in accordance with the type of machine used) is “Radial Drilling”. 5. Recording the contents of the operation in full form looks like this: “Drill 6 through holes Ø18H12 in series, withstanding
9 d \u003d (280 ± 0.2) mm and surface roughness Ra \u003d 20 μm, according to the drawing. 6. The record of the content of transitions in full form is as follows: 1st transition (auxiliary). Install the workpiece in the conductor and secure. 2, ..., 7th transitions (technological). Drill 6 holes Ø18H12, maintaining dimensions d \u003d 280 ± 0.2; Ra20 in series with the conductor. 8th transition (auxiliary). Size control. 9th transition (auxiliary). Remove the workpiece and place in the container. Task 1.2. Set the name and structure of the operation in the conditions of mass production for the processing of structural elements of the part (Fig. 1.4). Option numbers are shown in Roman numerals. I, IIIII, IV 3 R a 5 R a Ç 3 4 h 1 0 M g V, VI 4 0 ± 1 VII, VIII Ç 6 0 H 1 2 R a 1 2, 5 R a 5 Ç 6 0 H ± 0 , 3 I Õ, X 1 5 H 1 0 Figure Operational sketches 9
10 Establishing the type of production on the site Example 1.3. On the site of the machine shop there are 18 jobs. During the month, 154 different technological operations are performed on them. Required: to establish the load factor of operations on the site; determine the type of production: state its definition in accordance with GOST Solution. 1. The coefficient of consolidation of operations is established by the formula (1.1): K s.o. \u003d 154/18 \u003d 8.56. In our case, this means that an average of 8.56 operations are assigned to each workplace on the site. 2. The type of production is determined according to GOST and Since 1<К з.о <10, тип производства крупносерийное. 3. Серийное производство характеризуется ограниченной номенклатурой изделий, сравнительно большим объемом их выпуска; изготовление ведется периодически повторяющимися партиями. Крупносерийное производство является одной из разновидностей серийного производства и по своим техническим, организационным и экономическим показателям близко к массовому производству. Задача 1.3. Известно количество рабочих мест участка (Р) и количество технологических операций, выполняемых на них в течение месяца (О). Варианты приведены в табл Требуется: определить тип производства. Таблица 1.2 Данные для расчета коэффициента закрепления операций варианта I II III IV V VI VII VIII IX X Количество рабочих мест (Р) Количество технологических операций (О)
11 2. ACCURACY OF MECHANICAL PROCESSING One of the main tasks of technologists and other participants in the production of machine shops is to ensure the necessary accuracy of the manufactured parts. The real machine parts made by machining have parameters that differ from ideal values, that is, they have errors, the size of the errors should not exceed the permissible maximum deviations (tolerances). To ensure a given processing accuracy, the technological process must be correctly designed taking into account the economic accuracy achieved by various processing methods. Norms of average economic accuracy are given in the sources. It is important to consider that each subsequent transition should increase accuracy by quality. In some cases, using calculation methods to determine the possible value of the processing error. So determine the errors of turning, from the action of cutting forces arising from the insufficient rigidity of the technological system. In some cases, an analysis is made of the accuracy of processing a batch of parts using mathematical statistics. Determination of economic accuracy achieved with various methods of processing the outer surfaces of revolution Example 2.1. The surface of a step of a steel shaft 480 mm long, made from forgings, is pre-processed on a lathe to a diameter of 91.2 mm (Fig. 2.1). R a 2 0 Ç 9 1, 2 Rice Stepped shaft Define: economic accuracy of processing size 91.2; the quality accuracy of the machined surface and its roughness. eleven
12 Solution. To determine the economic accuracy, use the tables "Economic accuracy of machining", which are given in various references. In our case, after rough turning, the accuracy of the machined surface should be within the go qualification (we accept the 13th qualification). Given that with l / d \u003d 5.3, processing errors increase 1.5 ... 1.6 times, this corresponds to a decrease in accuracy by one quality. Finally we accept accuracy according to the 14th qualification. Since during rough turning, the workpiece size is intermediate, this size is set for the outer surface with a tolerance field of the main part of Ø91.2h14, or Ø91.2-0.37. The surface roughness Ra \u003d μm (in the practice of plants with well-made workpieces and normal production conditions, higher processing accuracy is achieved). Task 2.1. One of the steps of the shaft is machined in one of the specified ways. The numbers of options are given in the table. Required: to establish the economic accuracy of processing; execute an operational sketch and indicate the size, accuracy qualification, tolerance size and roughness on it. Assume that the surface of the shaft stage in question has a tolerance field of the main part (h). options Initial data Table 2.1 Processing method and its nature Shaft length, mm I Lapping II Finishing semi-finished III Fine grinding IV Grinding single-use V Superfinishing Step diameter, mm VI Fine grinding VII Fine grinding VIII Final grinding IX Diamond smoothing X Final grinding
13 Determination of the accuracy of the shape of the surfaces of the part during processing Example 2.2. On the outer surface of the shaft (Fig. 2.2), a tolerance of the shape is indicated, indicated by a symbol for STSEV. The final processing of this surface is supposed to be carried out by grinding on a circular grinding machine model ZM151. Required: to establish the name and content of the symbol of the specified deviation; to establish the ability to withstand the requirement of accuracy of the shape of this surface during the proposed treatment. 0, 01 Ç 7 0 Figure Shaft sketch Solution. 1. According to the sketch, the accuracy of the shape of the cylindrical surface is expressed by the tolerance of roundness and is 10 microns. According to GOST, this tolerance corresponds to the 6th degree of accuracy of the form. The term "Tolerance" means the largest allowable deviation from roundness. Particular types of deviations from roundness are ovality, cut, etc. 2. On the ZM151 circular grinding machine, it is possible to process workpieces with a largest diameter of up to 200 mm and a length of up to 700 mm. Therefore, it is suitable for processing this workpiece. The deviation from roundness during processing on this machine is 2.5 microns. Based on the foregoing, we conclude that it is possible to perform processing with a given accuracy. Task 2.2. In fig. 2.3 and table. 2.2 shows the options for surfaces with tolerances. Required: to establish the name and content of the designation of these deviations; establish the ability to perform processing on the specified machine, observing the specified accuracy. Missing sizes to ask. 13
