Types of production and methods of work. Single, serial, mass production

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1. Rationale for the choice of workpiece

The optimal method for obtaining a blank is selected depending on a number of factors: the material of the part, the technical requirements for its manufacture, the volume and serial production, the shape of the surfaces and the dimensions of the parts. The method of obtaining the workpiece, providing manufacturability and minimum cost is considered optimal.

In mechanical engineering, the following methods are most widely used to obtain blanks:

casting;

pressure treatment of metals;

welding;

combinations of these methods.

Each of the above methods contains a large number of ways to obtain blanks.

As a method of obtaining a workpiece, we accept metal forming by pressure. The choice is justified by the fact that the material of the part is 40X structural steel. An additional factor determining the choice of a workpiece is the complexity of the configuration of the part and the type of production (we conditionally assume that the part is manufactured in mass production. We accept stamping on horizontal forging machines.

This type of stamping makes it possible to obtain workpieces with a minimum weight of 0.1 kg, 17-18 grades of accuracy with a roughness of 160-320 microns in small-scale production.

workpiece engineering route detail

2. Development of the part processing route

Part processing route:

Operation 005. Procurement. Stamping on CGSHP.

Preparatory shop.

Operation 010. Milling.

Drilling-milling-boring machine 2254VMF4.

1. Mill the plane, keeping dimension 7.

2. Drill 2 holes D 12.5.

3. Countersink hole D 26.1.

4. Countersink hole D32.

5. Countersink hole D35.6.

6. Ream hole D36.

7. Countersink the chamfer 0.5 x 45 0.

Operation 015. Turning.

Screw-cutting 16K20.

1. Cut the end, keeping the size 152.

2. Sharpen surface D37, maintaining size 116.

3. Sharpen 2 bevels 2 x 45 0.

4. Cut the thread M30x2.

Operation 020. Milling

Vertical milling 6P11.

1. Mill the surface keeping dimensions 20 and 94.

Operation 025. Vertical drilling.

Vertical drilling 2H125.

Set 1.

1. Drill 2 holes D9.

2. Drilled a hole D8.5.

3. Cut thread K1/8 / .

Set 2.

1. Drill hole D21.

2. Drill hole D29.

Operation 030 Locksmith.

Blunt sharp edges.

Operation 035. Technical control.

3. Choice technological equipment and tool

For the manufacture of the "Tip" part, we select the following machines

1. CNC drilling-milling-boring machine with tool magazine 2254VMF4;

2. Screw-cutting lathe 16K20;

3. Vertical milling machine 6P11;

4. Vertical drilling machine 2H125.

We use a 4-jaw chuck for turning operations, and special devices for other operations.

In the manufacture of this part, the following cutting tool is used:

Face milling cutter with mechanical fastening of multifaceted inserts: milling cutter 2214-0386 GOST 26595-85 Z = 8, D = 100 mm.

Twist drill with a tapered shank of normal accuracy, diameter D = 8.5 mm. with a normal shank, accuracy class B. Designation: 2301-0020 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 9 mm. with a normal shank, accuracy class B. Designation: 2301-0023 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 12.5 mm. with a normal shank, accuracy class B. Designation: 2301-0040 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 21 mm. with a normal shank, accuracy class B. Designation: 2301-0073 GOST 10903-77.

Twist drill with a tapered shank of normal accuracy, diameter D = 29 mm. with a normal shank, accuracy class B. Designation: 2301-0100 GOST 10903-77.

One-piece countersink with a conical shank made of high-speed steel, diameter D = 26 mm. 286 mm long for through hole machining. Designation: 2323-2596 GOST 12489-71.

One-piece countersink with a conical shank made of high-speed steel, diameter D = 32 mm. 334 mm long. for blind hole machining. Designation: 2323-0555 GOST 12489-71.

One-piece countersink with a tapered shank made of high-speed steel, diameter D = 35.6 mm. 334 mm long. for blind hole machining. Designation: 2323-0558 GOST 12489-71.

One-piece machine reamer with a tapered shank D36 mm. 325 mm long. Designation: 2363-3502 GOST 1672-82.

Conical countersink type 10, diameter D = 80 mm. with an angle at the top of 90. Designation: Countersink 2353-0126 GOST 14953-80.

Cutter right through thrust bent with an angle in the plan 90 o type 1, section 20 x 12. Designation: Cutter 2101-0565 GOST 18870-73.

Threaded turning tool with high speed steel blade for metric thread with step 3 type 1, section 20 x 12.

