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Contents

Introduction

1. OBJECTIVES AND TASKS OF COURSE WORK. SHORT CONCEPT OF ACCURACY

2. Service purpose of the product

3.Base selection of fits on all mating surfaces

(key, pin, etc.)

4. Justification of tolerances of form, mutual arrangement

and surface roughness

5. Justification of selection of main mating dimensions from the rows of preferred numbers: (GOST 6636-69, GOST 8032-56)

6. Measuring Circuit Calculation

7. Connections to rolling bearings. Assigning Tolerance Fields

8. Justification of tolerances of shape, mutual arrangement and roughness of shaft part surface

9. Substantiation of part surface roughness parameters

"pinion shaft"

10. Selection of measuring instruments

Literature

Introduction

Parts of operating machines are stationary or in relative motion. For example, the parts of the reduction gear: housing, covers, cups, etc. - are stationary; shafts with all parts installed on them rotate relative to fixed housing. At the same time, a number of parts located on the shaft, such as, for example, gears, rings of rolling bearings, bushings, etc. are stationary relative to the shaft.

When assembling a machine, parts are installed one relative to the other in a certain position. Installation (basing) of parts is performed by flat, cylindrical, end surfaces or by combination of these surfaces. The accuracy of a single surface can affect the accuracy of the assembly and the quality of the assembly (s).

The solution of the problem, which contributes to ensuring the necessary processability and high quality of products, is associated with the choice of the necessary accuracy of manufacturing products, calculation of dimensional chains, selection of surface roughness, as well as selection of tolerances of deviations from the geometric shape and arrangement of surfaces.

Some issues of accuracy are discussed on the example of parts and assembly of a conical gear box.

Standardization, metrology and certification are tools for ensuring the quality of products, works and services - an important aspect of multifaceted commercial activity.

These quality assurance methods are defined as follows:

Metrology is the science of measurements of physical quantities, methods and means of ensuring their unity and ways to achieve the required accuracy.

Standardization is an activity aimed at achieving an optimal degree of streamlining in a certain area by establishing provisions for universal and reuse with respect to actual or potential tasks (ISO/IEC2).

Certification is a procedure of confirmation of compliance which means the organization, independent of the manufacturer (the seller, the performer) and the consumer (buyer), certifies in writing that products conforms to the established requirements (The act of the Russian Federation of 10.06.93 No. 51511" <certifications of products and services" (in an edition of 31.07.98)).

Abroad already in the early 80s. came to the conclusion that business success is determined, first of all, by the quality of products and services. 80% of respondents in the survey of 200 largest US firms responded that quality is the main factor in selling goods at a favorable price [8, c.7]. Hence the conclusion; mastering quality assurance methods, triad-based standardization, metrology, certification, is one of the main conditions for the supplier to enter the market with competitive products (service), therefore, and commercial success.

The problem of quality is relevant for all countries, regardless of their market economies. It is enough to recall how in Japan and Germany, which were defeated and crushed in World War II, the skillful use of metrology standardization methods made it possible to ensure the quality of products and thereby give the old time to renew the economies of these countries. Now they often recall the statements of the Russian philosopher and political thinker I. A. Ilyin (18831954... "the Russian people have only one outcome and one salvation - a return to quality and its culture." Because quantitative ways of an iskhozhena, are gained, exposed, and quantitative illusions are before our eyes got rid up to the end" [by the 8th page 7].

Today, the manufacturer and its reseller, striving to raise the reputation of the brand, win the competition, enter the world market, are interested in fulfilling both the mandatory and recommended requirements of the standard. In this case, the standard acquires the status of a market incentive. Process and Document Standards (Management! shipping, technical) contain rules that industry and trade specialists must be aware of to conclude mutually beneficial transactions.

Thus, standardization is a tool to ensure not only competitiveness, but also effective partnership of the manufacturer, customer and seller at all levels of management.

Today, it is not enough for a supplier to strictly follow the requirements of progressive standards - it is necessary to support the production of goods and the provision of services with a safety or quality certificate. Consumer customers have the greatest confidence in a quality system certificate. It creates confidence in the stability of quality, in the reliability and accuracy of the measured quality indicators, indicates a high culture of the production processes of products and the provision of services.

In the future, for a number of goods and services, confirmation of compliance with the established requirements will be carried out not only through certification, but also by the manufacturer of the product or service provider, i.e. < the first party. Under these conditions, the role and responsibility of the head of the organization in the competent application by staff of the rules for standardization of metrology and certification increases.

Compliance with the rules of metrology in various areas of commercial activity (trade, banking, etc.) allows to minimize material losses from unreliable measurement results.

