Re: cable drive for X axis

Hello,

Machines using cable drive often account for this "walking" by
providing for it in the design. Which means the cable is NOT parallel
to axis travel, but rather at a "helix" angle which matches
the "walking"... (Using multiple wraps is no problem)

In the Yahoo French hobby CNC group (CNC Fraise or some similar),
their "standard" machine uses cable drive, hardware store parts, and
this angled cable drive system...

Hope this helps,

Ballendo

P.S. There is also a site (try "otocomp CNC" in a yahoo search) that
details a largish vertical machine that used cable drive. AIRC, the
builder upgraded to rack/pinion in the re-design...

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Johnson <johnatl@m...>
wrote:

> If you have multiple wraps on the drum, the cable will walk from

side

> to side the diameter of the cable for each revolution. If you have

a

> drum with a 12" circumference, and 0.250" cable, the cable will

walk 10

> * 0.250" or 2.5" for a 10' move. At least that's what it will want

to

> do.
>
> That's why I mentioned slippage. Since the cable will walk with
> multiple turns, I assumed you would use a single, incomplete, turn
> around the drums.
>
> My employer uses timing belts over 24' long. Not sure what the

vendor

> is, but could probably find out, if you want.
>
> Regards,
> JJ
>
> On Monday, Jan 19, 2004, at 03:53 US/Eastern, onthemarcxyz wrote:
>
> > I don't know if I could find a timing belt 24' long and would have
> > the same problem with it slapping around. I will have to run a low
> > tech test on cable with 12' span and weight with multiple

reversals

> > in direction.
> > I'm not sure what slippage you refer to. The cable would be a

closed

> > loop system with a fixed end on the drum. The wraps on the drum
> > would be side by side so the same
> > feed rate would come from each revolution.
> >
> > Marc
> >
> >
> >
> > -- In CAD_CAM_EDM_DRO@yahoogroups.com, "onthemarcxyz"
> > <onthemarcxyz@y...> wrote:
> >> Hi all my name is Marc,new to this group.
> >> I am thinking of building a CNC router with a 12' X axis.
> >> I was first thinking of rack and pinion drive but was concerned
> >> about backlash. Then I was thinking of using cable prestressed
> >> between two drums driven by the servo seems this would have no
> >> backlash?
> >> what do you think.
> >>
> >> Marc
> >
> >
> >
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