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

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.

The mysteries never end...

Cheers, Peter


JanRwl@... wrote:

> In a message dated 30-May-02 00:27:05 Central Daylight Time,
> elson@... writes:
>
>
>
>>The current approach is to mount a hollow round
>>cavity to the shaft, and have a heavy metal disc free floating in the
>>cavity.
>>The cavity is partially or completely filled with a viscous oil to give the
>>desired vibration absorption.
>>
>
> I wonder if the machining and bearings of the axis in question have not been
> done so fine that there is simply insufficient FRICTION for steppers to work?
> Some DRAG can do magic things to a stepper-system, sometimes! Jan
> Rowland, Troll who's BEEN there, done that!
>
>
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