Folks,
I have an issue with the spindle drive and motor on my Yamaguchi YMV-60 mill. The machine has sat for a year and a half or more unpowered. Recently I got it fired up. I ran the spindle slow, 100 rpm at first. I let it run for a couple minutes, then stopped it for a minute or so, then started it again. After a few minutes of that I ran it at 500 rpm, then 1000. Everything seemed to be going well. Then I got brave. I started it back up at 1000 then kicked it up to 2000. It ran for a few seconds, then made a sort of a squawk sound and now the motor makes noise. It not tremendously loud, but noticeable. Definitely not good as the load meter is higher now than before the noise. I noticed that when I was running it at 100 rpm before the noise the spindle speed was not very steady. It would speed up/slow down and the load meter fluctuated between 5% and nearly zero. Now the load meter is at least 10% @ 100 rpm with the noise. I ran the spindle (with no tool holder) on and off for around 20 minutes or so give or take. I don't have the drive information right handy. I will be able to add that to this post later tonight.
I have taken the belts off the motor, so I know that it is not spindle bearings. I checked the resistance between all 3 windings. They're about the same as far as my meter could tell, 0.7 ohms. No winding was shorted to ground. I did find something interesting, however. While running at 500 rpm the voltage across the two phases was 50 volts, two other legs was about 100 volts. I would think they should be a lot closer to each other than that. I checked the voltage at the main disconnect of the machine and got 234-242 volts. I have this running on a phase converter that I have used previously with my Mazak lathe with T1 control.
I investigated a bit further. I am quite certain it is in the drive or motor. The link below is a short video of it running. The first half is 100 rpm, then I sped it up to 500 rpm.
https://plus.google.com/104092800892...ts/AThiM2Chh7R
Picture of the motor:
Attachment 244238
I am hoping someone can educate me on these drives so that I can trouble shoot the failure. Perhaps the SCR's have faiiled, but what cause them to fail?
Thanks for your help,
Aaron