A CNC machining center with FANUC 6ME CNC control system, FANUC DC servo drive and SIEMENS 1HU3076 DC servo motor, the X axis motor runs high speed as soon as the power is on, and there is ALM410 alarm on the CNC controller then the machine stops.

This could be caused by the wrong connection of the armature or the analog tach.

The machine was re-conditioned earlier and the X axis motor was re-install, SIEMENS IHU3076 DC servo motor has no tachgenerator, so the actual motor speed return signal is transform from the F/V of the encoder, so the most possible reason is the wrong connection of the motor armature.

Disconnect the motor and the mechanical parts, this prevent damage from the motor impact, then exchange the armature polarities, power on and try, the problem solved.