I recently added CNC to my RF31 Mill. While testing its ability to precisely repeat cutting a 2 inch square, I noticed that on the second pass (and on) it cuts an additional .010 on the bottom of the square along the X axis, each which is then reflected on the X axis cut along the top of the square. For each time I repeat this the path along the Bottom and top of the square becomes wider. Cuts along Y axis sides of the square stay in their original width. I have checked everything as far as offsets, wrongly tuned motors, etc, and I am stumped.
Has anybody experienced this problem and how was it resolved?

Thanks
Mel Stanley, Utah

Hi Mel,
your machine is gaining/losing steps in the Y axis.

May I suggest as an experiment swap the drive signals to the  X and Y axes stepper drivers and run the same program.

If the drivers and steppers are good the fault will stay on the Y axis and you can look closer at your Mach installation
or BoB. If the driver  and/or stepper are faulty the fault will now be on the X axis.

Gives you a means to focus on the right area.

Craig

And to add to what Craig said, this is a new install correct?  If that axis is  binding in some way or the steppers are not geared right it will miss steps.  I added CNC to my RF31  mill - drill years ago and it was very disappointing, so slow.

Yes it is a new install with a "newbie" steering it and i might as well be blindfolded.
I thank you for your advice and thank you for posting it. At least now i have a way to isolate the problem.