Re: [CAD_CAM_EDM_DRO] First machine/plans recommendation?

>
>
>need to be able to mill cobalt at 6m/second either :) It just needs
>to be able to show me all the basic elements of CNC machining.
>(Like, what the hell is a ballscrew!)
>

Believe it or not, a ballscrew is exactly what it says. Helpful, huh?

OK...go get a bolt, or anything else with a screw thread. Look at
it...I mean, really look at it. You'll notice that, more than likely,
the teeth are cut as a triangular section...they look like a "sawblade"
when viewed on the edge. The mating nut has the same profile. Now, put
a nut on the bolt. Try to wiggle it, without turning the screw --
you'll notice there is a significant amount of play. This is backlash.
(Keep this in mind) It's a result of the poor fit of the two parts.
There are many ways to deal with this...a ballscrew is one of the best.

On a ballscrew, the threads are cut as semicircles, so that ball
bearings can ride in them. The nut has the matching part on the
outside, and contains (and in some cases circulates) the balls around
the screw. The ballscrew is not a screw, in the traditional sense -- it
is quite literally a helical ball bearing. And, consequently, its
friction is VASTLY lower than screw threads, when used as a drive screw.

A happy part about ballscrews is that they're very accurately made, and
can be adjusted to have ZERO backlash, while not increasing friction to
a high level. The sad part about them is that they are very expensive.
And I mean VERY...

>I'd like to hear from anyone that successfully built a small machine
>from scratch. Preferrably ones that didn't have part sourcing
>problems :D WHich plans did you get? Which controller? I don't care
>if it was less than stellar, tell me anyway :D
>

It's not done yet, but here's my CNC diary...it's the story of a
scrounger who has put darned near the minimum possible amount into a
machine.
http://makeashorterlink.com/?C55F63745

Perhaps it'll be of some help. My working area is 18x24" which is kind
of "medium" in the world of CNC. There are the giant machines, and on
the other end, the stuff used to cut out watch gears. Mine is somewhere
in the middle.

Hope it serves to inspire you, at the very least.

-- Chuck Knight

If you don't mind premade plans, John C. Kleinbauer (
http://www.crankorgan.com if I remember right) has complete plans for
machines available, for around $30. He also has a LOT of pictures up,
so if you're even halfway handy you can just "take inspiration" from them.