I have a 2001 Mini Mill that's has been giving me some problems for the last couple of months.
It used to happen once in a while but now the machine won't make it through a single program.
Error code 123.
Fault happens during spindle start.
Programmed RPM doesn't matter, happens at 500rpm and up to 6000rpm.
Also happens during a tool change occasionally.
All the voltages are correct at 240 single phase with a large ground wire installed.
None of the drives are showing a red fault light.
Fans are running on the drives and the power source.
Ambient temperature is a comfortable 70deg F.
More likely to happen after the machine has run for an hour or two vs. first thing in the morning.
I measured the spindle motor winding at 0.001ohms between all three pairs.

Any ideas?

Timothy