Hi Brandon:
Welcome to the world of Sinker EDM.
It is a sometimes intensely frustrating but very cool metalworking technique that will enable many things unobtainable any other way.
You have made a good machine choice too; Charmilles is a very good brand indeed; I'm not familiar with your specific machine control, but Charmilles controls in general are very powerful and capable and make many of the intrinsic challenges of sinker EDM easier once you figure out how to turn it on and run it.
Having said all the positive stuff; here's what you're up against getting a machine like this productive:
First of all, the machine is only a smallish part of your new problems; you've now got to make electrodes.
If you go with the most common electrode material choice, they'll be graphite, and that means a helluva mess in your shop unless you're willing to do all the things needed to keep the housekeeping under control.
Graphite dust isn't just messy; it's abrasive as hell, so it kills machine tools, and it's conductive, so it kills computers.
It also needs better cutters than run-of-the-mill coated carbide, so you're looking at diamond coatings and their expense.
I chose to use tellurium copper and copper tungsten instead of graphite for these reasons, but I pay a significant penalty in reduced burning performance.
If you want to get into any production, you'll need electrode holders and you'd better be sitting down when you check out the prices for any of the top brands.
Then there's the cost of dielectric oil for the tank (a thousand bucks or so for a 55 gallon drum).
So this is not a cheap undertaking.
Moving on to the work you'll try to attract.
My machine hums into action mostly when I'm building injection molds.
It will run sometimes for as much as a month, then might stand idle for a half a year or more.
I get occasional work for it on other stuff; I'm cutting a set of tiny stamping punches right now, and I've cut some other weird stuff for surgical instruments and the like, but it's pretty sporadic work without the molds.
Sinker work in my experience, is almost never specifically sought after by an engineer or purchasing manager; I get my sinker work because I specialize in the kind of work others won't even bid on, and it's a part of my unusual arsenal of machines that I deploy when I think it's the best or only choice.
So advertising sinker capability hasn't been very effective for me in bringing work onto the machine table, but having a reputation for pulling off screwball jobs has kept the machine busy enough to justify the floorspace it occupies.
Another point about sinker work: it is amazingly easy to lose your ass bigtime on the sinker.
It is one of the least predictable machining technologies, and the details that matter can be really un-obvious.
Of these, the principal one is flushing; one fluid-starved spot in a corner somewhere, and the whole process grinds to a halt and sometimes goes backward, blasting an unrepairable hole in your beautiful part.
Last weeks half hour job can easily turn into this weeks ten hour hair tearer.
One of the most frequent killers is burning out broken taps; a tiny loose bit like a chip or a broken tap fragment, and she no want to cut, no matter how you curse.
Price your jobs accordingly and warn your customers.
I tell them I'll try.
It will either take an hour, a day or it won't be possible, and they still have to pay.
I let them put an upper cost limit on the job after which I'll abandon it, but they have to pre-pay and I'll refund them the balance if it turns out to be easy and fast.
If they won't play by those rules, then I won't put their job on the machine.
I've had my ass handed to me too many times on this kind of work; so making them prepay is a great way to keep cheap shysters away!
The other big one is underestimating the finishing time.
Roughing can go at a good clip at times followed by hours and hours to take out the last tenths.
Your Charmilles will be way better than my Hansvedt, because yours likely has an adaptive control that is given a goal for finish and finds its own way to get there most efficiently, which is a HUGE help compared to mine which must be set up manually.
To answer your specific questions: the C axis can be used to orient the electrodes and also be used to spin round electrodes.
Spinning an electrode improves its ability to make a round hole and also aids in flushing spark gap debris out of the cutting zone.
It's a useful feature; so be happy the machine came with it.
Electrodes wear, sometimes quite substantially, so the burn will often require several trodes to complete.
Corner wear is the big problem.
The standard practice used to be to make an undersized roughing electrode, followed by a set of finishing trodes.
The development of orbiting capability changed that approach, so now electrodes are usually all made the same amount undersize then orbited out to the proper size to make the desired part.
On a CNC sinker, you can burn in any direction, and along vectors generated by combining axis movements, all with good precision and without any actual contact between cutter and workpiece, so frail trodes and parts are possible in ways you cannot do by any other means.
As far as books are concerned, I recommend a book by Bud Guitrau; he's one of the EDM gurus and his book is well written, describing both the theory (simplistically but very usefully) and the practical nuts and bolts.
On a last note, you can have a look at my Implant Mechanix website; there are lots of examples of sinker EDM machined parts scattered throughout the site.
Cheers
Marcus
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining
