[Fonzi]

Machine:
2004 Fryer MC-60 VMC with Anilam 6000 touch Controller

Symptom:
The Y axis loses about .020" after making a single circle interpolation.

Frequency of Issue:
I ran a large test 20" spiral style pocket with a 3/8" endmill to see if the position offset would be greater, and it was not, still about .020".
It seems that it loses about .020" with each program run.

Detail:
I have a vacuum table set as my fixture with the center of the vacuum table as my (G53O01) fixture offset.

If I set my offsets to the center of the vacuum table, home the machine, then move to X0Y0 (center of table), the mill returns to the correct center location.
Then if I make a circle motion of any radius, then return to X0Y0 the Y-axis is about minus .020" from the center of the vacuum table.
If I make another circle motion and return to X0Y0 the Y-axis is about minus .040" from the center of the vacuum table. So on and so forth.

This machine hasn't had any issues in the 5 years that I have had it. This problem started a couple days ago and has been doing it since.

My Theory:

My original thought is an encoder issue.

There is a linear encoder on the Y-axis, which originally I thought was causing the problem.
I went into the Setting Option to disable the linear encoder to find that it wasn't enabled.

I then enabled the Y-axis linear encoder, restarted the unit and homed the machine.
The Y-axis now homes to a different position.
The Y-axis machine zero is now about 3" less than it was before enabling the linear encoder.

I then set the New Offsets of the vacuum table, re-homed and made a move to fixture center X0Y0. The machine moved to the correct position.
I ran a program, and returned to fixture center and the Y-axis was off again by .020".

My understanding is that the purpose of having a linear encoder and servo mounted rotary encoder on a single axis is to account for any axis discrepancy. ie Backlash.

I'm now assuming that the rotary encoder may be at fault.
I contacted Fryer to inquire about a new rotary encoder, this is not an option, a whole servo motor must be purchased with the encoder.

I don't have an issue with spending the money to get this machine running correctly, but with not being 100% sure of the issue, I write you this long novel
of a post to get another opinion from someone who may have some experience with this issue.

Thanks in advance.
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UPDATE: SOLVED
Turned on Backlash Compensation for the Y-Axis, and set the value at .0012".
Works like it should, I will take care of the backlash at a later date.

[mario349]

The backlash comp should have been ON already. Some one messed with it somewhere along the line. You may want to go to .0010 for comp, you may be slightly over corrected at .0012. If you need further help you can contact me at [email protected].