Someone I know is having a strange problem that really has me stumped. The machine is a bed mill, with AC servos. It will do unlimited, perfect, single-axis moves, cutting exactly to correct dimension every time. But when cutting a square, rotated 45 degrees so diagonals drawn between opposite corners would be parallel to the X and Y axes, the square becomes a rectangle, with on pair of sides about 0.04" too close, and the other pair of sides about 0.040" too far apart. There is NEVER any position loss. It returns to exactly X0, Y0 perfectly, every time. A square cut so the sides are parallel to X/Y will come out *exactly *on dimension every time. Steps per is set correctly, and confirmed by measurement. Backlash is well under 0.001" on all axes.

As I said, I am stumped. We've tried it running with a UC100 motion controller, and with the PP, and results are exactly the same. Reducing velocity and acceleration, even dramatically, makes no difference whatsoever. Running exactly stop makes no difference. DROs always show the "correct" position (i.e. - where the machine should be, as opposed to where it actually is). We've tried several different versions of Mach3 from 3.043.066 down to somewhere in the 050s, and get the same result with all of them.

Any ideas or suggestions?

Regards,

Ray L.