Environmental approach in architecture. Man and architecture

Program algorithm for dimensional analysis technological processes

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 technological design, and also allows you to create databases 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;

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- 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 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 workflow, 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 contents

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 dimension, a dimensional chain with the minimum amount links.

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. Graphics systems CAD: Practical. allowance / V. E. Klimov; Ed. V. A. Petrova. - M.: Higher. school, 1990. - 142 p.ISBN 5-06-000744-8.

Goal and tasks.

Mastering the methodology of dimensional analysis, which makes it possible to ensure the accuracy of the obtained dimensions in the manufacture of parts from blanks, is one of the main tasks of technologists.

The purpose of this work is to master the methods for identifying dimensional chains that determine the position of the surfaces being machined relative to bases or other surfaces, and solving them to build the technological process of processing.

This work perform according to the following scheme.

Calculation of technological dimensional chains.

Dimensions and accuracy values.

An example of dimensional analysis.

The design of the part is given.

Material - steel 40X

Blank - stamped

Manufacturing route

Op. 010. Turning

End trimming

Op. 015. Sanding

End face grinding

Rice. 1. Sketch of operations.

Rice. 2. Stages of processing bodies of revolution.

Rice. 3. Stages of processing flat surfaces.

The number of necessary operations and transitions during processing and economically viable qualifications of dimensional accuracy and surface roughness are assigned in accordance with the recommendations indicated in Fig. 2, 3.

For those shown in Fig. 1. operations, we assign tolerances to the resulting sizes in accordance with the recommended qualifications.

op. 010 size - 0.20

op. 020 - 0.15

According to the sketches of the operation and the drawing of the part, we will open the dimensional chain with the closing link T, which is not directly maintained and is obtained as a function of the remaining links (Fig. 4).

Rice. 4. Scheme of the dimensional chain

T = - +

We check the possibility of solving

T \u003d \u003d 80 - 0.2:

The tolerance on the size of the master link must be

0,20 + 0,15 + 0,08 = 0,43

Since it is required to obtain a tolerance of 0.2 mm, the proposed processing route does not allow working without defects.

It is necessary to reduce the tolerances of the resulting dimensions. Let us introduce an additional operation.

020 - grinding the end of the rod (Fig. 5).

Op. 020 grinding

Grind the end, maintaining the size.

Rice. 5. Sketch of grinding the end of the rod

Let us analyze the obtained dimensional chains, in which the allowance is the closing link.

(1)

Size allowance (op. 020; op. 010) (2)

The closing link is an allowance, which is assigned according to experimental - statistical data from tables or calculated.

We accept grinding allowance

Grinding tolerance (-0.06)

We solve the dimensional chain

We substitute the found value into equation (1) and find the solution

From equation (1):

Taking into account that the size of the workpiece is double-sided, we assign

Free size chart

4. The order and features of the construction of dimensional chains

Draw a detail drawing coordinate axes. The detail is depicted in the required projections, not necessarily to scale.

Number all surfaces by coordinates.

Draw vertical lines from each surface.

Draw the corresponding dimensions of the part between the vertical lines.

Dimensions are affixed so that the dimensional chain is not closed.

In accordance with the accepted route, the dimensions obtained at each operation are applied. Each operation is separated by a horizontal line.

The resulting sizing system forms a dimensional chain.

R.Ts. should not include allowances of the closing links of other chains as constituent links, i.e. the allowance, which is the closing link, should be one.

By the decision of R.Ts. determine the operational dimensions, including the dimensions of the workpiece with the appointment of economically justified tolerances for them. Calculations start from the last chain going to the initial operation.

The tolerances for the size of the transitions of all operations, except for the final ones, are set in accordance with the economic qualification of the accuracy of each processing method (Fig. 1.2). It is recommended to set the tolerances "into the body", i.e. for male (shafts) - with a minus sign, and for female (holes) - with a plus sign.

When setting tolerances, it must be borne in mind that the dimensions of the workpiece have maximum deviations in both directions from the nominal values.

Before deciding R.Ts. it is necessary to assign operating allowances, tk. they are usually the closing links.

