Sedov Alexander Sergeevich ,

master student of the mechanical engineering faculty of the Volgograd State Technical University .

Application of automation systems design work(CAD) significantly reduces the complexity of design and process design, and also allows you to create a database of ready-made design solutions for their subsequent modification and use.

The task was to create a CAD dimensional analysis of the axial dimensions of parts of the "stepped shaft" type. At the same time, the input of initial data and the output of calculated data should be carried out in an interactive mode, which is most rationally carried out using built-in software. operating system, equipped with a graphical user interface (for example, Windows XP).

Modern programming tools allow you to create advanced CAD systems with a high degree of interactivity. The use of visual and object-oriented programming, which are standard for these programming tools, reduces the time for developing a program project and contributes to streamlining its logical-hierarchical structure.

The program "Size32" presented in this article was created in a free programming environment Lazarus (Object Pascal language ) - analogue of a commercially distributed environment Delphi , and was originally compiled to run on the architecture i 386 running 32-bit OS Windows XP / Vista /7. Cross platform compiler Free Pascal allows you to get executable code, including for free operating systems based on the kernel linux , which is important if the task is to reduce the costs associated with the introduction of CAD. The text of the program has 1542 lines, in the compiled under Win 32 form the program takes 13 megabytes.

The structure of the program is a set of 3 connected linear algorithmic systems:

- initial data entry system;

- data processing system;

Video surveillance kits for a private house

- calculation information output system.

Input data includes:

- workpiece geometry (number of shaft steps, their relative diameters);

- axial dimensions of the workpiece (deviations);

- axial dimensions of the part (values ​​with deviations);

- name of operations;

- sequence of operating sizes on each operation.

The main structural element of the program data area is a record of type TRazm.

TRazm = record

BS : byte ;//dimension is plotted from this surface

FS : byte ;//to this surface

Nom : real ;// face value, mm

ei: real ;//lower deviation, mm

es: real ;//upper deviation, mm

end;

The program has an array Razm [ j , i ] of N _ OP _ MAX * N _ RAZ _ MAX records of type TRazm (where N _ OP _ MAX - maximum number of operations (10), N_RAZ_MAX - the maximum number of dimensions in the operation (5).At the stage of entering the initial data, the array is filled Razm [ j , i ], where j - transaction number i - serial number of the size.

Fragment describing reading data from fields:

//intermediate entry from size fields

Razm2.BS:= StrToInt(Razm_Inp.Caption);

Razm2.FS:= StrToInt(Razm_Inp.Caption);

Razm2.Nom:= StrToFloat(Razm_Inp.Caption);

Razm2.ei:= StrToFloat(Razm_Inp.Caption);

Razm2.es:= StrToFloat(Razm_Inp.Caption);

index:= GetRazmIndex(Razm2.BS, Razm2.FS);

Here the data is read into the intermediate record Razm 2, which is then copied into an array element Razm[j, i]. GetRazmIndex function returns the ordinal number of the size if the contents of the input fields indicate an existing size or 0 if the size does not exist.

The following snippet shows the entry in Razm[j, i].

// enter data

with Razm do

begin

BS:= Razm2.BS;

FS:= Razm2.FS;

Nom:= Razm2.Nom;

ei:= Razm2.ei;

es :=Razm2.es;

end;

(Here CurrentOp is the number of the transaction in question.)

Data can be entered manually by creating a new technological process, and can also be read from disk. The native file extension of the program is *. tpd .

A fragment of the algorithm for reading data from a file.

AssignFile( F, OpenDialog.FileName);// assign file name

Reset(F);//open file for reading

Read(F, FB);//read file content

CloseFile(F);//close file

N_St : = FB.N_St;//number of steps

D_St : = FB.D_St;//step diameters

countop : = FB.CountOp;//number of operations

Opnames : = FB.OpNames;//names of operations

Razm := FB.Razm;//size records

RazmOpCount : = FB.RazmOpCount;//number of sizes in each operation

FB here – an intermediate record of the same type with F.

Writing to disk is done in a similar way, but instead of Reset (F ) is called by Rewrite (F ).

Dimensional analysis of the process is carried out as follows.

1. A list of all dimensions from the workpiece to the finished part is compiled (taking into account the surfaces that occur during processing) (1).

2. A list of closing dimensions is compiled.

3. The first closing dimension is selected, and for the given dimension, a recursive traversal of the list of dimensions (1) is performed, counting the number of links and their type (increasing, decreasing). If the bypass reaches a "dead end", it starts along a new path. As a result, for a given closing size, a dimensional chain with a minimum number of links is selected.

4. Move to the next closing dimension, and so on.

5. Analysis of dimensional chains by known methods.

Literature

1. Korsakov, V. S. Automation of the design of technological processes in mechanical engineering / V. S. Korsakov, N. M. Kapustin, K. -X. Tempelhof, X, Lichtenberg; Under total r units N.M. Kapustin. - M.: Mashinostroenie, 1985. - 304 p.

2. Klimov, V. E. CAD development: In 10 books. Book. 7. Graphic CAD systems: Prakt. allowance / V. E. Klimov; Ed. V. A. Petrova. - M.: Higher. school, 1990. - 142 p.ISBN 5-06-000744-8.

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

NATIONAL NUCLEAR RESEARCH UNIVERSITY MEPhI

NOVOURAL TECHNOLOGICAL INSTITUTE

V. N. Ashikhmin

DIMENSIONAL ANALYSIS OF TECHNOLOGICAL PROCESSES

Moscow 2010

UDC 621.0 + 621.91 LBC 34.5

Ashikhmin VN DIMENSIONAL ANALYSIS OF TECHNOLOGICAL PROCESSES: Workshop. M.: NRNU MEPhI, 2010. - 60 p.

The manual contains guidelines and recommendations for implementation practical work on the course "Dimensional analysis and justification technological solutions”and is intended for students of the specialty 151001 - Engineering Technology (full-time, part-time, part-time forms of education). Work 1 is also used when performing practical exercises on the course "Mechanical Engineering Technology".

Prepared within the framework of the NRNU MEPhI Creation and Development Program.

