Development of process of recovery of ZIL-130 gearbox drive shaft

Contents

Contents

Introduction

1. Source Data

2. Analysis of source data

3. Select Annual Program

4. List of possible defects of ZIL- gearbox drive shaft

5. Punch List Generation

6. Description of the part to be restored

7. Selecting Datum Surfaces When Restoring a Part Surface

8. Route the surface to be restored

9. Choosing a Rational Way to Restore a Part

10. Calculation of cutting modes, time standards, selection of process equipment

Conclusion

List of literature

Introduction

To restore the full operability of worn out parts, it is necessary that they have the original dimensions, geometric shape and surface properties, primarily hardness, since all the properties of the core are usually preserved, except for individual cases of fatigue cracks. In this case, the interchangeability of the parts and fits of the mates are fully restored.

However, in practice, only the geometrical shape of the parts is restored by giving them repair dimensions that are larger or smaller than the initial one. Although the fit of the mates is restored, interchangeability is only partially preserved, within only this standard size, and with free repair sizes it is completely violated.

The main methods of restoring parts: mechanical processing, the method of repair dimensions, additional parts, pressure, welding and surfacing, chroming, ironing (leaving), synthetic materials, etc. All these methods, although not equivalent, are used in repair production to a greater or lesser extent depending on its volume, equipment, etc.

To date, the cost of restoring the operability of some cars can be calculated as a fraction of the total cost of the vehicle. In most cases, the owner of the car has to choose between replacing the part with a new one and repairing the old one. The main selection criterion will be the cost of the new part and the cost of restoration, as well as its originality and availability. In some cases, it will be more profitable to make repairs. Modern equipment and methods for restoring parts allow not only to ensure the original properties of the part, but also to improve them.

The purpose of the course design is to develop a technological process for restoring the drive shaft of the ZIL130 gearbox, calculating cutting modes, and compiling a set of process documentation.

Analysis of source data

The gearbox is manual, three-way, four-speed, with four gears forward and one back. Gears of the first, second, third and fourth gears are helical. Drive and driven reverse gears are spur gears. The intermediate reverse gear is oblique.

The gearbox crankcase is a block structure divided by partitions into three sections. Main gear is arranged in first section on flywheel side. Second section accommodates gears of first and second gears and reverse gears while third section accommodates gears of third and fourth gears. The first and second sections communicate with each other and have a common oil drain hole closed by a plug with a fixed magnet glued in to collect metal particles caught in the oil. The third section communicates with the rear cover cavity and also has an oil drain hole closed by the same plug. In the third section between gear wheels of the third and fourth gears there installed is gear wheel of speedometer drive. A clutch case is attached to the front of the gearbox crankcase, and a rear cover is attached to the rear. The gearbox crankcase seats are processed together with the clutch crankcase, so they are replaced in the kit.

The drive shaft of the gearbox rotates on two bearings: the front end of the shaft on a needle bearing pressed into the flywheel bolt, and the rear end on a bearing installed in the gearbox crankcase hole. The thrust split ring mounted on the drive shaft prevents the bearing and shaft from moving backwards. From forward displacement, it is held by the cover of the rear bearing, which is fixed by bolts with tightening torque of 1.62 kgf-m. Splines for sliding fit of driven clutch disk are cut at front end of drive shaft. In the middle part of the shaft inside the gearbox, a helical gear is cut, which is in constant engagement with the driven gear of the first gear and the intermediate driven gear of the reverse gear. The axial force generated by the torque transmission by the drive shaft is sensed by the ball bearing. Behind the gear on the rear end of the drive shaft there are involute splines engaged with the hub of the intermediate shaft.

Select Annual Program

For parts m < 20 kg, for small-scale production, the annual number of parts of one type is 1000... 5000 pieces. Accepted as per assignment N = 3000 pcs.

4. List of possible defects of ZIL-130 gearbox drive shaft:

1 - fragments and cracks; 2 - neck wear for front ball bearing; 3 - painting of working surface of teeth; 4 - dents from rollers or wear of hole for roller bearing; 5 - wear of internal engagement teeth; 6 - wear of teeth in thickness; 7 shows wear of cone surface under synchronizer ring; 8 - wear of splines in thickness; 9 - wear of external engagement teeth; 10 - wear of journal for rear bearing.

