[TiagoSantos]

Howdy, I have a G540 running 3 425oz nema 23 steppers at 3A each, with a 48V 7.3A power supply..

I just finished converting one of my machines (Rong Fu 40 milling machine) with ballscrews (direct drive, 5mm pitch screws) and I was surprised that I can easily move X or Y at 120IPM. It will actually go a bit faster, 150ipm seemed ok, but 180 would stall randomly, so I left it at 120. Like I said, I can move X or Y independently at 120IPM to the limits of each axis with no trouble. But the instant I try to move BOTH at the same time, one will stall and the other will slowly try to keep moving..

I lowered the rapids to 100IPM and set the acceleration way down, but it didn't help. Seems like the fastest I can move both X and Y is around 60IPM.

I'm wondering if anyone has any ideas of what it could be. The power supply should be enough to provide the current required by both steppers, shouldn't it?

One other thing I just thought about is Mach3's kernel speed - right now I have it set to 45kHz. Is the pulse speed per axis though? My settings are at 10160 pulses per inch on X/Y, at 120IPM that's 40360 pulses per second. To have 2 motors moving at that speed, would I need 80000 pulses, or will Mach3 send the command for each axis in the same pulse? I'm assuming it's the later, with it being a "parallel" port, but who knows..

Any thoughts would be greatly appreciated!

[ger21]

Open the Task Manager to the performance tab, and check your CPU usage while jogging both axis. If you hit 100% than your PC is the problem.

[TiagoSantos]

Thanks, I'll give that a try tonight. I don't suspect it'll be the PC, it's a fairly quick machine (Core 2 Duo E5400, 2gb ram, fresh XP install with only Mach3 on it) but it's definitely worth a try!

[mrcodewiz]

Are you using backlash comp?

[TiagoSantos]

Yes, 0.0025 on each axis.. Would that cause trouble?

[TiagoSantos]

Ah, found this old thread with exactly the same issue - http://www.cnczone.com/forums/bencht..._backlash.html

Good call!

Now I'll give Hoss's settings a try and see if that'll work, otherwise I'll turn backlash comp off and learn to live with it.. I can always add dual nuts when I move things over to the RF45, but no room to do it in the RF40, I don't think..

[TiagoSantos]

And voila, problem seems to be fixed! Turned backlash comp off and everything worked, then played with the settings a bit to get it back on without causing trouble. The magic setting seemed to be the shuttle speed in the general config window. Not even sure what that's supposed to do, but it worked!