Grinding and unexpected axis movement if rapiding 2 axis

[DarkSabre]

So I've got an issue that cropped up after moving the mill to a new location, though it may have been present slightly before. So enough things changed from the move that it has been hard to track down the cause.

I normally keep the motor tuning at 20IPM velocity and 4 acceleration. That's where it had been since purchase, basically. Rapids and standard movement were all fine for the previous months.
I start using it in the new location and when I do a rapid in two axis at once (any combination of 2 axis seem to cause the problem, X&Y/X&Z/Y&Z), I get a grinding noise and the axis that I wasn't moving is turning slightly (though Mach 3 does not reflect this). I can replicate the problem with either G0 commands or using my joystick.

You can hear the issue in this mp3...
http://www.ecceecce.com/TerribleTaigNoises.3793.mp3

At Nick Carter's suggestion, I swapped out what electronics I could. I don't have any spare Geckos or steppers, but I swapped out my C10 board and the parallel cable out to no effect.
I checked for voltage drop at the power supply when it was happening and there was none. The current draw at the wall didn't look too high either. So I don't think the power supply is having trouble sourcing the current to drive the rapids all of a sudden.

The Z and X axis lead screws seemed to be in good condition. We didn't open up the Y axis, but I don't see how a mechanical issue could cause another axis to move.

The problem went away entirely when we dropped the motor tuning numbers to 8IPM at 2 accel. If the feedrate is increased to above 100% while it is running, the next time it rapids the grinding noise and axis rotation happens, so 8IPM seems to be our hard limit at the moment

What I'm using:
NEMA 23 BIPOLAR STEPPER MOTOR 270 oz-in (KL23H276-28-4B)
C10 - Bidirectional Breakout Board
KL-600-48 48V/12.5A PSU
Gecko G251
Mach3

SpeedsCustom seemed to have a perhaps similar, though not identical, problem here: What would cause the z-axis to gain steps? Or appear that way?
There seemed to be a suspicion that the power supply was at fault, but as I mentioned I don't think that's my issue. He had previously swapped out steppers and drivers, I believe, without resolving the issue permanently.

More similar sounding problems here: Taig Z axis stepper screaming!
and people were replacing stepper motors and controller boards.

but neither of them seemed to have the unexpected rotation of one of the axis. Seems like it might be signal leakage or something? But why would that only occur during rapids? I'm fairly confident that all of my wires are well insulated from each other, though they are not shielded. Something to check into I guess.


Any thoughts? It is functional right now, I just can't run it near as fast as I'd like.

[holbieone]

try using an earth ground , sounds like you are getting some feed back

[DarkSabre]

Okay, ground the mill itself or other parts too?

[holbieone]

ground every thing

mill

all electronics and boxes

also shielding on the cables , for a quick fix use aluminum foil

[DarkSabre]

Well, [crosses fingers], I think it might be fixed...

I grounded lots of things, to no effect. Then eventually figured out that the AC side of the 48VDC PSU for the stepper motors was not grounded. Now I can rapid at 20+ instead of maxing at 8IPM, so things seem to be going well.

Thanks