14 I 0, V, V I Ç, 0 5 Ç 5 0 I I, I I I 0, 02 À 0, 02 V I I 0, À I V 0, 0 2 V I I I 0, 1 5 I X, X 0, Figure Operational sketches 14
15 Initial data Table 2.2 options Surface shape Machine type I Hole Internal grinding II Plane Surface grinding III Plane Surface grinding IV Face Grinding V, VI Hole Honing VII Cylinder Turning screw-cutting VIII Plane Longitudinally planing IX Cylinder Turning multi-cutting X cylindrical cross-section Cylinder Precision cylindrical Cross cutting cylinder during processing Example 2.3. The sketch (Fig. 2.4) indicates the technical requirement for the accuracy of the relative positioning of the surfaces of the part. It is supposed that the upper plane should be finished by finishing milling on a vertical milling machine according to the operational sketch shown in Fig. 2 / x 0, 2 / x À À Rice Design requirements À Rice Operation sketch Required: state the name and content of the technical requirement; establish, according to technological manuals, the accuracy of the relative positioning of the surfaces of the part, depending on the type of equipment; to conclude that it is possible to fulfill the specified requirement. Decision. 1. The symbol of the drawing shows the tolerance of parallelism of the upper plane relative to the lower plane indicated by the letter A. The parallel tolerance is understood to mean the maximum allowable deviation from 15
16 parallelism. In our case, the tolerance is 0.2 mm over an area of \u200b\u200bmm. 2. In the tables of technological manuals, for example, we find the maximum deviations of our case: they are equal to microns and microns over a length of 300 mm, which means that over a length of 150 mm they will be 12, microns. Of all these data, we accept for guarantee the largest value of 100 μm, i.e. 0.1 mm 3. We conclude that the required accuracy of the relative position of the machined plane relative to the base plane A will be provided. Task 2.3. In fig. 2.6 shows the options for surface treatment. Required: to decipher the designation of the content of the admission; to develop technological measures to ensure compliance with this requirement. À I, I I 0, À À I I I, I V 0, À V, V I V I I, V I I I 0, 1 5 À Á 0, 0 4 À Á I X, X 0, 0 5 À À Rice Surface treatment options 16
17 3. BASES AND PRINCIPLES OF BASING In order to process a workpiece on a machine, it must be fixed on it, after selecting the base. By basing is meant giving the workpiece the desired position relative to the machine and tool. The accuracy of processing depends on the correctness of the base. When developing a basing scheme, they decide on the selection and placement of control points. In production conditions, there are always processing errors ε mouth, depending on the installation conditions, i.e. from basing ε bases, fixing ε closing of the workpiece, and from inaccuracy of fixture ε etc. Installation error is expressed by the formula: ε \u003d ε + ε + ε. (3.1) mouth of bases In order to reduce these errors, it is important to follow the rules of basing: the rule of “six points”, the rule of “constancy of the bases”, the rule of “combining bases”, etc. Error values \u200b\u200bcan be determined by various methods. The tabular method allows you to determine the installation errors depending on the production conditions. The calculation method for determining the errors of basing, fixing and caused by inaccuracy of the device is performed using formulas given in the literature. If the rule of “combining the bases” is not respected, it becomes necessary to recalculate the design dimensions into technological ones (Fig. 3.1). The purpose of the recalculation is to determine the error of the size of the closing link and compare it with the tolerance of the design size. Á Ê closed pr H \u003d 7 5 h 9 h \u003d 3 0 H * À 1 Ò \u003d À 2 À S Á Ò Fig Technological dimensional chain 17
18 Calculation of dimensional chains is carried out in accordance with GOST and one of the methods specified in them (“maximum minimum”, probabilistic, etc.). For these calculations, the formulas for determining the nominal size of the closing link are used: h \u003d H T, (3.2) where H is the size linking the design and technological bases; T is the size connecting the technological base with the surface to be treated. The error in the size of the closing link ε h \u003d ε Δ when solving by the "maximum minimum" method is determined by the formulas: ε \u003d T + T; ε \u003d T \u003d, (3.3) h H T n h Σ T i 1 where Ti is the tolerance on the size of each chain link; T N tolerance for size N established by the drawing; T T tolerance on the technological size, the value of which depends on the processing method and is set in accordance with the standard of average economic accuracy of processing; n is the number of constituent links. When calculating by the probabilistic method, the formulas T n 2 \u003d t λiti, (3.4) i \u003d 1 are used, where t is the risk coefficient (t \u003d 3); λi is the coefficient of relative scattering (for the normal distribution law, λi \u003d 1/9). When the distribution laws are unknown, take t \u003d 3 and λi \u003d 1/6, therefore n T i i \u003d 1 2 T 1,2t. (3.5) \u003d As a result of the calculation, the condition T h T Σ must be met. (3.6) 18
19 à Choosing the technological base taking into account the technical requirements for the part Example 3.1. In the manufacturing process of the case, an operation is provided for boring a hole with a diameter of D (Fig. 3.2). When making the hole, the size a and the technical requirements regarding the correct positioning of the hole relative to other surfaces of the part must be maintained. Â H 0, 1 À 6 Ã Á 6 Â D 4 5 4, 5 Á 0, 1 Â 22 0, 1 Á Fig. Working drawing À À, Fig. 3.3. Base scheme Required: select the technological base for the operation in question; develop a basing scheme. Decision. 1. One of the design bases is the base plane A. It should be taken as a technological installation base, having created three reference points 1, 2 and 3 for its basing (Fig. 3.3). The technological guide base should take the plane B with two reference points 4 and 5. This base will allow you to process the hole perpendicular to this plane. To ensure the symmetry of the location of the hole relative to the outer contour, surface B can be used as a technological base, but it is structurally easier to use the surface D of the half cylinder and use a device with a movable prism for this purpose. Based on the foregoing, we apply the technological base of three surfaces: A, B and D (Fig. 3.3). 2. The basing scheme, which is the location of reference points on the workpiece bases, is shown in Fig.
