Re: Threaded Rod/Cable Driven Encoders

Roger,
The problems with the cable driven encoders is linearity.
Repeatability will be ok(.001) if things don't slip. Some problems I
have dealt with are the cable diameter and spool diameter screwing up
the circumference through out a length of travel. The accumulated
error will annoy the heck out of you. You may be better off with a
rack and pinion driven encoder for the type of machine you describe.
I don't know what type of resolution you will be expecting. Another
option would be to just drive the encoder off of the screw and
compensate in the software.

Look forward to hearing your progress,

DC

--- In CAD_CAM_EDM_DRO@y..., "vrsculptor" <vrsculptor@h...> wrote:
> Gents,
> If I followed the thread correctly on threaded rod backlash isn't a
> problem if you use a plastic nut. The problem seems to be
cumulative
> cyclic error. It seems to me that you could get around this problem
> pretty easily with a http://www.usdigital.com/products/ S2 or H3
2K
> pulse/revolution encoder driven by a cable streched along the axis
> and wrapped around a capstan attached to the encoders shaft. I
recall
> seeing something about this last year where someone was using this
on
> a lathe but can't find it now.
>
> Do any of you have any long term experience with cable driven
> encoders? Are they working out and staying accuarate?
>
> I'm still dreaming about builing a realy big router...
>
> Roger
>
> PS. My 3d laser stripe digitizer is coming along pretty well. Its
now
> controlling the mill for automated scanning. I hope to post
software
> and a tutorial in the next couple of months.