spindle drive fault

Mark McGrath · Mar 13, 2003

We have a Bullard lathe with a GE2000 control.
Today when the operator pressed cycle start,the spindle went straight to max rpm.The control shut the machine down and gave us a "spindle drive error" message.My first thought is that the tacho is faulty.How do I check it and has anyone any ideas of what the problem could be?
Mark

mikel · Mar 13, 2003

I'm not sure about your lathe but most have a belt that drives the encorder or tack. See if it broke or came off. Also does the drive ready light come on when you power up the machine?
Mike

Mark McGrath · Mar 13, 2003

The tacho is direct coupled to the motor which is a General Numeric.Anyone know the maker?
Mark

jon · Apr 3, 2003

hello
i believe general numerics were made by fanuc. there should be a board that provides a +/- 10 volt speed command from the control to the drive. zero volts being zero speed an 10 volts being max rpm. you could check this voltage. i had this problem on a cincinnati milacron control one time. as soon as you turned the machine the ref voltage went to 15 volts and maxed the spindle motor.
jon

Mark McGrath · Apr 3, 2003

Hi.The fault was the tacho.These things generate a voltage proportional to the speed.This particular one puts out 20V/1000rpm.As the old one was only attaining 15V the control thinks the motor is only doing 750 revs and keeps speeding it up.A new one was quoted at £490/$780,luckily I had a brand new motor that I had picked up at auction for£10 that had the same tacho.
Regards,Mark

GregCNC · Apr 4, 2003

General Numerics was a company formed to market Fanuc controls and Siemans servo/spindle drives. You most likely have a 6RB or 6SC series spindle drive. Look inside the side wall of the drive unit to find a paper with the numbers. Good show on getting the tach. Siemans wants quite a bit for their parts. When Fanuc got bigger, they ditched General Numerics and then you got a Siemans control like the 810 series. Finally, Siemans got big enough and General Numerics went away. There should be a set of schematics available if you want to troubleshoot and repair your own drive problems. We have several different sets. Good luck with your machine.

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