Designation: 2660-2503 2 GOST 18876-73.

Machine tap 2621-1509 GOST 3266-81.

To control the dimensions of this part, we use the following measuring tool:

Caliper ШЦ-I-125-0.1 GOST 166-89;

Caliper ШЦ-II-400-0.05 GOST 166-89.

To control the size of the hole D36, we use a plug gauge.

A set of roughness samples 0.2 - 0.8 ShTsV GOST 9378 - 93.

4. Determination of intermediate allowances, tolerances and dimensions

4.1 Tabular method on all surfaces

The necessary allowances and tolerances for the machined surfaces are selected according to GOST 1855-55.

Machining allowances for the part "Tip"

4.2 Analytical method per transition or per operation

Calculation of allowances by the analytical method is carried out for the surface Roughness Ra5.

The technological route of hole processing consists of countersinking, roughing and finishing reaming

The technological route of hole processing consists of countersinking and rough, finishing reaming.

Allowances are calculated according to the following formula:

(1)

where R is the height of the profile irregularities at the previous transition;

- depth of the defective layer at the previous transition;

- total deviations of the surface location (deviations from parallelism, perpendicularity, coaxiality, symmetry, intersection of axes, positional) at the previous transition;

- installation error on the performed transition.

The height of microroughness R and the depth of the defective layer for each transition are found in the table of the methodological manual.

The total value characterizing the quality of the surface of forged blanks is 800 µm. R= 100 µm; = 100 µm; R= 20 µm; = 20 µm;

The total value of spatial deviations of the axis of the hole being machined relative to the center axis is determined by the formula:

, (2)

where is the displacement of the treated surface relative to the surface used as a technological base for countersinking holes, microns

(3)

where is a size tolerance of 20 mm. = 1200 µm.

- dimensional tolerance 156.2 mm. = 1600 mm.

The amount of warping of the hole should be taken into account both in the diametrical and in the axial section.

, (4)

where is the value of specific warpage for forgings. = 0.7, and L is the diameter and length of the hole being machined. = 20 mm, L = 156.2 mm.

µm.

µm.

The value of the residual spatial deviation after countersinking:

P 2 \u003d 0.05 P \u003d 0.05 1006 \u003d 50 microns.

The value of the residual spatial deviation after rough development:

P 3 \u003d 0.04 P \u003d 0.005 1006 \u003d 4 microns.

The value of the residual spatial deviation after finishing reaming:

P 4 \u003d 0.002 P \u003d 0.002 1006 \u003d 2 microns.

When determining the installation error d U on the transition being performed, when determining the intermediate allowance, it is necessary to determine the fixing error (the basing error for bodies of revolution is zero). The error of fixing the workpiece when fixing it in a prismatic clamp: 150 microns.

Residual error for rough reaming:

0.05 150 = 7 µm.

Residual error for fine reaming:

0.04 150 = 6 µm.

We calculate the minimum values ​​of interoperational allowances: reaming.

µm.

Draft deployment:

µm.

Net Deployment:

µm.

The largest limit size for transitions is determined by successive subtraction from the drawing size of the minimum allowance of each technological transition.

The largest diameter of the part: d P4 = 36.25 mm.

For fine reaming: d P3 = 36.25 - 0.094 = 36.156 mm.

For draft deployment: d P2 = 35.156 - 0.501 = 35.655 mm.

For reaming:

d P1 = 35.655 - 3.63 = 32.025 mm.

The values ​​of the tolerances of each technological transition and workpiece are taken from the tables in accordance with the quality of the processing method used.

Quality after finishing deployment: ;

Quality after rough deployment: H12;

Quality after reaming: H14;

Workpiece quality: .

The smallest limit dimensions are determined by subtracting tolerances from the largest limit dimensions:

dMIN4 = 36.25 - 0.023 = 36.02 mm.

dMIN3 = 36.156 - 0.25 = 35.906 mm.

d MIN2 = 35.655 - 0.62 = 35.035 mm.

dMIN1 = 32.025 - 1.2 = 30.825 mm.

Maximum limit values ​​of allowances Z PR. MAX are equal to the difference of the smallest limit sizes. And the minimum values ​​of Z PR. MIN, respectively, the difference between the largest limit sizes of the previous and executed transitions.

Z PR. MIN3 = 35.655 - 32.025 = 3.63 mm.

Z PR. MIN2 = 36.156 - 35.655 = 0.501 mm.

Z PR. MIN1 = 36.25 - 36.156 = 0.094 mm.

