Re: gearmotors,encoders

Jon, what do you think about the rigidity of a 1.25" screw 36" long--
moving a 36" x 12" table plus the work. The encoder will have a
thousand lines (as soon as I figure out how to recode 1968 line
output to 1000 line). Maybe on a sharp accel you'd loose a count ...
maybe only your ME knows for sure.

Now on the Y screw maybe I'd take the bet that it doesn't.

--- In CAD_CAM_EDM_DRO@egroups.com, Jon Elson <jmelson@a...> wrote:
>
>
> Mariss Freimanis wrote:
>
> > Jack,
> >
> > Good morning! I see no problem mounting the encoder at the farr
end.
> > It's hard to imagine a leadscrew torsionally twisting even 1
encoder
> > count.
>
> Huh? It is most defintely possible. The longer and narrower the
leadscrew
> is, the worse the problem, of course. But, if you have screws 40"
long
> and under 1" diameter, the torsional deflection of the leadscrew
> can become quite significant with just tens of in-lbs of torque
applied.
> Take a long, narrow shaft, clamp one end, and see how little torque
> it takes to cause observable deflection with a wrench on the other
end.
> That will be far more than one encoder count!
>
> If this is a high power servo system, it would be a bad idea. For
a very
> low performance system, with low bandwidth, or if the screws are
fairly
> short and of large diameter, it will probably work OK.
>
> Jon