The spindle was told to turn, but the drive saw it wasn't turning, or it lost the speed signal. Spindle amplifier alarm 31.
What causes Fanuc alarm SP9031?
Spindle mechanically locked by a crash or seized bearings. Tool or drawbar problem holding the spindle. Lost signal from the spindle motor's speed sensor. Belt broken.
How do I fix Fanuc alarm SP9031?
Power off and try to turn the spindle by hand. It should turn smoothly. Check belts. Look for crash damage. If the spindle is tight or rough by hand, the spindle needs a tech, and probably a rebuild.
Alarm numbers and text can differ by control model, software version and machine builder. This page is a starting point from people who have worked on these machines, not a replacement for your machine builder's manual.
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