Allowances for machining surfaces of stamped blanks are presented in the table. The distribution of allowances by processing stages is carried out in accordance with the assigned processing route.

Allowances (per side) for machining stamped blanks, mm

Bibliography.

1. Handbook of technology - machine builder. In 2 volumes. Ed. A.G. Kosilova and R.K. Meshcheryakova, M.: Mashinostroyeniye, 1986 V.1.

2. A.A. Matalin. Technology of mechanical engineering, L .: Mashinostroenie, 1585.

Laboratory work №12

When developing a technological process for assembling products, the problem of choosing a method and means of ensuring the accuracy of the device (product) almost always arises. It is solved by calculating the dimensional chain of the product (node), which is carried out in order to determine the resulting deviation of the accuracy of the product, to identify the deviation of each component of the dimensional chain from among the components that have the greatest impact on the output parameters or functional indicators of the device (product).

In the design documentation, the dimensions and tolerances for the output parameters of the product are usually indicated based on the service purpose of the part, assembly or device. However, in some cases, such a specification of dimensions or such a system for arranging them either does not correspond to the chosen technology, or these dimensions cannot be directly measured. In addition, when developing a TP assembly, it is almost always necessary to solve the problem of choosing a technological method and technological means to ensure the accuracy of the device. Eliminate deficiencies that appear as a result of different task sizes, allow technological inspection of design documentation, analysis and calculation of dimensional chains of the product, according to their results, design dimensions and tolerances can be replaced by technological ones. However, with such a replacement, all design dimensions and tolerances must be maintained. The design and technological dimensions specified in the documentation can be recalculated to a maximum or minimum, when it is assumed that all dimensions of the product that make up the dimensional chain are carried out according to their limit values ​​or according to probability theory, when combinations of individual dimensional deviations are considered as phenomena of a random nature. The methodology for calculating the maximum-minimum most fully corresponds to industrial practice.

Fig.4

On fig. 4 shows the studied GM.

Sizes A2, A3, A5 - increasing; A1, A4 - decreasing.

AΔ - closing - the size of the gap between the rotor and the housing.

We also take into account the displacement of the inner w/n ring relative to the outer one. Offset amount

The gap is:

7. Control device.

7.1 Description and principle of operation of the device.

As part of course project a device for control was developed, which should carry out the sending of the outer ring of the w / h into the GM body. It is necessary to apply an axial force of 15 kg to the outer ring of the w/n, it is also necessary to register the movement of this ring with an accuracy of at least 0.0001 mm.

One of the options for such a device is shown in Fig.5.

The device is a Plate pos.10 which stands on 4 racks.

The body of the device with the w/n ring is separately installed in the plate pos.15, and then inserted into the flange pos.18 by means of the bayonet pos.1, while the upper free end of the body abuts against the sealing ring pos.25, glued to the plate 10, which allows you to exclude possible backlash and protect the surface of the GM body from mechanical damage.

Fig.6. Plate pos.15 with GM body.

The flange pos.18 is fixed under the plate with six screws pos.20. A bracket is installed on the plate, which holds an eccentric, during rotation of which around the axis pos.9, the pusher pos.16 moves forward. The pusher compresses the spring pos.12, which transfers the force from the rotation of the eccentric to the shaft pos.3, which presses on the w / n ring, creating the necessary force of 15 kg. The magnitude of the force in the process of performing the operation must be monitored on a scale at the end of the pusher pos.16. The pointer poz.17 is screwed into the shaft poz.3. In the process of measuring the force, its position can be considered unchanged (it moves by tenths of a micron), while the pusher can move up to 8 mm (after which, to protect the product and extend the life of the fixture spring, the lower end of the pusher reaches the stop in the bracket pos. 8) .

According to the TT on the GM, it is fit for further assembly if a force of 15 kg causes a relative movement of the microcutter needle with a 3-fold measurement by no more than 0.0004 mm. And to check the relative movement in the device there is a microcutter 01IGPV pos. 28, the clamp (pos. 7) of which is mounted on the rack pos.13. Adjustment of the position of the microcutter along the guide post will be carried out by the screw pos.4, and the fixation of the microcator in the clamp pos.7 is carried out by the nut pos.23. Before applying force to the w/n ring, the measuring head of the microcator must be brought to the shaft console pos. 3 and set the microcator scale to zero. The displacement of the shaft pos.3, measured by the microcutter, is equal to the displacement of the w/n ring.

