I bought a Charmilles Andrew wire EDM about a year ago. After trying on/off for many days over the last year, I hired a fella to come out. The guy is a genius at WEDM! He had us going in minutes by finding the broken wire that had a feedback voltage working poorly.
Anyway, I'm going to do nothing but run my new toy for the next few weeks. I've got a few parts I need, but I really could use more work. Anyone need something?
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?
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?
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.
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.
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 :-)