I'll do some more testing on this problem, but maybe you have some experience with it already.
I have a job where the PM45CNC with WIndows Vista & USB motion controller & normal (not variable/VFD motor) is tapping about 160x 4-40 holes, all in a row, 90 rpm spindle speed via gearbox.
It uses a G84 cycle and Mach3 is configured to wait about 1.5 seconds in between spindle reversals to allow the spindle to coast to a full stop before turning on again (in either direction). I have checked that even after the machine is very warm (longer coast down times), it always comes to a full stop before reversing in either direction.
I may actually have two problems.:
1) G84 is a modal cycle with 160 x-y tapping coordinates following it.
After some amount of holes ..could be around 70, Mach3 will throw an error "Spindle not turning clockwise" ...and so it pauses, if I hit F5 to turn the spindle CW , I am able to continue, and it will continue for many cycles as it should. This seems like a Mach 3 issue as there is no feedback to Mach 3 from the mill for it to know if the spindle is turning. It could only "know" the spindle is not turning because it did not command the controller to turn on...but why did it not command the controller to turn on after many cycles of normal behavior.....buffer problem or such maybe?
2) Other times , I will get a sever "buzzing" noise from the motor when it turns the motor CW...I think it only fails in the clockwise start from zero rotation, not CCW. (need to do more tests) . It may buzz for a few cycles in a row, but eventually it will trip the breaker.
I am experimenting with electrical fans on the motor as it may be heat related....or time related...However with #1 happening sometimes I think it may be a software problem with the Mach3 to the controller, my gut says it may be trying to rapidly tell the motor to go clockwise then counterclockwise rapidly...So far I have not noticed any problems with the earlier holes only the later holes (with respect to run time,not line number)...and it if it does occur and I restart the cycles without either a cooldown or a reboot it does seem to recur sooner than from a fresh start.
I'll do a lot more testing but....maybe someone has experience with this already