A CNC machining center with Fanuc 6ME CNC system, when the X axis is not moving the machine works fine, but if the X axis moves there will be vibration and noise.

As there is no alarm and the machine works fine when the X axis is still, so the CNC system and driver should be no problem, and considering the X axis moves in position, the X axis position loop works normal too.

After check then found out the vibration is related to the moving speed of X axis, the speed is higher, the vibration is stronger, so this problem must be from feedback loop, causes could be below:

1-      Speed generator problem

2-      Speed generator connection problem

3-      DC servo motor problem

So we could check the connection between the X axis motor and speed generator, no problem found for this case. Then checked the X axis servo motor and inner speed generator, there were lots of carbon powder on the surface, clean it but the problem was still there.

Measure the resistance value between the speed generator and the motor phase switcher, compare and found the resistance value of one pair of phase switcher is much higher than the others, this means there was open loop inside the speed generator, change it then the machine resumed.