Re: [CAD_CAM_EDM_DRO] Re: I need some feedback on using wire rope for driving...

use a timing belt and lay it flat on the surface and they gear the
encoder to that.

On Dec 14, 2007 1:59 AM, Dave Halliday <dh@...> wrote:
> Sitting here skinning cats and eating crow...
>
> My concern was that as you moved the axis, the feed-point of the cable would
> travel up the rod so far as to introduce trigonometric distortion. What once
> was the base is now the hypotenuse and you would need a way to let out slack
> as needed.
>
> At 8 turns/inch and one inch diameter, to travel four feet, you would only
> need to rotate a bit more than fifteen turns or about two inches of travel,
> something that could be compensated for with a spring-loaded pulley
> follower. Your movement would not be accurate but the distortion would be
> linear and the software could compensate for it.
>
> I had it in my brain that we were looking at a foot or so.
>
> Played around a lot with early large-format pen-plotters (knew some people
> in companies around Boston when I was living there) and they did cable drive
> but it was always a pulley about 8-12" in diameter and only a few turns
> wrapped around.
>
> I really hate to think of how many of those machines went into dumpsters
> when reliable ink-jet came out...
>
> Dave
>
>
> > -----Original Message-----
> > From: CAD_CAM_EDM_DRO@yahoogroups.com
> > [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of David LeVine
> > Sent: Thursday, December 13, 2007 5:16 PM
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: Re: [CAD_CAM_EDM_DRO] Re: I need some feedback on
> > using wire rope for driving...
> >
> > Dave Halliday wrote:
> > > I am thinking that you would have to go through some
> > extreme gyrations to
> > > get this to work over more than a foot or two of spindle travel.
> > >
> > > You can get Acme Threaded rod in large diameters but
> > imagine the inertia of
> > > a 15" by 2' bar of metal.
> > > http://www.keystonethreaded.com/acme.htm
> > >
> > > I would use thick-wall Schedule 80 PVC pipe with a belt
> > reducing system to
> > > the motor.
> > >
> > If you are using something like 1"-8 all thread for the spindle,
> > consider making two of them. Let's call them A and B. Cable
> > 1 goes from
> > A to B, Cable 2 goes back from B to A. A threaded follower
> > (think a nut
> > with extensions to hold pulleys) goes on each spindle and guides the
> > wire rope into the grooves. With the cables parallel to the spindle,
> > each turn of A moves its follower to the right a small fraction of an
> > inch and moves the follower on B the same distance in the same
> > direction. The cables move PI * the spindle effective
> > diameter plus or
> > minus the pitch per turn, so for a 1"-8 spindle, 3.14159 inches plus
> > (or minus) 1/8". No complex mechanism, just two spindles and two
> > followers. The followers will ensure that the rope will lay in the
> > grooves (threads). Of course tension is maintained and the
> > rope has a
> > predictable movement.
> >
> > Just another way to skin the cat.
> >
> > --
> > David G. LeVine
> > Nashua, NH 03060
> >
> >
> >
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> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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