In the usage of high-speed CNC milling machine, the protection of the spindle is crucial. During high-speed operation, the spindle is prone to overheating, abnormal vibration, and power overload issues. To address these problems, effective protection strategies must be implemented to ensure the high-speed CNC milling machine operates efficiently and stably.
When the spindle rotates at high speed, the bearing temperature rises significantly. Therefore, to protect the high-speed CNC milling machine spindle, a dedicated cooling system must be equipped in the design. The spindle typically includes three bearings at the front end, middle, and rear end. To monitor the spindle bearing temperature in real-time, temperature sensors are installed near the bearings. These sensors collect signals via the PLC analog input module, with signal types categorized as 4~20mA and PT100. The control program calculates the temperature based on the sensor signals and sets two threshold limit values to protect the bearings. When the bearing temperature exceeds the set value, the system will automatically stop the coordinates and spindle operation to prevent damage caused by excessive temperatures.
High-speed CNC milling machines must maintain balance during high-speed rotation. If the spindle is imbalanced, it will result in significant vibration, affecting machining accuracy. To address this issue, we install a vibration detection device inside the electric spindle, which can monitor the spindle's vibration in real-time. Since spindle vibration is higher during acceleration compared to normal machining, we set two vibration limit values: one for the acceleration process and another for the normal machining process. The vibration monitoring module and the machine control program work together to ensure the vibration values are within the permissible range. If the vibration value exceeds the limit during acceleration, the system will alarm and stop the spindle rotation. During normal machining, if the vibration value exceeds the constant-speed processing limit, the system will also alarm and stop the coordinate operation. The operator must check the machine condition and restart cutting after fixing any issues.
During the high-speed CNC milling machine cutting process, if the cutting load is too large, the spindle may reach the upper limit of its rated power, which is crucial for spindle protection. At this time, real-time monitoring and control of the spindle current is necessary. In the spindle control system, we set up current monitoring. Once the current exceeds the limit value, the system will notify the NCK via the PLC DB interface and trigger a timer to control the stop of spindle and coordinate operation. This measure not only ensures the safe operation of the spindle but also maximizes its utilization, ensuring that the high-speed CNC milling machine can operate stably under high load conditions.
Through the above measures, we can effectively protect the spindle of the high-speed CNC milling machine, ensuring its efficient and stable operation under various working conditions. Spindle temperature protection, spindle vibration protection, and spindle power protection are indispensable key links in high-speed CNC milling machines. Only by achieving perfection in these aspects can we truly leverage the advantages of high-speed CNC milling machines.