Re: Threaded Rod/Cable Driven Encoders

Chris,
Let me say I am sorry if you feel ridiculed. I just wanted to
point out 1/4-20 rod works great with a 1/2" thick piece of Delrin.
One must remember there are people who can only afford to build a
cheap CNC machine. They don't have the money period! Telling them how
they can make a machine is my point. The software at the hobby level
is not the problem. They need a cheap machine. After they get it
running then they can save up for a machine. They can build a
complete machine for under $200. There are several sites now that
sell plans. I can understand why you would want the best. Please
understand some people don't have the money. CNC is still possible
for them at a hobby level. Go back and look at all the people in past
messages who bought parts to build CNC machines. They are gone! Some
people have a different way of doing things. I buy a cheap tennis
racket and wear regular cloths to try it out. If I like tennis then
I pluck down more money.

Bob

--- In CAD_CAM_EDM_DRO@y..., Chris L <datac@l...> wrote:
> I have been ridiculed (just a tiny bit) when I did not "recommend"
using
> common threaded rod.
>
> I was quickly corrected, that the "thought and the goal" of using
threaded
> rod was to cut costs. Great ! I agree this is one way to do it.
>
> But, if you want to cut costs, I am confused as why you would add
encoders to
> bring the accuracy "back up"................. Sounds like a "round
robin" to
> me. Whether Stepper or Servo, Encoder adds to the final cost, time
spent
> making it work and hassle for a first project. Save your time and
energy.
> Build a Solid Stepper system with Rolled Lead screws and
Antibacklash nuts.
> They are not all that expensive for what you will get. 6 feet of
1/2"
> diameter screw...... 3 nuts.... $200. Thats only 20 or so 12 packs
of beer
> ! (may be a bad example) But, then your done for a long time. The
nuts will
> last for years on a Router, without backlash or slop.
>
>
> Individuals can use threaded Rod and homemade nuts if they'd like.
Some rod
> is rather abrasive in nature so be careful with that. The Nuts,
even on a
> smooth thread will exibit wear faster than one may think. This wear
turns
> into additional backlash and slop. I guess this is not a problem as
you can
> take it all apart and make a new nut and put it in (your doing that
while I
> am cutting stuff).
>
> On a side note, Has anyone made a Antibacklash nut out of Delrin
that works
> like the "economy" OEM nuts ? ( three fingers and spring that
pushes them
> onto shaft)
>
> I know some pointed out that they feel a few thousandths does not
matter
> because it's only "woodworking". Well, I guess It depends on what
you are
> making. I've been there, And, its a real thrill to see your
> "chickenscratchin" of "lines" on screen go to cutting something.
But that
> thrill does not last but a day or two as you start rethinking how
you could
> have made this "cheap" project better.
>
> No big deal..... Hardware stores have lots of Sandpaper to
straighten out
> all those "steps" in your work.
>
> So, you can try to get around the problem..... But, it might just
be easier
> to do it a little more right the first time.
>
> Chris L
>
> vrsculptor 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.
> >
> > Addresses:
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