Dyna Mite 2400 Drill Problem / Repair?

I have a Dyna Mite 2400 drill with cnc control, etc. All of a sudden a few weeks ago, a strange problem started. I drill holes in small circles (like watch bezels) in various radii, sizes, # of holes etc. All of a sudden as the machine is going around in its program, it goes off track. like it will be making a circle and then jump to the left and continue the circle. When we turn the machine on the Y-axis is for example .0355, then turn it off and on again and its .0415 then off and on again and its .0315, etc. The X and Z axii are staying the same. IT seems as if the Y-axis backlash is changing between runs, and sometimes DURING the run. The machine, when it initializes, measures the backlash and compensates for it, and between runs, or during one, when the backlash changes, the machine is not changing its compensation, but rather compensating for the original # (which is now wrong), etc. Has anyone run into a similar problem and had it fixed?

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"Ratedr" wrote in news:1155830545.054640.309380 @b28g2000cwb.googlegroups.com:

The control can only compensate effectively for a certian amount of backlash, generally, once you get past .20 mm you will start to see problems. The stepping off circle could be a result of that, or it could be a result of a bad encoder cable/encoder/resolver/etc. I would check the mechanical backlash in each axis as a start.

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Pretty sure those are plain stepper drives having no feedback device at all.

As such, I would suspect binding or excessive friction at the gibs or leadscrew.

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  1. do you know how to measure backlash, using a dial indicator?
  2. If it is not backlash, then the problem is a dirty encoder, or tach/resolver. or possibly a loose coupling.
  3. Is the Dyna-Mite a stepper driven machine. If so that would explain the encoder postion changing from on/off/on. but you would see a similar result on the other axis's too.
  4. If it is a servo based machine, then it sounds like the servos go through a calibration motion at startup. So small that the display may not register it, but if you have a bad encoder/resolver etc... than that would explain the position jump too.


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