Description of the part to be restored

The shaft of the primary gearbox of the ZIL130 car belongs to the class of parts "round rods with a shaped surface." It is made of 25XGM steel, and it is cemented to a depth of 0.50.7 mm. After heat treatment, the hardness of the surface layer HRC 60... 65, and the hardness of the core HRC 35... 45 are obtained. When machining the shaft, the installation bases are mainly center holes and less often external cylindrical surfaces. The roughness of the gear teeth and the surface of the roller bearing hole should correspond to Ra = 0.32? 0.25 μm, the remaining surfaces - Ra = 1.25? 1.0 μm. The primary shaft of the ZIL130 gearbox operates under contact loads accompanied by bending forces.

Contact loads, bending and friction are destructive factors.

Route the surface to be restored

To eliminate each of the defects of the part, a technological process is being developed.

Workflow:

005 Defects (detection of defects)

010 Surfacing (metal surfacing at wear points)

015 Boring (boring hole for additional bushing)

020 Press (press bushing)

025 Turning (turning)

030 Boring (boring hole in bushing for bearing)

035 Grinding operation (rolling of working surfaces under splines, part bearings)

040 Milling Operation (Spline Milling)

045 Control (control of part repair works performance)

Choosing a Rational Way to Restore a Part

The durability of repaired cars depends to a large extent on the ways in which the parts are repaired and how it is organized. The application of the most effective methods ensures long service life of parts, reduces the consumption of spare parts, materials, labor costs, etc. Along with the use of rational methods, for high-quality restoration of parts with the least labor costs. Of the means, the organization of production is of great importance - centralized restoration of parts in specialized plants and in workshops well equipped with modern equipment, devices, tools.

The choice of restoration methods depends on the structural and technological features and working conditions of the parts, the amount of their wear, the operational properties of the methods themselves, determining the durability of the repaired parts, and the cost of their restoration. The structural and technological features of the parts are determined by their structural characteristics: geometric shape and dimensions, material and heat treatment, surface hardness, manufacturing accuracy and surface roughness, the nature of the interface (type of fit), working conditions - the nature of the load, the type and type of friction, the amount of wear over the operational period. Knowledge of the structural characteristics of the parts and their technological features and operational properties of the methods allows us to decide in the first approximation the question of the applicability of one or another of them to the restoration of individual parts. Using this analysis, you can determine which parts can be restored in all or several ways and which in their structural characteristics in only one way.

Wear of conical holes for expansion bushings is eliminated by brewing, before they are drilled to larger diameter, with subsequent drilling of through hole and its countersinking to the required size as per working drawing. Splines worn in thickness are restored by surfacing under flux layer with longitudinal suturing. After the diameters are swept and the splines are milled, the necessary heat treatment and finishing operations are performed.

How to restore parts:

Processing for the following repair category size.

Repair of parts by mechanical machining is the achievement of repair dimensions and the use of additional repair parts.

Treatment for repair dimensions consists in the fact that one of the two mating parts (usually more expensive) is machined for a repair size smaller or larger than that of the working drawing. Another mating part is replaced with a new or repaired part up to the corresponding repair size.

In our case, the working surfaces and necks are spread under the next increased repair size, and the bushing and valves are replaced by new ones of the corresponding category repair size.

Repair of parts by welding and surfacing consists in the fact that defective part, cracks are welded or metal is laid on worn-out surfaces of part, after which parts are machined. This method is well used to eliminate cracks on parts of blocks, frames, bodies, walls of the head cooling jacket and engine cylinder block, as well as to weld surfaces of various parts.

This method is applicable in connection with the geometric dimensions of the part to eliminate a crack defect.

Repair of parts with surfacing. Molten metal or composite composition is sprayed onto the part surface prepared accordingly by means of special installations using working gas mixtures. After spraying, the part is processed for repair size.

The machining of the worn holes of the bushing parts is done in various ways, most often by boring, drilling and unfolding the holes or only by drilling, this is often the case, for example, when restoring threads.

We choose mechanical and mechanical restoration of the shaft by treatment for repair size.

Conclusion

As a result of the work, the technological process of restoring the drive shaft of the ZIL130 gearbox was developed, an analysis of restoration methods was carried out, that is, the chosen method from the point of view of economy, complexity of equipment and processability is the most acceptable of the known. As a result of the work, the part recovery process, sketch maps of the selected processes were developed and the operating and process charts of the part recovery process were compiled. Therefore, there is a need to restore the part instead of replacing it with a new one, because from the point of view of cost savings this is more profitable than buying a new part.