Milling cutter is used for machining plane, step, groove, forming surface and blocking workpiece on CNC machining center milling machine, which has a great influence on the quality of machined parts, so how to choose the appropriate milling cutter? What are the principles?
The milling cutter used in CNC machining center should be made of all cemented carbide, and the one used in general milling machine should be made of white steel. The hardness of white steel milling cutter and carbide milling cutter is relatively soft. Cemented carbide milling cutter has good thermal hardness, wear resistance, but poor impact resistance. If you drop the blade at will, it will be broken. Cemented carbide is made by powder metallurgy. Its hardness can reach about 90hra and its thermal property can reach 900-1000 degrees.
1. Number of teeth of milling cutter
When selecting a milling cutter, the number of teeth should be considered. For example, a thick tooth milling cutter with a diameter of 100 mm only needs 6 teeth, while a close tooth milling cutter with a diameter of 100 mm can have 8 teeth. The size of tooth pitch will determine the number of cutter teeth participating in cutting together during milling, and affect the stability of cutting and the requirement of cutting rate of machine tool.
2. Chip holding tank
Rough tooth milling cutter is often used for rough machining because it has a large chip groove. If the chip holding groove is not large enough, it will cause chip rolling difficulty or chip conflict with cutter body and workpiece. Under the same feed rate, the cutting load of coarse tooth milling cutter is larger than that of dense tooth milling cutter.
CNC machining of aluminum shell
3. Cutting depth
In finish milling, the cutting depth is shallow, generally 0.25-0.64mm. The cutting load of each tooth is small (about 0.05-0.15mm), and the required power is not large. It can select the dense tooth milling cutter and select a larger feed rate.
4. Application of rough milling
In heavy load rough milling, excessive cutting force can make the machine tool with poor rigidity vibrate. This kind of vibration will cause the carbide blade to break and then shorten the tool life. The use of coarse tooth milling cutter can reduce the requirement of machine power.
The price of milling cutter used in CNC machining center is relatively expensive. The price of a face milling cutter with a diameter of 100 mm may cost 3000 yuan, so it should be selected steadily. Many people who have operated CNC machining center have encountered over cutting problem. How to deal with this situation?
The workpiece processing process of CNC machining center is no longer like the traditional processing equipment. It needs to continuously control the machine tool to finish, and control the functional parts of the machine tool to carry out messy and precise actions, and then finish the processing process with high precision and high efficiency. The programming of workpiece processing is the key of machining center. However, if the programming is not reasonable or the parameters are not set properly, the machining accuracy and power of the workpiece will be seriously affected, such as over cutting. Overcutting is a serious problem in workpiece processing, which can lead to the invalidation of workpiece. For some reason, the front-line processing personnel have worked out the machining program which is sure to occur overcutting. The system can announce the alarm signal in advance in the working process, so as to avoid the occurrence of over cutting. How to judge the cause of over cutting in CNC machining center?
CNC machining of aluminum parts
1. Overcutting in arc machining of machining center
In machining center, if the tool radius RD is too large and exceeds the required arc radius r r, it is likely to cause over cutting. The NC machining program is compiled according to the practical summary track of workpiece, without considering the motion track of tool in the process of practical machining. Because of the existence of tool radius, the tool practice track becomes thick and does not coincide with the programming track. In order to get the correct summary of the workpiece surface, it is necessary to set the tool radius compensation command between the tool path and the programming track. Otherwise, over cutting of workpiece will be inevitable.
2. The discrimination of cutting straight line
In CNC machining center, if the tool radius is too large, it is very likely to cause overcutting and then void the workpiece. It can distinguish the positive and negative of the scalar product of the programming vector and its corresponding correction vector.
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