anyone need free WEDM work

Likely, but by the time I sort through my crud to see what's worthy of having you spend time on, you'll be a mile deep in "free work", Karl.

Tiny tungsten carbide cribbage board? Pointless, but...

One of the things on my list is to try cutting some custom carbide grooving tools. And maybe a custom boring bar. I already bought some HSS blanks to make custom slotting tooling for my bridgeport slotter.

The tech. fella told me this is one of the few machines that will cut pure diamond. Anyone need their SO's diamond cut in half?

Karl

Is diamond conductive enough??? jk

Polycrystalline diamond compacts, which are the basis for most diamond cutting tools, have enough electrical conductivity that they can be wire EDMed -- just barely. It's a slow process, but it's used to make shaped cutters for commercial woodworking, and to a lesser degree, for metalworking.

The compacts are sintered with a small amount of cobalt, usually, but it's not quite like the cobalt binders in sintered tungsten carbide cutters. I'm not up on the details but the cobalt serves more to dissolve the diamond, or to aid in the diffusion of diamond-to-diamond, rather than acting like a matrix, or binder, as it does in tungsten carbide.

But a small amount of metallic cobalt remains in the diamond compacts and that aids conductivity. It also makes polycrystalline diamond compacts slightly less hard (but more shock resistant) than single-crystal diamond tools.

Even pure diamond has some conductivity, and various forms of synthetic diamond can be quite conductive. But the wire EDMing is generally applied to the compacts rather than to pure, single-crystal diamond. There are wire EDMs made exclusively for the cutting diamond compacts to shape. They have specially tuned power supplies.

The really old Andrew machines used a conventional (for the time) RC relaxation circuit, so I'm not sure why it would be especially good for cutting diamond. Is this one of the granite-base machines with the moving head?

-- Ed Huntress

Yes. According to Mike, there were three major generations of wire burn circuits on the Charmilles Andrew machines, the focus of technology at the time. The machine I have was made just before pulling the Andrew name off the machine. Again, according to Mike, the next focus was making the burn circuit more user friendly by computerizing the control of the burn circuit. This worked, but you actually lost ability to do the tuff stuff if you knew the machines well.

Karl

Interesting. I don't remember what settings were used for diamond -- maybe it was a high-voltage, short pulse. But don't count on that. It was too long ago.

Good luck with your machine, Karl. It should be a lot of fun.

-- Ed Huntress

How about making a few custom pasta extruder dies to go on the KitchenAid grinder? Dies with people's initials, logos, etc. ought to make good holiday gifts.

--Here ya go; I've wanted a little injection molding die for this widget for a decade and more. Ping me offlist and maybe we can talk further?

Something like this?

Essentially, but more personalized to the recipients.

Interesting, however the little squeeze-to-release nuts sold for the purpose are cheap, and easy to fab yourself if you want. I just bought one for the $5 or so.

Interestingly, diamond has great thermal conductivity and great electrical conductivity. Can you say heat sink insulators?

Uh, actually diamond is one of the materials with the phonon-carrier anomaly. It's a great thermal conductor (better than silver) but it's an electrical insulator.

There are some surface-conductivity phenomena which have only recently been understood, but the bulk electrical resistance of diamond is very high. Impurities and intentional additives in synthetic diamonds can alter this.

-- Ed Huntress

Why bother with a thing like that which need an air hose when the spring closed split nut works so well????? That was one of the first things I made when starting on the mill. ...lew...

Hmm ... insulators with "great electrical conductivity"? I don't think so. :-)

Enjoy, DoN.

On Fri, 24 Oct 2008 12:01:03 -0400, the infamous Spehro Pefhany scrawled the following:

Is that what they use to make that pasta putanesca dish?

-- "The latest documents released this week showed that priests with drug, alcohol and sexual abuse problems continued in the ministry as recently as two years ago. That doesn't sound like a church, it sounds like Congress with holy water." -Jay Leno

I suspect that should read resistivity. The covalent bonds in the diamond crystal do not leave free valence electrons floating around to conduct any electricity. I suggested it to my employers as an insulated wedge block material for salient pole rotor AC machines in the late 70's. Oddly enough, they weren't amused :-)

Mark Rand RTFM

My typo; that was what I meant to type....

I had a boss at NASA-LeRC who was trying to make diamond-like films for space apps because of this anomoly. Most electrical insulators are crummy thermal conductors...