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I have a 12Z mill I bought from Aaron many years ago. I also got the CNC kit as well.
Within the past year I began to have a problem when I turned the motor on. If I have the speed set at 3 the spindle turns
at only about 40 rpm. I then gear down to 2 and it starts fine. I have to leave it running in 2 for 5-10 minutes before I can
switch it back to 3 and have it go to full rpm. I suspect I am having problems on the spindle bearings. Is this a reasonable
diagnosis?
Jim
Very possible. I had to replace the bearings almost right away. After opening up the gearbox there were at least two that had been pressed into undersized pockets so hard that the races actually split! I was lucky enough to know a machinist who bored the pockets out a few thousandths and I was back in business with quality bearings. If you can find the parts (I've actually forgotten who was making them now, but it's all over this forum) for a belt drive, you might consider converting.
Replacing the spindle bearings made a difference too. Particularly the top bearing. Check for resistance turning it in neutral.
Good luck either way.
are you running the original motor? that one had a start and run capacitor. sounds like the start capacitor has died and the motor doesn't have enough torque to get started in gear 3. if your running a servo motor then it maybe a a capacitor in the vfd.
Yes, I am running the original motor. I had considered that the motor might have problems. It seems that it may have dead spots on the armature. Sometimes when I turn the motor on it just hums and does not turn the spindle. I rotate the spindle just a little bit manually and then it starts.
I just ran some further tests this morning. With speed set to H1, H2 or H3, I can stop the spindle from turning by hand. With speeds set to L2 or L3 I can manually stop spindle rotation. On L1, I cannot quite stop the spindle rotation. These symptoms kind of
indicate a motor problem. But if it is a capacitor failure, this does not explain why I can run in H2 for about 5 minutes and then H3 will then work.
Ksanalytical,
My mill does not have a neutral position per se, but I placed both levers out of the detents and had no problem turning the spindle by hand.
Runner4404spd,
I am kind of leaning towards believing the motor has issues. If I had spindle bearing issues I would expect some friction heating. I ran the mill for 30 minutes and the gearbox was warm to the touch, but not hot. It was about 80 degrees. The spindle stickout was
cooler than that.
If I have to replace the motor, I might as well go all the way to a VFD.
I took the motor to an electric shop. The found the starting armature was in the wrong position and fixed it.