1, the phenomenon: high-speed gantry machining center, CNC system for the FANLiC OM a processing center in either the MDI mode or AUTO mode, give the spindle speed command, press the start button, machine PLC immediately sent "spindle unit failure" alarm information The Observe the alarm number of the spindle servo unit in the cabinet is AL-12.

Fault diagnosis: alarm number AL-12, meaning the spindle unit inverter circuit DC side of the over-current occurred. Remove the front panel of the machine tool spindle unit and the middle of the power control board, revealing the bottom of the two 150A high-power IGBT transistor module. Each ICBT module encapsulates six IGBT transistors and six damped diodes to form two sets of three-phase full-bridge, which are used for rectification and inverting, respectively. Using a multimeter to measure the pin diagram, it was soon found that one of the transistor modules in the ICBT tube has a short circuit phenomenon.

2, the fault has been identified, it seems that as long as the outsourcing of a transistor module put on, the spindle unit will be able to repair. But can not be so simple to deal with, the important question is to find out the root cause of the failure. The warp operation I inquires about the fault process. The operator says that when the spindle box moves to a different position, the spindle sometimes works normally and sometimes does not work properly. In particular, when the spindle box moves along the machine beam (ie, the r-axis), the spindle can run normally at some locations. In order to determine the occurrence of the fault and the location of the spindle box contact, climb the beam to carefully observe the movement of the spindle box, and soon found the cause of r failure. The original spindle box as the machine's r-axis along the beam movement, the spindle motor power line and feedback line is connected through the cable towline and electrical cabinet, towline with the spindle box on the beam movement. The material of the towline is engineering plastic, but the connection pin between each section is metal. When the cable in the towline moves with the towline, the insulating sheath of the cable friction with the connecting pin, The metal wire in the cable collides with the connecting pin of the metal, and the connecting pin is directly connected with the bed of the machine tool, resulting in the power line of the spindle motor. When the spindle is moved to a certain position, Short to ground, the power transistor module of the machine tool spindle drive unit is punctured. This is the root cause of ICBT module damage.

3, troubleshooting: replace the transistor module, the worn cable for processing and replacement of the cable chain in the way to improve the cable, so that the cable and connecting pin no longer friction. After this repair did not occur after a similar failure.