21 Basic Common Sense Of CNC Engraving Machining (1)
13. There is a phenomenon of holding back during the processing of a new knife, and the processing is very laborious. What parameters need to be adjusted at this time?
The reason why the machining is very laborious is that the power and torque of the spindle cannot withstand the current cutting amount. A reasonable approach is to remake the path to reduce the depth of the tool, the depth of the groove, and the amount of trimming. If the overall processing time is less than 30 minutes, you can also adjust the cutting speed to improve the cutting state.
14. What is the role of cutting fluid?
Pay attention to cooling oil for metal processing. The role of the cooling system is to take away the cutting heat and flying chips, and to lubricate the processing. The coolant will remove the cutting heat, reduce the heat transferred to the tool and the motor, and increase their service life. Take away flying chips to avoid secondary cutting. Lubrication can reduce the cutting force and make processing more stable. In the copper processing, the selection of oily cutting fluid can improve the surface quality.
15. What are the stages of tool wear?
Tool wear is divided into three stages: initial wear, normal wear, and sharp wear.
In the initial stage of wear, the main cause of tool wear is that the temperature of the tool is low, and the optimal cutting temperature is not reached. At this time, the wear of the tool is mainly abrasive wear. Such wear has a relatively large impact on the tool, and it is easy to cause the tool to collapse Knife.
This stage is a very dangerous stage. If it is not handled well, it may directly cause the tool to collapse and fail. When the tool passes the initial wear period, the cutting temperature of the tool reaches a certain value. This is the main wear is diffusion wear, and its function is mainly to cause local spalling. Therefore, wear is smaller and slower. When the wear reaches a certain level, the tool fails and enters a period of rapid wear.
16. Why do tools need to be run-in and how to run-in?
We mentioned above that the tool is easy to collapse in the initial wear stage. In order to avoid the phenomenon of collapse, we must run-in the tool. The cutting temperature of the tool is gradually increased to a reasonable temperature. It is verified by experiments that the same processing parameters are used for comparison. It can be seen that after running-in, the tool life has increased by more than 2 times. The method of running-in is to reduce the feed rate by half while maintaining a reasonable spindle speed, and the processing time is about 5-10 minutes. Use a small value when processing soft materials, and a large value when processing hard metals.
17. How to judge severe tool wear? The method of judging severe tool wear is:
1) When listening to the processed sound, there is a harsh call;
2) Listening to the sound of the main shaft, the main shaft is obviously holding back;
3) It feels that the vibration increases during processing and the machine tool spindle has obvious vibration;
4) Looking at the processing effect, the knives on the processed bottom surface are sometimes good and sometimes bad (if this is the case at the beginning, it means that the depth of the knife is too deep).
18. When should I change the tool?
We should change the tool at about 2/3 of the tool life limit. For example, if the tool is severely worn in 60 minutes, the next time it is processed, the tool should be changed within 40 minutes, and the habit of changing the tool regularly should be developed.
19. Can severely worn tools continue to be processed?
After the tool is severely worn, the cutting force can be increased to 3 times the normal. The cutting force has a great influence on the service life of the spindle electrode, and the service life of the spindle motor is inversely proportional to the third power. For example, when the cutting force is increased by 3 times, processing for 10 minutes is equivalent to the spindle using 10*33=270 minutes under normal conditions.
20. How to determine the protruding length of the tool during roughing?
The shorter the extension of the tool, the better. However, in actual processing, if it is too short, the length of the tool must be adjusted frequently, which will affect the processing efficiency too much. So how should the protruding length of the tool be controlled in actual processing?
The principle is as follows: a φ3 diameter cutter bar can be processed normally if it extends 5mm. The φ4 diameter tool bar can be processed normally if it extends 7mm. The φ6 diameter cutter bar can be processed normally if it extends 10mm. Try to go below these values when loading the knife. If the length of the upper knife is greater than the above value, try to control the depth of the machining when the tool is worn. This is a bit difficult to grasp and requires more exercise.
21. What should I do if the tool breaks suddenly during processing?
1) Stop processing and check the current serial number of processing.
2) Check the broken knife to see if there is a broken knife body, and remove it if there is one.
3) Analyze the reasons for tool breakage. This is the most important. Why did the tool break?
If we want to analyze, we must analyze the various factors that affect the processing mentioned above. But the reason for the broken tool is that the force on the tool suddenly increases. Or the path problem, or the tool jitter is too large, or the material is hard, or the spindle motor speed is incorrect.
4) After analysis, change the tool for processing. If the path is not changed, the original serial number should be advanced one serial number for processing. At this time, the feed speed must be reduced. One is because the broken tool is hardened severely, and the other is the tool running-in.
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