The issue of harmonization of domestic rules of standardization, metrology and certification with international rules is very acute! since this is an important condition for Russia's accession to the World] Trade Organization (WTO) and further activities within this organization.

Thus, the transition of the country to a market economy with its inherent competition for consumer confidence will force commerce specialists to make greater use of the methods and rules of standardization, metrology and certification of their practical activities to ensure the high quality of goods, slaves and services.

The purpose of the "Metrology, Standardization and Certification" discipline is to develop knowledge, skills and skills in these areas of activity in order to ensure effective commercial activity.

1. OBJECTIVES AND TASKS OF COURSE WORK

SHORT CONCEPT OF ACCURACY

The purpose of the course work is to systematize, consolidate and expand the theoretical and practical knowledge of the course and apply this knowledge in solving the set tasks, develop skills in calculating tolerances and fits of typical joints, in normalizing the tolerances of the form and the arrangement of surfaces, its roughness in machine building products.

The concept of accuracy and error.

When designing machine parts, their geometric parameters are determined by the dimensions of the elements, as well as the shape and mutual arrangement of their surfaces. During manufacturing, deviations from the geometric parameters of real parts from the designed values ​ ​ occur. These departures are called errors. Errors can also occur during storage and operation of machines under the influence of the external environment, internal changes in the structure of the material, wear, etc.

The degree of approximation of real parameters to ideal parameters is called accuracy. The concept of accuracy and error is interrelated. Accuracy is characterized by actual error or limits limiting the error value (normalized accuracy). The narrower these limits are, the smaller the error and the higher the accuracy.

Service purpose of the product

Shaft gear module m = 2.25 number of teeth z = 27, is fixed by splined joint. The pinion shafts serve to transmit torque from one shaft to another at a given gear ratio. The mechanism in which this gear wheel operates is a cylindrical transfer box of the car.

The transfer box serves to distribute torque between driving bridges of an off-road vehicle, as well as to turn on and off the front driving bridge. The transfer box is combined with an additional two-speed gearbox, which allows increasing transmission ratios and doubling the total number of gears, which makes it possible to use the car more efficiently in various road conditions.

Transfer gearbox is installed on frame behind gearbox and connected with it by means of cardan gear.

The primary shaft of the transfer box rotates in the bearing supports, the forward torque from the gearbox to the secondary shaft, due to the gear being in constant engagement. Also, the primary shaft transmits torque to the power take-off box through the splined joint (bushings and forks).

Transfer boxes, regardless of their design scheme, shall meet the following requirements:

1. Distribute torque over the driving axles in such a way as to ensure the best cross-country ability of the car.

2It is possible to create large gear ratios to overcome increased resistance to the movement of the car.

3. Have devices that prevent overload of transmission parts (| when the demultiplicator is turned on.

4. Do not create increased noise levels.

5. Have high efficiency.

Handout Box Classification

The main characteristic of the classification of transfer boxes is the type of drive. If all the output shafts of the transfer box have a rigid mechanical connection, the drive is called blocked. If the output shafts of the dispenser are connected through a differential, the drive is called differential. There are also transfer boxes that provide temporary connection of one of the transmission branches through automatic power takeoff devices.

Justification of selection of fits on all mating surfaces (key, pin connections, etc.)

Interchangeability - the property of independently manufactured parts (or assemblies) to take their place in the assembly without additional processing during assembly and perform their functions in accordance with the technical requirements for the operation of this assembly (or machine). In order to increase the level of interchangeability of products, develop co-operation and specialization of production, reduce the nomenclature of a normal tool, fields of tolerances of shafts and holes of preferred application are established.

Fits are selected depending on purpose and operating conditions of equipment and mechanisms, their accuracy, assembly conditions. In this case, it is necessary to take into account the possibility of achieving accuracy in various methods of processing the product. Preferred fits should be used first. Mainly, fits are used in the hole system. Shaft system fits are useful when using some standard parts (such as rolling bearings) and when using a constant diameter shaft along the entire length of installation of several parts with different fits.

We assign to all mating surfaces of the "Front driving axle" article of the fit, taking into account the above listed requirements.

Justification of tolerances of form, mutual arrangement

and surface roughness.

Deviations of the shape and location of the surfaces distort the fit of the joint, reduce the accuracy of the product and its reliability, and increase the labor input of the assembly. Therefore, all surface feature deviations must be limited to tolerances. Nominal surface - an ideal surface, the nominal shape of which is specified by the drawing or other technical documentation. The deviation of the surface shape is the deviation of the shape of the real surface from the shape of the nominal surface .

