Causes and solutions to the failure of the CNC tool holder to keep rotating, and not stop at the right position.

During the automatic operation of this lathe, the tool holder occasionally runs continuously or a certain tool position does not stop. Sometimes, it runs continuously for 2 to 3 tool positions and then stops and locks. When continuous operation or a certain tool position does not stop, the alarm number "301" appears on the display (tool holder failure). The machine tool automatically stops. When 2 to 3 tool positions stop and lock after continuous operation, the alarm number is not displayed. The machine tool automatically runs. normal.
 
Since the fault is random and irregular, it is difficult to locate the maintenance personnel and determine that it is an electrical control fault after inspection. After measuring the output voltage of the tool post control system, it is normal to check that the relay of the tool post control system is also normal. Then the protective cover on the top of the tool holder was removed and the input voltage of the Hall element signal line was measured one by one. It was found that the copper core in the middle of one signal line was broken and was temporarily connected by the wire protective rubber skin. When the tool holder was rotated to a certain position, the wire protective rubber skin was damaged. If the two ends of the copper core wire are tightened and cannot be connected normally, the program control system cannot find the corresponding knife number and a "301" alarm will appear. When the machine tool is reset and the tool holder is manually rotated to a certain position, the protective rubber covering of the wire is loosened and both ends of the copper core wire are connected. The tool holder rotates normally and no alarm signal appears anymore. Troubleshooting: After the maintenance personnel replaced the Hall element connection signal line, the test run fault was eliminated and the machine tool ran normally.
 
Comprehensive analysis of the fault finding and troubleshooting processes in the above two cases shows that CNC machine tool faults not only occur in the electrical part but also in the mechanical part. For CNC lathes equipped with the above two systems, they are semi-closed-loop control systems and do not have mechanical fault feedback functions. Routine maintenance and upkeep must be strengthened during operation and use. If an "alarm number" is not displayed after a fault occurs, it is likely to be a mechanical fault, which should be focused on during maintenance. Checking the mechanical part will help maintenance personnel troubleshoot the problem more accurately and in a timely manner.