Re: [CAD_CAM_EDM_DRO] Are there CNC-only jobs, or is it only for duplicates?

Doug Warner wrote:

> I've been following this group for some time, and have been amazed at
> the amount of work (and money) people spending to automate their
> machine tools. I can see the application for doing for-pay work, 100
>
> items, exactly alike, but for hobby use, is there an advantage where
> duplicates aren't important? Are there parts that simply can't be
> made by twisting the screws by hand?

Yes, there are a number of one-off parts that really can't be made
easily, on a manual
machine, even with sophisticated tooling. How about a part that has a
round OD, but
different diameters, like the bayonet breeches of large guns? How about
a part that
has a combination of round and straight sections. If you really HAD to
do this manually,
you'd use a rotary table, and it would take quite a while to calculate
the right points
to mount the piece properly on a rotary table, and then much care to get
the curves
to blend into the straight sections correctly. I've done this manually,
and it is a BIG
pain. With CNC, it is no biggie. How about a part that has 2 parallel
sides, and one
side that needs to be a 30 degree angle? You could mill this with a
rotary table or
a swivel base vise, but if you needed it accurate, it could be a pain.
With CNC, you
just cut on a 30 degree angle. VERY hard to do by hand!

How about a piece that needs 15 odd-size, large holes in it? You can
bore it on
a lathe, re-locating the part for each hole. You can use a boring head,
but that's
slow. Ir, you can have the machine orbit such that a hole of the right
diameter
is cut with an end mill in just a minute or two. The centers of the
hole will be
located more accurately than just about any other way you could do it.
I do this all the time for meter cutouts, fan holes, big holes for other
things
to bolt to, etc. If the hole needs to be real precise, I orbit it out a
little
undersize, then use a boring head to make a finish pass at the desired
diameter.
This saves about 1 hour per hole over drilling a 1/2" hole and then
slowly
boring it up a little at a time with a manual boring head.

Clearly, anything that has a round side or pocket cannot be done
manually,
without a rotary table. If it has a complex 3-d curved surface on it
cannot
be done manually at all.

Jon