Reviewer tech. Sciences, Associate Professor V. I. Zanko

Foreword …………………………………………………………….4

FOREWORD

The quality of products in mechanical engineering is determined primarily by the quality of the development of technological processes. For the qualitative development of technological processes when using equipment tuned to the size, it is necessary to carry out a dimensional accuracy analysis.

AT during the dimensional analysis, all dimensional and accuracy relationships in the technological process, ranging from the dimensions of the original workpiece to the dimensions of the finished part. It is this approach that is considered in the proposed manual. The relevance of this manual is due to the fact that in recent years in the domestic technical literature there are practically no books published on the dimensional analysis of technological processes.

When solving problems of dimensional analysis, a technique based on the application of graph theory was used. This is the most effective mathematical apparatus for modeling the dimensional-accuracy relationships of technological processes. The use of this apparatus contributes to the development of mathematical modeling skills in a specialist - technologist.

AT unlike traditional methods, in which the identification of dimensional chains is carried out on a combined graph, which is associated with certain difficulties, the manual uses an improved technique for applying graph models in the dimensional analysis of technological processes.

Considering the importance of dimensional analysis in the process of training technologists in a number of universities in curricula technological departments provide relevant disciplines. So, for example, at the Departments of Mechanical Engineering Technology of USTU - UPI and NGTI, the course "Dimensional analysis and justification of technological solutions" is taught. The proposed work is based on many years of experience in studying this discipline at USTU - UPI. The manual can be used during practical exercises within the framework of the courses "Fundamentals of Mechanical Engineering Technology" and "Mechanical Engineering Technology".

Practical work No. 11

PROBLEMS OF DIMENSIONAL ANALYSIS OF TECHNOLOGICAL PROCESSES. DEVELOPMENT OF THE STARTING STRUCTURE OF THE TECHNOLOGICAL PROCESS, ASSIGNMENT OF STAGES, METHODS AND PLANS OF SURFACE TREATMENT

The purpose of the work is to clarify the need and general provisions carrying out dimensional analysis, mastering the skills of developing the starting structure of the technological process as the initial stage of solving the direct (project) problem of dimensional analysis.

The task is to develop the starting structure of the technological process for a part of the bushing class based on the drawing of the part and the conditions of medium-scale production using the method of bottom-up synthesis (bottom-up).

The work is scheduled for 8-12 hours.

Problems of dimensional analysis and methods for calculating dimensional chains

Dimensional analysis of a technological process is the identification and fixation of dimensional relationships between transitions and operations of a particular technological process. Thus, to solve a design problem, when there is only a drawing of a part, it is necessary to develop an initial, starting version of the technological process.

The purpose of dimensional analysis is, first of all, to ensure the accuracy of the dimensional relationships of the surfaces of the part indicated in the drawing. Dimensional analysis reveals the most efficient structure technological process that guarantees the achievement of the goal. As a result of dimensional analysis

1 Work No. 1 is carried out in parallel at the practical classes in the course "Technology of Mechanical Engineering" and in the course "Dimensional Analysis and Justification of Technological Solutions".

technological operations and transitions are formed in the most rational way, the adopted basing schemes are checked and refined, all operational dimensions and dimensions of the original workpiece are determined. In addition, dimensional analysis makes it possible to identify and eliminate unacceptable fluctuations in the allowance, which is especially important in finishing operations.

The type of task is determined by what is specified and what needs to be defined. If a new technological process is being developed, then the design dimensions of the part are known and, therefore, given. Consequently, in a number of technological dimensional chains, the design dimension with all its parameters is known. This size will be the closing (initial) link in such dimensional chains.

If we analyze the existing technological process, then all technological (operational) dimensions and their parameters are known. These dimensions are the constituent links of dimensional chains. Thus, in chains where the closing link is the design size, we will be able to determine the parameters of the closing link that will be provided in the considered technological process.

In the theory of dimensional chains, these problems are called, respectively, direct (design) and inverse (verification).

With a direct problem, the nominal size, tolerance, limit deviations of the closing (initial) link are given, and it is required to determine the nominal values, tolerances and limit deviations of all components of the links of the dimensional chain.

When solving the inverse problem for the given nominal values, tolerances, limit deviations of the constituent links, it is required to determine the same characteristics of the closing link or the stray field and the limiting values ​​of the closing link.

The most common are two methods for calculating dimensional chains: the maximum-minimum method (max-min) and the probabilistic method.

The first method is sometimes called the complete interchangeability method, and the second the incomplete interchangeability method. According to many authors, the maximum-minimum method should be used to calculate technological dimensional chains. it

It is also substantiated by the fact that the number of constituent links in technological dimensional chains usually does not exceed 4–5.

This manual considers the solution of a design (direct) problem, when the technological process does not yet exist, and the source document is only a drawing of the part. In addition to the detail drawing, it is known work environment, in which the technological process will be implemented, or the type of production.

The starting version of the technological process is formed on the basis of the developed structure of the technological process. It initially assigns only the values ​​of tolerances for technological dimensions and minimum allowances removed when performing technological transitions. Thus, in contrast to the verification task, here it is necessary to determine the nominal dimensions and maximum deviations of operational dimensions for all technological transitions. Problems of this type are called mixed by some authors.

Methodological instructions for the performance of work

During practical classes, each student works on an individual assignment. On fig. 1.1 shows a sketch of a part of the "sleeve" type, in relation to which the implementation of all stages of the task is shown.

1. Analysis of the drawing of a given part, selection and determination of the parameters of the original workpiece. A part is specified - a bushing (see Fig. 1.1). Material - steel 30. Part weight - 2.49 kg. Medium production. Provides for the use of versatile equipment, includingturret lathemachine tool with a vertical turret axis.

The concentricity of surfaces 4 and 6 will be provided according to the "FROM THE HOLE" scheme. Hole 4 is finally processed on a turning-turret operation with a measuring tool - a reamer. The end surfaces 1 , 5 , 7 , as well as the radial hole 3 are connected by linear dimensions. The outer cylindrical surface 2 does not require precise machining. Surface 6 is machined in a cylindrical grinding operation based on hole 4 .

