Re: [CAD_CAM_EDM_DRO] Digitizing arm

Howdy! This is an idea I've been fascinated with for a long time, but I keep running up against the problem of tip offset. Somehow
you have to keep the normal to the surface at all times, but it is soluble since somebody is making money at it. <G> At the
Auburn-Cord-Dusenburg Museum in Auburn Indiana, they have the clay model that was used for the 812 Cord. While I could rhapsodize
about the car, the method they used to loft the prints was way too cool.

Picture a gantry on parallel tracks aligned with the long axis of the car. The X is the movement along these tracks. The Y is the
travel along the bridge of the gantry and the Z is a rod that is dropped from the Y cradle down to the surface of the clay model.
Very much like the CNC router that someone on the list has. It was accurate enough in the 30's to go from a 1/12th scale clay model
to full size plans with no mockup in between.

How's that for agile manufacturing? <G> On a relatively small scale you could use the guts out of a wide carriage dot matrix printer
for the X & Y and a servo/encoder in the Z to drive some sort of sensor up and down to sense the surface. Maybe an IR
transmitter/receiver in relective mode, or a phonograph cartridge/needle, or...

Rick Dulas

richard_damian@... wrote:

> Anyone out there built a 3D digitizing arm? That is a 3-axis arm with
> stylus that is used to trace a 3D object and supply coordinates in 3-space
> for creating a Cad model. I have an old profile mill in my shop that does
> a similar thing - it mechanically feeds a milling head by tracing a 3D
> shape.
>
> Just wondering, people are paying big bucks in Cad magazines for what
> appears to be a couple of metal arms, 3 encoders, a sylus and some
> software....
>
> Dick
>
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