Source of machining process
In the machining production process, the process of changing the shape, size, position and properties of the production object to make it into a finished product or a semi-finished product is called a machining process.
The machining process can be divided into casting, forging, stamping, welding, machining, assembly and other processes. The mechanical manufacturing process generally refers to the sum of the machining process of the parts and the assembly process of the machine.
To formulate the machining process, it is necessary to determine the order in which the workpiece has to go through several processes and processes. Only the abbreviated process of the main process name and its processing sequence is listed, which is called the process route.
The formulation of the process route is to formulate the overall layout of the process. The main task is to select the processing methods of each surface, determine the processing order of each surface, and the number of processes in the whole process. The process route is drafted in accordance with certain principles.
The principle of drafting the machining route of machined parts:
1. Firstly process the reference surface: When the part is in the process of processing, the surface as the positioning reference should be processed first to provide a fine reference for the processing of the subsequent process as soon as possible. Called "baseline first."
2. Dividing the processing stage: The surface with high processing quality is divided into processing stages, which can be generally divided into three stages: roughing, semi-finishing and finishing. Mainly to ensure the processing quality; conducive to the rational use of equipment; easy to arrange heat treatment process; and easy to find blank defects.
3, the first face after the hole: For the box, bracket and connecting rods and other parts should be processed first plane processing holes. In this way, the hole can be machined in a plane to ensure the positional accuracy of the plane and the hole, and the processing of the hole in the plane is facilitated.
4. Finishing: The finishing of the main surface (such as grinding, honing, fine grinding, rolling, etc.) should be carried out at the final stage of the process. The surface finish after processing is above Ra0.8um, a slight collision. It will damage the surface. In Japan, Germany and other countries, after finishing, it must be protected with flannel. It is absolutely not allowed to directly touch the workpiece by hand or other objects, so as to avoid the surface of the finishing process, due to the transfer and installation between processes. And suffered damage.
Other principles for developing a machine tool routing:
The above is the general case of the process arrangement. Some specific situations can be dealt with according to the following principles.
(1) In order to ensure the processing accuracy, the roughing and finishing are preferably carried out separately. Because of the large amount of cutting during roughing, the cutting force and clamping force of the workpiece are large, the heat is generated, and the machining surface has a significant work hardening phenomenon. There is a large internal stress inside the workpiece. If rough and rough machining Continuously, the precision of the finished part will be quickly lost due to the redistribution of stress. For some parts with high machining accuracy requirements. After roughing and before finishing, a low temperature annealing or aging treatment should be arranged to eliminate internal stress.
(2) Reasonable selection of equipment. Roughing is mainly to cut off most of the machining allowance, and does not require high machining accuracy. Therefore, roughing should be carried out on machine tools with high power and low precision. The finishing process requires higher precision. Machine tool processing. Roughing and finishing are processed on different machine tools, which can fully utilize the equipment capabilities and extend the service life of precision machine tools.
(3) In the machining process route, a heat treatment process is often arranged. The arrangement of the heat treatment process is as follows: in order to improve the cutting performance of the metal, such as annealing, normalizing, quenching and tempering, etc., it is generally arranged before the machining. In order to eliminate internal stress, such as aging treatment, quenching and tempering treatment, etc., it is generally arranged after roughing and before finishing. In order to improve the mechanical properties of the parts, such as carburizing, quenching, tempering, etc., it is generally arranged after machining. If there is a large deformation after heat treatment, the final processing procedure must also be arranged.
When formulating the process of machined parts, the addition methods, machine tools, tool holders, blanks, and technical requirements for workers are very different due to different types of parts.
