Re: rough circle

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "afogassa" <afogassa@y...>
wrote:

> thank's Fred,
> If it can do all axis at the same time why there is no provision

for

> helical milling ? or interpolating three axis.
> here is what happens, I'm using powermill to generate the gcodes
> from 3d surfaces to machine a stearing wheel mold, finish looks good
> at the outside radius, but at the center ofthe stearing wheel there
> is smaller radius curves where I'm having problems with finish.
> the code generated is all line segments not arcs and I have the

same

> resolution for x y z .

Helical milling has very limited usage on hobby and desktop machines.
Thread milling, a fairly common use, can easily be done with 3 axis
interpolation and most any decent 3D cad-cam system.

DeskCNC is superb at simultaneous 3 or 4 axis interpolation, provided
you don't exceed the 300 blocks per second throughput limit.

If you examine your Powermill program, you will probably find that you
have interpolated the surfaces at an accuracy tolerance more fine than
necessary, and probably at a much higher resolution than your home-
built machine can actually cut. Simply set the interpolation at a
more reasonable level and regenerate your CNC program.

It may be that you need to apply a different cutting strategy to the
inner radius than the outer. A uniform cutting pattern may be causing
too high a block density near the center, compared to the distance
traveled.

Hopefully this will help you solve your problems.

Fred Smith - IMService
http://www.cadcamcadcam.com/hobby