Ra6.3()

Ra 3.2

Rice. 1.1. Sketch of the “sleeve” part (unspecified limit deviations of dimensions: H 14; h 14; IT 14/2; position numbers correspond to the types of surfaces to be machined)

The numbering of the surfaces of the part, connected by linear dimensions parallel to the axis of the part, must be carried out according to strictly defined rules:

- surface numbers increase along the accepted axis of the part;

- chamfers are not numbered;

- only odd numbers are accepted for numbering;

- the scheme of design dimensional relationships (Fig. 1.2) is drawn to scale.

Rice. 1.2. Scheme of design dimensional relationships

2. The choice of the type of the original workpiece and the method of its production.

Factors determining the choice of workpiece:

- part material - steel 30 (quality carbon steel, carbon content 0.3%);

- part configuration - bushing with collar and through hole;

- type of production - medium-scale. It is more rational for this type of production to choose a workpiece, the shape of which is as close as possible to the shape of the finished part (Fig. 1.3). This will minimize cutting and waste into chips.

Plane

Rice. 1.3. Sketch of the original workpiece

We choose the method of hot forging in open dies. With a ratio of dimensions D max > L, stamping is performed on hammers or crank hot stamping presses. Through holes in the original blanks are made provided that their diameter is not less than 30 mm. In addition, the length of the hole should not exceed the diameter of the hole being punched. If the latter condition is not met, then a basting (deepening) with a depth of up to 0.8 of the hole diameter can be performed in the manufacture of the workpiece on hammers and presses. If D max< L , то для деталей типа втулок рациональнее выбрать горячую объемную штамповку на горизонтально-ковочных машинах (ГКМ). Предельная длина получаемого отверстия при штамповке на ГКМ – до трех диаметров. С учетом применения газопламенного нагрева класс точности поковки Т5 по ГОСТ 7505-89.

Rice. 1.4. Simplified sketch of the original workpiece

(1, 5, 7 - end surfaces connected by linear dimensions;

2 , 4 , 6 – cylindrical surfaces with stamping slopes)

3. Determination of general allowances for processing and tolerances for the dimensions of the original workpiece.

Determination of the original forging index. Factors

defining the original workpiece index, which is the key to finding the total allowances and tolerances for forgings:

1) estimated weight of the forging M p.r. , kg.

2) steel group M1, M2, M3.

3) degree of difficulty C1, C2, C3, C4.

4) accuracy class (for stamping in open dies T4 or

The estimated mass of the forging is determined by the formula

M p.r = M d K p,

where K p is the consumption coefficient.

For round parts in terms of (hubs, gears, etc.) is taken

K p \u003d 1.5–1.8. Let's take K p = 1.7, then M p.p = 2.49. 1.7 = 4.23 kg.

This article is devoted to a review of methods for automating the dimensional analysis of technological processes, which includes a large number of complex and time-consuming computational and analytical procedures necessary for the design and analysis of technological processes of mechanical processing. The methods of I.A. Ivashchenko, V.V. Matveeva, V.Yu. Shamina, B.S. Mordvinova, Yu.M. Smetanina, O.N. Kalacheva, V.B. Masyagin with co-authors and the dimensional analysis module in KOMPAS-AVTOPROEKT. For each method, a description of the features is given, advantages and disadvantages are noted. At the end of the article, the main directions for improving methods for automating dimensional analysis of technological processes are listed: further simplification of the preparation and improvement of methods for diagnosing initial data, the inclusion of structural and parametric optimization algorithms, visualization of dimensional analysis, improvement of methods for automatically assigning tolerances and allowances, the use of more advanced theoretical models of dimensional analysis that increase the adequacy of the results.

dimensional chain

technological dimensions

1. Antipina L.A. Method of computer-aided design of machine tools based on integrated models of elements of a technological system: Ph.D. dis. ... cand. tech. Sciences. - Ufa, 2002. - 16 p.

2. Bondarenko S.G., Cherednikov O.N., Gubiy V.P., Ignatsev T.M. Dimensional analysis of structures. - Kyiv: Technika, 1989. - 150 p.

3. Volkov S.A., Ryabov A.N. Calculation of operating dimensions using the Techcard software package // STIN. - 2008. - No. 3. - S. 20–23.

4. Dorofeev V.D., Savkin S.P., Shestopal Yu.T., Kolchugin A.F. Implementation of the procedure for the formation of equations of dimensional analysis in the decision-making system CAD TP // Sat. scientist tr. Penz. state tech. university: ser. Engineering. - 2001. - No. 3. - S. 73–79.

5. Ivashchenko I.A. Technological dimensional calculations and methods for their automation. - M.: Mashinostroenie, 1975. - 222 p.

6. Ivashchenko I.A., Ivanov G.V., Martynov V.A. Automated design of technological processes for the manufacture of engine parts aircraft: studies. allowance for universities. - M.: Mashinostroenie, 1992. - S. 336.

7. Kalachev O.N., Bogoyavlensky N.V., Pogorelov S.A. Graphic modeling of the dimensional structure of the technological process on an electronic drawing in the AUTOCAD system // Bulletin of Computer and information technologies. - 2012. - No. 5. - P. 13–19.

8. Kuzmin V.V. Dimensional technological analysis during design technological preparation production // Vestnik mashinostroeniya. - 2012. - No. 6. - P. 19–23.

9. Kulikov D.D., Blaer I.Yu. Calculation of operating dimensions in systems of computer-aided design of technological processes // Izv. universities. Instrumentation. - 1997. - T. 40. - No. 4. - S. 64, 69, 74.

10. Masyagin V.B. Automatic provision of design tolerances in dimensional technological calculations using linear programming // Handbook. Engineering magazine with application. - 2015. - No. 2 (215). – P. 26–30.

11. Masyagin V.B. Automation of dimensional analysis of technological processes of mechanical processing of parts such as rotation bodies // Omsk Scientific Bulletin. Series Devices, machines and technologies. - 2008. - No. 3 (70). – P. 40–44.

12. Masyagin V.B. Dimensional Analysis of Technological Processes of Parts of the Rotation Body Type Taking into Account Location Deviations Based on the Application of an Edge Model of Parts. Spravochnik. Engineering Journal. - 2009. - No. 2. - S. 20–25.

