Re: Math for constant speed ellipse (Again)

--- 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