The deviation of the location is the deviation of the actual location of the element in question from its nominal location. Datum-A part feature (or combination of these) that defines one of the planes or axes of the coordinate system to which the location tolerance is set.

The rings of rolling bearings are very pliable. They facilitate the mounting surfaces of the shafts and take the form of these surfaces. Therefore, in order to distort the race of the inner rings to a minimum extent, the tolerance of the bearing mounting surfaces of the shafts is set.

Cillindricity tolerance is the highest allowable deviation from cillindricity. In addition, the tolerance of cillindricity is indicated by the shaft with the key slot, since the gear wheel sits on the shaft with interference and it is necessary to limit the pressure concentration. We take the values ​ ​ of these tolerances from the tables, taking into account the quota according to GOST 2464381.

To limit the misalignment of the bearing rings, set the alignment tolerances of the bearing mounting surfaces relative to their common axis. In case of bearing rings skewing, shaft rotation resistance and energy loss increase and their durability decrease. The tolerance of coaxiality in diametrical expression is twice the maximum allowable value of deviation from coaxiality. We also set the tolerance of alignment relative to the common axis of the bearing mounting surface, because it is necessary to provide standards of kinematic accuracy and standards of contact of the gear train. We take tolerance values from the tables, also taking into account the quota according to GOST 2464381.

On the two surfaces of the shaft, face run-out tolerances are assigned, since the bearings abut the end surfaces of the shaft and bearing deformation is possible. End biennium - difference of greatest and smallest distances from points of real profile of end surface to plane perpendicular to base axis. To base narrow rings, set the face run-out tolerance. Similarly, all tolerance values are taken from tables as per GOST 2464381.

On the surface of the shaft for the gear, a radial run-out tolerance is set relative to the common axis of the bearing mounting surface in order to reduce the amplitude of oscillations of this surface. Radial run-out tolerance includes deviation from coaxiality and deviation from round surface of shaft. Tolerance value is taken from the table as per GOST 2464381.

Justification of selection of main mating dimensions from the rows of preferred numbers: (GOST 663669, GOST 803256)

Nominal linear dimensions (diameters, lengths, steps, depths, distances between axes, etc.) of parts, their elements and connections shall be assigned from among the standard ones as per GOST 663669. In this case, the original dimension value obtained by calculation or otherwise, if it differs from the standard, should be rounded usually to the nearest total standard size. The use of standard nominal dimensions gives a great economic effect as it creates the basis for reducing the size of products and parts, as well as technological equipment, primarily dimensional cutting tools, calibers, etc.

The standard for normal linear dimensions is based on the series of preferred numbers (GOST 803256), adopted worldwide, including ISO and CMEA standards, as a universal system of numerical values ​ ​ of parameters and sizes of products of all sectors of the national economy. The rows of preferred numbers are geometric progressions with denominators,,,, which in each decimal interval contain, respectively, 5, 10, 20, 40, which is reflected in the symbols of the series.

The two parts of the elements that fit into each other form joints. Such parts are called mating parts, and the surfaces of the connected elements are called mating surfaces.

The difference in dimensions prior to assembly determines the nature of the joint of the parts, or fit, i.e. greater or lesser freedom with respect to the movement of the parts or the degree of resistance to their mutual displacement. The difference between the size of the hole and the shaft if the size of the hole is larger than the size of the shaft is called a gap. The difference in size between the hole and the shaft before assembly, if the shaft size is larger than the hole size, is called interference. A transition fit is a fit in which both clearance and tension can be obtained.

The difference between the largest and smallest limit dimensions is called tolerance. The zone enclosed between the two lines corresponding to the top and bottom deviations is called the tolerance field.

Two CMEA standardization recommendations apply to preferred numbers: RS 185769 and RS 185869. Recommendation PC 185769 establishes four rows of preferred numbers (R5, R10, R20, R40), the terms of which are rounded values ​ ​ of the terms of geometric progression.

When you set dimensions, parameters, and other numerical characteristics, you must take their values from the main series of preferred numbers. At the same time, the dimensions of row R5 should be preferred to the dimensions of row R10, R10 > R20; R20>R40. The additional series R80 should be applied as an exception.

When choosing sizes, rows with larger gradation and the dimensions included in them should be preferred: the Ra5 series should prefer the Ra10 series; Ra10>Ra20; Ra20>Ra40. The selection of dimensions for these parts in the development of the course design uses rows of normal linear dimensions according to GOST 663669 (lengths and diameters); R80 should be used as an exception.

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