13. Masyagin V.B., Mukholzoev A.V. Methods of dimensional analysis of technological processes of machining using a computer program // Problems of development, manufacture and operation of rocket and space technology and training of engineering personnel for the aerospace industry: materials of the IX All-Russia. scientific conf., dedicated memory ch. designer of software "Flight" A.S. Klinyshkova (Omsk, February 17, 2015). - Omsk: Publishing House of OmGTU, 2015. - S. 226–236.

14. Matveev V.V., Boykov F.I., Sviridov Yu.N. Design of economical technological processes in mechanical engineering. - Chelyabinsk: Yuzh.-Ural. book. publishing house, 1979. - 111 p.

15. Matveev V.V., Tverskoy M.M., Boikov F.I. Dimensional analysis of technological processes. – M.: Mashinostroenie, 1982. – 264 p.

16. Mordvinov B.S., Yatsenko L.E., Vasiliev V.E. Calculation of linear technological dimensions and tolerances in the design of the technological process of machining. - Irkutsk: Irkutsk State University, 1980. - 104 p.

17. Mukholzoev A.V. Automation of dimensional analysis // Dynamics of systems, mechanisms and machines. - 2014. - No. 2. - P. 349–352.

18. Mukholzoev A.V., Masyagin V.B. Calculation of tolerances of the closing links of dimensional chains based on the Floyd-Warschel algorithm. scientific conf., dedicated memory ch. designer of software "Flight" A.S. Klinyshkova (Omsk, February 17, 2015). - Omsk: Publishing House of OmGTU, 2015. - S. 276–283.

19. Skvortsov A.V. Parallel Engineering in Reverse Engineering technological operations Machining in an integrated CAD/CAM/CAPP environment // Vestnik mashinostroeniya. - 2005. - No. 12. - P. 47–50.

20. Smetanin Yu.M., Trukhachev A.V. Guidelines for dimensional analysis of technical processes using graphs. - Ustinov: Publishing House Ustinovsk. fur. in-ta, 1987. - 43 p.

21. Fridlender I.G., Ivanov V.A., Barsukov M.F., Slutsker V.A. Dimensional analysis of technological processing processes. - L .: Mashinostroenie: Leningrad. department, 1987. - 141 p.

22. Harmats I. Compass - Auto project: precise control over technological information. New modules and new features of the system // CAD and graphics. - 2004. - No. 6. - P. 17–19.

23. Shamin V.Yu. Theory and practice of dimensional accuracy design. - Chelyabinsk: Publishing House of SUSU, 2007. - 520 p.

Dimensional analysis of technological processes is a set of a large number of complex and time-consuming computational and analytical procedures necessary for the design and analysis of technological processes of mechanical processing. Reducing the complexity of dimensional analysis is possible with its automation. Let us consider methods for automating dimensional analysis developed in Russia.

The automation of dimensional analysis is understood as the systematic use of computers in the process of solving problems of dimensional analysis with a reasonable distribution of functions between a person and a computer: the distribution of functions between a person and a computer should be such that the designer - designer or technologist - solves problems of a creative nature, and the computer - tasks, associated with the performance of non-creative, routine or mental-formal processes.

One of the first works on the automation of dimensional analysis of technological processes in Russia are the works of I.A. Ivashchenko and co-authors, which set out a method for the automated construction of dimensional chains and the calculation of linear and diametrical technological dimensions. The initial data for the calculation are prepared in the form of a table using a pre-compiled dimensional scheme of the technological process. The general block diagram of the algorithm for calculating linear technological dimensions has linear structure and includes the following steps: input of constant information, input of variable information about the part and the technological process, construction of dimensional chains, ordering (establishing a solution sequence) of dimensional chains, calculation of dimensional chains (determining allowances, operating dimensions and tolerances). When solving the problem of calculating allowances on the surface of revolution and diametrical dimensions, the block diagram additionally includes the steps of determining the operating tolerances for the runout of the machined surface relative to the base, constructing dimensional chains of beats and their verification calculation to check the fulfillment of drawing tolerances and determine the runouts of the allowances. Later, the method was improved and it included the calculation of not only beats, but also other location deviations based on the compilation of dimensional chains.

The method proposed by V.V. Matveev et al., includes the conversion and verification of part and workpiece drawings to perform dimensional analysis. Dimensional analysis begins with the transformation of the drawing and its verification. In each of the projections of the drawing, the dimensions are placed horizontally. Therefore, the number of projections must be sufficient for this condition to be met. Usually, two projections are required for bodies of revolution, and three projections for body parts. However, in some cases, for details of a complex configuration, there is a need for additional projections or sections. When converting the drawing of the workpiece, a drawing of the part is drawn with thin lines on the contour of the workpiece. It is noted that when performing a dimensional analysis without converting drawings, even experienced designers experience errors that take much more time to find than to perform converted drawings. Errors resulting from dimensional analysis are dangerous for production, as they lead to significant material costs and undermine the credibility of these methods. In addition, the transformation allows you to perform dimensional analysis on a computer much better than without it. Therefore, the conversion of part and workpiece drawings is a necessary step in dimensional analysis.

At present, with automated dimensional analysis by the method of V.V. Matveev et al. use the program of V.Yu. Shamina et al. Visual KursAR. Before entering into the computer, the initial data for the calculation are encoded on the basis of manually constructed dimensional schemes. When encoding, a symbol is indicated that characterizes the dimensional parameter that acts as a link, and a symbol characterizes the location of the link. When constructing dimensional contours by the machine, the division of links according to projections is carried out automatically. When you enter the original data, they are converted into the form of average values. For automatic rounding of denominations in the process of solving design problems, a rounding subroutine is provided. The program provides for the possibility of calculating chains of location deviations. It is envisaged to include in the program a special subroutine for constructing diagrams of dimensional chains and a diagnostics module.

Thus, the method of V.V. Matveev et al. is a universal method that provides not only the calculation of linear and diametrical dimensions, but also all types of location deviations for parts, both for parts such as bodies of revolution, and for body parts.

In the automated calculation of linear technological dimensions according to the method of B.S. Mordvinova et al., the following initial data are required: a drawing of a part, a plan of operations for the technological process of machining, including a blanking operation, a scheme for the formation of linear technological dimensions, a graph of linear dimensional chains, on which you can easily identify all dimensional chains and, if necessary, optimize it, upper and lower deviations of tolerance fields of technological dimensions, minimum allowances. The calculation is carried out using a computer and includes entering the initial data into the computer, obtaining preliminary results (equations of dimensional chains, expected errors of design dimensions), comparing the expected errors with the specified tolerances of design dimensions, while the condition for ensuring design tolerances must be satisfied (expected errors should not be more than the specified design tolerances), in case of violation of which the route of the technological process of machining this part is corrected.

