Accuracy and precision are two important concepts in measuring of CNC machined parts, accuracy refers to the closeness of the measured result to a specific value. But we often encounter the fault of CNC machines tools causes abnormal machining accuracy, the error is usually hidden and difficult to diagnose. Follow us to explore the reasons that reduce CNC parts accuracy and how to find out the problems.
The changes in the modification of the parameters of the CNC system, mechanical failure, and electrical parameters not optimized are common causes of abnormal CNC machining accuracy in production. Find out the related failure reasons and deal with it, the machine can return to normal and produce more accurate parts.
1. The parameters of CNC system changed or modified
The system parameters include machine feed unit, null offset, back lash and more. There are two kinds of feed units: Metric system and the English system. In the process of repairing CNC machines, the null offset and back lash often affected by some operations. On the other hand, serious machinery wear or loose connection also may cause the measured value of parameters change, the parameters need to be modified accordingly to meet the requirements of machining accuracy
2. Mechanical faults
Mechanical faults can cause cutting error, then affect machining accuracy. When you exclude the possibility of hard fault of electrical control, check the machining program section that is running when the accuracy is abnormal, especially the tool length compensation, the calibration and calculation of the machining coordinate system, and judge whether there is any hidden danger in the mechanical aspect through seeing, touching and listening.
3. The electrical parameters are not optimized, and the machine operation is abnormal
Use the parameter function of the CNC system, debug the motor, compensate the back lash, adjust the servo gain parameter and eliminate the motor jitter.
4. Positional error
The positional error, programming, selection of cutting tools and other factors will also lead to abnormal machining accuracy
1. From exterior to interior. CNC machine tool sets mechanical, hydraulic, electrical as one machine, so we can check out the problems from these three aspects. The repair personnel should check one by one from outside to inside, try to prevent the machine from being unsealed and disassembled at will, otherwise the fault may be expanded.
2. From mechanical to electrical. Mechanical faults are easier to detect, while it’s more difficult to figure out the problems of the CNC system, eliminate the mechanical failure first can improve the efficiency of troubleshooting.
3. From off to on. Investigate, test and analyze without electricity, to confirm there are no non-destructive faults, then power on the machine tool, in the running condition, inspect and test to find the problem. For destructive faults, the risk must be eliminated before switch on.
4. From simple to complex. When there are many kinds of faults in a messy, we should start with the simple problems, then consider complicated ones.