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Hardinge CHNC Servo motor/system problems


Sep 21, 2008
Tualatin, Oregon
This Hardinge CHNC is a project. I have been having fun learning with it and on the day of failure I was setting tool offset. I was sneaking up to touch off X and after several clicks I realized the axis wasn't moving, In hindsight using old dc servo motors, without any inspection, was a bad decision. in spite of them having a good reputation.
Apparently the motor took out the servo driver on the Centroid ALLIN1DC - a regret that is growing. The problem with the ALLIN1DC is if one servo driver goes it puts the entire system into question. I would have rather had a failure on an individual servo drive because that isolated item could more easily be identified as a problem. My X axis failed and since a lathe only uses two of three drivers on board the ALLIN1DC, I should be able to switch X to the unused channel. However It appears that the X drive may have taken out some other components...I can return the board, that is under warranty, back to Centroid but the first words they said was it will cost you $475. They have already "guessed" the problem was caused by me rather than a board failure.
Let me say that I am a terrible troubleshooter; the coils on the X motor are not open; 1.2 Ohm and there is 1.2 MOhm to ground, which is not good. I will open the motor and take a look at the brushes/commutator. There is a local shop that may be able to work on them - I would refurbish both, if the direction is to continue with DC
At this point I could consider other options. It seems modern motors are AC and that would require a new controller...
I have been considering my options for a week and it's not clear, to me, what the direction forward should be.
What voltage do the servos run on? Haas brush motors run on 160 VDC and if carbon dust gets in the windings it causes a short. Particularly a problem if you blow out the dust through the brush holders which pushes it into the armature. The armature needs to be washed with something that does not remove the varnish coating.
I have 130 vdc going to the motors. Not sure how far into the motors I want to get. Now they are out of the machine, I'm going decide on whether I return them with the board for analysis. The timing for repairing the board then refurbing the motors, when they return, is easily a month. It's not like production is down but time is a factor.
One item that may affect the decision of what to do with the motors is that they were made by Redcom. Never heard of them - can't find them now.
Another bit of info is that the encoders are on the ballscrews not the motor. I would just need motors
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I got both motors rebuilt. The failed motor had to be rewound and both got new bearings, brushes and turned. Less that the cost of one new motor.
A general question about encoders, that are on the ball screws; there is adjustment but I am not sure how I will get it set up correctly or if I need to...?
What kind of signal does the centroid use? If analog+/- 10v, look for a couple AMC 25a20 amps on eBay. My guess is they use either step and direction or straight pwm. The blown up stuff shouldn't be to hard to find.
I had the board repaired - It has 3 servo drives. In hindsight I would prefer not to use the drives on the board but for now that's what I got. The motor position is controlled by an encoder mounted to the ball screw. The motor gets it's DC voltage via the board.
If I was to start over ( and I won't ) I would use AC servos with seperate drivers