20 a Task 3.1. For the machine operation to process the specified surface of the part, it is required to select a technological base and draw up a basing scheme. The options are shown in Fig. 3.4 and in table d I, IIIII, IV, V à 0 0 d 1 dd 2 VI, VII, VIIIIX, X ahb 0, 1 A À D 1 Á d 1 0, 1 Á À d 2 Á d 1 d 2 0 , 1  0, 1 À 0, 1 Á Figure Operational sketches  of option I Name and contents of operations Name of operation Description of the operation Vertical drilling Drill a hole in the ball Table 3.1 II Turning Drill a hole in the ball III Turning Sharpen the surface completely Grind the specified IV, V Final grinding surface VI, VII Horizontal milling Milling groove VIII Vertical milling Milling groove IX Vertical drilling Drill 2 holes X Fine boring Bore 2 holes 20
21 Determination of the technological base and drawing up the basing scheme of the workpiece Example 3.2. Required: to consider the installation elements of the existing fixture (Fig. 3.5) and to establish the surface of the workpiece, which constitute the technological base when fixing the workpiece in the device; develop a workpiece basing scheme and conclude that the six-point rule is being followed Decision. 1. In the device shown in the figure, we identify its mounting elements: the plane of the body 2, the mounting cylindrical pin and the mounting cut-off finger 3. The technological base of the workpiece is the following surfaces: the lower plane of the workpiece A and two diagonal openings. 2. In accordance with the identified technological bases and used installation elements, we develop a basing scheme (Fig. 3.6): three reference points are formed for basing the plane (installation base) (1, 2, 3); for basing along the first hole (using a cylindrical finger) two more reference points are formed (4, 5), and for basing along the second hole, a cut finger (6) is used to form the 6th base point. 3. As can be seen from Figure 3.6 and the above considerations, the basing rule for six points is observed, the workpiece is deprived of six degrees of freedom À Fig Basing of the workpiece 21
22 Fig. The basing scheme 6 Problem 3.2. In fig. 3.7 shows the device for processing on the machine. It is necessary, using the figure, to identify the technological base adopted for basing the workpiece, and to present a basing scheme for the workpiece; to conclude that the selection of control points by the number and placement of them is correct. The option number is shown in the figure in Roman numerals. I, I I A - A I I I, I V, V À À V I, V I I V I I I, I X, X Fig Devices 22
23 Calculation of a linear technological dimensional chain Example 3.3. On a tuned horizontal milling machine, working on commissioning, the specified plane is finally processed. In this case, the coordinating size h \u003d (70 ± 0.05) mm (Fig. 3.8) must be maintained. Size tolerance h \u003d 0.1 mm. Required: establish whether the specified dimensional accuracy will be maintained during processing. Á - ð ñ 8 8 8 8 8 8 h 8 (- 0,) À Σ \u003d h \u003d 7 0 ± 0, 0 5 À 1 \u003d 8 5 h 8 (- 0,) À - è è è Рис Рис Рис Рис Рис Рис Fig Technological dimensional chain Solution. 1. From the conditions of the example and the operational sketch shows that the technological base is the lower plane A of the workpiece. The design and measuring bases for controlling the size h is the upper plane B. Due to the fact that the bases do not match, it became necessary to recalculate the design dimensions to technological ones. In this case, it is necessary to calculate the error with which the size h can be fulfilled and compare it with the tolerance T h of this size, the condition ε h T h must be met. 2. The dimensional chain under consideration is linear and consists of three links: the size h \u003d 70 mm of interest to us will be considered as the closing link, and the first component link, the dimension A 1 \u003d 85h8 (85-0.04) between the previously machined planes, is a magnifying link; the second component link size A 2 is technological, reducing, and its accuracy is determined by the norms of economic accuracy of processing on machines (see GOST). For our case, the error of this size is 0.06 mm. The nominal dimensions of this circuit are related by equation 23
24 A \u003d A 1 A 2 \u003d \u003d 70 mm. 3. When calculating the linear dimensional chain (Fig. 3.8) by the method of complete interchangeability, ie using the minimum method, the maximum deviations (processing error) of the initial (closing) link are determined by the formula (3.3): T n \u003d Ti \u003d (TA 1 + TA2) \u003d (0.06) \u003d 0, 114 mm Σ. i \u003d 1 As follows from the solution, the tolerance in the drawing T h \u003d 0.1 mm is less than the possible error during processing T \u003d ε h \u003d 0.114 mm, which is completely unacceptable. Therefore, it is necessary to take measures to achieve the fulfillment of the condition ε h T h For this, firstly, we can raise a question for the designer about reducing the accuracy of the size h, i.e. on expanding the tolerance T h to 0.12, then T \u003d ε h \u003d (0.06) T h. Secondly, apply fine milling or fine grinding as the final (finishing) treatment. The economic accuracy of these processes is higher and with them T A2 \u003d 0.025 mm (GOST). Then T \u003d (0.025) \u003d 0.079 mm. The condition T T h is satisfied. Thirdly, the component size A \u003d 85h8 was obtained by processing the planes A and B before the operation in question. If the previous processing is performed more precisely by one quality, then the size tolerance will be 85h7 (-0.035). Then the processing error T \u003d (0.035 + 0.06) \u003d 0.095 mm. The condition is met T T h. Fourth, when calculating the dimensional chain, you can use the probabilistic method according to the formula n T i i \u003d 1 2 T 1,2t. 2 2 Then T \u003d 1.2 0.060 \u003d 0.097 mm and the condition T Th is met. Fifth, the tolerance of the closing link is calculated using probability theory for the case of dispersion of deviation errors according to the law of normal distribution according to formula (3.5). In our case, 2 2 TΣ \u003d 0.060 \u003d 0.08mm. The condition T T h is satisfied. Sixth, with a small volume of production of parts, that is, in single or small-scale production, it is possible to work not for commissioning, but, for example, with the removal of test chips. Each part is controlled by size h. \u003d 24
25 Task 3.3. In fig. 3.9 and table. 3.2 options for operations are presented. Required: to determine the possible error of the base size as a result of the specified processing. I, IIIII, IV 1 2 l V, VI l 2 l 1 lh 9 Ç Ç Ç l 1 l 2 VII, VIII h 9 1 l 2 l 1 2 Ç Ç Ç hhh 1 0 l 1 IX, X 1 2 l 2 Fig. Options for calculating dimensional chains. Initial data. Table 3.2. Options. Contents of the operation. Size l, mm I Plan plane 1 preliminary l 1 \u003d 150 + 0.2 II Plan plane 2 finally l 2 \u003d 170 ± 0.1 III Trim end 1 preliminary l 1 \u003d 60 + 0.3 IV Trim end 2 completely l 2 \u003d 30 + 0.1 V Trim end 1 previously L 1 \u003d 100 + 0.2 VI Trim end 2 finally l 2 \u003d 50 + 0.1 25
