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

On Thu, 30 May 2002 22:20:11 -0400, you wrote:

>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 had the same problem recently - I was loosing steps in one direction
on the Y - Axis. Tried all sorts of changes to IPS, acceleration etc.
Somebody suggested lack of drag - Then I remembered I'd loosened one
of the jib screws to fit a bracket for limit switches. I'd put it back
- but not tight enough. Adjusted it up and the problem disappeared!

It would seem some steppers like a bit of friction to work against.

Steve Blackmore
--
Pilot Consultancy Limited ***** Computer Consultants
Telephone 01744 752256 Mobile 07831 768478
Email: steve@... WWW: http://www.pilotltd.net