In the process of production, the shape and position of finished products are changed, which is called machining process.

Machining process can be divided into casting, forging, stamping, welding, machining, assembly and other processes;

Mechanical manufacturing process generally refers to the sum of the machining process of parts and the assembly process of the machine. To formulate the machining process, it is necessary to determine how many processes the workpiece will go through and the sequence of the processes. Only the brief process of listing the main process name and its processing sequence is called the process route.

The main task is to select the processing method of each surface, determine the processing sequence of each surface, and the number of processes in the whole process. Certain principles must be followed in the process route planning.

1、 Principles for drawing up machining parts process route:

1. First machining datum plane: during the machining process of parts, the surface as positioning datum shall be machined first, so as to provide precise datum for subsequent processing as soon as possible. It is called "benchmark first".

2. Division of processing stage: the surface with high quality requirements is divided into three stages: rough machining, semi finishing and finishing. It is mainly to ensure the processing quality, to use the equipment reasonably, to arrange the heat treatment process, and to find the blank defects easily.

3. Face before hole: for parts such as box, bracket and connecting rod, the plane shall be machined first and then the hole shall be processed. In this way, the hole can be processed by plane positioning, which ensures the position accuracy of plane and hole, and brings convenience to the processing of hole on the plane.

4. Finishing: the finishing of the main surface (such as grinding, honing, finishing grinding / rolling, etc.) should be carried out at the last stage of the process route. The surface finish after processing is above ra0.8um, and slight collision will damage the surface;

In Japan, Germany and other countries, after finishing, flannelette should be used for protection. It is absolutely forbidden to directly contact the workpiece with hands or other objects, so as to avoid damage to the finished surface due to the transfer and installation between processes.

2、 Other principles for drawing up machining parts process route:

The above is the general situation of process arrangement. Some specific cases can be dealt with according to the following principles.

1. In order to ensure the machining accuracy, the roughing and finishing should be carried out separately. During rough machining, the cutting amount is large, the cutting force and clamping force on the workpiece are large, the heat generation is more, and the machining surface has obvious work hardening phenomenon, and there is a large internal stress in the workpiece;

If rough machining and rough machining are carried out continuously, the precision of parts after finishing will be lost quickly because of the redistribution of stress. For some parts with high machining accuracy. After rough machining and before finishing, low temperature annealing or aging treatment should be arranged to eliminate internal stress.

2. Reasonable selection of equipment. Rough machining is mainly to cut off most of the machining allowance and does not require high machining accuracy. Therefore, rough machining should be carried out on machine tools with high power and low precision, while the finishing process requires high-precision machine tools. Rough machining and finish machining are processed on different machine tools, which can not only give full play to the equipment capacity, but also extend the service life of precision machine tools.

3. In machining process route, heat treatment process is often arranged. The arrangement of heat treatment process is as follows: in order to improve the cutting performance of metal, such as annealing, normalizing, quenching and tempering, it is generally arranged before machining.

In order to eliminate internal stress, such as aging treatment, quenching and tempering treatment, it is generally arranged after rough machining and before finishing. In order to improve the mechanical properties of parts, such as carburizing, quenching, tempering, etc., they are generally arranged after machining.

If there is large deformation after heat treatment, the final processing procedure must be arranged. When drawing up the technological process of machining parts, due to the different production types of parts, the addition method, machine tool equipment, fixture and measuring tools, blank and technical requirements for workers are very different.