I am having a problem with my  Y axis.  I am trying to cut 2 small parts out of aluminum - 3/4x 1.  Mirrored so there is a left and right.   I have the Gecko 540, a taig mill, I use Rhino and Rhino Cam for cad/cam generation.  This is not a new set up I have been using the mill for more than a year.
When I first ran the program for the exterior profile, the Y axis looked like it was loosing steps in the +Y direction. The cuts keep creeping towards - Y.  the X axis is working fine as is Z.   I stopped the program before it could cut both parts. I replaced my power supply and stepper motor.  I reran the same program in wax letting it cut both profiles. It steps toward -Y on the first piece and then towards  +Y on the 2nd piece. On the Second piece the steps are reversed.

  I rechecked the Rhino Cam Paths and regenerated them, deleted the original file in Mach and transfered the new file and its still doing the same thing.
I have another mill with a seperate controller/computor,I took the same file loaded it into Mach and it runs fine. No wierd stepping.

Both mills have dedicated computors and controllers. I do my cad cam on a seperate computor. 

ANy thoughts?

I thought I would post my findings incase anyone else has this issue.   I decided to cut tick marks on a 2 inch disc since the Y axis would not be moving. The A axis moved 10 degrees as it was supposed to for the first cut. But it did not rotate properly to make the 20 degree tick mark second cut, and hardly even turned for the thirty degree tick mark.  I went to the MDI screen and prompted G0 A10 and it rewound quickly to 10 degrees except it wasnt where the first cut had been made.  After a trying a couple of MDI prompts with no problems and rechecking that the problem persists when running the program I thought to check the G540 for heat. Yep hot as a fire cracker.   I cut a hole in the top of the controller box and installed a Dayton axial fan.  the controll box already had slots for air flow but it didnt have a fan.  Problem solved.