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

"D.F.S." wrote:

>
> The creep issue mentioned above is another issue.
> IT may or may not be important, the answer is the same
> as before though, build it and test it.

I have a Calcomp plotter (E size = 34 x 44") that uses a steel
band about 1" wide, with a shot peened surface to ride on the drum
that drives it. This thing exceeds 50 IPS, with acceleration that
they claim to be up to 6 G's, but I think they must be hiding a
scaling factor in there, it sure looks more like 60 G's. It has
servo motors and encoders with resolution of 2056 counts/inch.
It really resolves that fine, that is not an artificial software
resolution!
So, there is no hard indexing between pen position and the encoder,
just the friction and repeatability of the drum to band interface.
It keeps in sync very well, and can run for hours without the index
position drifiting. Since it homes the pens to cap them off when
not drawing, if drift of the band ocurred it would crash into a stop,
and that never happens. I can't say about losing a few thousandths
over time, but I suspect it doesn't. Note that this band POWERS
the print carriage, it is not just for position sensing.

Jon