Re: [CAD_CAM_EDM_DRO] G02 - G03

Art Fenerty wrote:

> Hi:
>
> I am trying to update MasterControlCNC to do G02
> and G03 circular interpolation and although I now have working code (
> thanks
> to Doug Fortune) I don't quite understand which is the most common
> form of
> interp.
> My post processor on the software I use the most does
> not generate circ. only linear. Am I better off using R registers or
> IJK
> interp? or both? Is IJK now pretty much obsolete?

You should try to accept both. There are some reasons why a particular
CAM or postprocessor uses one over the other. The radius of the circle
is clearly stated with the R word, while the endpoint is clearly stated
with
the IJK words. There are some errors that accumulate as the circle
algorithm works its way around the path, and so the IJK may get you a
little closer to the exact point desired, while the R will get more
precisely
to the desired radius. I used to use IJK until there was a problem with
the
early EMC program. With IJK, you can calculate radius from the start
and end points, and if they differ by more than some tolerance, flag an
error. The original tolerance was set so tight that roundoff errors in
xx.xxxx coordinates were sufficient to trip that error. It needed the
start and end radius to match to more than 6 decimal places.
Really, there is just a tiny bit of additional syntax decoding to take
both. Once you've got the numbers read in, the arc processing
is the same.

Jon