E-bay EDM plans

Spent any time playing with Mach3 or EMC2? If it isn't in them currently, it can be added with relative ease. I use Mach3 myself on a little mini mill. The voltage sensing back off sounds very similar to the torch height control process used in either package when driving a plasma cutter.

Stepper systems are the cheapest and easiest anyway, and both common software packages handle the trajectory and acceleration / deceleration quite nicely.

I know if I were to build one, I'd certainly prefer to use water.

No expert on wire EDM, but from the units I've seen during my CNC service days it looks like the wire feed, threading, tensioning and guide system would be a royal pain to DIY.

Both challenging and also very specialized. Wire EDM just doesn't seem to be something very useful for a typical HSM.

Pete C.

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Hmm ... for a CNC one, how about making a form tool from a HSS lathe blank to cut a specific pitch and tooth count of gear? That sounds like an excellent use of wire EDM in a hobby shop. (Or for that matter -- perhaps even cutting the gear teeth themselves, complete with keyways. You need a 127 tooth gear to cut metric threads on your old Imperial lathe -- there you are. :-)

Enjoy, DoN.

Much easier and more versatile to just convert that old lathe to CNC itself.

Cutting gears has been a big prototyping and short-run job for wirecut EDMs. The older ones only approximated an involute but that's been long solved.

-- Ed Huntress

[Pete: This never appeared on my newsreader, but I saw it on Google Groups when I was trying to figure out what was happening with my news server, so I copied it. -- Ed]

[You were referring to the multi-axis servo requirement for wirecut]

No, I'm not familiar with them. I don't doubt if someone is good with control software they could make something work. But there were problems with the early systems in caching chunks of the program for servo purposes, setting step-thresholds for different low voltages, and so on. It may not be as trivial as you may think.

I'm just curious about this, but why? Water is faster; it's just a productivity issue, though, and I don't think it means much to a hobbyist.

Wire *feed* is just a tension roller driven by a servo motor, a jockey wheel with an adjustable clutch, and a spool for the wire. Regarding automatic threading, don't bother with it. The early ones didn't have it and it took years before the commercial manufacturers ever got one to work right, anyway. The basic guides are just donuts with a hole around 0.002" larger than the wire size (I'd recommend 0.010" wire).

Actually, I think it would be great. I always wanted one for cutting out the rectangular holes in falling-block rifle receivers. They're also good for cutting hard materials, including carbide (although you'd want a good commercial one for that).

But I really don't think that one you could build at home would be much of a machine, compared to an old commercial one. The big trick to the whole design is keeping the wire from breaking. They'll break if you look at them cross-eyed. A broken wire really is a PITA, because you have to move back to the home position, re-thread the wire, and then travel forward through the machining path, retracing what you've already cut. A few wire breaks can really ruin your day.

-- Ed Huntress