26 Continuation of table 3.2 VII. Grind plane 1 previously l 1 \u003d 75 + 0.1 VIII Grind plane 2 finally l 2 \u003d 175 + 0.2 IX Mill plane 1 previously l 1 \u003d 70 + 0.4 X Mill plane 2 finally l 2 \u003d 30 + 0.2 4. TECHNOLOGY OF THE CONSTRUCTION Successful solving of the problems that stand and will continue to be confronted with mechanical engineering is possible only when creating new and improving existing machines in order to achieve higher performance while reducing their weight, size and cost, increased durability, ease of maintenance and reliability. At the same time, in engineering itself, it is necessary to improve the technological processes of manufacturing products, improve the use of all means of technological equipment, and introduce progressive methods of organizing production into production. One of the effective ways to solve these problems is to introduce the principles of manufacturability of structures. This term refers to such a design that, subject to all operational qualities, ensures the minimum labor input, material consumption and cost, as well as the ability to quickly master the production of products in a given volume using modern processing and assembly methods. Technological effectiveness is the most important technical basis, ensuring the use of design and technological reserves to fulfill the tasks of improving the technical and economic indicators of manufacturing and product quality. Work to improve manufacturability should be carried out at all stages of design and development in the manufacture of manufactured products. When performing work related to manufacturability, one should be guided by a group of standards included in the Unified System of Technological Preparation for Production (ESTPP), namely GOST, as well as GOST "Technological control in design documentation". The manufacturability of the construction of parts is determined by: a) a rational choice of the initial blanks and materials; b) the manufacturability of the shape of the part; c) rational installation 26
27 sizes; d) the appointment of optimal accuracy of the size, shape and relative position of the surfaces, roughness parameters and technical requirements. The manufacturability of the part depends on the type of production; selected technological process, equipment and equipment; organization of production, as well as the working conditions of the part and the assembly unit in the product and repair conditions. The technological design features of a part, for example, a shaft subclass are indicative of the presence of small differences in the step diameters of stepped shafts, the location of stepped surfaces with decreasing diameter from the middle or from one of the ends, the availability of all machined surfaces for machining, the ability to use a progressive-looking initial workpiece for manufacturing a part , which in shape and size is close to the shape and size of the finished part, the ability to use high-performance methods for processing. Improving the manufacturability of the initial blank Example 4.1. Two variants of the design of the initial billet obtained by casting were made for the manufacture of the support body (Fig. 4.1, a, b). It is required to establish which of the options has a more technologically advanced design of the original workpiece. Decision. The housing (Fig. 4.1, a) has a tubular cavity in the lower part. To form it in a mold, it is necessary to use a cantilever rod, and this will complicate and increase the cost of manufacturing the casting. A smooth hole of considerable length in the upper part will complicate the machining. The case (Fig. 4.1, b) in the lower part has a cross-shaped cross section, which has high strength and rigidity, and a rod is not needed for the manufacture of castings. This greatly facilitates the manufacture of molds. The casting is symmetrical about the vertical plane and will easily be molded in two flasks. The hole in the middle part has a recess and therefore the length of the surface of the hole to be machined has been reduced, and this, in turn, greatly facilitates and reduces the cost of machining. Based on the above considerations, we can conclude that the second option is more technological. 27
28 À À À - À à) b) Figure Variants of the casting form Problem 4.1. When designing the initial billet or its elements, two designs were proposed (the options are given in Table 4.1, in Figure 4.2). Table 4.1. Initial data of a variant. Part name Type of workpiece I; VI II; VII III; VIII IV; IX V; X Gear wheel Lever Cover Body neck Round body Forged stamped Same Castings Welded Castings I, V I I I, V I I I I I, V I I I I V, I X V, X Fig Workpiece options 28
29 It is required to state considerations for evaluating the manufacturability of the design of each of the variants of the initial billet and to establish a more technologically advanced one. Improving the manufacturability of parts and their elements Example 4.2. In order to improve the technical and economic indicators of the technological process, two options are proposed for the details of elements in the structure of the body made of castings (Fig. 4.3, a, b). It is required to evaluate their manufacturability. Decision. The bosses and platiks on the part body (Fig. 4.3, a) are located at different levels, and each boss must be processed according to individual adjustment. The insufficient rigidity of the upper part of the part does not allow the use of high-performance processing methods. In the design in Fig. 4.3, b all the machined surfaces are located in the same plane and therefore can be machined on the same machine, for example, vertically milling or longitudinal milling. à) á) Rice Casting options The ribs added on the inside of the part increase the rigidity of the body. During processing, this will help to reduce the deformation of the workpiece from cutting and fixing forces and will allow processing with high cutting conditions or several tools at the same time. This will increase the accuracy and quality of the treated surfaces. 29th
30 The level of non-machined surfaces available to the part is below the machined surfaces. This will allow more efficient processing "on the pass." Task 4.2. One and the same structural element of a machine part can be structurally solved differently. These solutions are represented by two sketches (options in Fig. 4.4). It is required to analyze the compared design sketches for manufacturability and justify the choice of the structural element of the part. I, I I V I I, V I I I I I I, I V V, V I I X, X R Fig. Design options Determination of quantitative indicators of the manufacturability of the part design Example 4.3. A case weighing m D \u003d 2 kg is made of cast iron of the grade SCH 20 GOST Method of obtaining the initial billet cast in earthen mold, according to class I accuracy (GOST); the mass of the workpiece m 0 \u003d 2.62 kg thirty
31 The complexity of machining a part T i \u003d 45 min with the basic complexity (analog) \u003d 58 min. Technological cost of parts C t \u003d 2.1 rubles. at the base technological cost of the analogue C b.t \u003d 2.45 rubles. The data of the design analysis of the part by surface are presented in Table 4.2. Initial data Surface name Number of surfaces Number of unified elements Main hole 1 1 Flange end 2 Chamfer 2 2 Threaded hole 8 8 Base top 2 Base holes 4 4 Base bottom 1 Total ... Q e \u003d 20 Q c.u. \u003d 15 It is required to determine the indicators of manufacturability of the design of the part. Decision. 1. The main indicators of technological design include: an absolute technical and economic indicator of the complexity of manufacturing parts T and \u003d 45 min; the level of manufacturability of the design for the complexity of manufacturing K U.T \u003d T and / T b.i \u003d 45/58 \u003d 0.775. The detail on this indicator is technologically advanced, since its labor intensity is 22.5% lower compared to the base analogue; the technological cost of the part With t \u003d 2.1 rubles .; the level of manufacturability of the design at the technological cost To. s \u003d C t / C b.t \u003d 2.1 / 2.45 \u003d 0.857. The detail is technological, since its cost compared to the base analogue decreased by 14.3%. 2. Additional indicators: the coefficient of unification of the structural elements of the parts To. e \u003d Q y.e / Q e \u003d 15/20 \u003d 0.75. 31
