Re: Re: Re: Polar Coordinates CNC?

Hi Hoyt

I can see the "inherent differences in accuracy" issue but let me pose a
question based on the assumption that we build Fred's 12" square
prototype. In order to do this we would need a 17 inch platter.

My math may be all squirreled up so correct this. The distance out to a
corner of the 12 inch square should be be about 8.5 inches. That works
out to about 53.41 inches around the circumference at that size. (zero
diameter tool for outside cutting) Assume that we want 0.0005 for the
smallest move at a corner of the square. There should be about 106814
of those arcs.

If we select a quadrature encoder or used a stepper motor with
gearing/belting sufficient to get that resolution, do you think that the
greater accuracy as we approach the center would still cause problems?

Ray

> From: bjammin@...
> Subject: Re: Re: Polar Coordinates CNC?
>
> Yes but moving from x(0)y(0) to x(1)y(1) requires the same sort of
> calc. However you cut it though, the inherent differences in accuracy
> at differing radii in polar machine, is the death knell for
> practicality.
>
> At 08:23 PM 11/4/02 -0600, you wrote:
> >Fred, I have to agree with the other Ray H. A Polar
> >machine/software making a move from X(1) to X(2) must