RE: [CAD_CAM_EDM_DRO] Re: Adding friction to an axis? - or some other solution...

If I can toss in an idea - could it be that you're getting some kind of
round-off error that essentially means that moving the same distance cw and
ccw (assuming no backlash) does not put the carriage in exactly the same
position.

-- Jerry

|Jan, the machine in question is a BP clone with rockford ball screws on
|all axes and 1800 oz-in NEMA42 steppers direct coupled via helical
|couplings. The machine is in near new condition and all axes move
|freely. The problem I have is with long CAM generated files - I seem to
|experience a cumulative error somewhat in Y & mostly in Z it seems. If
|after running a 3D contour program for say 90 minutes if I return to
|machine zero, I could be .015" out in Z and say .005" out in Y and bang
|on in X. Accel rates etc have all been played with ad-nauseum. It
|seems to occur more as a function of run time, rather than speed. And
|while it would seem plausible that this could be a thermal problem or a
|lack of friction problem - I can't imagine what could be getting so warm
|as to cause a thermal problem.
|
|I'm running a Flashcut controller with '201 Geckos in full (10)
|microstep mode and even though I have been conservative with my
|accelerations, I guess it is still possible that I'm losing steps.
|
|For all 2.5D CNC work - even at higher step rates, everything works
|flawlessly.
|