32 According to this indicator, the part is technologically advanced, since K u. e\u003e 0.6 mass of the part m D \u003d 2 kg; the coefficient of use of the material K and m \u003d m d / m 0 \u003d 2 / 2,62 \u003d 0,76. For the initial workpiece of this type, this indicator indicates the satisfactory use of the material. Task 4.3. About the part in question, its initial blank and its basic analogue or prototype are known; basic data are given in table. 4.3 for ten options. It is required to determine the indicators of manufacturability of the design of the part. Table 4.3 Initial data of the variant Number of part surfaces Qе Number of standardized elements Q.u. Weight, kg Details md Initial workpiece m0 Labor input, min Parts T and Base analog Tb.i Cost, rub. Details of the St Basic analogue C6.d I; VI, 8 1.7 2.1 II; VII, 3 0.9 1.3 III; VIII, 1 3.4 4.1 IV; IX, 2 0.2 1.4 V; X, 8 5.8 5.3 5. MACHINERY ALLOWANCES. OPERATIONAL DIMENSIONS AND THEIR TOLERANCES When considering the elementary surface of the initial billet and the corresponding surface of the finished part, the total machining allowance is determined by comparing their sizes: this is the difference in size of the corresponding surface on the initial billet and the finished part. When considering the outer surface of rotation (left in Fig. 5.1), the total allowance: 2P total d \u003d d 0 d D; (5.1) 32
33 at the inner surface of rotation (in the center in Fig. 5.1) the total allowance: 2P total d \u003d D D D 0; (5.2) the flat surface (on the right in Fig. 5.1) has a total allowance on the side: P totalh \u003d h 0 h D, (5.3) where d 0, D 0, h 0 are the sizes of the initial workpiece; d D, D D, h D the corresponding dimensions of the finished part; 2P general and 2P general general allowances for diameter, outer surface and holes; P the total allowance on the side (end face, plane). The machining allowance is usually removed sequentially in several transitions and therefore for surfaces of revolution and for flat surfaces 2P total d \u003d 2P i; 2P total d \u003d 2P i; P totalh \u003d 2P i, (5.4) where Pi is the intermediate allowance performed during the i-th transition, and at each subsequent transition, the size of the intermediate allowance is smaller than at the previous one, and with each subsequent transition, the accuracy increases and the roughness of the surface being machined decreases. Ï Ï d ä d 0 D ä D 0 h ä h 0 Ï Ï Ï Rice Types of machining allowance An important and responsible work in the design of technological processes for machining parts is to establish the optimal intermediate allowance for a given transition, after which it is possible to determine the very important part processing technology parameters intermediate dimensions of the workpiece, which appear in the technological documentation, depending 33
34 from which the performers select cutting and measuring tools. Intermediate allowances for each transition can be established by two methods: the experimental-statistical method, using tables in GOSTs, in technology directories, departmental guidance technological materials and other sources. These sources often do not have tables for determining operating allowances for the first roughing. The operating allowance for the roughing transition is determined by the calculation according to the formula P 1 \u003d P total (P 2 + Pz P n), (5.5) where P total general machining allowance established during the design of the workpiece; P 1, P 2; ..., P p intermediate allowances for the 1st, 2nd, ..., nth transitions, respectively; calculation and analytical method according to special formulas, taking into account many processing factors. When calculating by this method, operational allowances are less than those selected according to the tables, which saves metal and reduces the cost of processing. This method is used in the design of technological processes for processing parts with a large annual output. In the technological documentation and in the practice of processing, intermediate nominal sizes are used with tolerances. As you can see in the diagram (Fig. 5.2) the location of the allowances and tolerances during processing, the nominal intermediate sizes depend on the nominal allowances, which are found by the formula P nomi \u003d P min i + T i-1, (5.6) where T i-1 tolerance on intermediate size at the previous transition. For different surfaces, the following formulas are used: for surfaces of revolution, except for the case of processing at centers: 2P nomi \u003d 2 (R zi-1 + h i Δ i 1 + ε) + T i-1; (5.7) 2 i for surfaces of revolution during machining in centers: 34
35 for flat surfaces 2P nomi \u003d 2 (R zi-1 + h i-1 + Δ Σi-1) + T i-1; (5.8) P nomi \u003d 2 (R zi-1 + h i-1 + Δ Σi-1 + ε i) + T i-1; (5.9) for two opposite flat surfaces while simultaneously processing them: P nomi \u003d 2 (R zi-1 + h i-1 + Δ Σi-1 + ε i) + T i-1, (5.10) where R Zi-1 the height of microroughnesses on the surface after the previous transition; h i-1 is the thickness (depth) of the defective layer obtained at the previous adjacent transition, for example, casting peel, decarburized or riveted layer (this term is not taken into account for cast iron parts, starting from the second transition, and for parts after heat treatment); Δ Σi-1 the total value of the spatial deviations of the interconnected surfaces from the correct shape (warping, eccentricity, etc.) remaining after the previous transition (the total value of the spatial deviations decreases with each of the following transitions: Δ Σi \u003d 0.06 Δ Σ0; Δ Σ2 \u003d 0.05 Δ Σ1; Δ Σ3 \u003d 0.04 Δ Σ2. When the workpiece or tool is loosely fixed, for example, in swinging or floating holders Δ Σi-1 \u003d 0); ε i the error in the installation of the workpiece on the machine when performing the transition under consideration: 2 bases 2 closes 35 2 increment ε \u003d ε + ε + ε, (5.11) where ε bases, ε closes, ε asc respectively the errors of basing, fixing and adaptation (when installing in centers ε i \u003d 0, when processing on multi-position operations when changing positions take into account the indexation error ε ind \u003d 50 μm according to the formula ε i \u003d 0.06 ε i-1 + ε ind); T i-1 tolerance on the intermediate size (when determining the allowance for the first roughing transition for external surfaces, only the minus part of T is taken into account, and for the internal 0 surfaces the plus part of the tolerance of the initial workpiece). The intermediate dimensions when processing the outer surfaces of rotation (shafts) are set in the reverse order
36 technological process of processing this surface, i.e. from the size of the finished part to the size of the workpiece by sequentially adding to the largest limit size of the finished surface of the part (initial design size) allowances P nom4; P nom3; P nom2; P number 1. Tolerances of these sizes are established according to the shaft system with a tolerance field h of the corresponding quality. The initial design dimension is taken as the largest limit size of the finished surface. Rounding of the intermediate sizes is carried out in the direction of increasing the intermediate allowance to the same sign as the tolerance of this size. Features of the calculation of intermediate allowances and sizes for internal surfaces are as follows: a) tolerances of intermediate (interoperational) sizes are established by the hole system with a tolerance field H of the corresponding quality; b) the nominal dimensions and nominal allowances, at all transitions except the first, are related by the dependence П nomi \u003d П mini + T i-1, (5.12) and the nominal allowance for the first (draft) transition is determined by the formula where П nomi \u003d П mini + T 0 +, (5.13) + T 0 plus part of the tolerance of the workpiece; c) the intermediate sizes are set in the reverse order of the technological process from the size of the finished hole to the size of the workpiece by subtracting from the smallest limit size of the finished hole (initial size) allowances P nom3; P nom2; P number 1. Their tolerances are set according to the hole system with the tolerance field H; d) for the initial design size take the smallest limit size of the finished hole. The scheme of tolerance fields of the outer surface of the part, workpieces at all stages of processing and the initial workpiece, and the margins of the general and intermediate allowances are presented in Fig.