Method B.S. Mordvinova et al. have, like the methods of I.A. Ivashchenko and V.V. Matveev with co-authors, the following advantages: reducing time and improving the quality of design; the ability to choose the most effective option; reducing the number of errors. A common disadvantage of these methods is the presence of time-consuming manual operations associated with the preparation of the initial data: the construction of a processing scheme or a graph.

The method of automation of dimensional analysis, described in the works of Yu.M. Smetanina et al., is a matrix representation of the equations of dimensional chains. Manually or with the help of a computer, two matrices are formed for further calculations - the initial one, in which the closing links of dimensional chains (design dimensions and allowances) are expressed only through component links (technological dimensions), and the inverse matrix, in which each technological size is expressed only through design dimensions and allowances. In this case, no restrictions are imposed on the system of equations of dimensional chains, and the solution is obtained with any system of setting technological dimensions that is not even solved from the point of view of other methods.

Methods I.A. Ivashchenko, V.V. Matveeva, B.S. Mordvinov and Yu.M. Smetanina and co-authors include all the main stages of automated calculation of dimensional chains using the apparatus of dimensional chains, graphs and matrices, and as a result, they were the basis for a large number of later methods.

Attempts have been made to incorporate dimensional analysis into CAD systems.

Method of automation of dimensional analysis of technological processes O.N. Kalacheva is based, like the method of B.S. Mordvinov, on the use of a dimensional scheme and a graph, but all constructions are carried out on a computer in an interactive mode in the AutoCAD system.

The source information is the detail drawing file. The system, through a graphical dialogue with the user, creates a primary model of dimensional changes directly on the screen based on the configuration of the part in the reverse order of processing, i.e. recreates the surfaces of the workpiece in a given coordinate direction, completing the allowances, indicating the position of the workpiece dimensions and the technological processing dimensions. At the same time, the system “loads” the workpiece dimensions and technological dimensions with technological information entered using the dialog menus about the methods and nature of processing, the expected location of tolerances, etc. Based on the boundaries of technological dimensions specified by the user-technologist and methods for obtaining them, the system generates a secondary model of dimensional changes, which is drawn up in the form of a list structure, which is then converted into a matrix of initial data for subsequent search for the composition and solution of dimensional chains in the program module. The tool for analyzing the part model, organizing a dialogue and creating a secondary model in AutoCAD is the AutoLISP language.

The positive aspects of this technique are that the initial information is the part drawing file, and the result is also stored in the file as a matrix of initial data for further calculations. The disadvantage is that all constructions are carried out in a dialogue with the computer, and the user has to independently choose the boundaries of dimensions, allowances and assign tolerances to dimensions, which requires a long time to prepare the initial data for calculating linear technological dimensions. It is difficult and practically impossible to build a dimensional model for complex parts with superimposed lines (for example, external and internal surfaces for a sleeve). In addition, the program is only with early versions of AutoCAD and for calculations the KOH7 module is currently used, the data for which can be prepared without using AutoCAD by entering data from a manually prepared dimensional diagram.

Automated calculation of technological dimensional chains in a specialized module of the KOMPAS-AVTOPROEKT program has the following features(I. Harmats). In the module window, the user forms a part manufacturing route in the form of operational sketches. The module for calculating technological dimensional chains is launched. In the module window in the form of a tree, a list of all operations of the generated route is shown. Fill in the data on the technological process and design dimensions. Ready source data can be viewed in the file. After starting the calculation, the calculated data are inserted into the empty places of the source data. The design data includes data on design beats that were not specified and which the module assigned itself (beats can be enabled in the settings). Values ​​not specified by the technologist (nominal value, upper and lower deviation, technological beats) fall into the technological data. The number of iterations in the calculations can be any - until the result satisfies the technologist. If the technologist is satisfied with all the results obtained as a result of the calculation, he can start writing a detailed technological process. By standard means of KOMPAS-AUTOPROJECT, the technology is stored in the archive. Together with the technological process, the complete dimensional structure of the technological process is placed in the archive. If necessary, the technologist can extract the technological process from the archive, change the initial data and recalculate everything again.

Virtues this method is that it is not necessary to build dimensional schemes, but at the same time the laboriousness of data preparation remains, due to the need to calculate and organize digital and graphic data that are manually entered using special "windows" in order to be able to perform the calculation. Unfortunately, due to the end life cycle KOMPAS-AUTOPROEKT program became unavailable and the module of automated dimensional analysis built into it.

An increase in the degree of automation of the dimensional analysis of technological processes is provided by the developed by V.B. Masyagin, computer programs “Automatic calculation of linear technological dimensions “AUTOMAT””, “Dimensional analysis of technological processes of axisymmetric parts “NORMAL”” and the algorithm proposed by A.V. Mukholzoev. Characteristics of the program "AUTOMAT": automatic verification of the correctness of the initial data; application of the graph adjacency matrix for direct calculation of dimensions and tolerances without solving the algebraic system of equations of dimensional chains; automatic detection of basing error; automatic assignment of technological tolerances and allowances; automatic provision design tolerances; calculation by the min-max method; calculation for two options for the distribution of tolerance fields; setting (at the discretion of the technologist) tolerances that take into account the actual accuracy of the equipment, bypassing regulatory framework program data; adaptation of the database to specific production conditions. The NORMAL program has the following features: taking into account all types of location deviations characteristic of parts such as bodies of revolution, and their mutual influence through the use of an edge model of the part, in contrast to known methods based on separate calculation of design and technological dimensions and location deviations; visualization of the scheme of allowances according to the calculated dimensions.

The main advantage of these programs, as well as the dimensional analysis module of the KOMPAS-AVTOPROEKT program, is the use of only drawing and technological process information for preparing initial data. The time-consuming stage of constructing dimensional diagrams, which is typical for other programs, was excluded from the data preparation process, which is replaced by a description of the geometric models of the part and the technological process.

