Re: [CAD_CAM_EDM_DRO] Re: Digitizing arms??

If you or anyone else needs a tablet, I have a 36"X48", E-size Calcomp 9500
series with puck that I will sell cheap.
These things are heavy and in the original crate. Contact me off list.

----- Original Message -----
From: "Jason Spangle" <jasonspangle@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, June 24, 2004 8:54 AM
Subject: [CAD_CAM_EDM_DRO] Re: Digitizing arms??


> I agree,
>
> Get one of those summagraphics tablets on ebay real cheap... those
> have a crosshair puck, most accurate hand-tracing you can get.
>
> Jason
>
> > If your only after 2 axis, use a tablet and trace.
> >
> >
> >
> > ----- Original Message -----
> > From: "Jon Elson" <elson@p...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Wednesday, June 23, 2004 9:09 PM
> > Subject: Re: [CAD_CAM_EDM_DRO] Digitizing arms??
> >
> >
> > >
> > >
> > > doug98105 wrote:
> > >
> > > >Group,
> > > >
> > > >Looking for some ideas on making a two axis digitizing arm.
> > > >
> > > >Back in the days of Apple II computers I saw a couple of crude
> > > >digitizing arms built using potentiometers and inputting through the
> > > >game controller input. Position was determined by the resistance
> > > >readings.
> > > >
> > > >With high resolution encoder devices it seems like a much more
> > > >accurate digitizer could be made.
> > > >
> > > >Any thoughts?
> > > >
> > > >
> > > Yeah, look at Faro for how they did it. The problem with these things
> > > is that certain arm positions lead to poor accuracy, because a
> very small
> > > movement of one joint makes a big change in position.
> > >
> > > No doubt a 1000 cycle/rev, or even 2500 cycle/rev encoder would be
> > > a HUGE improvement over the ancient Apple digitizer with pots.
> > > Unless they used special pots, you couldn't possibly get better than
> > > 1% angular accuracy, and that is 3.6 degrees! Yikes!
> > >
> > > I worked for a medical computer company in the WAY distant past,
> > > and they made "Rho - Theta" and "Phi-Theta" digitizing arms using
> > > very expensive mil-spec rotary and linear pots, and had all sorts of
> > > trouble getting enough resolution with a 12-bit ADC to digitize
> > > the location of a patient's tumors, etc. Linearity was no problem, as
> > > the software had cal tables built for the individual digitizing arm.
> > >
> > > Jon
> > >
> > >
> > >
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> Addresses:
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timg@...
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[Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>
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>