37 + T 0 - d 0 î \u003d \u003d d 1 í + + 2 Ï 1 í ì Ï 2 Ï 1 ì T 1 d 1 \u003d \u003d d 2 + 2 Ï 2 2 Ï 2 ì - ï - - - - - - - - - - - - - - - - - - - 2 2 2 2 2 2 2 2 2 2 T 2 d 2 Om \u003d \u003d d 3 î + + 2 Ï 3 2 2 Ï 3 í ì T 3 d 3 \u003d \u003d d 4 + 2 Ï 4 Ï ì 2 Ï 4 Ï T T 4 I II ð II II II II II ð III III III III III ð õ IV IV IV ð î Рис Рис Рис Рис Рис Рис Рис Рис Fig. scheme tolerance fields à î ò î â à ÿ ä å ò à ë ü Selection allowances intermediate shaft in the processing and calculation rolled intermediate sizes Example 5.1. A stepped shaft with a length of L D \u003d 480 mm (Fig. 5.3) is manufactured under conditions of small-scale production of steel round hot-rolled steel of ordinary accuracy with a diameter of d 0 \u003d 100 mm. The largest diameter shaft step Ø90h10 (90-0.35) with a surface roughness of Ra5 (Rz20) is processed twice: preliminary and final turning. Required: to establish a general allowance for machining diametric size; to establish intermediate allowances for both transitions of processing by a statistical method; calculate intermediate size. R a 5 Ç 9 0 h * Rice Stepped shaft 37
38 Solution. 1. The total allowance for machining the diameter is determined by the formula 5.1: 2P total d \u003d \u003d 10 mm 2. Intermediate diameter allowance for fine turning of the shaft. 2P 2tabl \u003d 1.2 mm. For the small-scale nature of production, the allowance is increased, for which a coefficient K \u003d 1.3 is introduced, that is, 2P 2calc \u003d 1.2 1.3 \u003d 1.56 mm 1.6 mm. Since there are no indications of the size of the operational allowance for diameter during rough turning in technological manuals, we determine it by calculation using the formula (5.4): 2P 1 \u003d 2P total 2P 2calc \u003d 10 1.6 \u003d 8.4 mm. So, the initial calculated diameter size (the largest limit size) is d and cx \u003d 90 mm, the operational allowance for fine turning 2P 2 \u003d 1.6 mm. The diameter of the workpiece after rough turning is equal to d 1 \u003d d ref + 2P 2 \u003d 91.6; it is with a tolerance: d 1 \u003d 91.6h12, or d 1 \u003d 91.6-0.35; surface roughness Ra20. In the technological documentation, operational sketches for both transitions are performed (Fig. 5.4, a, b) R a 20 Ç 9 1, 6 h 1 2 à) R a 5 Ç 9 0 h 1 0 á) Fig Operation sketches Task 5.1. For the manufacture of a stepped shaft (Fig. 5.5), steel round hot-rolled steel of usual accuracy with a diameter of d 0 was used as a billet. The largest step in diameter of this shaft with a diameter of d D, manufactured with an accuracy of 11th grade and surface roughness Ra10, is processed 38
39 twice preliminary and final turning. The options for the task are given in table d 0 d ä L ä Rice Harvesting circle Initial data Table 5.1 of option I II III IV V VI VII VIII IX X d D mm 75h11 85a11 65b11 95a11 60d11 95d11 70a11 90h11 80d11 55h11 do mm L D mm Required: set using tables, general and intermediate stocks; calculate intermediate size and perform operational sketches. Establishment of intermediate allowances for each transition by statistical method (according to the tables) and calculation of intermediate sizes of the workpiece Example 5.2. A multi-stage shaft (Fig. 5.6) is made of stamped forgings of increased accuracy (I class). The workpiece went through milling-central processing, as a result of which the ends were cut and center holes were created. 39
40 Ç 8 5 p 6 Ç 9 1, 2 + 0, 3-0, * Rice. Forgings. The outer cylindrical surface of one shaft step has a diameter d \u003d 85p6 (85) * with a roughness of Ra1.25. Stage D of the initial workpiece (see example A1.2) has a diameter d 0 \u003d 91, and a roughness of Rz250 (Ra60). The accepted sequence of processing the specified surface is given in the table. Required: to analyze the source data; establish by statistical method (according to the tables) operational allowances for each transition; calculate intermediate sizes for each technological transition. Decision. 1. The total machining allowance for the diameter is 6.2 mm. Coefficient of tightening the size of the treated surface is K tou.r. \u003d T 0 / T D \u003d 2000/22 \u003d 91. Table 5.2 Initial data Processing sequence (transition content) Grind the surface before grinding Grind the surface before grinding Grind the surface before grinding Grind the surface finally Accuracy level Roughness parameter Ra, μm 20.0 5.0 2 , 5 1.25 Note that the tolerance of the diameter of the initial workpiece corresponds to approximately the 16th accuracy class (IT16), and the finished part to the 6th accuracy class (IT6). Thus, accuracy in processing increases by approximately ten qualifications. Such a difference in accuracy can be achieved in four stages of processing, so 40
41 how each processing step increases size accuracy by an average of quality. 2. The choice of operating allowances for diameter is performed according to the tables. The total allowance 2P total \u003d 6.2 mm The table value of the operational allowance for the diameter during grinding is 0.5 mm, we distribute it for grinding preliminary and final (approximately in the ratio 3: 1) and we get 2P 3 \u003d 0.375 mm and 2P 4 \u003d 0.125 mm. Roundedly take 2P 3 \u003d 0.4; 2P 4 \u003d 0.1. The allowance for turning for grinding 2P 2 \u003d 1.2 mm. From here we find the allowance for rough turning: 2P 1 \u003d 2P total 2P 2 2P 3 2P 4 \u003d 4.5 mm. The surface parameters after machining for each transition are presented in table. According to table. 5.3, the following conclusions can be drawn: a) the total allowance is divided by transitions in the ratio of 72.5%, 19.5%, 6.5% and 1.5%, which corresponds to the rules of the machining technology; b) after each transition, the accuracy increases in this sequence (according to qualifications): and, accordingly, the size tolerance decreases (the tolerance is tightened) by 4.3; 3.8; 2.6 and 2.1 times; Table 5.3 Transition initial data Designation and size of intermediate allowance for diameter 0 2P total \u003d 6.2 mm Tolerance field IT 16 (class I according to GOST) 1 2P 1 \u003d 4.5 mm h13 2 2P 2 \u003d 1.2 mm h10 3 2P 3 \u003d 0.4 mm h8 4 2P 4 \u003d 0.1 mm p6 41 Permissible size deviation, mm +1.3 0.4 0 0.054 +0.059 +0.037 Surface roughness, μm Ra60 (Rz250) Ra20 Ra-5.5 Ra-2.5 Ra1.25
PRACTICAL WORK 5 Topic "Bases and principles of basing" Purpose of practical work: To form the ability to choose technological bases taking into account the technical requirements for the part, draw up basing schemes
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Ministry of Education and Science of the Samara Region
GBOU SPO Togliatti Engineering College
Reviewed Approving
at a meeting of MK Deputy. Director for NMR
specialties 151901 __________ Lutsenko T.N.
Protocol No. ______
"___" ___________ 2013 "___" ___________ 2013
Chairman MK
__________ / Bykovskaya A.V. /
Instrumentation
discipline "Engineering Technology"
specialties STR: 151901 Engineering Technology
for 4 year students
Developed by teacher Ivanov A.S.
Specialty ACT: 151901 Engineering Technology
Discipline: Engineering Technology
Section 1: Specification of Training Elements
№ p / p
Name of training items
(Didactic units)
The purpose of training
must know
must know
must know
must know
must know
must know
must know
must know
must know
Technological setup diagrams
must know
must know
The norm of time and its structure
must know
must know
must know
must know
must know
must know
must know
must know
Technology assembly machines.
must know
must know
must know
must know
Section 2 Test Tasks
Option 1
Block a
Task (question)
Answer standard
№ tasks
Possible answer
1
1-B, 2-A, 3-B
Match the surface name to the graphic
1 - B;
2 - B;
3 - A;
4 - G.
PICTURE
Superficiality:
A) the main
B) auxiliary
B) executive
D) free
Set the correspondence between the name and designation
1 - G;
2 - D;
3 - A;
4 - B;
5 B.
Name
A) cylindricity
B) roundness
C) flatness
D) straightness
D) the tolerance of the longitudinal section profile
To establish compliance with which varieties of directions of irregularities are indicated on the diagrams.
