Defects and improvement methods of gearbox shift block in machining

　　The shift guide block is an important part of automobile transmission. For a long time, the gearbox shift block is very prone to defects when processing. These defects affect its performance and quality. Today, we will discuss its improvement methods.

　　Defects in processing

　　Generally, when the manufacturer is in production, the processing procedure is: reaming → car positioning surface and chamfering → hole drawing. A total of 3 sets of processing equipment are used, and 3 operators are required.

　　Due to longer working hours in reaming, positioning surface and chamfering processes, insufficient production capacity and overtime rush often occur.

　　The reaming process adopts the vertical drilling machine with ordinary twist drill, the outer round blank surface positioning clamping, there is the phenomenon of large hole, offset, when the last process of the outer round blank surface positioning clamping car positioning surface and chamfering, clamping point is prone to deviation, resulting in the positioning surface of the car out of the verticality difference with the bottom hole, and then the drawing process can not completely pull out the hole phenomenon.

　　Process improvement plan

　　In view of the above process defects, CNC lathe is used to improve the process. After putting in hydraulic tooling and cutting tools, the hole expansion is changed to the bottom hole, and the car positioning surface and two end chamfering are completed together. Compared with the original process parts, two processes are completed by clamping at one time.

　　1. Design of hydraulic jig for CNC lathe

　　According to the product structure, one end is tight, with φ26mm blank cylindrical positioning clamping, the design of CNC lathe fixture through the hydraulic system to drive the connecting rod before and after the movement, and then drive the movement of the movable rod, to achieve the clamping and loosening of the guide piece of the claw and V-shaped press block.

　　The main body of the fixture is full of oil to ensure that the moving parts are fully lubricated. The top block limits the blank end face of the workpiece and prevents the chip from entering the main body. The design of the chip hole is to allow the workpiece to achieve internal chamfering.

　　2. Selection of cutting tools

　　According to the work to be completed in this process, namely, flat end face, bottom hole, inner chamfer and outer chamfer, the tool selected is the inner hole turning tool.

　　3. Calculation and selection of cutting parameters

　　Refer to the metal cutting manual, leave a drawhole allowance of 0.6mm, so the inner hole to φ (15.5±0.1) mm.

　　Using this technology, on the one hand, the stability of the drawing front bottom hole is improved, on the other hand, the perpendicularity of the drawing front bottom hole and the positioning surface is greatly improved, and the problem that the drawing hole cannot be processed is completely eliminated. It can be known that the improved processing process of gearbox shift block is: bottom hole → flat end face and chamfering → hole drawing.