Shenzhen hardware processing factory: Principle of CNC milling cutter and over-cutting problem handling
by：QY Precision 2020-03-23
Shenzhen jinboshi precision hardware teaches you how to look at the principle of CNC milling cutter and the problem of CNC machining over-cutting. Everyone must take notes!
If you don't understand anything, you can leave a message for consultation or call for negotiation. The following contents are for reference only!
The milling cutter should be used for machining planes, steps, grooves, forming surfaces and intercepting workpieces on the CNC machining center milling machine, which has a great impact on the quality of the machined parts, so how to choose the right milling cutter? What are the principles?
Milling cutters used in CNC machining centers should be made of all cemented carbide, while those used in general milling machines should be made of white steel.
White steel milling cutter and cemented carbide milling cutter are softer in hardness.
Cemented carbide milling cutter has good heat hardness and wear resistance, but has 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 properties can reach 900-About 1000 degrees.
1. Number of teeth of milling cutter when selecting an milling cutter, its number of teeth should be considered.
For example, a coarse tooth milling cutter with a diameter of 100 only needs 6 teeth, while a dense tooth milling cutter with a diameter of 100 can have 8 teeth.
The size of the pitch will determine the number of cutters that participate in cutting together during milling, affecting the stability of cutting and the requirements for the cutting rate of the machine.
2. Coarse tooth milling cutters in chip-containing slots are mostly used for rough machining because they have larger chip-containing slots.
Assuming that the chip-containing groove is not large enough, it will make it difficult to roll chips or the conflict between chips and the cutter body and workpiece will increase.
At the same feed speed, the cutting load per tooth of the coarse tooth milling cutter is larger than that of the dense tooth milling cutter.
3. The cutting depth is shallow during fine milling, generally 0. 25-0. 64mm. The cutting load per tooth is small (About 0. 05--0. 15mm)
The required power is not large, the dense tooth milling cutter can be selected, and a larger feed can be selected.
4, the 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 can cause the hard alloy blade to collapse and then shorten the tool life.
The selection of coarse tooth milling cutter can reduce the power requirement of the machine tool.
The price of milling cutter used in CNC machining center is relatively expensive. The price of a 100 diameter surface milling cutter may be 3000 or 4000 yuan, so it should be selected steadily.
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 CNC machining center is no longer the same as that of traditional machining equipment, requiring uninterrupted control of machine tools to end, and controlling various functional components of machine tools to perform messy and precise actions, then finish the processing process with high precision and high efficiency.
The compilation of workpiece machining program is the key to workpiece machining in the machining center.
However, if the programming is unreasonable or the parameter setting is improper, it will seriously affect the machining accuracy and processing power of the workpiece, such as over-cutting.
Over-cutting is a serious problem in workpiece processing, which can lead to invalid workpiece when it is severe.
For some reason, the first-line machining personnel have worked out a machining program that must have been cut, and the system can announce alarm signals in advance in the work process, it can avoid the occurrence of the incident.
How to judge the reason for the over-cutting phenomenon in the CNC machining center?
1. If the radius rD of the selected tool is too large, when the radius R of the arc to be processed is exceeded, it is likely to be over-cut.
The numerical control machining program is compiled according to the workpiece practice summary track, regardless of the moving track of the tool in the practice machining process.
Because the existence of the tool radius makes the tool practice track bulky and does not coincide with the programming track, it is necessary to set the tool radius compensation instruction between the tool track and the programming track in order to obtain the correct workpiece surface generalization. Otherwise, the workpiece over-cutting will be inevitable.
2. Over-cutting discrimination during linear machining when the workpiece composed of linear segments is processed in the CNC machining center, if the tool radius is too large, it is very likely that over-cutting will occur, then the workpiece is invalidated.
It can be judged by the positive and negative of the scalar product of the programmed vector and its corresponding correction vector.