Z PR. MAX3 = 35.035 - 30.825 = 4.21 mm.

Z PR. MAX2 = 35.906 - 35.035 = 0.871 mm.

Z PR. MAX1 = 36.02 - 35.906 = 0.114 mm.

General allowances Z O. MAX and Z O. MIN are determined by summing up the intermediate allowances.

Z O. MAX \u003d 4.21 + 0.871 + 0.114 \u003d 5, 195 mm.

Z O. MIN \u003d 3.63 + 0.501 + 0.094 \u003d 4.221 mm.

The obtained data is summarized in the resulting table.

Finally we get the dimensions:

Blanks: d ZAG. =;

After reaming: d 2 = 35.035 +0.62 mm.

After rough deployment: d 3 = 35.906 +0.25 mm.

After fine reaming: d 4 = mm.

The diameters of the cutting tools are shown in point 3.

5. Purpose of cutting conditions

5.1 Assignment of cutting conditions by the analytical method for one operation

010 Milling operation. Mill the plane, maintaining a size of 7 mm.

a) Depth of cut. When milling with a face mill, the depth of cut is determined in the direction parallel to the axis of the cutter and is equal to the machining allowance. t = 2.1 mm.

b) The milling width is determined in the direction perpendicular to the cutter axis. H = 68 mm.

c) submission. When milling, a distinction is made between feed per tooth, feed per revolution, and feed per minute.

(5)

where n is the rotational speed of the cutter, rpm;

z is the number of cutter teeth.

With machine power N = 6.3 kW S = 0.14.0.28 mm/tooth.

We accept S = 0.18 mm / tooth.

mm/rev.

c) Cutting speed.

(6)

Where T is the period of resistance. AT this case T = 180 min. - general correction factor

(7)

- coefficient taking into account the processed material.

nV (8) HB = 170; nV = 1.25 (1; p. 262; table 2)

1,25 =1,15

- coefficient taking into account the material of the tool; = 1

(1; p.263; tab.5)

- coefficient taking into account the state of the surface of the workpiece; = 0.8 (1; p. 263; table 6)

C V = 445; Q = 0.2; x = 0.15; y=0.35; u = 0.2; p=0; m = 0.32 (1; p.288; tab.39)

m/min.

d) Spindle speed.

n (9) n rpm

We correct according to the machine passport: n = 400 rpm.

mm/min.

e) Actual cutting speed

(10)

m/min.

e) District power.

(11)

n(12)

where n = 0.3 (1; p.264; tab.) 0.3 = 0.97

With P=54.5; X = 0.9; Y = 0.74; U=1; Q=1; w = 0.

5.2 Tabular method for other operations

The assignment of cutting modes by the tabular method is carried out according to the reference book of metal cutting modes. The resulting data is entered into the resulting table.

Cutting conditions for all surfaces.

6. The layout of the machine tool for one of the machining operations

We design a machine fixture for vertical drilling and vertical milling machines.

The device is a plate (pos. 1.) on which 2 prisms (pos. 10) are mounted using pins (pos. 8) and screws (pos. 7). On the side of one of the prisms there is a stop (pos.3) with a finger located in it, which serves to base the workpiece. The clamping of the part is provided by the bar (pos. 3), which rotates freely around the screw (pos. 5) with one edge, and the screw enters its other edge, which has the shape of a slot, followed by clamping with a nut (pos. 12).

To fix the fixture on the machine table, 2 dowels (pos.13) are made and mounted in the body of the plate, which serve to center the fixture. Transportation is carried out manually.

7. Calculation of the fixture for the accuracy of machining

When calculating the accuracy of the fixture, it is necessary to determine the permissible error e pr, for which we determine all the components of the error. (we take D29 +0 .2 8 as the coordinating dimension)

In the general case, the error is determined by the formula:

where is the tolerance for the coordinating dimension. In this case, T = 0.28 mm;

- coefficient of accuracy, taking into account the possible deviation of the dispersion of the values ​​of the constituent quantities from the law of normal distribution (= 1.0 ... 1.2 depending on the number of significant terms, the more there are, the lower the coefficient), we accept;

- coefficient taking into account the share of processing error in the total error caused by factors independent of the fixture: = 0.3 ... 0.5; accept = 0.3;

The remaining values ​​of the formula are a set of errors defined below.

1. Basing error b occurs when the measurement and technological bases do not match. When machining a hole, the locating error is zero.

2. The error in fixing the workpiece e s occurs as a result of the action of the clamping forces. Fixing error when using manual screw clamps is 25 µm.

