Dimensional analysis of worm gear box and development of process of worm workpiece machining

Contents

Introduction

1. General part

1.1. Service assignment, technical specification and description of part and assembly

1.2. Design Input

1.3. Justification of the form and type of production

2. Process Part

2.1. Manufacturing Part Constructability Analysis

2.2. Dimensional Node Analysis

2.3. Justification for Selection of Source Procurement

2.4. Process Route and Base Selection

2.5. Calculation of machining allowances

2.6. Justification and description of the operational process of part workpiece machining

2.7. Calculation of cutting modes

2.8. Technical rationing (unit time determination)

2.9. Quality control of manufactured parts

3. Design Part

3.1. Service purpose of the accessory

3.2. Design Input

3.3. Kinematic diagram of accessory

3.4. Calculation of workpiece fixing force and selection of drive. Accuracy calculation. Calculation of weak link for strength

3.5. Description of the work of the designed accessory

Conclusion

Literature used

Introduction

Worm gears are widely used in mechanical engineering, and due to their advantages are used in various mechanisms, so the production of worm gears is relevant in any branch of mechanical engineering. Production should not stand still, but should develop with the advent of new equipment and progressive means of equipping, because with the development of production the quality of products should increase, labor intensity should decrease, working conditions should improve. But the main thing is that with the development of production there is also a development of the country's economy, an increase in the quality of life of its citizens. Therefore, this course project is aimed at improving technology, at introducing rationally selected equipment and progressive equipment into the manufacturing technology.

General part

1.1. Service assignment, technical specification and description of the part and assembly.

Worm reduction gear serves to transfer torque between shafts with crossing axes. Worm mechanisms have the ability to reduce speed (i = 6... 80), self-braking, noiselessness, smooth engagement, and have a relatively small transmission mass per unit of transmitted power. This gearbox is single-stage. Rotation from motor shaft is transmitted to worm shaft 17, and from it - through composite worm wheel (hub 12, rim 11) to shaft 14. Rim is pressed on hub and is additionally fixed by two mounting screws. The worm shaft supports are rolling bearings 37 and 38. The shaft supports of the worm wheel are sliding bearings 13, which are lubricated through the lubricants. Pins 35 pressed into housing 1 keep bushings 13 from turning.

In the gear box, the worm is the driving element of the transmission. By design, this worm belongs to the class of shafts. The worm is a stepped shaft with a screw surface cut into the middle stage. The symbol of the worm type according to GOST 1903694 - ZA, this means that the worm has an Archimedean screw surface. The screw surface of the worm shall be of low roughness to reduce friction in the gear; on this worm, the roughness of the screw surface is Ra 1.6. Also, this part has 2 precise journals for bearings. The accuracy of these necks is specified by the tolerance for size (k6), tolerance for deviation of the mold (tolerance for deviation from cylinders), tolerance for mutual arrangement of surfaces (tolerance for deviation from alignment). To prevent the bearing skew after installation, a tolerance is set for deviation from the perpendicular of the end surface against which the bearing rests. The key groove also has a sufficiently high accuracy and roughness (Ra3.2), since the key is a stress concentrator and it is necessary to avoid excessive clearance or interference in this connection. Worm fabrication material - 50 steel (carbon structural steel). Material of a worm has to have high hardness therefore a worm subject to training after which hardness is HRC of 56...62 pieces .

1.2. Design Input.

Gearbox assembly drawing and worm working drawing, pos.17. Output volume 30000 pcs/year. New equipment is used.

1.3. Justification of the form and type of production.

Production type - a classification category of production, distinguished by the characteristics of the breadth of the nomenclature, regularity, stability and volume of production of products.

The accepted output volume corresponds to the average production type.

The production form will be in-line, since the designed part will be produced at a specially created enterprise for this purpose. In this form, the workpiece is in motion during manufacture having a certain stroke value.

Process Part

2.1. Analysis of constructability of the manufactured part.

The purpose of the analysis is to identify design flaws based on the information of the drawings and technical requirements, possible improvement of the processability of the design in question. [4, page 10]

Technological analysis of the design provides improvement of technical and economic parameters of the developed process. The tasks of the analysis include reducing labor and metal consumption, the desire for processing by high-performance methods. Improved technological effectiveness of the design will reduce the cost of its manufacture without compromising the service purpose. [4, p.10-11]

The analysis consists of the following items:

1) Simplification of design and expediency of material replacement. The design of the part is as simple as possible and has no complex elements (not counting the standardized screw surface of the worm), and the steel 50 material is often used for the manufacture of worms. Moreover, the worm material is selected by the designer based on the calculation of the worm gear for strength.

2) Application of high-performance processing methods. The cylindrical surfaces of the worm, as parts belonging to the class of shafts, are suitably treated with a conventional pass-through cutter, and this construction of the part allows this to be done, so in this paragraph the structure can be considered technological. Also, the rigidity of the worm allows you to obtain the necessary accuracy. To improve performance, you can choose a more productive method for the most time-consuming operation - obtaining the screw surface of the worm.

3) Analysis of structural elements for processability. I believe that all structural elements are quite technological.

4) Possibility of combining process and measurement bases. Aligning bases for this part is impractical. The measuring bases of this worm are the surfaces of the supporting necks, however, their use as technological bases for processing external surfaces is difficult, therefore, in most operations, the surfaces of the center holes at both ends of the workpiece are taken as technological bases. This allows you to treat all the external surfaces of the worm on single bases with its installation in centers.

5) Possibility of direct measurement of dimensions specified in the drawing. All linear dimensions are measured directly by measuring means. Neck diameters can also be directly measured with gauges. The profile of the screw surface, the dimensions of the key slot, the thread are controlled by templates, calibers;

6) Surfaces used for basing. Center holes at worm ends must be used as basing surfaces. This allows you to treat all the external surfaces of the worm on single bases with its installation in centers.

7) There are no specific requirements for the part, therefore additional technological operations are not required;

8) Selection of rational method of procurement taking into account economic factors. From the conditions of course work, the workpiece can be obtained by stamping on hammers or a crank hot stamping press (KGShP). It should be said that stamping on CGWP gives higher surface accuracy and roughness, smaller stamping slopes and greater Kim, but the final method will be determined after calculation.

Design Part

3.1. Service purpose of the device.

The tool used in the milling-centering (005) and key-milling (020) operations serves to clamp the workpiece to be processed. For processing, the blank is installed in prisms and pressed from above by a tack, which eliminates the possibility of turning the blank during processing. The main requirement of the device is to provide sufficient clamping force for the blank. It is also necessary to ensure the accuracy of the accessory, and the strength of all parts of the accessory.

Conclusion

In the course of this work, a dimensional analysis of the assembly was carried out, the initial workpiece was selected and its drawing was made, the technological process of manufacturing the part was compiled, the drawings of technological adjustments were made, and an accessory for fixing the workpiece was designed. The development of all these points makes it possible to ensure in the medium-term production of products of the required quality, reduce labor intensity, and quickly solve problems encountered during production. A properly constructed and resolved dimension chain guarantees that when assembled using the incomplete interchangeability method, all products will be assembled, with the exception of a small number of products that fall into the scrap percentage. The rational choice of the method of obtaining the initial procurement made production more economical. Calculation of allowances by analytical method allows to reduce costs for mechanical processing, since it is more accurate and the calculated allowance is less than the allowance selected according to the table. The process using new equipment and advanced equipment reduces the labor input of the product. The development of technical documentation, such as drawings of parts, workpieces, process adjustments, and the preparation of process maps allows you to qualitatively organize production.