Re: Back to the rack - nuts to the nuts

Doug,

Is this a stepper or servo machine? If it's a servo, you can focus on
getting accurate FEEDBACK, and let the drive fall where it may, since
you will be driving to the beat of the feedback...

There were some older large metalworking mills which used belt drive
with linear scales... You may not use/need linear scales, but
changing the "location" of the problem may help. Your feedback device
is not likely to be so thermally stressed...

But there is a steel tape based encoder I saw awhile aback that
wasn't too expensive, and had very good accuracy. (NOT the UK "tape
measure" one(s).)

Could even use a small sectioned fine, high quality rack/pinion for
feedback only. Large,cheap, coarse rack/pinion for drive
Hope this helps.

Ballendo

P.S. What material is the machine to be used for? (I know you said
wood and metal already; them're two purty broad groups!) What type of
spindle? Structure is steel box beam weldments? (guessing from the
thermal masses you've mentioned)

--- In CAD_CAM_EDM_DRO@y..., "Doug Harrison" <prototype@c...> wrote:
> ----- Original Message -----
> From: vrsculptor <vrsculptor@h...>
>
> > Doug,
> > Look at the gates belt catalog. They sell a linear cog belt that
is
> > meant to be stretched along a surface and used as a rack with a
> > matching pully. I looked a while back, cost was good, accuracy was
> > good and strenght was amazing. Should be no backlash with zero
> > thermal affects.
> >
> > Roger
> >
>
> I've always liked Gates products and gotten good support in the
past. For
> this reason I specified their stuff in a major plantwide retrofit
(many
> thousands of dollars) for one of my clients last year. The Georgia
Gates
> rep (Paul Clark) treated my client so badly that I have since made
it a
> point to avoid their products when possible.
>
> As for cog belting in general, I have looked at several. The new
steel or
> kevlar reinforced belting is incredibly stiff. However, I think
its thermal
> coefficient is still quite high. Guess I need to verify before I
make
> another dumb assumption though.
>
> Doug