1 - B;
2 - D;
3 - G;
4 - A;
5 B.
Name of irregularities
parallel
intersecting
perpendicular
arbitrary
radial
Designation on schemes
AND. G.
B. D.
The completed part of the technological process performed by the worker at one workplace is
operation
Series production is characterized by
the number of products does not affect the type of production
The criterion for determining the type of production is
product range and operations consolidation ratio
product cycle
3. qualifications of workers
accuracy can be achieved in metalworking by methods
method of passes and measurements
on customized machines
paragraphs 1 and 2
surface measurement
The minimum operating allowance for bodies of revolution is determined by the formula
surface roughness not subjected to processing is indicated by the mark
1. 3.
2. 4. all of the above
The base used to determine the position of the workpiece in the manufacturing process is called
design base
technological base
main base
auxiliary base
Operational time is determined by the formula
T OP \u003d T O + T B
T DOP \u003d T SB + T OP
T W \u003d T O + T B + T V + T OT
T W-K \u003d T W + T P-Z / N
A base depriving a workpiece of three degrees of freedom is called
double support
installation
guide
The base of the workpiece, manifested in the form of a real surface, is called
open
measuring
Determine the type of production, if the coefficient of consolidation of operations TO 3 =1
small batch production
medium production
large-scale production
mass production
The set of all irregularities on the surface under consideration is called
non-straightness of the surface of the part
surface undulation
not parallel to the surfaces of the part
surface roughness
The set of sizes forming a closed loop and assigned to one part is called
dimension line
dimensional chain
size group
dimensional link
Define the term - general allowance
Base errors occur if they do not match
design and technological bases
technological and measuring bases
design and measuring bases
When choosing finishing bases during processing for all operations, you must use
principle of combining bases
principle of constancy of bases
installation bases only
installation and design bases
The ability of a structure and its elements to resist the effects of external loads without collapsing is called
rigidity
sustainability
strength
elasticity
Block b
Task (question)
Answer standard
The limited application of the principle of interchangeability and the use of fitting work is characteristic of ____________
single assembly production.
The main basing schemes in metalworking are _________________________________________________
basing of prismatic blanks, basing of long and short cylindrical blanks.
The degree of compliance of the part with the given dimensions and shape is called ________________________________
precision machining.
The value of tool movement per revolution of the workpiece is called ___________________
By designation, the surfaces of the parts are classified into __________________________________________________
on the main, auxiliary, executive, free
The working drawing of the part, the drawing of the workpiece, technical specifications, and the assembly drawing of the part are the initial data for the design _____________________________
technological process.
To compensate for errors arising when choosing blanks, __________________________________
machining allowance.
The set of periodically alternating elevations and depressions with a ratio is called _____________________
surface waviness.
One of the sizes forming a dimensional chain is called ________________________________
dimensional link.
The assembly of workpieces, components or the product as a whole, which are subject to subsequent disassembly is called _________________________
pre-assembly
Option 2
Block a
Task (question)
Answer standard
Instructions for the implementation of tasks No. 1-3: correlate the contents of column 1 with the contents of column 2. Write in the corresponding lines of the answer form the letter from column 2, indicating the correct answer to the questions in column 1. As a result of execution, you will get a sequence of letters. For example,
№ tasks
Possible answer
1
1-B, 2-A, 3-B
Set the correspondence: to determine what parameters of the workability analysis of the part, these formulas
1 - G;
2 - B;
3 - A;
4 - B
Coefficient
A. Processing accuracy factor
B. Surface Roughness Coefficient
B. Material utilization
D. The coefficient of unification of structural elements
Set the correspondence between the graphic designation and the name of the support, clamp and installation device.
1 - B
2 - B
3 - A
4 - D
graphic designation
1. 3.
name
A - collet mandrel
B - floating center
B - motionless support
G - adjustable support
Set the correspondence between the sketch of processing and its name
1 - B
2 - G
3 - A
4 - B
Name
A. Parallel multi-tool single.
B. Sequential multi-tool single.
B. Parallel-sequential multi-tool single.
G. Parallel single-tool single
Instructions for completing tasks No. 4-20: Select a letter that corresponds to the correct answer and write it in the answer form.
- this is the formula for determining
piece time
main time
auxiliary time
technological rate of time
route map
process chart
operational card
technological instruction
Machine tools intended for the manufacture of products of the same name and different sizes
universal
specialized
special
mechanized
Determine the type of production, if the coefficient of consolidation of operations K C \u003d 8.5
small batch production
medium production
large-scale production
mass production
surface roughness formed by the removal of a layer of material is indicated by
2. 4.
Mass production is characterized by
narrow range of products
limited range of products
a wide range of products
different nomenclature of products
– this is the formula for determining
cutting speeds
minute feed
spindle speed
cutting depths
An item or set of production items to be manufactured at an enterprise is called
assembly unit
product
4. set
Connections that can be disassembled without damage to mates or fasteners are called
movable
detachable
inseparable
motionless
When planning a site in front of machines, a working width is provided
– this is the formula for determining
design interference
interference fit
temperature of mating parts
forces when fitting parts
Define the term defective layer
metal layer intended for removal in one operation
minimum required metal layer thickness for the operation
surface layer of metal, in which the structure, chemical composition, mechanical properties differ from the base metal
metal layer intended for removal during all operations
When basing a workpiece in a fixture on technological bases that are not related to measuring
fixing errors
installation errors
processing errors
basing errors
Single, not regularly repeating deviations from the theoretical shape of the surface deviations are called
surface undulation
macrogeometric deviations
surface roughness
microgeometric deviations
The error that occurs before the application of the clamping force and when clamping is called
basing error
installation error
fixing error
device error
To ensure high hardness of the working surfaces of the teeth of the wheels using the type of heat treatment
carburizing followed by hardening
nitriding followed by hardening
cyanide followed by hardening
oxidation followed by hardening
the property of the product allowing to manufacture and assemble it at the lowest cost is called
repair workability
manufacturability
operational manufacturability
manufacturability of the product
Block b
Task (question)
Answer standard
Instructions for completing assignments No. 21-30: In the corresponding line of the answer form, write down a short answer to the question, the end of the sentence, or missing words.
To clearly illustrate the process use ____________________
sketch map
Automated process control systems in which the development of corrective actions on a controlled process occurs automatically is called ________________________
managers
Roughnesses in the surface resulting from the action of the cutting edge of the tool on the surface to be treated are called _________________________
microgeometric deviations.
Deformation and wear of machines, wear of a cutting tool, clamping force, thermal deformation affect __________
processing accuracy
The product, the components of which are interconnected, are called ____________________________
assembly unit.