3. The error of installing the fixture on the machine depends on the gaps between the connecting elements of the fixture and the machine, as well as on the inaccuracy in the manufacture of the connecting elements. It is equal to the gap between the T-slot of the table and the setting element. In the fixture used, the size of the groove width is 18H7 mm. The size of the dowel is 18h6. Limit deviations of dimensions and. The maximum gap and, accordingly, the maximum error in installing the fixture on the machine = 0.029 mm.

4. Wear error - an error caused by wear of the setting elements of fixtures, characterizing the deviation of the workpiece from the required position due to wear of the setting elements in the direction of the dimensions being performed.

Approximate wear of the installation elements can be determined by the following formula:

where U 0 - average wear of the setting elements for cast iron blanks with clamping force W = 10 kN and basic number of installations N = 100000;

k 1 , k 2 , k 3 , k 4 - coefficients that take into account, respectively, the effect on wear of the workpiece material, equipment, processing conditions and the number of workpiece installations, which differ from those adopted in determining U 0 .

When mounted on smooth base plates U 0 = 40 µm.

k 1 = 0.95 (steel not hardened); k 2 = 1.25 (special); k 3 = 0.95 (blade cutting of steel with cooling); k 4 = 1.3 (up to 40,000 installations)

µm.

5. Geometric error of the machine e st after finishing is 10 µm.

6. Machine setting error for size e n. st depends on the type of processing and the size to be maintained. In this case e n. st =10 µm.

We determine the error of the device:

µm.

The total error in processing the workpiece according to the coordinating size using the fixture should not exceed the tolerance value T on it indicated in the drawing. The given condition looks like:

where are the static errors associated with the fixture, as well as errors that explicitly affect the accuracy of the fixture.

- errors, dependent on the technological process and in an explicit form do not affect the accuracy of manufacturing fixtures.

The error values ​​of the first group are found above.

The total machining error, independent of the fixture, is defined as part of the tolerance for the coordinating dimension:

micron

µm.

µm. - The condition is met.

Literature

1. Handbook of mechanical engineering technologist; - M .: "Engineering" edited by A.G. Kosilova, R.K. Meshcheryakov; 2 volumes; 2003

2. N.A. Nefedov, K.A. Osipov; Collection of tasks and examples on cutting metals and cutting tools; - M.: "Engineering"; 1990

3. B.A. Kuzmin, Yu.E. Abramenko, M.A. Kudryavtsev, V.N. Evseev, V.N. Kuzmintsev; Technology of metals and construction materials; - M.: "Engineering"; 2003

4. A.F. Gorbatsevich, V.A. Shkred; Course design on engineering technology; - M.: "Engineering"; 1995

5. V.D. Myagkov; Tolerances and landings. Directory; - M.: "Engineering"; 2002

6. V.I. Yakovlev; General machine-building standards for cutting conditions; 2nd edition; - M.: "Engineering"; 2000

7. V.M. Vinogradov; Engineering technology: introduction to the specialty; - M.: "Academy"; 2006;

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Department of technology and organization of machine-building production

Discipline

"Technological foundations of mechanical engineering" (TOM)

Lecture notes

E.P. Vyskrebentsev

For students of the specialty "Metallurgical equipment"

3rd day course

4th course distance learning

Main

1. Kovshov A.N. Mechanical engineering technology: a textbook for universities. - M .: Mashinostroenie, 1987

Additional.

2. Gorbatsevich A.F., Shkred V.A. Course design for engineering technology. - Minsk: Higher school, 1985.

3. Vorobyov A.N. Engineering technology and machine repair: Textbook. - M .: Higher School, 1981.

4. Korsakov V.S. Engineering technology. - M .: Mashinostroeniya, 1987.

5. Reference technologist-machine builder: in 2 books. under. ed. Kosilova A. G, - 3rd ed. - M .: Mashinostroenie, 1985.

6. Balabanov A.N. A brief guide to the technologist-machine builder. – M.:

Ed. standard. 1992.

