Re: [CAD_CAM_EDM_DRO] Threaded Rod/Cable Driven Encoders

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:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/