The main part of the device is the spring pos. 12, on which the force transmitted to the shaft pos.3 depends. Below is the calculation of this spring.

7.2. Spring calculation. We will calculate the spring based on the need to create a force of F 2 \u003d 15 kg (~ 150 N) with a margin of at least 15-20% (F 3 \u003d 180 N) and possible dimensions. The outer diameter is not more than 15 mm and the height of the spring in a free state is not more than 20 mm, with a working stroke h=7 mm.
Material:	Wire according to GOST 9389. Carbon steel, hardened in oil.
Design options for support coils:	Tightened, polished
Wire (rod) diameter d=
Outer diameter D1=
Average diameter D=
Spring length without load L0=
Working number of turns n=
Total number of turns n1=
Working length L2=
Length at contact of turns L3=
Spring constant c=
Spring travel h=

Let's make a preliminary calculation of the diameter of the wire and spring.

Let's take the index of the spring c=6

Set of influence of the curvature of the coils k=1.24

τ for this material at ∅ 2…2.5 mm ~ 950 MPa

Wire diameter:

Spring diameter:

D=c*d=13.2 - average diameter

D n \u003d D + d \u003d 15.4 - outer diameter

We will select a spring according to GOST 13766-86.

The most suitable option is position 407.

For this spring:

Let's clarify the calculations of the average diameter:

D=15-2.1=12.9mm

Spring stiffness:

Number of working turns:

n=C1 /C=97/21.5=4

Maximum deformation:

λ 3 \u003d F 3 / C \u003d 180 / 21.5 \u003d 8.3 mm

Total number of turns:

n 1 \u003d n + n 2 \u003d 4 + 2 \u003d 6

Spring pitch:

Spring height at maximum deflection:

Free spring height:

Technological analysis

Technological analysis of the part provides an improvement in the technical and economic indicators of the developed technological process and is one of the most important stages of technological development.

The main task in the analysis of the manufacturability of the part is reduced to a possible reduction in labor intensity and metal consumption, the possibility of processing the part by high-performance methods. This allows you to reduce the cost of its manufacture.

The pinion shaft can be considered technological, as it is a stepped shaft, where the dimensions of the steps decrease from the middle of the shaft to the ends, which provides a convenient supply of the cutting tool to the surfaces to be machined. Processing is carried out with a unified cutting tool, surface accuracy is controlled with a measuring tool. The part consists of unified elements such as: center holes, keyway, chamfers, grooves, linear dimensions, slots.

The material for production is 40X steel, which is a relatively inexpensive material, but at the same time has good physical and chemical properties, has sufficient strength, good machinability, easy heat treatment.

The design of the part makes it possible to use typical and standard technological processes for its manufacture.

Thus, the design of the part can be considered technological.

1. Surface 1 is made in the form of a slotted part.

2. Surface 2 is a carrier, so there are no strict requirements for it.

3. Surface 3 is used for external contact with inner surface cuffs. Therefore, it is subject to stringent requirements. The surface is polished to a roughness of Ra 0.32 µm.

4. Surface 4 is a carrier, so there are no strict requirements for it.

5. Surface 5 is also load-bearing and is intended for bearing seating. Therefore, it is subject to stringent requirements. The surface is ground to a roughness of Ra 1.25 µm.

6. Surface 6 Made in the form of a groove, which is needed for the withdrawal of the grinding wheel. It is inappropriate to impose strict requirements on it.

7. Surface 7 is a carrier and there is no need to impose strict requirements on it.

8. The sides of the teeth are involved in the work and determine both the durability of the assembly and its noise, therefore, to the sides of the teeth and their relative position impose a number of requirements both on location accuracy and surface quality (Ra 2.5 µm).

9. Surface 9 is a carrier and there is no need to impose strict requirements on it.

10. Surface 10 Made in the form of a groove, which is needed for the withdrawal of the grinding wheel. It is inappropriate to impose strict requirements on it.