INTRODUCTION 5

1 TYPES OF PRODUCTION, FORMS OF ORGANIZATION AND TYPES

TECHNOLOGICAL PROCESSES 6

1.1 Types of production 6

1.2 Types of technological processes 9

1.3 The structure of the technological process and its main

features 11

1.3.1 Process characteristics 15

1.4 The complexity of the technological operation 16

1.5 Basic principles process design 21

2 PRECISION MACHINING 23

2.1 Accuracy and its determining factors 23

3 BASIC BASES AND WORKING BASES 27

3.1 Fixing error ε z, 36

3.2 The error in the position of the workpiece ε pr, caused by

fixture inaccuracy 37

3.3 Positioning the workpiece in fixture 38

4 SURFACE QUALITY OF MACHINE PARTS AND

BLANKS 41

4.1 Influence of technological factors on the value

roughness 41

4.2 Methods for measuring and evaluating surface quality 46

5 PREPARING MACHINE PARTS 49

5.1 Selection of the initial workpiece and methods of its manufacture 49

5.2 Determination of machining allowances 51

6 MAIN STAGES OF DESIGNING TECHNOLOGICAL

MACHINING PROCESSES 60

6.1 General provisions development of technological

processes 60

6.2 Selection of process equipment 63

6.3. Tooling selection 64

6.4. Choice of controls 65

6.5. Forms of organization of technological processes and their

development 65

6.6. Development of batch processes 67

6.7. Development of standard technological processes 70

7 TECHNOLOGY OF MANUFACTURING STANDARD PARTS 72

7.1 Shaft technology 72

7.2 Technology for the production of body parts 82

7.2.1 Technological route for processing workpieces

buildings 84

7.3 Cylinder technology 92

7.4 Machining gears 94

7.4.1 Design features and technical requirements to the tooth

Chat wheels 94

7.4.2 Machining gear blanks with a central hole. 95

7.4.3 Gear cutting 97

7.4.4 Production of large gears 100

7.4.5 Machining workpieces before cutting teeth 101

7.5 Lever technology 102

8. TECHNOLOGICAL ASSEMBLY PROCESSES 111

INTRODUCTION

Engineering technology is a science that studies the patterns of machine manufacturing processes in order to use these patterns to ensure the production of machines of a given quality, in the quantity established by the production program and at the lowest national economic costs.

Mechanical engineering technology developed with the development of large-scale industry, accumulating appropriate methods and techniques for the manufacture of machines. In the past, mechanical engineering technology has received greatest development in weapons workshops and factories where weapons were made in large quantities.

Yes, in Tula arms factory back in 1761, for the first time in the world, the manufacture of interchangeable parts and their control with the help of calibers was developed and introduced.

Mechanical engineering technology was created by the works of Russian scientists: A.P. Sokolovsky, B.S. Balakshina, V.M. Kovana, B.C. Korsakov and others

Mechanical engineering technology includes the following areas of production: casting technology; pressure treatment technology; welding technology; machining technology; machine assembly technology, i.e., machine building technology covers all stages of the process of manufacturing machine-building products.

However, mechanical engineering technology is usually understood as a scientific discipline that studies mainly the processes of machining blanks and assembly of machines, as well as the methods of their manufacture that affect the selection of blanks. This is due to the fact that in mechanical engineering, the specified forms of parts with the required accuracy and quality of their surfaces are achieved mainly by mechanical processing. The complexity of the machining process and the physical nature of the phenomena occurring in this process is caused by the difficulty of studying the entire complex of issues within one technological discipline and led to the formation of several such disciplines: metal cutting; cutting tools; metal cutting machines; fixture design; design of machine-building shops and factories; interchangeability, standardization and technical measurements; technology construction materials; automation and mechanization of technological processes, etc.

1 TYPES OF PRODUCTION, FORMS OF ORGANIZATION AND TYPES

TECHNOLOGICAL PROCESSES

1.1 Types of production

Type of production- the classification category of production, allocated on the basis of the breadth of the range, regularity, stability and output of products.

The volume of output of products - the number of products of a certain name, size and design, manufactured or repaired by the association, enterprise or its division during the planned time interval.

Implement the following types of production: single; serial; mass. One of the main characteristics of the type of production is the coefficient of consolidation of operations. The transaction consolidation ratio is the ratio of the number of all different technological operations completed or to be completed within a month, to the number of jobs.

Single production - production, characterized by a wide range of manufactured or repaired products and a small output of products.

AT single production products are made in single copies, various in design or size, and the repeatability of these products is rare or completely absent (turbine construction, shipbuilding). In this type of production, as a rule, universal equipment, fixtures and measuring tools are used, the workers are highly qualified, the assembly is carried out using locksmith work, i.e. on site, etc. The machines are located on the basis of uniformity of processing, i.e. - sections of machine tools are created designed for one type of processing - turning, planing, milling, etc.

Transaction consolidation ratio > 40.

Mass production - production, characterized by a limited range of products manufactured or repaired by periodically repeating production batches.

