Re: [CAD_CAM_EDM_DRO] Re: DRO encoders- Rotary or Linear?

----- Original Message -----
From: Jon Elson <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, October 30, 2002 2:09 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: DRO encoders- Rotary or Linear?


>
>
> alex wrote:
>
> >This may be a stupid question, but why not to use a normal bicycle
> >chain\sprocket combination for driving an encoder?
> >Is it a backlash issue?
> >
> >
> Sprockets and chains, unless very carefully designed have an inherent
> cogging effect
> that causes cyclical errors every tooth, and then the chains have
> variations in pitch
> from roller to roller, which varies as the chain ages, and the rollers
> and pins wear.
> There may be instrument-grade chains, but normal bicycle chain, besides
> being heavy
> enough to break an encoder, are certainly not manufactured to the
> tolerances needed.
>
> W. M. Berg has all sorts of miniature instrument-type cable-chains that
> use plastic
> molded over aircraft cable. These are not instrument-grade accuracy,
> but might work
> better than the bicycle chain. I use them in my mill, but only for
> tachometer drive,
> not the encoders.
>
> Jon
>
>
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