The main function of the gearbox housing is to support the transmission shaft, ensure the center distance and parallelism between shafts, and ensure the correct installation of gearbox components and engine. Therefore, the processing quality of automobile gearbox box parts not only directly affects the assembly accuracy and motion accuracy of automobile gearbox, but also affects the working accuracy, service performance and service life of automobile. The automobile gearbox mainly realizes the speed change of the automobile and changes the driving speed of the automobile. The top surface of the automobile gearbox is used to install the gearbox cover, and the front and rear end support holes are used to install the transmission shaft to realize its speed change function.

Process analysis of parts

According to the automobile gearbox box parts drawing. Automobile gearbox box is a thin-walled shell part, and its outer surface has five planes to be machined. The support hole is connected to the front end face and the rear end face. In addition, a series of threaded holes need to be machined on each surface. So it can be divided into three groups of machining surfaces. They have certain job requirements for each other. The analysis is as follows:

(1), with the top surface as the main processing surface. This set of machining surfaces includes: milling the top surface; Screw hole processing; Hole machining based on. Among them, the surface roughness of the top surface is required, the position of 8 screw holes is required, and the position of 2 process holes is also required.

(2) Machining surface with bearing holes of, and as the main machining surface. This set of machining surfaces includes: 2 holes, 2 holes, 1 hole; The dimensions of the front and rear end faces are perpendicular to the axes of the four holes; 3. 16 screw holes and 4. 2 holes on the front and rear end faces; On the same center line, there are two other reversing gear shaft holes perpendicular to two end faces, their inner end faces and two screw holes. Among them, the front and rear end faces require surface roughness 3 and 16 screw holes, holes 4 and 2 require positions, and the inner end faces of the two reversing gear shaft holes require dimensions and surface roughness.

(3) The machining surface with the window surfaces on both sides as the main machining plane. This set of machining surfaces includes: two side window surfaces with sizes and; 12 is perpendicular to the screw holes of the windows on both sides; Tapered pipe threaded holes (oil injection holes) with dimensions at a certain angle to both sides. Among them, the surface roughness on both sides of the window surface is required to be, and the position of all 12 screw holes is required to be.

1.2 main problems in gearbox processing and corresponding measures to be taken in process design.

As can be seen from the above analysis. The main machining surfaces of box parts are plane and hole system. Generally speaking, plane is easier to ensure machining accuracy than hole system. Therefore, for the gearbox case, the main problem in the machining process is to ensure the dimensional accuracy and position accuracy of the hole and handle the relationship between the hole and the plane.

Due to the large output of automobile gearbox. How to meet the productivity requirements is also the main consideration in the process of gearbox processing.

Machining sequence of holes and planes

The machining of box parts should follow the principle of first face and then hole: that is, the datum plane on the box should be machined first, and other planes should be machined with datum plane positioning. Then process the hole system. The processing of gearbox case naturally follows this principle. This is because the plane area is large, plane positioning can ensure reliable positioning and firm clamping, and it is easy to ensure the machining accuracy of holes. Secondly, the plane can be machined first, and the roughness of the casting surface can be cut off first. It creates conditions for improving the machining accuracy of holes, facilitates the alignment and adjustment of tools, and is also beneficial to protecting tools.

The machining technology of gearbox box parts should follow the principle of separation of rough machining and finishing, and the machining of holes and planes should be clearly divided into two stages, to ensure the machining accuracy of holes.

Selection of machining scheme for hole system

The machining scheme of gearbox box hole system should choose the machining method and equipment that can meet the machining accuracy requirements. In addition to considering machining accuracy and efficiency, economic factors should also be properly considered. Under the condition of meeting the accuracy requirements and productivity, the machine tool with the lowest price should be selected.

According to the accuracy and productivity requirements of the gearbox shown in the automobile gearbox parts drawing, it is more suitable to use boring die method on the combined machine tool at present.

That's all I have.