Depending on the number of products in a batch or series and the value of the coefficient of consolidation of operations, small-scale, medium-scale and large-scale production is distinguished.

The coefficient of consolidation of transactions in accordance with the standard is taken equal to:

a) for small-scale production - over 20 to 40 inclusive;

b) for medium-scale production - over 10 to 20 inclusive;

c) for large-scale production - over 1 to 10 inclusive.

The main features of serial production: machines are used in various types: universal, specialized, special, automated; personnel of various qualifications;

work can be done on customized machines; both markings and special devices are used; no-fit assembly, etc.

The equipment is located in accordance with the subject form of work organization.

Machines are arranged in a sequence of technological operations for one or more parts that require the same order of operations. In the same sequence, obviously, the movement of parts (the so-called subject-closed sections) is also formed. Processing of blanks is carried out in batches. At the same time, the time for performing operations on individual machines may not be consistent with the time for operations on other machines.

Manufactured parts are stored during operation at the machines and then transported as a whole batch.

Mass production - production, characterized by a narrow nomenclature and a large volume of output of products that are continuously manufactured or repaired for a long time.

The coefficient of consolidation of operations for mass production is taken equal to one.

Depending on the size of the production program, the nature of the product, and the technical and economic conditions implementation production process There are three main types of production: single, serial, mass.

It should be noted that in the same enterprise and even in the same workshop, there may be different types of production. For example, in heavy engineering, which has the nature of a single production, small parts that are required in large quantities can be manufactured according to the principle of serial or even mass production.

Solitary (individual) This is a production in which products are made in single copies, various in design or size, and the repetition of these products is rare or completely absent.

Single production is universal, i.e. covers various types of products, and therefore, must be flexible, quickly - reconfigurable.

The technological process of manufacturing parts in this type of production has a "compacted" character: several operations are performed on one machine and often complete processing of workpieces of various designs and from various materials is performed.

For a single production, the following features are characteristic:

equipment is placed according to the types of machines;

universal equipment is used;

service personnel of high qualification;

long processing time;

high processing cost;

poor performance;

high processing precision.

Serial production is called in which the release of products is carried out in batches or series, consisting of products of the same name, of the same type in design and of the same size, launched into production at the same time. The basic principle of this type of production is the production of the entire batch as a whole, both in the processing of parts and in assembly.

In serial production, products are produced in repeating series according to unchanged drawings. Depending on the number of products produced and their repeatability during the year, production can be small-, medium- or large-scale. In terms of organization, small-scale production is approaching a single one, and large-scale production is approaching mass production.

Attribution of serial production to one or another type is carried out on the basis of the coefficient of consolidation of operations - the ratio of the number of all technological operations performed or to be performed within a month to the number of jobs. For small-scale production, the values ​​of this coefficient are in the range of 20 ... 40, for serial production - 10 ... 20, for large-scale production - I ... 10 inclusive.

In mass production technological process differentiated. Individual operations are assigned to certain machines. Universal, specialized, special, automated, modular machines are used. After the production of one series of parts is completed, the machines at this production site are readjusted for the manufacture of another series of parts.

Serial production is much more economical than a single one, since the equipment is better used, the specialization of workers is higher, and the cost of production is lower.

mass production is called, in which, with a sufficiently large number of identical product releases, manufacturing is carried out by continuously performing the same constantly repeating operations at the workplace.

Mass production is characterized by the following main features:

most workpiece processing operations are assigned to individual machines;

on the processing line, there is a continuous movement of workpieces from one workplace to another;

equipment specialized or special;

low labor intensity and processing cost;

short technological cycle.

The coefficient of consolidation of operations in this type of production is taken equal to one. Mass production allows you to make significant costs for equipment, since the latter is easily paid off.

In mass production, it is possible to use the most high-performance equipment and technological equipment. Mass production can be organized according to in-line and non-in-line methods. The equipment in this case is installed in the form of continuous automatic or automated lines.

The highest form of mass production is continuous flow production, characterized by the fact that the execution time of each operation is equal to or a multiple of the time for the entire flow, which allows processing without backlogs with a certain release cycle, which is calculated by the formula

where P is the fund of time (per year, shift, etc.), min; N - product release assembly units for the corresponding period of time, pcs.

On operations, the duration of which does not fit into a certain cycle of release, the optional equipment. With a continuous flow, the transfer of the workpiece from position to position is carried out continuously in a forced manner, which ensures the parallel simultaneous execution of all operations on the production line.

