Re: Digest Number 5

On Mon, 10 May 1999 10:21:57 +0100, Andrew Werby <drewid@...>
wrote:

>[I've got an Immersion Microscribe digitizing arm
>...
>All the joints, with the exception of the
>swiveling base, are parallel, operating in the same plane of movement.
>These are also very heavy-duty joints, in what appears to be die-cast
>metal. If someone could figure out the angular encoders and software
>interface, the rest could probably be done in a simpler manner if someone
>had a reasonably well-equipped machine shop.]

Not to mention that the arms themselves could be made using available
carbon-fiber tubing, which is VERY stiff. My guess is the trick is in
the encoders. For example, just using the highest res rotary encoders
from USD, a 360deg pie chopped up via quad into 8192, sensing the
position of the end of a mere 10" arm, yields about a 0.008" resolution,
just in the first arm's position, so with 4-5 joints, it adds up pretty
fast. Unless of course I've inadvertantly used some "new math" and
comfoosed meself.

>[I participated in that too, which is how I got involved in selling the
>program when it came out. It was a rare privilege, as a user, to be
>allowed to communicate directly with the writers of a program and to find
>them so responsive to such various wishes and needs. I preserved and
>categorized some of the most useful questions and answers we exchanged, and
>have them archived on my site under "Rhinotes". ]

Excellent, yeah I saved lots of stuff too; probly not very organized,
tho. Good to know your notes are there.

>[While these are handy devices, the thing I drool in my dreams about is a
>home-made laser-scanner.

I think this feeling is shared widely. I know that the esteemed "Dr.
Foot" aka Chris Ellacott in his recent postsNaspirations here on
applying 3D-digitizing to his "orthotics", fancies laser digitization.

Maybe someone onlist who's familiar with the technology could comment on
the relative difficulty of making a laser-based scanner.

Gar