Talking about Precision Machining Process
Today I would like to briefly introduce the precision machining process with you. The technicians of Shanghai Jindong Precision Parts Processing tell us that the precision machining process is generally based on the establishment of mechanical processing procedures. It can be divided into two steps. The first is to draw up the process route for precision parts processing. To put it plainly, first analyze the parts that need to be processed. Without the real object, you can analyze the drawings of the parts. Then according to the analyzed and prepared report, the process size of each process, the equipment and process equipment used, as well as cutting specifications, man-hour quota, etc. are then determined.
The formulation of the process route is to formulate the overall layout of the process. Whether a component is processed well or not, the main task is to select the processing method of each surface, determine the processing order of each surface, and the number of processes in the entire process. This step is very important. You can only do all the preparations to the end, and the following things will be easy to handle.
General principles for drawing up a process route (this step is generally done by the design engineer)
1. First process the reference surface. During the processing of the part, the surface used as the positioning reference should be processed first, and the general part shape should be processed according to the drawing or the previously analyzed parameters. In order to provide a precise benchmark for subsequent processing as soon as possible. Called "benchmark first."
2. Divide the processing stages. Surfaces that require high-quality machining of precision parts are divided into processing stages, which is very important and complex. Generally can be divided into three stages of roughing, semi-finishing and finishing. The main purpose is to ensure the processing quality; it is conducive to the reasonable use of equipment; it is convenient to arrange the heat treatment process; and it is convenient to find the blank defects when it is convenient.
3. Face first and then hole. For boxes, shafts, and connecting rods, planes should be machined first and then holes should be machined. In this way, the holes can be machined in a plane position, the accuracy of the plane and hole position is ensured, and the machining of the holes in the plane is facilitated. Because the processing plane is relatively simple and the holes are more complicated, it is reasonable to do the short answer first and do the complicated ones.
4. Finishing. Finished workpiece. This is also the last step, which is also very important. The finishing of the main surface (such as grinding, honing, finishing, rolling, etc.) should be carried out in the final stage of the process route. The surface finish after processing must meet the customer's requirements, and it must be ensured. Place the processed precision parts, and try to handle them lightly, because slight collisions will damage the surface. In Japan, Germany and other countries, after finishing, you must use flannel to protect them. Never use your hands or Other objects directly contact the workpiece, so as to avoid the surface of the finishing process being damaged due to the transfer and installation between processes. After all, it is a precision component, so the requirements of the component are relatively high. A slight surface error will affect the use of the component.
The above is the general situation of processing procedure arrangement. Of course, there are some special cases, and some specific cases can be handled according to the following principles.
(1) In order to ensure the accuracy of parts processing. Roughing and finishing are preferably performed separately. During rough machining, the cutting amount is large, the cutting force and clamping force of the workpiece are large, the heat generation is large, and the machining surface has a significant work hardening phenomenon. There is a large internal stress in the workpiece. If the machining is continued, the precision of the finished part will be quickly lost due to the redistribution of stress. For some parts requiring high machining accuracy. After roughing and before finishing, low temperature annealing or aging treatment procedures should also be arranged to eliminate internal stress. This is very important. As far as possible, it is still necessary to separate the finishing and roughing as far as possible. You must know that you can save time when you plan, which may cause a large part of the parts to be unqualified and the loss will be greater. It depends on the situation.
(2) Reasonably select precision parts processing equipment. Roughing is mainly to cut off most of the machining allowance, and does not require high machining accuracy, so roughing should be performed on a machine with higher power and less precision. The finishing process requires higher precision machining. Roughing and finishing are processed on different machine tools, which can fully utilize equipment capabilities and extend the service life of precision machine tools. At this point, the company did a very good job, buying Japanese imported machine tools for precision machining.
(3) In the machining process route, there are often heat treatment processes. The location of the heat treatment process is as follows: In order to improve the cutting performance of the metal, such as annealing, normalizing, and quenching and tempering, it is generally arranged before machining. In order to eliminate internal stress, such as aging treatment and quenching and tempering treatment, it is generally arranged after roughing and before finishing. In order to improve the mechanical properties of parts, such as carburizing, quenching, and tempering, it is generally arranged after machining. If there is a large deformation after heat treatment, a final processing step must be arranged.