Still losing steps in M5 or Mach1

Hello all:

I still seem to have rough motor running when simulating in 2D, a
circle being cut using the x and y motors.

They are new steppers, and 5 amp boards from Camtronics. I have
gotten to the point where a "simulated" square works well. Motors run
smoothly with little or no step loss. But that's different, in that
one motor fully stops working, then another starts, with there never
being 2 motors on at the same time. It seems to run well like that.

But when I load in a circle, the motors will go through the motions,
but run roughly. Sometimes even lock up and just squeal, not turn,
even though the program runs through on Mach1. I seem to have better
and somewhat smoother operation on Master5 then Mach1, which leads me
to think I still have to learn how to tweak Mach1 better.

But why am I still not able to run a smooth circle in a bench test? I
have tried every combo of motor speed, pulses per inch (although I'd
like to keep that set at 2000, which represents my future setup) and
acceleration that I can think of, with varied results, but never
smooth.

I have made my own shielded parallel cable with twisted shielded
pairs, and connected all of the shields to the computer casing at one
end only.

How important is it to shield the short low-power wires from the
junction board to each driver?
How important is it to plug the logic 5VDC supply into a different
wall outlet then the 35VDC motor supply, thus avoiding a ground loop?
I tried that, with no obvious improvement.

I keep saying this, but progress IS being made. Single motions now
seem quite smooth, even if a fews steps are lost here and there. I am
hoping that once I hook the motors up to a mill table, the added drag
will help filter out the last remaining step loss.

Thanks for all help.

Tom Kay.