Re: [CAD_CAM_EDM_DRO] Re: Math for constant speed ellipse (Again)

Hi, if you go to some of the ametuer astronomy sites you will find them
using all kinds of steppers to track stars for long photo shoots, and for
finding stars. one uses 2 boards with a hindge driven by steppers to find
stars with a computer..Have a look at my friends site
http://www.astronomyboy.com/ to see some stepper stuff. cul brian f.

----- Original Message -----
From: <davemucha@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, January 06, 2003 7:09 PM
Subject: [CAD_CAM_EDM_DRO] 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
>
>
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