Mechanical engineering is the leading industry of any developed and developing country. As in any other industry, mechanical engineering has its own tasks and goals, and, accordingly, the methods by which they are achieved, and it does not matter whether it is a processing process or research.

Accuracy and methods for achieving it

Definition 1

Accuracy is the conformity of the manufactured product to the given sample.

The part produced with the help of mechanical and machine processing should correspond to the given drawings as much as possible and specifications manufacturing.

Methods for achieving accuracy when processing a part on a metal-cutting machine:

1. Machining a part according to the markup, or using test passes, as close as possible to the specified shape and size. After each pass, the equipment takes measurements to decide which pass to make in the next step. In this case, the accuracy of the work performed depends on the qualifications of the worker.
2. The method of automatically obtaining dimensions, setting the equipment to right size. The product is processed in a fixed position, in which case the manufacturing accuracy depends on the equipment adjuster.
3. Automatic processing on machine tools with program control and on copy machines, in which the accuracy depends on the accuracy of the control.

Remark 1

However, it is worth noting that no matter how accurately the machine is set up, some parts will still differ from each other, this is called an error.

Reasons for errors:

• The inaccuracy of the machine itself, which may indicate an inaccuracy in the assembly or inaccuracy of the parts from which the machine is assembled
• Workpiece installation errors
• Cutting machine wear
• Elastic and thermal deformations in the system
• Residual deformations in the workpiece

Methods for manufacturing engineering parts

Mechanical engineering is engaged in the production of parts of different sizes, specific gravity, difficulties. Some parts are made of light and brittle metals, while others, on the contrary, are made of heavy and not malleable. And for each type of raw material and product there is a manufacturing method.

The main methods for manufacturing parts:

1. Casting. Parts are made by pouring liquid raw materials (cast iron, steel, non-ferrous and ferrous metals) into molds.
2. Forging and stamping. Plastic materials are used (except cast iron). Stamping is the deformation of the workpiece in the tool cavity. Forging is a free deformation in the longitudinal and transverse direction of the workpiece.
3. Rental. More than 90% of manufactured parts pass through rolled products (rails, wire, sheets, pipes, etc.) in production. rental is divided into hot and cold. Cold rolling is used for more accurate dimensions.
4. Stretching and drawing. This processing improves the mechanical properties of the product, the blanks are pulled through a special tool, which exposes it to at least 30% deformation. In addition, the surface of the product becomes light and frequent.
5. Welding. This process can be quite different: gas welding, chemical, electric welding, etc.
6. Soldering. With this type of connection, the connecting metals do not melt, since the temperature does not reach the melting point.
7. Heat treatment.
8. Mechanical restoration.

Measurement methods in mechanical engineering

In the production of parts, direct and indirect methods measurements.

With direct measurements, the size is determined by the indicators of the device itself.

With indirect measurements, the size is determined by the results of direct measurements of one or more quantities associated with a certain relationship. For example, measuring angles using the legs and hypotenuse.

Measurements can be carried out by absolute and relative methods.

Again, in absolute measurement, all readings are obtained from the data of the device. Whereas with a relative measurement, only deviations from the established ones can be measured. When using this method, the devices require additional adjustment to a given measure, which leads to extra time. However, this can be applied in mass production, where more precise execution of the part is ensured.

There are also complex and differentiated measurement methods.

The complex method is a comparison of the existing body of the manufactured part with its limiting contours, determined by the values ​​and location of the tolerance fields. An example of such a measurement is the control of gear wheels on an intercentrometer.

The differentiated method is to check each detail separately. However, this method does not guarantee the interchangeability of parts. This method It is used as a rule when checking tools, as well as identifying the reasons why the dimensions of a part go beyond the error.

Statistical methods in mechanical engineering

Remark 2

Often these methods are called statistical methods quality management is aids based on the conclusions and provisions of the theory of probability and mathematical statistics, which help to make decisions related to the quality of the functioning of technological processes.

These are process diagnostic tools, and the assessment of quality deviations. It should be noted that in all industries where static methods were introduced, there have been significant improvements in the quality of production work.

The used method of static analysis and defect prevention allows, based on mathematical statistics and accumulated data on errors previously detected in production, to create a new sustainable process for assembling and processing parts.

First, it is required to collect all the data on errors and compare them, draw up a monthly return schedule to eliminate errors, if the number of errors exceeds a critical number, then this means that the normative process of the technology is violated and the intervention of technical personnel is required.

Type of production- a classification category, allocated on the basis of the breadth of the range, regularity, stability and volume of manufactured products. Depending on the needs of a person, institution, industry or state, products are produced by enterprises in various quantities. Accordingly, production is conditionally divided into single, serial or mass production.

