My '95 Parter I occasionally jumps in the X axis. It can happen any time, such as when edgefinding, peck drilling in a program, or during part changes. It can be as much as an inch, but usually it's around .3 or .4, can't seem to find a pattern such as which direction. Any ideas?

Other than verifying the cables are in good shape and no connections are lost.

Most of the time an axis jumps is when the tach commutator gets dirty from carbon as the brushes wear and the velocity feedback is lost.

You can remove the cap from the end of the motor, remove the encoder plate as an assembly. There will be a phenolic disk that covers the tach with the tach brushes attached to it. Note/mark its position and carefully lift it out of the housing. Now you can flush the commutator off with some contact cleaner. A small toothbrush helps to scrub between the copper commutator poles. Soak up the remaining cleaner and let dry. Flush out the brush assembly and place it back in the housing paying close attention when the brushes are going back onto the commutator, as you will need to get them to slide into their holders as the brush mounting disk goes in place.

If the axis is losing accuracy, there may be an issue with the encoder itself. I have heard that the encoder glass disk can come loose from its hub. Otherwise its output may be failing from age.

DC

I had a similar problem on my Partner 1, the axis was running away though. It turned out to be an accumulation of small problems, the biggest one being an open armature. Then there was the weak motion control board, wires with to much resistance. All is well now, works great.

Dave

ill bet you anything you are getting coolant into where the encoder is,check for loose cable at the motor and check the condition of the motor,extreme build up of brush dust cause big problems too,my buddies partners y axis was getting coolant leaked on it for years,didnt know it,finally it bit the dust,is the x the only axis doing this?if so that rules out the controll and amp board,leaves the motor,cables,servo drive board,could always swap the board with the y,just to see if its that,good luck
steve