The main directions for further automation of the dimensional analysis of technological processes are, firstly, further simplification and quality assurance of the preparation of initial data by embedding TP into CAD and improving the methods for diagnosing initial data, and secondly, the inclusion in the methods of dimensional analysis of algorithms for structural and parametric optimization of dimensional chains, tolerances and allowances, thirdly, the visualization of the initial data, the process and results of dimensional analysis, fourthly, the improvement of methods for automatically assigning tolerances and allowances, and finally the use of more advanced theoretical models of dimensional analysis that increase the adequacy of the results of automated dimensional analysis.

Reviewers:

Akimov V.V., Doctor of Technical Sciences, Associate Professor, Professor of the Department "Automobiles, construction materials and technologies”, Siberian State Automobile and Road Academy, Omsk;

Rauba A.A., Doctor of Technical Sciences, Associate Professor, Professor of the Department of Technology of Transport Engineering and Rolling Stock Repair, Omsk State University means of communication, Omsk.

Bibliographic link

Part material: SCH - 21.

Billet type: casting in sandy-clay raw molds.

Detail sketch

Technical requirements:

2R 9 , 2R 8 =±0.04.

Part manufacturability analysis

The part does not have complex and special elements. Sizes and tolerances are standard. Dimensional accuracy corresponds to surface roughness. Axial dimensions are given from different surfaces.

As a blank, we choose casting in sandy-clay raw molds by machine molding, since the material of the part is Sch - 21.

Blank sketch

Technical requirements:

2R 0 6 ,2R 0 8 =±0.5; 2R 0 9, 2R 0 8 \u003d ± 0.7. 2R 0 7 , 2R 0 6 \u003d ± 0.7

We choose the most accurate surfaces as the main bases for all operations. At the same time, we take into account the principles of the constancy of bases and the combination of measuring bases with technological ones. Thus, the technological bases will be ends 1 and 4, diameters 6 and 8.

We develop a route technological process. To do this, we determine the processing plan for each surface based on its roughness and accuracy. The sizes 2R8 and 2R9, B1 (7 sq.) have the greatest accuracy. The misalignment specified in the drawing can only be obtained in the finishing operation. We assign the stages of processing the part: Turning roughing, Turning finishing, Grinding rough, Grinding finishing.

Taking into account the processing on both sides of the inner and one outer side, we offer a technological process:

Operation 0: Procurement - casting.

Operation 10: Turning - turret roughing;

Operation 20: Turning - turret roughing;

Operation 30: CNC turning finishing;

Operation 40: CNC lathe finishing;

Operation 50: Internal grinding preliminary;

Operation 60: Internal grinding final.

Development of process operations

Operation 10. Turning - turret roughing

The workpiece is installed in a 3-jaw chuck at the end face and outer dimension 2R 6 .

We assign technical requirements for the location of surfaces (misalignment): 2R 0 6, 2R 10 8 \u003d ± 0.1; 2R 10 9 , 2R 10 8 =±0.1.

Operation 20. Turning - turret roughing

The workpiece is installed in the collet along the already machined end face and the internal dimension 2R 8 .

The roughness and thickness of the defective layer is determined: Rz 40 (corresponds to Ra 10), h=50 µm.

Tolerances for dimensions are assigned according to the tables of the average statistical error of machining.

We assign technical requirements for the location of surfaces (misalignment): 2R 20 6, 2R 10 8 \u003d ± 0.1; 2R 20 7 , 2R 20 6 =±0.1.

Operation 30. CNC turning finishing

The workpiece is installed in a 3-jaw chuck at the end face and outer dimension 2R6.

The roughness and thickness of the defective layer is determined: Rz 20 (corresponds to Ra 5), ​​h=20 µm.

Tolerances for dimensions are assigned according to the tables of the average statistical error of machining.

We assign technical requirements for the location of surfaces (misalignment): 2R206,2R308=±0.06; 2R309, 2R308=±0.06.

Operation 40. CNC turning finishing

The workpiece is installed in the collet along the already machined end face and the internal dimension 2R 8 . Assign Ra 5, h=50µm

Tolerances for dimensions are assigned according to the tables of the average statistical error of machining.

We assign technical requirements for the location of surfaces (misalignment): 2R 40 6, 2R 30 8 \u003d ± 0.06;

Operation 50. Internal grinding rough

The roughness and thickness of the defective layer is determined: Rz 10 (corresponds to Ra 2.5), h=20 µm.

Tolerances for dimensions are assigned according to the tables of the average statistical error of machining.

We assign technical requirements for the location of surfaces (misalignment): 2R 20 6, 2R 50 8 \u003d ± 0.05; 2R 50 9 , 2R 50 8 =±0.05.

Operation 60. Internal grinding finishing

The workpiece is installed in the fixture along the end face and outer dimension 2R 6 .

The roughness and thickness of the defective layer is determined: Rz 5 (corresponds to Ra 1.25), h=20 µm.

Tolerances for dimensions are assigned according to the tables of the average statistical error of machining.

We assign technical requirements for the location of surfaces (misalignment): 2R 20 6, 2R 60 8 \u003d ± 0.015; 2R 60 9 , 2R 60 8 =±0.04.

Dimensional scheme and dimensional chains of diametrical dimensions

Dimensional scheme and dimensional chains of axial dimensions

Calculation of dimensional chains manually

Determination of the actual axial dimensions of the part and actually removed allowances at each transition.

Equation (1) dimensional chain

A 50 - A 60

We determine the actual stray field of the closing link:

Minimum allowance

Z min \u003d Rz + T \u003d 0.01 + 0.02 \u003d 0.03

Maximum allowance

Zmax = Zmin +=0.03+0.87=0.9

Initial average size of the closing link

Average component link size

A 60sr \u003d 125 + (0-0.62) / 2 \u003d 124.69

We calculate the average size of the determined link

A 50sr \u003d (A 60sr) / 1 \u003d 0.465 + 124.69 \u003d 125.155

Let's find the nominal size of the determined link

\u003d - (EIA def + ESA def) / 2, A 50nom \u003d 125.155-(0-0.25) / 2 \u003d 125.28

Tolerance margin for master link

V= EIA+ESA-= Z max - Z min - =0.9-0.03-0.87=0

Since V=0, then we do not round off the nominal size of the link being determined.