The assignment of an enterprise (factory) or workshop to one or another type of production is called conditional because the simultaneous existence of different types is possible, i.e. individual products or parts can be manufactured in accordance with different principles: some - in a single order, others - serial or some - mass, others - serial, etc. Thus, at heavy engineering enterprises, characterized by a single production of complex large-sized products (for example, walking excavators), small unified or standardized parts required for them in large quantities can be manufactured according to the principle of serial and even mass production.

Single (individual) production is understood as the production of single copies of products according to unchanged drawings, which is not repeated or rarely repeated, after an indefinite time.

Distinctive features of a single type of production are: myogonomenclature of manufactured products; lack of permanent assignment of certain products to workplaces; use of universal equipment, fixtures and tools; placement of equipment in groups of the same type; the presence of highly skilled workers-universals; a large amount of manual operations; high duration of the production cycle, etc. It includes the production of experimental or unique samples of engineering products, any non-standard equipment.

Under serial production is understood as the manufacture of products according to unchanged drawings in periodically repeating batches for a certain period of time.

Depending on the number of products in the batch, it is divided into: small-scale, serial and large-scale. Such a division is rather conditional. For the same number of items in a batch, different sizes and complexity, production can be attributed to different types. For example, the production of 25 tunneling machines for the development of potash ore deposits can be attributed to medium-scale production, 25 Ruslan heavy transport aircraft - to large-scale production, and 25 small-sized lathes - to small-scale production. Approximate serial production is determined by the table. 1.1.

Table 1.1

serial production

Mass-produced products are products produced in significant quantities: metal-cutting machines, pumps, compressors, etc. In this case, high-performance universal and specialized equipment is used; specialization of jobs to perform several fixed operations; universal, reconfigurable high-speed devices; universal and special tool. CNC machines, multi-purpose machines and flexible reconfigurable systems (FMS) are widely used. Serial production is also characterized by a small amount of manual operations, the presence of semi-skilled workers, an insignificant duration of the production cycle, etc.

Under massive Manufacturing refers to the production of products according to fixed drawings in large quantities and over a long period of time.

Mass-produced products are products of a narrow range and standard type, such as cars, bicycles, electric motors, sewing and washing machines, bearings, etc. In most workplaces, only one fixed, constantly recurring operation is performed. Mass production is characterized by the following features: a limited range of products; subject specialization of jobs; location of equipment in the sequence of operations; the use of high-performance automated and robotic equipment, special devices and tool; widespread use of transport devices for transferring blanks along production line; mechanization and automation of technical control; the presence of low-skilled workers; the minimum duration of the production cycle, etc.

The type of production is determined by the coefficient of consolidation of operations To z.o

where Q- the number of operations performed or to be performed during the planning period equal to one month; P is the number of workers performing various operations.

The coefficient of consolidation of operations is one of the main characteristics of the type of production (GOST 3.1121–84). The value for mass production is To z.o = 1, for large-scale – 1–10, for serial – 10–20. For single production To z.o. may be more than 40.

In mechanical engineering, two forms of production are distinguished: non-flow and flow.

non-streaming called production, in which its objects in the manufacturing process are in motion with different durations of operations and breaks between them. This form is typical for a single production.

In-line production is called production, in which operations are assigned to certain jobs, located in the order they are performed, and the production object is transferred from one job to another with a certain tact.

This is the most perfect form of organization of mass production from the point of view of minimizing costs. According to this principle, automatic processing and assembly lines are built. Peculiarity automatic production- performance of operations without the direct participation of the worker or under his supervision and control. In-line production can also be non-automatic if the installation of blanks and their removal after processing is performed by a worker.

For organization mass production the same or multiple performance is required for all operations. On the line, processed blanks or assembled units are released at a strictly defined time interval, called the release cycle.

Release stroke(min/pcs) – time interval T c between the release of two products or blanks of certain names, following one after another,

where Fd is the actual fund of time in the planned period (month, day, shift), h; N- production program for the same period (number of products, pcs.).

Cycle- the interval of calendar time from the beginning to the end of the execution of any repetitive technological or production process, regardless of the number of simultaneously manufactured products.

A distinction is made between the manufacturing cycle of the product as a whole, individual assembly units and parts, and the performance of individual operations.

Each production has a certain production capacity , which is understood as the maximum possible release products of the established nomenclature and quantity, which can be carried out for a certain period of time under the established mode of operation.