A machining center equipped with the FANUC-0MC system has been modified by CNC. After a period of use, a tool change failure occurs. When the tool is inserted into the spindle hole, there is no alarm message on the misaligned machine tool.
Analysis and repair process:
After careful observation of the machine tool failure, it was found that the tool insertion was misaligned because the spindle was oriented and then deviated from the original position. When using manual method to check the orientation of the spindle, there is a strange phenomenon: the position of the spindle is correct after the orientation is completed. When the spindle is moved by hand, the spindle will slowly rotate a small distance in the opposite direction of the force.
When it rotates counterclockwise, it only rotates a little after the orientation is completed, and it can return to the original position after turning clockwise after the force is applied. In order to confirm whether the electrical part is normal, the related signals are checked after the spindle orientation. Since the directional control is detected by the encoder, there is doubt about the encoder.
Check the electrical and mechanical connection of this part. When the encoder is disconnected from the main shaft, it is found that the coupling backscrew on the encoder has been loosened and moved backward, so the encoder and the detection gear cannot be synchronized when working , Making the orientation of the spindle inaccurate, causing tool change misalignment.