Hi all,
My system:
I'm using Smoothstepper USB to a breakout board with step/direction servo drives. The machine is using ballscrews and linear bearings, no backlash compensation, very little friction/sticking in axis movement.
The problem:
I've been struggling with a mysterious loss of position with my machine. It is extremely bad such that I'll run some G-code for 20 seconds then send it back home, only to find it off of zero by an inch. It seems to only happen mostly to one axis, although sometimes I can readily see both X and Y positions off. Also, if I feed rate override to a lower speed (like 10%), it seems to exacerbate the problem, or at least make it more obvious. It's strange because I can run a lot of code at high speed (feedrate override 200%) and be off by less than if I ran the same code at a low speed (feedrate override 10%).
My troubleshooting:
I've swapped drives, swapped signal cables, fiddled with Mach3 settings, all without a good result. I think I may be on to something, though. Last night I tried disconnecting all the signal cables (enable, step, direction, GND) from every axis except one. With only one axis wired up, it seems that the problem goes away. However, once I connect another axis to the breakout board, the problem resurfaces. It doesn't matter if the drive is disabled in Mach, just the fact that the other axis is wired to the breakout board seems to induce the position loss.
Any ideas of the cause?
Many thanks!