Re: [CAD_CAM_EDM_DRO] Re: Threaded Rod WORKS!

Chris Stratton probably indicates the real issue better than me.

He, (best I can tell) has gone through the method of "lets do it fast",
"cheap", "quick"...... Only to WISH he had done it much different from the
start.

Those "Cyclic" errors that one ends up with by doing it the "quick" way, ends
up making your skin crawl until you get it fixed ! Somehow, you just can't
live with those errors and this can go right down to the .001 level. So, you
without even knowing it, have forced yourself into the second machine without
even really getting use out of the first one !

Take it from those who have been there. You will have PLENTY to get your feet
wet on, Plenty to learn, long "after" you have the ultimate hardware
platform. You just won't have to do the hardware part *twice*.

The Hardware part, if done right will not be a continuous source of grief.
You''ll have enough "excitement" and "Grief" just making the controllers and
driver cards to work the way they should ! :-)

Build it as best you can with the money available (or limit of credit card
!). That's all one can shoot for !


Chris L

ccs@... 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,
>
> The education value is of course there, and with carefull planning one
> could probably replace the cheap screw with better ones as an upgrade.
> However some of the problems can show up very quickly in certain
> common uses of a machine.
>
> If one only tried to use the CNC machine as an automated manual
> machine - only feeding one axis at a time, doing circular bores with a
> boring head, angles with a rotating vise, turning lathe tapers with
> the compound, etc. Then yes you can produce good work with a machine
> that has substantial absolute and cyclic errors.
>
> The problem is that many people use the CNC capability to avoid
> complicated fixturing by resolving angles and even arc segments into
> X, Y, and maybe Z components. Then you get in trouble if the
> increments in all these axis are not constant over their travel, and
> in many cases (especially milling) also if you have backlash in your
> screws.
>
> The point of my story was that I thought I didn't need absolute
> accuracy right away - didn't really care at first if my trumpet bells
> were .020" oversize at 4" diameter. But having a cyclic error of just
> a fraction of that superimposed nearly ruined the part, since curves
> that were supposed to be smooth turned out wavy.
>
> Chris Stratton
>
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