Re: Digitizing arm - CMM

I have been following this thread a bit and would be interested in any results and willing to lend a hand in it. I am not much
use with programing and electronics, although I can follow a circuit diagram and have built a CCD camera for my telescope. But I
am a machinist with lots of available machines to work with and own a copy of Rhinocad. Aside from the mechanical part of the
arm you are going to need an interface box that can convert the signals of the 4-6 encoders and either store the points for
export to rhino or have a little program that will introduce the points to rhino as they are taken. There are several little
programs that people have designed for Rhino like the calculator add-on Rhinolator. It can generate a group of random points and
then send them to Rhino and make a surface from them. With the I/O toolkit available for Rhino I guess that a knowledgeable
person could make up the interface program( but that not me :-)

Gar Willis wrote:

> From: garfield@... (Gar Willis)
>
> On Wed, 12 May 1999 20:28:40 -0700, Tom Kulaga <tkulaga@...>
> wrote:
>
> >>the resolution per count is about 0.007", and that's just for the first joint.
> >
> >Well, my understanding is that there's a rotary table, and an attached
> >arm with a shoulder, elbow, and wrist. Is that about right?
>
> Appears so for the Microscribe arm. If I understand it's construction
> aright, it has 5 degrees of rotary freedom: one for the base table
> rotation, one for the first joint in pitch only, two for the next joint
> in pitch and roll (twist), and one in pitch for the joint that
> terminates in the probe. The Faro arms appear to have 6 (or more!).
>
> Figure 1 in the Microscribe patent (# 5724262) is easier to understand
> than my description above. B)
>
> >I just did a quickie calculation, it backs up your numbers. So,
> >being only slightly optimistic, we could probably hit .015"
> >resolution staying on the cheap side and doing the best machine and
> >measuring job we can. We could spend more, but I got a hunch it
> >would be a big price jump before there was any real improvement in
> >performance. Does this sound useful?
>
> It SURE does to me, anyway. Perfectly acceptable accuracy for roughing
> out models that you then refine within a 3D editor/modeling program. As
> far as available sensors, etc. to "stay cheap", even their patent itself
> refers to use of HP Optical Sensors and LS7166 chips with the sensors in
> quad+index mode, so I think our own combined group USDigital/HP sensor
> experiences are indeed adequate to the task.
>
> >Wow, Rhino does that?
>
> Ahh, yup. Sanity check me by a visit to their site, and a quick read of
> the described support for the Microscribe and Faro digitizing arms:
> www.rhino3d.com

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James P Crombie
Summerside PEI Canada

http://www3.pei.sympatico.ca/jpcrombie/ My Astronomy stuff
http://www3.pei.sympatico.ca/jpcrombie/RHINOFILES/ RhinoCad 3D Stuff

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