Nominal size correction amount

K=-=125.28-125.28=0

Actual average size of the master link

Actual smallest master link size:

0,465-0,87/2=0,03

Actual largest master link size:

0,465+0,87/2=0,9

Margin at the lower limit of the closing link:

V n \u003d 0.03-0.03 \u003d 0

Margin on the upper limit of the closing link:

Equation (2) of the dimensional chain:

A 40 - A 50

Z 1 50min =Rz+T=0.02+0.02=0.04 Z 1 50sr =0.04+0.5/2=0.29

A 40cp \u003d (0.29 + 125.155) / 1 \u003d 125.445

A 40nom \u003d 125.445-(0-0.25) / 2 \u003d 125.57

V=0.54-0.04-0.5=0

A 40okr \u003d 125.57

K=125.57-125.57=0

• 0,29+0=0,29
• 0,29-0,5/2=0,04
• 0,29+0,5/2=0,54

V n \u003d 0.04-0.04 \u003d 0

V B \u003d 0.54-0.54 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (3) of the dimensional chain:

A 30 - A 40

Z 4 40min \u003d Rz + T \u003d 0.02 + 0.02 \u003d 0.04 Z 4 40av \u003d 0.04 + 0.5 / 2 \u003d 0.29

A 30sr \u003d (0.29 + 125.445) / 1 \u003d 125.735

A 30nom \u003d 125.735-(0-0.25) / 2 \u003d 125.86

V=0.54-0.04-0.5=0

A 30okr \u003d 125.86

K=125.86-125.86=0

• 0,29+0=0,29
• 0,29-0,5/2=0,04
• 0,29+0,5/2=0,54

V n \u003d 0.04-0.04 \u003d 0

V B \u003d 0.54-0.54 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (4) of the dimensional chain:

A 20 - A 30

Z 1 30min \u003d Rz + T \u003d 0.04 + 0.05 \u003d 0.09 Z 1 30av \u003d 0.09 + 0.88 / 2 \u003d 0.53

A 20cp \u003d (0.53 + 125.735) / 1 \u003d 126.265

A 20nom \u003d 126.265-(0-0.25) / 2 \u003d 126.39

V=0.97-0.09-0.88=0

A 20okr \u003d 126.39

K=126.39-126.39=0

• 0,53+0=0,53
• 0,53-0,88/2=0,09
• 0,53+0,88/2=0,97

V n \u003d 0.09-0.09 \u003d 0

V B \u003d 0.97-0.97 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (5) of the dimensional chain:

A 10 - A 20

Z 4 20min \u003d Rz + T \u003d 0.2 + 0.4 \u003d 0.6 Z 4 20av \u003d 0.6 + 1.26 / 2 \u003d 1.23

A 10cp \u003d (1.23 + 126.265) / 1 \u003d 127.495

A 10nom \u003d 127.495-(0-0.63) / 2 \u003d 127.81

V=1.86-0.6-1.26=0

A 10okr \u003d 127.81

K=127.81-127.81=0

• 1,23+0=1,23
• 1,23-1,26/2=0,6
• 1,23+1,26/2=1,86

V B \u003d 1.86-1.86 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (6) of the dimensional chain:

A 0 - A 10

Z 1 10min \u003d Rz + T \u003d 0.2 + 0.4 \u003d 0.6 Z 1 10av \u003d 0.6 + 5.63/2 \u003d 3.415

A 0av \u003d (3.415 + 127.495) / 1 \u003d 130.91

A 0nom \u003d 130.91-(0-0.63) / 2 \u003d 131.225

V=6.23-0.6-5.63=0

A 0okr \u003d 131.225

K=131.225-131.225=0

• 3,415+0=3,415
• 3,415-5,63/2=0,6
• 3,415+5,63/2=6,23

V B \u003d 6.23-6.23 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (7) of the dimensional chain:

B 50 + A 50 - A 60 - B 60

Z 2 60min \u003d Rz + T \u003d 0.01 + 0.02 \u003d 0.03 Z 2 60av \u003d 0.03 + 1.29 / 2 \u003d 0.675 B 60av = 25 + (0.1-0.1) / 2 =25

B 50sr = (0.675-(125.155-124.69-25)/-1=25.21

B 50nom \u003d 25.21-(0-0.22) / 2 \u003d 25.32

V=1.32-0.03-5.29=0

B 50okr \u003d 25.32

K=25.32-25.32=0

• 0,675+0=0,675
• 0,675-1,29/2=0,03
• 0,675+1,29/2=1,32

V n \u003d 0.03-0.03 \u003d 0

V B \u003d 1.32-1.32 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (8) of the dimensional chain:

B 30 + A 40 - A 50 - B 50

Z 2 50min =Rz+T=0.02+0.02=0.04 Z 2 50av =0.04+0.94/2=0.51

B 30sr = (0.51-(125.445-125.155-25.21)/1=25.43

B 30nom \u003d 25.43-(0-0.22) / 2 \u003d 25.54

V=0.98-0.04-0.94=0

B 30okr \u003d 25.54

K=25.54-25.54=0

• 0,51+0=0,51
• 0,51-0,94/2=0,04
• 0,51+0,94/2=0,98

V n \u003d 0.04-0.04 \u003d 0

V B \u003d 0.98-0.98 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (9) of the dimensional chain:

B 10 + A 20 - A 30 - B 30

Z 2 30min \u003d Rz + T \u003d 0.04 + 0.05 \u003d 0.09 Z 2 30av \u003d 0.04 + 1.64/2 \u003d 0.91

B 10sr = (0.91-(126.265-125.735-25.43)/1=25.81

B 10nom \u003d 25.81-(0-0.54) / 2 \u003d 26.08

V=1.73-0.09-1.64=0

B 10ocr \u003d 26.08

K=26.08-26.08=0

• 0,91+0=0,91
• 0,91-1,64/2=0,09
• 0,91+1,64/2=1,73

V n \u003d 0.09-0.09 \u003d 0

V B \u003d 1.73-1.73 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (10) of the dimensional chain:

B 0 + A 0 - A 10 - B 10

Z 2 10min \u003d Rz + T \u003d 0.2 + 0.4 \u003d 0.6 Z 2 10av \u003d 0.6 + 8.77 / 2 \u003d 4.985

