Re: Don't give up!!!

Thanks Tim,

I will add that a tolerance easily better than .020 can be met by a
VERY cheap machine...

Machine wise, Resolution is easiest to get, and repeatability is not
far behind. Inherent accuracy will be nearly impossible at these low
prices, but the availablility of those first two above make it
achievable by correcting the repeatable error to the limit of the
resolution.

Mostly, cheap machines give up rigidity, speed and power.

I don't want someone thinking they have to live with .020 because
thy're poor!

Hope this helps,

Ballendo

P.S. another truth is that far more often than not, when we're
building something for ourselves, relative accuracy is much more
important than dimensional accuracy. as long as the parts fit
TOGETHER well, their being too big or too small often dpoes not
matter. even Joe Martin, of Sherline (who has a bit of experience
holding tolerances (decades of parts which mate each other!)
talksabout this in his instructions on threading. Cutting something
to fit something else which we have in hand is not the same as
meeting some dimensional standard so that parts from many machines,
vendors, and places can mate well.

One useful trick for a cheap (inaccurate, but repeatable) machine is
to use the same part of the travel(s) for mating parts. In other
words, if you're cutting an inlay near the origin of x and y, be sure
to cut the pocket in the same place. Will fit like a glove, even if
the machine IS out .020... (which it won't be, IMO)


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Tim Goldstein" <timg@k...>
wrote:

> Ballendo,
>
> Thanks for the post. This is a subject I keep harping on. Yes CNC

is an

> expensive hobby, but we (the royal collective we) often tech it to

death

> and make it far more difficult and expensive than it has to be. I

think

> it is very important to step back and look at the desired outcome.

If

> the goal is to make a machine that can cut balsa and hold a

tolerance of

> say .020" than there are some very low cost approaches to getting

the

> job done. As you mention there are low cost designs that do work

and you

> can cut balsa just fine with a small high speed bit. Not everything
> needs to be designed to hold micron accuracy.
>
> Tim
> [Denver, CO]
> Sherline products at Deep Discount
> Mach1 & DeskCNC with credit card ordering
> www.KTMarketing.com/Sherline
>
> > -----Original Message-----
> > Hello,
> >
> > Depends on what you're looking to do. And what you're WILLING to

do

> > to get there...
> >
> > So maybe you can't get a laser CNC setup for 300 bucks? You CAN

get a

> > balsa CAPABLE setup for 300 bucks (Dave rigotti, and John

Kleinbauer

> > come to mind, as well as Luberth, and others).
> >
> > So build one of these. Maybe you can sell some model balsa "kits"

to

> > others to finance the 500 more bucks you'll need to put a laser

on

> > Johns "Scrappy", or pipe dream, or daves Hobby CNC... Yeah, if

you're

> > willing to look, and learn, these prices ARE do-able. been there.
> > Done that.
> >
> > It's pretty easy to get caught up in the "professional" side of
> > looking at cnc, and forget that the hobby side doesn't HAVE to
> > cost "thousands"...
> >
> > Good luck,
> >
> > Ballendo
> >
> > P.S. Did anyone contact mr. linear to find out where he got his

diode?

> >