Re: Digitizing arm - CMM

On Tue, 11 May 1999 21:17:6 -0700, Tom Kulaga <tkulaga@...> wrote:

>The way you describe it, it only uses 4 encoders? That shouldn't
>be too difficult to do, I'd think. Using 2000cpr encoders you
>could probably get pretty darn accurate too.

Not sure; did you check my short math doodle I posted recently. Looks
like with 2048 cpr X 4 in quad, with even a short 10" single arm (just
for purposes of illustration), the resolution per count is about 0.007",
and that's just for the first joint. Course, that's resolution, not
accuracy. Still, I DO think even with whatever res we could muster with
inexpendo rotaries, such a simple device would have lots of valuable
uses.

>...gathering the point cloud would be really easy, but what do
>I do with it then? Output into some kind of CAD program or
>something? You'd need to stitch all those points together into
>surfaces or you wouldn't be able to do much with it.

Think Rhino ... presto, done deal. If you look on the Rhino3D site
(www.rhino3d.com), under the topic of 3D-digitization, you'll see that
Rhino provides the model creation poof, from the point cloud. That's why
I suggested earlier that I'm sure them guys would provide the necessary
info to make such a DIY gizmo compatible with say their Microscribe
driver, or some such.

>Give me a few ideas about how to use the output data, and we could
>really go somewhere with this. I've got a few rotary encoders
>sitting around here, and I could probably lash up something that
>would be really inaccurate but good enough to test the concept.

Sounds GREAT. An intrepid experimenter! Goodie. I trust the factoids I
mentioned above regarding Rhino3D providing the surface model creation,
are sufficient to stimulate your cerebral cortex further? B)

Gar