B 0sr \u003d (4.985-(130.91-127.495-25.81) / 1 \u003d 27.38

B 0nom \u003d 27.38-(1.3-1.3) / 2 \u003d 27.38

V=9.37-0.6-8.77=0

B 0ocr \u003d 27.38

K=27.38-27.38=0

• 4,985+0=4,985
• 4,985-8,77/2=0,6
• 4,985+8,77/2=9,37

V B \u003d 9.37-9.37 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Equation (11) of the dimensional chain:

[B] \u003d A 40 - A 30 + B 20

V cf =55+(0.23-0.23)/2=55

At 20 wd = (55-(125.445-125.735)/1=55.29

In 20nom \u003d 55.29-(0-0.19) / 2 \u003d 55.385

V=55.25-54.75-0.69=-0.019

At 20th \u003d 55.39

K=55.39-55.385=0.005

55,005-0,69/2=54,66

55,005+0,69/2=55,35

V n \u003d 54.66-54.75 \u003d -0.09

V B \u003d 55.25-55.35 \u003d -0.1

Equation (12) of the dimensional chain:

B 20 - A 20 + A 10 + E 0 - A 0

Z 3 20min \u003d Rz + T \u003d 0.04 + 0.05 \u003d 0.09 Z 3 20av \u003d 0.09 + 10.8 / 2 \u003d 5.49

E 0av = (5.49-(55.29-126.265+127.495-130.91)/1=79.88

E 0nom \u003d 79.88-(2.2-2.2) / 2 \u003d 79.88

V=10.89-0.09-10.8=0

E 0okr \u003d 79.88

K=79.88-79.88=0

• 5,49+0=5,49
• 5,49-10,8/2=0,09
• 5,49+10,8/2=10,89

V n \u003d 0.09-0.09 \u003d 0

V B \u003d 10.89-10.89 \u003d 0

13-14. Since V n \u003d V B \u003d 0, then the relative deficit indicators are not calculated.

Checking the received data in the design task using the PA6 program. Calculation of axial dimensions

Equation (1) of the dimensional chain:

A 50 - A 60

Coding for circuit calculation:

• 3 S 13 14 0.03 0.9
• 6 L 13 42 0 -0.25
• 7 L 14 42 125 0 -0.62

List of dimensional chains.

3=S=-(0014<+0042)+(0042<-0013)

Equation (2) of the dimensional chain:

A 40 - A 50

Coding for circuit calculation:

• 3 S 12 13 0.04 0.54
• 6 L 12 42 0 -0.25
• 7 L 13 42 125.28 0 -0.25

List of dimensional chains.

3=S= -(0013<+0042)+(0042<-0012)

Equation (3) of the dimensional chain:

A 30 - A 40

Coding for circuit calculation:

• 3 S 41 42 0.04 0.54
• 6 L 12 41 0 -0.25
• 7 L 12 42 125.57 0 -0.25

List of dimensional chains.

3=S= -(0042<+0012)+(0012<-0041)

Equation (4) of the dimensional chain:

A 20 - A 30

Coding for circuit calculation:

• 3 S 11 12 0.09 0.97
• 6 L 11 41 0 -0.63
• 7 L 12 41 125.86 0 -0.25

List of dimensional chains.

3=S= -(0012<+0041)+(0041<-0011)

Equation (5) of the dimensional chain:

A 10 - A 20

Coding for circuit calculation:

• 3 S 40 41 0.09 1.86
• 6 L 11 40 0 ​​-0.63
• 7 L 11 41 126.39 0 -0.63

List of dimensional chains.

3=S= -(0041<+0011)+(0011<-0040)

Equation (6) dimensional chain

A 0 - A 10

Coding for circuit calculation:

• 3 S 10 11 0.6 6.23
• 6 L 10 40 ±2.5
• 7 L 11 40 127.81 0 -0.63

Dimensional analysis consists in identifying dimensional chains and in calculating the tolerances of the dimensions included in them.

The identification of a dimensional chain involves:

1. Definition of the initial link (problem statement),

2. Representation of a dimensional chain in the form of a closed contour,

3. Selection of the closing link and classification of the constituent links into increasing and decreasing ones.

Dimensional chain - a set of dimensions that are directly involved in solving the problem and forming a closed loop.

The main features of the dimensional chain include: closedness, interconnection and interdependence of sizes; observance of the principle of the shortest chain.

Design dimensional chain - a dimensional chain that determines the distance or relative rotation between the surfaces or axes of the surfaces of parts in the product.

Technological dimensional chain - a dimensional chain that provides the required distance or relative rotation between the surfaces of the manufactured product during operations or a series of assembly operations, processing when setting up the machine, when calculating intertransitional dimensions.

The link of the dimensional chain is one of the dimensions that form the dimensional chain.

The closing link is the link of the dimensional chain, which is the initial one when setting the problem or the last one obtained as a result of its solution.

The constituent link is a link in the dimensional chain, functionally connected with the closing link. It is denoted by a capital letter of the alphabet with an index corresponding to its ordinal number. The closing link is assigned the index ∆.

An increasing link is a constituent link of a dimensional chain, with an increase in which the closing link increases. It is denoted

Reducing link - a component link of a dimensional chain, with an increase in which the closing link decreases. It is denoted

The compensating link is a component link of the dimensional chain, by changing the value of which the required accuracy of the closing link is achieved.

Linear dimensional chain - a dimensional chain, the links of which are linear dimensions.

The calculation of dimensional chains includes the solution of direct and inverse problems.

Direct task - a task in which the parameters of the closing link are specified (nominal value, permissible deviations, etc.) and it is required to determine the parameters of the constituent links.

An inverse problem is a problem in which the parameters of the constituent links are specified (tolerances, stray fields, coordinates of their midpoints, etc.) and it is required to determine the parameters of the closing link.

There are two ways to calculate dimensional chains:

1. Calculation method for maximum-minimum - a calculation method that takes into account only the maximum deviations of the links of the dimensional chain and their most unfavorable combinations.

2. Probabilistic method of calculation - a method of calculation that takes into account the dispersion of sizes and the probability of various combinations of deviations of the constituent links of the dimensional chain.