MitsTech......What ARE you talking about?....ever hear of "zero offset"?
Hollistergc has it right, thank you.
harrytm, yes. Of course the program can be run in G40.
But that does not change the properties of EDM, and that is there will ALWAYS be a spark gap between the wire and the part, on all three sides; front left, and right. If the slot was not larger than the wire, than there could be no spark gap, and thus no EDM. It would also run in contact all the time. So you can run in G40, but the spark gap will still be whatever is listed as a rough cut offset in the technology files.
Yes you can run with very little overburn by running very low power settings, but the feedrate slows down to thousandths per hour instead of inches or feet per hour. I think the original poster here is looking for speed over any other factor.
harrytm, take a look at a technology data sheet sometime. You will see thousands of different offsets and offset combinations depending on material, thickness, wire diameter, numbe of skims, accuracy requirements, speed requirements, etc. All of those offsets are given (at least in Mits books) from the edge of the wire, not the center. The machine comps the center to the edge of the wire just like a mill when it reads G41 or G42.
Anyway, you can figure the total overburn on two sides by looking at the tech table for a given power setting, finding the offset, multiplying it by two then adding the wire diameter. So if you're using .010" wire, and the offset is .0047", your total slot width will be .0047x2+.010=.0194. This is, of course, for a rough cut only scenerio.