Re: Math for constant speed ellipse (Again)

I have a desire to do an elsipse once I get the plasma cutter up, but
also thought about telescopes.

the telescope would track the celestial bodies for both the arc and
some declanation ?

In thinking about that application, seems steppeers might have too
much vibration, but anything would need to be geared way down to be
accurate.

I'm surprised that no one else brought this application up. maybe it
is just too far off topic ?

Dave





--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Fred Smith <imserv@v...>"
<imserv@v...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "jcc3inc <jccinc@o...>"
> <jccinc@o...> wrote:
> > Todd F:
> > My approach to making an ellipse was:
> > 1. Generate a circle with diameter = ellipse major diameter
> > 2. Since data is in X and Y registers, Multiply the Y register by
> > a number < 1.
> >
>
> JCC wrote:
>
> > I talked to Fred Smith, I M Service, asking about his CAD/CAM
> > capabilities and he said:
> > 1. You can use straight line approximations to generate the

ellipse

> > 2. You can use arc approximations
> > 3. Either form may be cutter compensated . Thus you may

accommodate

> > the cutter diameter speed effect for sharp radii also. Either of
> > these seems like a workable solution.
>
> Vector Cad 9.4 can also represent the ellipse as a single drawing
> entity, Nurbs curve. The Nurbs curve may also be offset to

compensate

> for the cutter radius, or interpolated as a linear approximation at
> the resolution of the target machine, or interpolated and arc fit
> also at the resolution of the CNC machine (or less if desired for
> more compact programs).
>
> The arc fitting and linear interpolations of ellipsis in Vector are
> at the drawing general accuracy, which is usually smaller
> (.0005mm/.00002in by default) than the least increment in a CNC
> machine (seldom less than .0001 except for wire EDM, cnc grinding,

or

> optical applications).
>
> Fred Smith - IMService