dro error after movement

[capsteve]

i have mach3 with the galil plugin running, and am having problems tweaking the movement of the table.
if i command x3 from x0 the x dro will read something like 2.994. its random and not far off but annoying.
i thought that mach would move until the dro exactly got where its supposed to be...

not really sure how to tackle this.. 

[smurph]

Mach will not move until it hits the numbers, but the Galil will try to.  The loop is closed on the Galil.  Mach simply reports the position. 

But you problem looks like friction to me.  PID tweak time!  I bet if you decoupled the servo from the screw, the motor would move to right numbers.  Try bumping up the proportional gain (P) and see what happens.  If you start overshooting the numbers and walking back to them, decrease the P until you get a happy medium or you might have to bump the D ever so slightly (I mean just breath on it).  If you get to a point where you hit your numbers but get unstable where it should be holding, bump up the I.

Steve

[capsteve]

Im not real sure on howto change the pid values. I have the wdsk software and ran it once. Tuned the servos but not even sure it saved the values. The servos always seemed to sound and run real smooth. I will revisit the tuning software and see what's up.   Thanks

[smurph]

To change the PID values on the Galil, use the KP, KI, KD commands.

KPA? will give you the current value of P for the Galil A(X) axis.

KPA=x.********* will change the P for for the Galil A(X) axis.

BV saves the values to NVRAM.

[kcrouch]

Steve,
BN saves the tuning parameters, BV saves any variables that were defined, and BP saves any defined programs that are to be run exclusively on the Galil controller. You must have been working very late again.
Kenny

[smurph]

No, I can't blame working late on this one.  Just a nut lose on the keyboard. 

[capsteve]

ha, i do some of my best work when there are no witnesses....
  after close inspection i found the pids at 50,0,0.
i ran wdsk and played untill i got good looking curves on all three axis.
now i am spot on, but i think i have a little backlash on the y



a concern i have is that movement with the mpg now is pretty noisy but running gcode seems well behaved..and less noisy.
i found the video tutorial on using the wdsk to tune the servos on galils website and it was very helpful.
i think i have decent tuning profiles based on that info.

 
another small issue i have is that while running some test code mach3 would stop mid-code. simply stop as if there was an optional stop
but there wasn't. no errors that i could find. i can only resume the program if i stop the program then hit the start from here and resume.
the problem did not duplicate running the same program consistently. (roadrunner)

thanks for the help, i can actually use the mill now......1 1/2 year trying to get camsoft to work.....threw that out.....5 months with mach and i'm makin chips......

[kcrouch]

Steve,
I use rather small incremental moves for my MPG. Mine are set to .0001, .0005, .001, and .0025 in config>general config. You will find that they work much smoother when set that way. Glad to hear that you're getting up and running.
Kenny