Re: [CAD_CAM_EDM_DRO] Rotary to linear translation - an interesting idea.

Jon Anderson wrote:

> I once had plans for a home made DRO. It used two disks machined with
> 45
> degree bevels at the rim. These were held apart by a spacer, with the
> bevels facing each other. This rolled against a round rod. The system
> was calibrated by altering the spacer thickness, moving the disk
> closer
> or further apart, thus altering the diameter at the point of contact.
> Travdial does the same thing by crowning the edge of the wheel and
> tipping the unit to alter the contact dia.

Hey, this sounds like it might work a LOT better than the cable/reel
type DRO!
A 1/8" hardened and ground shaft for a short one, or a 1/4" shaft for a
large
one might work REALLY well! As long as the wheel is very carefully made
true,
this could be quite accurate. I can imagine leaving most of the shaft
exposed,
and having the wheels enclosed in a box, with wipers where the wheels
enter
the box. Make it with a pretty high resolution, and just calibrate it
with gauge
blocks. Even if you have to replace the shaft every year, this wouldn't
be much
of a negative. The only problem would be getting a wheel small enough
to
turn freely, or getting a high enough resolution encoder.

Jon