Re: Interesting problem

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith" <imserv@v...>
>wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dan Mauch" <dmauch@s...>
> wrote:
> >
> > I couldn't figure out why I should be
> > getting these circles as the dxf file was perfect. It was also
>too
> early
> > in the year for mysterious crop circles to appear in my G code.
> > Knowing that there wasn't a bug in Mach1 I returned to bobcad. I
> > reloaded the G code and in the CAM program Selected All. Then I
> selected
> > Geometry from code.
> > To my shock the mysterious circles appeared on my drawing.
>
>
> Dan, this is the infamous "looping". It is caused by creating CNC
> code from geometry with arcs smaller than the least increment in
>your
> G-code. If you set your number of decimals to 6, 99.9% of your
>loops
> will be eliminated. What happens is the first arc cuts correctly,
> but the second one is extremely small, and results in the exact
>same
> G code line, which makes a full circle!
>

Dan. Fred is correct in what he says. When I used to use Bobcad I had
exactly the same problems in that the program wouldn't show the
spurious moves.
It pays to check the code with a third party progarm that is in no
way tied to the generated code.
I use a small program called Discriminator from http://www.cncedit.com
Any loops and this program shows them. You can step thru and spot the
loop occuring in the graphics screen , go back to the code window and
edit that part out.

John S.