In the CNC machine tools, especially in the machining center processing parts, the process is very complex, many parts only in a loading card to complete the entire process. But the rough machining of parts, especially forging blank parts of the reference surface, positioning surface and other parts of the processing, should be processed on ordinary machine tools to complete, in the card to CNC machine tools for processing. This can play the characteristics of CNC machine tools, maintain the accuracy of CNC machine tools, extend the service life of CNC machine tools, reduce the cost of using CNC machine tools. After rough machining or semi-finishing parts mounted on CNC machine tools, CNC machine tools in accordance with the prescribed procedures step by step for semi-finishing and finishing.
The choice of machining workpiece
Different types of parts should be machined on different types of CNC machines. CNC lathe is suitable for processing the more complex shape of shaft parts and complex curved rotary formation of the mold cavity. CNC vertical boring and milling machine and vertical machining center are suitable for processing box, box cover, plane cam, sample plate, complex shape of plane or three-dimensional parts, as well as the internal and external cavities of the mold. CNC horizontal boring and milling machines and horizontal machining centers are used to process various complex curves, curved surfaces, impellers, molds, etc. In short, different types of parts to use different CNC machine tools for processing.
1, the process division method for processing parts on CNC machine tools are.
① tool concentration division method The method is to divide the process according to the tool used, with the same knife to complete all the parts can be completed on the part. Then use the second tool, the third tool to complete the parts they can complete. This can reduce the number of tool changes, compress the empty travel time and reduce unnecessary positioning errors.
② Roughing and finishing sequencing method For a single part, roughing and semi-finishing should be done first, and then finishing. For a batch of parts, first all rough machining, semi-finishing machining, and finally finishing machining. Between roughing and finishing, it is best to be separated by a period of time, so that the deformation of the parts after roughing is fully recovered, and then finish machining, in order to improve the machining accuracy of the parts.
③ according to the processing part of the sequence method General first processing plane, positioning surface, after processing holes; first processing simple geometry, and then processing complex geometry; first processing lower precision parts, and then processing higher precision requirements of the parts.
In short, in the CNC machine tool processing parts, the division of the processing process according to the specific circumstances of the parts specific analysis. Many processes are arranged in accordance with the above-mentioned comprehensive arrangement of the sub-order method.
2, the workpiece loading card mode
In the CNC machine tool processing parts, because the process is concentrated, often in a card to complete all the processes. Therefore, the positioning of the parts, clamping method to pay full attention to the following issues.
① Try to use a combination of fixtures. When the workpiece batch is larger, the workpiece accuracy requirements are higher, you can design a special fixture.
② Parts positioning, clamping parts should be considered not to hinder the processing of various parts, tool replacement and measurement of important parts, especially to pay attention to not occur tool and workpiece, tool and fixture collision phenomenon occurs.
③ Clamping force should strive to pass through (or close to) the main support points or within the triangle formed by the support points; should strive to be close to the cutting part and in a place of better rigidity. Try not to be above the diameter of the hole being machined to reduce the deformation of the part.
④ Parts of the card, positioning to take into account the consistency of repeated installation, in order to reduce tooling time, improve the consistency of the same batch of parts processing. Generally the same batch of parts using the same positioning benchmark, the same mounting method.
3, the processing route to determine
Machining route refers to the trajectory and direction of tool movement during the machining process of CNC machine tools. The determination of each process machining route is very important, because it affects the machining accuracy and surface roughness of the parts. The following points should be considered in the determination of the machining route.
① Minimize tool-in and tool-out times and other auxiliary times.
② When milling the contour of the part, try to use the smooth milling processing method to reduce the machine chatter, improve the surface roughness of the part and machining accuracy.
③ choose a reasonable feed and retreat position, try to avoid normal cutting along the part contour and feed stop in the middle. Feed and retreat position should be selected in the unimportant position.
④ The machining route is generally to machine the outer contour first and then the inner contour.
