What are the principles for selecting milling cutters for cnc machining centers

The milling cutter should be used on the CNC machining center milling machine to process planes, steps, grooves, forming appearances and blocking workpieces, etc. This has a great impact on the quality of the processed parts, so how to choose a suitable milling cutter? What are the principles?

The milling cutter used on the CNC machining center should be made of all cemented carbide, and the general milling machine should be made of white steel. The hardness of white steel milling cutter and cemented carbide milling cutter is softer. Cemented carbide milling cutters have good thermal hardness and wear resistance, but poor impact resistance. If you drop the blade at will, it will break. The cemented carbide is made of powder metallurgy, the hardness can reach about 90HRA, and the thermal property can reach about 900-1000 degrees.

1. Number of milling cutter teeth

When choosing a milling cutter, consider the number of teeth. For example, a coarse-tooth milling cutter with a diameter of 100mm only needs 6 teeth, while a close-tooth milling cutter with a diameter of 100mm can have 8 teeth. The size of the tooth pitch will determine the number of cutter teeth that participate in the cutting during milling, and affect the smoothness of cutting and the requirements for machine tool cutting rate.

2. Chip flutes

Rough tooth milling cutters are mostly used for rough machining because they have large chip pockets. Assuming that the chip pocket is not large enough, it will cause difficulty in chip rolling or increase the conflict between the chips and the cutter body and workpiece. At the same feed rate, the cutting load per tooth of a coarse-tooth milling cutter is larger than that of a close-tooth milling cutter.

CNC machining aluminum shell

3. Cutting depth

When finishing milling, the cutting depth is shallow, generally 0.25—0.64mm. The cutting load of each tooth is small (about 0.05-0.15mm), the required power is not large, the close-tooth milling cutter can be selected, and the larger feed rate can be selected.

4. Application of rough milling

When carrying out heavy-duty rough milling, excessive cutting force can cause the machine with poor rigidity to vibrate. This chattering can cause chipping of the carbide inserts, and then shorten the tool life. The choice of coarse-tooth milling cutter can reduce the power requirements of the machine tool.

The price of milling cutters used in cnc machining centers is relatively expensive. A face milling cutter body with a diameter of 100mm may cost three to four thousand yuan, so you should choose carefully. Many people who have operated cnc machining centers have encountered over-cutting problems, so how to deal with this situation?

The workpiece processing process of the CNC machining center is no longer like the traditional processing equipment, which requires uninterrupted control of the machine tool to end, manipulate the various functional parts of the machine tool to perform messy and precise movements, and then end the processing process with high precision and efficiency. The programming of workpiece processing programs is the key to the processing of workpieces in machining centers. However, if the programming is unreasonable or the parameter setting is improper, it will severely affect the processing accuracy and processing power of the workpiece, such as overcutting. Overcutting is a serious problem in workpiece processing, and it can cause the workpiece to be invalid when it is severe. The front-line processing personnel have compiled a processing program that must have overcutting for some reason during the CNC programming. The system can announce the alarm signal in advance during the work process, which can avoid the overcutting incident. How to judge the cause of the overcut phenomenon in the CNC machining center?

CNC machining aluminum parts

1. Overcutting during arc machining of machining center

In the machining center for internal generalization arc processing, if the selected tool radius rD is too large, overcutting is likely to occur when it exceeds the required processing arc radius R. The NC machining programs are compiled according to the general track of the workpiece practice, without considering the movement track of the tool in the actual processing process. Because of the tool radius, the tool practice track becomes thicker and does not coincide with the programming track. In order to get the correct workpiece surface summary, it is necessary to set the tool radius compensation command between the tool track and the programming track. Otherwise, overcutting of the workpiece will be inevitable.

2. Judgment of overcutting during straight line processing

When the CNC machining center processes a workpiece composed of straight segments, if the tool radius is too large, it will most likely cause overcutting, and then cause the workpiece to be scrapped. It can be judged by the positive or negative of the scalar product of the programming vector and the corresponding correction vector.