CAD for simple 3-D metal & wood projects?

jim fired this volley in news:H8WdnTONgeg28Q_PnZ2dnUVZ snipped-for-privacy@bright.net:

Yup... I can make a piece of glass flat to about three angstroms by hand.

But your comments to the negative don't bear on the discussion. The discussion never was "how many of 'us' could do it"; But is it a realizable and realistic degree of precision?

Yes, it is... even with the sort of equipment I use (albeit newer and in better condition).

I'm not working with a table-top Tormach, and do this professionally. But even a lot of amateurs have older high-end industrial equipment. It sells for scrap value, if one is willing to do the work to rescue it and upgrade the electronics.

I just had an 'amateur/recreational' machinist friend buy a full-up Fanuc slant-bed turning center with 4th axis, 12' bar feeder, and live tooling (+ATC)... With a little TLC and good insert tooling, that machine will do sub-tenths work -- in his garage!

Lloyd

Lloyd

Guided missiles and rockets are two different things. Nuclear missiles are "ballistic" (even they are steerable), rockets, not so much. You can't orbit an object in a ballistic trajectory. They

*have* be able to correct their trajectory. Not only does/did the Shuttle have aerodynamic surfaces and steerable main engines for atmospheric corrections, it has/had OMS engines and thrusters fore, and aft, for extra atmospheric corrections.

Flat and round (spherical) are trivial problems and as you note it's been done for ages, at least since the middle ages. Other shapes are more difficult, as is size.

And there isn't much advantage in having a CAD model for those shapes.

And it is doubtful there is anyone reading this who is cutting complex shapes from CAD models with precision held to tenths.

There isn't much reason to have a CAD model for a board, either, but when you want to put a few dozen of them together, having a CAD model gets rather interesting.

Huh??? Have you ever heard of a mirror, or lens, system? Please explain your statement?

Me, for laser optics in the space program. They invited me in as the electronic tech, then I got the mechanical design and fab part of the job by demonstrating that I could center a gage pin to +/- one micron in a 4-jaw lathe chuck. jsw

With care and patience the half-century-old machines in my home shop can still hold around 2-3 tenths. jsw

How many have you modeled in CAD and then manufactured to within tenth of the designed part?

You must not have any personal experience (I do) in R&D in the semiconductor industry.

Nope never had anything to do with the semiconducter industry.

I thought we were talking about cutting metal.

You still make no sense. Are you saying that precision machining doesn't require the same level of modeling that sloppier work does? Really?

Yes, but that's how we got where we are. After all, somebody had to start with rocks and sticks. I'd still like to see a readable account of how it's done. Moore's "Foundations of Mechanical Accuracy" gives a good start, but the narrative is hard to follow beyond the basics.

bob prohaska

"Jim Wilkins" fired this volley in news:l6u4qk$qdf$2 @dont-email.me:

Jim, these guys who are harping on the issue have been working to maximum tolerance of 1/32" for so long that they cannot imagine anyone working to tenths of a thousandth of an inch.

And because THEY can't do it, they state flatly that "nobody" in this group can.

Lloyd

Now THAT'S an old computer - rock for zero, stick fro one...

Gunner Asch on Sat, 23 Nov 2013 20:00:04 -0800 typed in rec.crafts.metalworking the following:

I'll take your word for it. My experience differs. So what? I must have been in the wrong plants. Boeing only insisted on 30 thou. And Jorgensen only insisted that the part be consistently within 4 tenths of what ever final dimension in the "regular" tolerance you reached - over a ten to fifteen foot part. On a manual lathe. (But I never got to work on any of those jobs.)

OTOH, I have worked places where we measured each part, trying to keep up with the thermal expansion as the day warmed up.

Just lean on the machine, that will flex it enough. B-)

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

What shuttle?

You just had to stick that in here, didn't you? ;-)

"Lloyd E. Sponenburgh" on Sun, 24 Nov

2013 08:15:37 -0600 typed in rec.crafts.metalworking the following:

Probably developed a very precise definition of what constituted "sloppy". B-)

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

Well, I for one do. But my experiences with them had nothing to do with woodworking and were long ago :)