11. Surface 11 is load-bearing and is intended for bearing seating. Therefore, it is subject to stringent requirements. The surface is ground to a roughness of Ra 1.25 µm.

12. Surface 12 is a carrier, so there are no strict requirements for it.

13. Surface 13 is used to contact the inner surface of the cuff. Therefore, it is subject to stringent requirements. The surface is polished to a roughness of Ra 0.32 µm.

14. Surface 14 is a carrier, so there are no strict requirements for it.

15. Surface 15 is presented in the form of a keyway, which is designed to transmit torque from the pinion shaft to the belt pulley Rz 20 µm.

16. Surface 16 is represented by a groove, which serves to bring out the threading tool.

17. Surface 17 is made in the form of a keyway for fitting a lock washer Rz 40 µm.

18. Surface 18 is a thread for a nut, which serves to tighten the pulley Ra 2.5 µm.

The requirements for the mutual position of the surfaces, I consider appropriately assigned.

One of the important factors is the material from which the part is made. Based on the service purpose of the part, it can be seen that the part operates under the action of significant alternating cyclic loads.

In terms of repair this item is quite responsible, since in order to replace it, it is necessary to dismantle the entire assembly from the machine unit, and when installing it, align the clutch mechanism.

Quantification

Table 1.3 - Analysis of the manufacturability of the design of the part

Surface name	Quantity surfaces, pcs.	Number of unified surfaces, pcs.	quality accuracy, IT	Parameter roughness, Ra, µm
End faces L=456mm
End face L=260mm
Butt L=138mm
End faces L=48mm
Center holes W 3.15mm
Slots D8x36x40D
Chamfer 2x45°
Teeth Ш65,11mm
Groove 3±0.2
Groove 4±0.2
Keyway 8P9
Keyway 6P9
Thread M33x1.5-8q
Hole W5 mm
Threaded hole М10х1-7Н
Taper 1:15

The coefficient of unification of the structural elements of the part is determined by the formula

where Q.e. is the number of unified structural elements of the part, pcs;

Q.e.- total number structural elements of the part, pcs.

The part is manufacturable, since 0.896>0.23

The material utilization factor is determined by the formula

where md is the mass of the part, kg;

mz is the mass of the workpiece, kg.

The part is technological, since 0.75 = 0.75

The processing accuracy coefficient is determined by the formula

where is the average quality of accuracy.

The part is non-technological, since 0.687<0,8

The surface roughness coefficient is determined by the formula

where Bsr is the average surface roughness.

The part is non-technological, since 0.81< 1,247

Based on the calculations made, it can be concluded that the part is technological in terms of the unification factor and in terms of the material utilization coefficient, but not technological in terms of the processing accuracy coefficient and the surface roughness coefficient.

Dimensional analysis of the part drawing

Dimensional analysis of the drawing of the part begins with the numbering of the surfaces of the part shown in Figure 1.3

Figure 1.3 - Designation of surfaces

Figure 1.4-Dimensions of the working surface of the part

Dimensional graphs are being constructed in Figure 1.5

Figure 1.5 - Dimensional analysis of the working surface of the part

When constructing a dimensional analysis, we determined the technological dimensions and tolerances for them for each technological transition, determined the longitudinal deviations of dimensions and allowances and the calculation of the dimensions of the workpiece, determined the sequence of processing individual surfaces of the part, ensuring the required dimensional accuracy

Determining the type of production

We select the type of production in advance, based on the mass of the part m = 4.7 kg and the annual program for the production of parts B = 9000 pieces, serial production.

In the future, all other sections of the developed technological process depend on the correct choice of the type of production. In large-scale production, the technological process is developed and well equipped, which allows the interchangeability of parts, low labor intensity.

Therefore, there will be a lower cost of products. Large-scale production provides for a wider use of mechanization and automation of production processes. The coefficient of fixing operations in medium-scale production Кз.о = 10-20.

Medium-scale production is characterized by a wide range of products manufactured or repaired periodically in small batches, and a relatively small output.

At enterprises of medium-scale production, a significant part of the production consists of universal machines equipped with both special and universal-adjusting and universal-assembly fixtures, which makes it possible to reduce labor intensity and reduce the cost of production.

