Re: [CAD_CAM_EDM_DRO] Re: Threaded Rod WORKS!

I know there was some confusion as to the original posters intent and
application of the question.

Clearly, your point is valid. Everyone must decide just how much he can
budget for the project, then determine just what his exact needs are. I
subscribe fully to the "build what is needed" concept.

For those who really start from scratch in order to learn, I always like to
recommend some of the fine "package" offerings that are now available out
there using NEMA 17's or 23's. Sure, pretty small, but you can learn a lot
with spending little. Another really great option is to get your hands on an
older larger format Pen Plotter. Retro the control, Hang on a Diamond tip
tool and do some diamond drag engraving!

Those are great ways of getting your feet wet.

Getting your feet wet by building a CNC Router though....? Well, the only
warning I make is that the "work" involved of building a machine is about the
same. You "need" a reasonable way to allow for "linear movement", You need a
"drive mechanism" to move it there, you need a method to "control it" from a
PC, and you need it to be as "rigid" as possible to be worth the effort. To
do all of this, you can burn up a lot of time designing.

If you are going thru all that "work" to design and build it, and make it
run...... using slightly better components will likely be beneficial in the
long run. If it works a little better than expected, you might not be forced
as quickly into starting completely over! A RC model body and its overall
dimension and accuracy levels are one thing. All of the little dinky
components underneath are really something else. Some of the components I
look at for RC Helicopters can be very impressive. One must really consider
just what you want to end up making.

To me, the real "learning" part comes in when you find out, "gee, I should
have done this" or "if I only used that instead". "Time" IS our most
precious commodity. These days, you can get "money" anywhere !

Which brings to mind.... Maybe I need to buy a few 6 foot sticks of Leadscrew
and offer it available by the inch on e-bay for those who need short pieces
! (like the 6"X6" example)

See ! (making) "money" really is easy - (anywhere) !

Chris L


cncdxf wrote:

> Chris,
> What if the person has a 6" X 6" cutting area and the
> threaded rod is off by .005 or more over that distance. The
> machine will still be a learning tool and it can turn out great
> parts for RC cars and planes. Have you ever measured a handmade
> part. Looks great-works great but don't mic it out. I have
> been following lots of peoples progress. I see them selling
> their stuff off on Ebay after getting frustrated. To learn CNC you
> need a machine. After getting your feet wet you can then buy
> some expensive leadscrews. My guess is that at that point you
> will build a second machine using what you learned or buy one!
>
> Bob
>
> --- In CAD_CAM_EDM_DRO@y..., ccs@m... wrote:
> >
> > > Select only a good piece of threaded rod. Leave the rusted
> ones
> > > at the store. If you use threaded rod on your machine, don't be
> shy
> > > tell them how it works! Accuracy, everybody talks about accuracy.
> What
> > > is everybody using their machine for. I never see any project
> being
> > > descussed here anymore.
> >
> > Bob,
> >
> > I can see that threaded rod may be a good way to start out in some
> > situations. In fact I probably wish I had prototyped my bearing
> > mounts by machining the ends of allthread, rather than the ballscrew
> > (which wasn't that expensive by itself, but can't easily be replaced
> > as the outfit had a $200 minimum order)
> >
> > And many hobby machines may not need much accuracy, however there is
> > one aspect that I will call 'incremental precision' which they do
> > need. The primary reason I am building cnc machines is to make
> > calculated curves for musical instrument tooling. I did some of
> this
> > manually with a crude digital readout, not realizing that the
> readout
> > had a very small (maybe .002") amount of cyclic error due to the
> > unwise way I connected the encoder to the screw. This showed up in
> my
> > finished part as a very noticeable ripple superimposed on the
> contour
> > - it even transfered from the bell mandrel I had machined through
> into
> > the first few trumpet bells, until I carefully filed it out.
> >
> > So, absolute accuracy may not be important for many applications,
> but
> > cyclic error can really ruin your day if you are machining curves or
> > even diagonal paths. Of course, cyclic error over a short distance
> > may be as likely to result from poor screw mounting as from errors
> in
> > the screw itself.
> >
> > Chris Stratton
> >
> >
> > -------------------------------------------------
> > Christopher C. Stratton
> > Engineer, Instrument Maker, and Horn Player
> > ccs@m... 617 628 1062
> > http://web.mit.edu/~stratton/www/brassbuild.html
>
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