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General Mach Discussion / Odd Stepper behavior

« on: April 03, 2014, 08:51:34 AM »

I've just finished converting my G0704 Mill to CNC.  I am now tuning my steppers and dialing in the system. 

Here is the set-up:
2 Nema23 steppers on X & Y
1 Nema34 stepper on Z
3 KL-5056D drivers
C35 BOB
Kl-600-48v power supply
Mach3 - running Version .066
Older desktop dedicated to the mill.  600Mhz CPU, WindowsXP SP3.0.  Stripped of extra programs and crap.

25k Hz, Sherline 1/2 pulse checked, 8000 steps per (validated in the ballpark with tape measure for now)

The driver test checks out "Excellent".

So here is the oddity in behavior.  While I am in the Motor Tuning, I can set my XYZ axis velocities pretty high (about 250in/min) and the steppers sound great.  No stalling, no missed steps - nothing.  Just humm back and forth to my up/down keyboad commands.

Now as soon as I exit the Motor Tuning window and get back to the Mach screen and jog the axis, they sound like they are missing steps, like there is a chip in the bearing.

I've reconfigured for 1/4 and 1/2 micro stepping and get the same results.

Any ideas where to look or test?

Thanks for the help.

-Mike