DIMENSIONAL ANALYSIS AND DIMENSIONAL CHAINS

General information about dimensional analysis. Basic definitions.

Calculations of tolerances for the dimensions of landing parts (shaft - holes) are relatively simple. They allow solving many problems of the theory of accuracy and interchangeability in engineering. However, in practice, in machines and mechanisms, instruments and other technical devices, the relative position of the axes and surfaces of parts connected in products depends on a larger number (three or more) of mating dimensions. One of the means of determining the optimal tolerances for all structurally and (or) functionally related dimensions in the product is dimensional analysis, which is performed on the basis of calculations dimensional chains. The relationship of dimensions and their tolerances, which regulates the location of surfaces and axes of both one part and several parts, in an assembly or products, is called dimensional relationship of parts .

A dimensional chain is a set of dimensions, forming a closed loop, and directly involved in solving the problem. (GOST 16319-80)

Using the calculations of dimensional chains and dimensional analysis, the following tasks are solved:

Responsible dimensions and parameters of parts and assemblies are established that affect the performance of the machine, device;

The nominal dimensions and their maximum deviations are specified;

Accuracy standards for machines, devices and their components and parts are calculated and (or) specified;

Technological and measuring bases are substantiated;

Metrological calculations are carried out that determine the permissible error values ​​(based details when measuring measuring instruments and measurement methods);

Measuring instruments are selected for control operations in the processes of manufacturing, testing, quality control of products, parts, etc.

The problems of dimensional analysis are solved on the basis of the theory of dimensional chains. The calculation of dimensional chains is a necessary step in the design of machines and devices.

The main features of the dimensional chain:

The dimensional chain can only include those dimensions that, being functionally and (or) structurally related, allow solving design, technological, measuring or other tasks mentioned above;

The dimensions included in the dimension chain must always form a closed loop.

Dimensions, input boxes e in a dimensional chain, are called links.

The link of the dimensional chain, which is the initial one when setting the problem (for example, when designing), or the last one obtained as a result of solving the problem (for example, technological), is called closing.

The closing link in the dimensional chain is always one. The remaining links of the dimensional chain (any number (2 or more)) are called components. The constituent links are increasing and decreasing.

magnifying called the constituent link, with increasing whom increases closing link.

Reducing n called a constituent link, with increasing whom decreases closing link.

The links of the dimensional chain in the diagram are indicated by an uppercase (capital) letter with ordinal digital indices (1,2,..,n) for composite links and a triangular index (A) for the closing link.

For example, dimensional chain A,

To highlight the increasing and decreasing constituent links, they are marked with an arrow placed above the letter:

Arrow pointing to the right for increasing links A 1, A 2 ;

Arrow pointing to the left for reducing links: B 1, B 2 .

When constructing a dimensional chain diagram, the product drawing is analyzed

(for example, a drawing of a part (Figure 3.1, a); assembled products (Figure 3.1, b)).

1. Determine the surfaces of the part assigned as design and measurement bases;

2. Set the dimensions of the part, which can be measured by direct measurements directly from the design base;

3. Set the dimensions of the part, the accuracy of which will require the construction and calculation of dimensional chains, while the design base is preserved;

4. Set the dimensions of the part, to assess the accuracy of which it is advisable to assign a new base surface (not coinciding with the design base). Of these dimensions, it is required to select dimensions that can be measured by direct measurements from a new base, and dimensions, for the assessment of the accuracy of which it will be necessary to build and calculate dimensional chains.

The essence of the dimensional analysis of the designed technological process is to solve inverse problems for technological dimensional chains.

Dimensional analysis makes it possible to evaluate the quality of the technological process, in particular, to determine whether it will ensure the fulfillment of design dimensions that cannot be directly maintained during the processing of the workpiece, to find the limit values ​​of the processing allowances and evaluate their sufficiency to ensure the required quality of the surface layer of the surfaces to be machined and/or the ability to remove allowances without overloading the cutting tool.

The initial data for dimensional analysis are the drawing of the part, the drawing of the original workpiece and the technological process of manufacturing the part.