Re: Polar Coordinates CNC?

Hi Al,

This IS an interesting subject! Last week I was trying to develop a
tool path to cut some detail on the periphery of block of aluminum.
While I had digitized the surface I wanted (of a Stuart steam engine
cylinder), and COULD cut that as a final, what I wanted to do was
develop a tool path to "rough" it out first. Most of the surface is
cylindrical, with flat surfaces on one side tangent, and ending in a
flat on one end of the otherwise pear shape. Onto the surface would be
cuts to make flanges at either end of the cylinder, and projections at
several points for exhaust pipe, and drain cocks. Only way I know to
create this contour is by projecting the required radius at various
points along the periphery (like working sheet metal). I'm assuming a
4-axis CAD/CAM program will have a better way to do this, but I haven't
been able to afford this for a "hobby" project. SO, I'm looking for
better ways to design things like this!

I wouldn't call this a Rho-Theta type application, just a simple
cylindrical projection. Perhaps you'd like to describe a little more of
your project and approach.

Alan KM6VV


alenz2002 wrote:

>
> Ken,
> Here is one reason; it's called necessity :-) I wanted to make some
> decorative wooden gears that appeared to be too big to do on the
> Sherline. But, by mounting the blank on the rotary, I only had to
> access from the center of the rotary to the outermost point on the
> circumference yet could still cut anywhere on the full disk. There
> may be better ways, but I just drew it up in the normal X-Y fashion
> and wrote up a small VB app to convert the Y's to C's. The only
> tricky part was that a new feed rate has to be entered for each
> block, due to the way that my controller (CNCPro) handles rotary
> feeds.
> So, to answer your question, it basically doubled my capacity for
> this rather unique job.
> Hope this helps,
> Al Lenz