EDM Wire

Hello my fellow WEDM people. I wire machine primarily silicon carbide/silicon metal based ceramics. I have an ongoing job where I take a 4.25" x 1.125" x 8" long chunk, burn a series of 4mm holes through the 4.25" direction via hole popper EDM, and then move to the wire EDM (2003 vintage Sodick AQ750L), to EDM out the ID and OD, resulting in a tube 10.5mm ID x 16.5mm OD x 4.25" long. Are we good so far? :-) I have been running 0.012" brass wire, my average cutting speed was around 0.055"/min. Recently, I purchased and installed a spool of the ProCut Z (0.012", Cu/Zn 40, 900n tensile) from Sodick; I am impressed with the increase in speed..now averaging 0.070"/min, but I am not thrilled with the fact that when the wire breaks, it kinks and curls bad enough, that it will not rethread. Other details worth mentioning...the work is flat, therefore, I can get the upper/lower nozzles close for good flushing. I am currently running 6mm flushing cups, but I have a PO in the works to purchase 3mm cups with the thinking that this would be better...comments welcomed. Does anyone have an opinion as to a better cutting, more dependable threading wire? Any other thoughts that may come to mind? Most of my work is not precise or small...I have thought about, but not researched the advantages of going to an even larger diameter wire, if my machine can even handle it. I know someone has some good thoughts! Thanks in advance,
Mark Roberts

We use the Thermo SD wire from Sodick. Its great wire. We have no issues with threading tall parts and start holes down to .020" dia. It can handle up to 25 deg taper. Its clean with no zinc residue and we can really bump up the power with it. We have noticed about a 20-25% increase on burn times over brass wire.

Our 750 had the 60 amp high speed generator and this wire worked excellent with it.

What's the old NC milling adage? - increase your feed until the tool breaks, then back off a tick, right?

If you're getting wire breaks at .070", then you're actually going much slower. Back it down to .065" - you'll still get the speed advantages without the stoppages, and come out way ahead.

OF. Thank you for the reply, but in this case, that scenario doesn't quite work due to the uniqueness of the material, and sometimes the inconsistency of it...

I had the same issue with the ProcutZ wire on my Fanuc Robocut.

I was told that using a coated wire can sometimes cause unintended consequences. The burn zone creates a pocket of extreme heat. When that happens, the coating on the wire can burn off and react negatively, which causes the copper core to become extremely brittle and snap. Because of the combined tension, heat, and chemical reactions, it snaps so badly that it usually can't be recovered without operator intervention. Really good flushing is key to preventing this, but I never found that to solve the problem fully. I don't know how true this actually is, so take it with a grain of salt.

I've never run a Sodick, but on a Fanuc, you'll usually get better results by modifying your cutting data's on/off values. The pulses of current have a timing to them, and reducing my off time allowed for less breakage and faster cutting speed with standard brass.