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Geobrick motor positioning problems


John
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I have a 4 axis system, all the same motor, on which 2 of the motors drive mechanisms ( Festo HSP modules ) to load parts into a spindle for an OD turning operation. The motors are running in ABS mode. From time to time, one or both of these motors don't load the part all the way into the spindle. When I do some testing by commanding the motor to this position, the motor is going to the commanded position but it is clearly coming up short. Also, when the motor is commanded to the home position, the home position is a physical stop, it is not zero. To get to zero the motor would have to go past the stop. There is a planetary gearbox and coupling in the drivetrain that we have been over repeatedly thinking something is moving or slipping but cannot find anything like that. I suspect noise but the machine will run fine for weeks even months and then this starts to happen. We struggle with it for a few days and then for no reason at all, it will start to run fine again.

 

Any thoughts on where to look next would be greatly appreciated.

John

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I have a 4 axis system, all the same motor, on which 2 of the motors drive mechanisms ( Festo HSP modules ) to load parts into a spindle for an OD turning operation. The motors are running in ABS mode. From time to time, one or both of these motors don't load the part all the way into the spindle. When I do some testing by commanding the motor to this position, the motor is going to the commanded position but it is clearly coming up short. Also, when the motor is commanded to the home position, the home position is a physical stop, it is not zero. To get to zero the motor would have to go past the stop. There is a planetary gearbox and coupling in the drivetrain that we have been over repeatedly thinking something is moving or slipping but cannot find anything like that. I suspect noise but the machine will run fine for weeks even months and then this starts to happen. We struggle with it for a few days and then for no reason at all, it will start to run fine again.

 

Any thoughts on where to look next would be greatly appreciated.

John

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I suspect that you are losing encoder counts. What kind of encoders do you have?

I would monitor the encoder count error bit. Set it to zero on power up, and cycle the profile repeatedly to see if it trips.

 

Richard,

The motors are parker BE232....with 2000 pulse per rev encoders and hall sensors.

I thought about that, but if I was losing encoder counts, wouldn't that result in the motor moving further than expected? I will check it out.

 

John

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I suspect that you are losing encoder counts. What kind of encoders do you have?

I would monitor the encoder count error bit. Set it to zero on power up, and cycle the profile repeatedly to see if it trips.

 

Richard,

The motors are parker BE232....with 2000 pulse per rev encoders and hall sensors.

I thought about that, but if I was losing encoder counts, wouldn't that result in the motor moving further than expected? I will check it out.

 

John

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