RE: [CAD_CAM_EDM_DRO] EMC problem/question

Put CNC Pro demo on a bootable DOS floppy and see if you get the same
results. Because everything is untested you want to obviously get the
problem isolated. This would be the quickest way to see if it is software.

Tim
[Denver, CO]

> -----Original Message-----
> From: Hugh & Denise Currin [mailto:currinh@...]
> Sent: Saturday, August 04, 2001 6:21 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] EMC problem/question
>
>
> Crew:
>
> I am having a problem with EMC and don't know where to go from
> here. I am
> hoping someone more familiar with EMC can direct me.
>
> I've noticed my mill doesn't come back to zero after a number of
> moves. If
> I repeat
>
> g01 x0.1 f10
> g01 x0.0
>
> twenty times in a program the zero is off by 0.010". If I change the
> distance moved from 0.1" to 0.2" I get the same error, .010. I
> can do the
> same with moves in the y direction. Double the moves (40) gives
> double the
> error 0.020". I changed the feed rate to F5 and the errors are the
> same. I changed the default and maximum accelerations in the .ini file
> from 10 to 5 with no effect. Finally I wrote a program with
>
> g02 x0.2 y0.0 i0.1 j0.0 f5
> g02 x0.0 y0.0 i-0.1 j0.0
>
> a circle of 0.2" diameter, repeated ten times. This gave a final offset
> error of .005" in both x and y. Finally I did this last again using
> g03. The errors were the same and in the same direction (+
> reading on DRO
> in all cases). I did a small move from and to zero to eliminate any
> backlash as:
>
> g01 x.05 y.05 f5
> g01 x0.0 y0.0
>
> I have a hard time believing this is mechanical since it happens to the
> same degree in the x and y directions. Likewise the stepper motors and
> drivers are separate for the x and y, leading me to believe the
> problem is
> not there. That leaves the software EMC.
>
> I am running Red Hat linux (2.2.14), rtlinux 2.2 and the Aug 11, 2000 EMC
> on a 450 MHz P3 with 64M. The drivers are 5A Camtronics running
> half step
> to steppers of about 750 oz-in. These connect to ballscrews through 2:1
> timing belts on a 9x42 knee mill.
>
> Any ideas or suggested tests?
>
> Thanks.
>
> Hugh Currin
> Klamath Falls, OR
>
>
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