The technological process of manufacturing a group of products with common design and technological features is called ________________________
When processing the base surfaces of body parts, the primary base is _________________________
rough core holes
A part formed from a set of bushings interconnected by rods are called ______________________
Compliance with the exact conformity of the technological process of manufacturing or repairing the product with the requirements of technological and design documentation is called _________
technological discipline
Products that are not connected at the manufacturer, which are a set of auxiliary products, are called ______________________________________
kit
Section 3 Codification System
Name of the didactic unit
Option Number
Question numbers
Machining Processes
4; 5; 6; 10, 14, 25
Precision machining.
Surface quality of machine parts
The choice of bases when processing blanks
3, 12, 13, 18, 19, 22
Machining allowances
Design principles, rules for the development of technological processes
The concept of technological discipline
Auxiliary and control operations in the technological process
Calculations for the design of machine operations
Technological setup diagrams
Requirements for the development of calculation and technological cards for CNC machines
The norm of time and its structure
Methods of regulation of labor processes, standards for technical regulation
Organization of technical and normative work at a machine-building enterprise
Methods of processing the main surfaces of typical machine parts
Programming the processing of parts on machines of different groups
Technological processes, production of standard parts for general engineering applications
Technological processes for manufacturing parts in a flexible production system (GPS), on automatic rotor lines (ARL).
Automated process design
Technology assembly machines.
11; 12; 14; 25; 30
Methods of implementation, production debugging of technological processes, monitoring compliance with technological discipline
Product rejection: analysis of the causes, their elimination
Fundamentals of designing sections of machine shops
Section 4 References
Averchenkov V.I. and etc. Engineering Technology. Collection of tasks and exercises. - M .: INFRA-M, 2006.
Bazrov B.M.Fundamentals of engineering technology. - M.: Mechanical Engineering, 2005.
Balakshin B.S. Fundamentals of engineering technology - M .: Mechanical Engineering, 1985.
Vinogradov V.M. Engineering Technology. Introduction to the specialty. - M.: Mechanical Engineering, 2006.
Gorbatsevich A.F., Shkred V.A.Course design on engineering technology - Mn .: Higher School, 1983.
Danilevsky V.V.. Engineering Technology. - M.: Higher School, 1984.
Dobrydnev I.S. Course design in the subject "Engineering Technology". - M.: Mechanical Engineering, 1985.
Klepikov V.V., Bodrov A.N. Engineering Technology. - M .: FORUM - INFRA-M, 2004.
Matalin A.A.Engineering Technology - L .: Engineering, 1985.
Mikhailov A.V., Rastorguev D.A., Skhirtladze A.G. -Fundamentals of designing technological processes of mechanical assembly production. - T .: Tolyatti State University, 2004.
The solution of practical problems in all major sections of the discipline "Engineering Technology" is given. Variants of individual tasks for practical work are given with a description of the methodology for their implementation using the example of solving one of the task options. The appendices contain normative and reference materials necessary for the implementation of practical work.
The manual can be used in the study of the general professional discipline "Engineering Technology" in accordance with the Federal State Educational Standard of Higher Professional Education for specialty 151901 "Engineering Technology".
An electronic educational resource “Engineering Technology” has been issued for this tutorial.
For students of educational institutions of secondary vocational education.
DEFINITION OF SIZES OF ALLOWANCES.
A workpiece is a production item, the shape of which is close to the shape of the part, from which the part or one-piece assembly unit is made by changing the shape and roughness of the surfaces, their sizes, and also the properties of the material. It is considered that for any operation the workpiece arrives, and the part leaves the operation.
The configuration of the workpiece is due to the design of the part, its dimensions, material and working conditions of the part in the finished product, i.e., all types of loads acting on the part during operation of the finished product.
The initial procurement is the procurement received for the first operation of the technological process.
An allowance is a layer of a workpiece material that is removed during its machining to obtain the required accuracy and parameters of the surface layer of the finished part.
An intermediate allowance is a layer of material that is removed during one technological transition. It is defined as the difference between the size of the surface of the workpiece obtained in the previous operation, and the size of the same surface of the part obtained during this transition on processing the surface of the workpiece in one operation.
TABLE OF CONTENTS
Foreword
Chapter 1. Fundamentals of engineering technology
1.1. Production and technological processes of a machine-building enterprise
Practical work №1.1. The study of the structure of the process
1.2. Determining the size of the allowances
1.3. Sizing workpieces
1.4. Preliminary assessment of the options for obtaining blanks
and their manufacturability
Practical work No. 1.2. Purpose of operating
allowances for machining parts with a graphical representation of the location of allowances and tolerances on operational dimensions
1.5. The choice of bases when processing blanks
1.6. Sequence of operations
1.7. Installation Base Selection
1.8. Source base selection
Practical work No. 1.3. Base workpieces in the processing zone of the machine
1.9. Machining accuracy
1.10. Determining Expected Accuracy with Coordinate Sizing Automatically
Chapter 2. Technical regulation of technological operations
2.1. Piece Time Structure
2.2. Rationing operations
Practical work No. 2.1. Process Turning Rationing
Practical work No. 2.2. Rationing of a milling operation of a technological process
Practical work No. 2.3. Rationing of the grinding process operation
2.3. Operations Development
Practical work No. 2.4. Development of a round grinding process operation
Practical work No. 2.5. Development of surface grinding process operations
Chapter 3. Surface treatment methods used in the manufacture of basic parts
3.1. Shaft manufacturing
3.2. Making discs
3.3. Gear manufacturing
3.4. Cylindrical Gear Manufacturing
3.5. Bevel gear manufacturing
Chapter 4. Production of ring parts
Chapter 5. Production of parts from sheet materials
Chapter 6. The choice of devices for basing (installation and securing) blanks
Chapter 7. Assembly of joints, mechanisms and assembly units
7.1. Development of a route and assembly scheme
7.2. Assembly dimension chains
7.3. Ensuring precision assembly
7.4. Monitoring assembly and process parameters
7.5. Balancing parts and rotors
Chapter 8. Course design
8.1. The main provisions of the course project
8.2. General requirements for the design of the course project
8.3. General methodology for working on a project
8.4. Technological part
Applications
Appendix 1. An approximate form of the title page of the explanatory note
Appendix 2. The approximate form of the form of the assignment for the course project
Appendix 3. Units of measurement of physical quantities
Appendix 4. Rules for the design of the graphic part of the course project
Appendix 5. Tolerances in the hole system for external dimensions according to ESDP (GOST 25347-82)
Appendix 6. Sample routes for obtaining parameters of external cylindrical surfaces
Appendix 7. Sample routes for obtaining parameters of internal cylindrical surfaces
Appendix 8. Operating allowances and tolerances
Appendix 9. Temporary indicators of technological operations
Appendix 10. Technical characteristics of technological equipment and materials
Appendix 11. Cutting parameters and processing modes
Appendix 12. Indicators of accuracy and surface quality
Appendix 13. The dependence of the type of production on output
Appendix 14. Sample indicators for economic calculations
Appendix 15. Surface treatment methods
Appendix 16. Values \u200b\u200bof coefficients and quantities
Appendix 17. Brief technical specifications of metal cutting machines
List of references.
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