Axis random freezing with SS=2H044MA stepper drivers??

[gerrymoore]

Hi all...been a member here for quite a while but not posted before....so be very grateful for any help offered......

I am currently using 3 SD-2H044MA stepper drives in my small home built plasma CNC machine. I am having problems with one or other of the axis 'freezing' in mid program and the red fault light coming on the drive. I have to stop Mach3 and turn off the power to the stepper drivers even have to reboot Mach3 sometimes to get going again. I am using 1.7NM Nema 23 drives and running them from two separate PSU's - one a 27volt 13amp for the Z axis and the other a 36volt 10 amp for the X and Z axis. The current setting for the motors is only set at 2.2 amps. The Nemas run cold. I have everything shielded and grounded. I have capacitors on all the BOB inputs. I have a very large and expensive mains filter on the electronics and I have the debounce setting at 400us on Mach3 but still I have the axis freeze...not the same one but random X Y and Z. It seems to happen mostly, but not always, whenever the plasma cutter 'stutters' at the beginning or end of a cut. I have the plasma cutter on a separate mains supply to the PC and drive electronics. It is ruining a lot of my work and I wonder if I should change my drivers or is something else causing the problem? I would be grateful for any ideas on this.......cheers Gerry