Wire EDM Steep Taper...Procedure?

I have some parts I need to wire cut a 30 degree taper on. My machine is a Mits 90C. Wire is .012, and parts are a bit under 7/8". I am pretty sure I have enough travel in U to do this. (Only need to tilt one axis)

But on my machine the heads are fixed and don't tilt. I am pretty sure I need to change the flush cups to ones that have a bigger hole for the angle of the wire when tilted. Do I need soft brass wire or will half hard work?

Is something with this steep of angle even possible?

Thanks, this is new territory for me!!!

I haven't cut an angle that steep on any of my machines, nor do I have experience with a 90C, but I don't think you can get quite that much taper per side. Using our CX-2 for comparison, I believe it's 1.94" max offset in the U axis, which comes out to about 24* on a part .875" tall. I do remember the Mits. tech telling me (all this from memory, so maybe, maybe not) the flush cups need to be sized up to 14 or 16mm, the diamond guides need to be replaced with "large lead-in" guides, the power settings (epacks) need to be pulled back (maybe eliminating a skim?), and different wire needs to be loaded (Mega-T?). If this cut is just on one outside edge, it would probably be easier to just fixture the part at the appropriate angle, even as a second op.

EDIT-My mistake. Bad math...I was thinking from the other plane. Looks like the offset would only be around .5052", so this would probably be doable on that machine.

Hey E!

First - Haven't forgotten about your brother's splines. Ping me later.

Second - I don't believe the 90C does more than 12 degrees. I could be wrong, but I believe I saw it in the specs last week when looking at purchasing one. I've used it a number of times but only for far more shallower tapers.

Hope you're doing well.

Best regards.

Toolmaker, great info thanks!

I did a little bit of playing with my machine yesterday and it looks it can achieve the angle, and with the taper cutting flush cups, and stock guides, everything is okay clearance wise.

However I just have I think its either half hard or hard brass wire. (Versacut E) and it "waves" ALOT back and forth as it goes through the guides...I am thinking if I get some soft wire this shouldn't be a problem.

Z, the max taper specs I believe is at the Z capacity, so shorter work can be greater taper...I think at least!

Will shoot you a PM about the spline project!

Quote: "Z, the max taper specs I believe is at the Z capacity, so shorter work can be greater taper...I think at least! "

You got it. Max taper angle is determined by the limit of offset in U and V, so the taller the part, the lesser the angle.

Machinery_E,

just a couple of additional thoughts to consider on your taper application-

.012" wire is probably not the best choice for this amount of taper. In addition to the striations you've already seen, it will most likely give you a significant angular error (angle is larger than intended) because of the large wire diameter combined with the resulting bending axis of the wire.

The specifics of this: The thicker the wire is, the less compliant it is to bending. This combined with the work-hardening that takes place as the wire bends results in a longer (higher) bending axis in relation to the guide land as well as curling of the wire (which is now work-hardened as well as curled), which will invariably produce a "streaked" or striated finish.

The usual work-around for this sort of application is to use a smaller and softer wire such as .008" "type T" (soft) or at most a half-hard wire. This will help to minimize the work-hardening of the wire and maximize its compliance to bending. As well, it will give you much better taper accuracy (assuming that you have the correct guides to utilize the smaller wire, that is), and there will be far less striations left on the work piece.

Excellent info, thank you!!! That makes alot of sense there...I got a roll of .012 soft brass already coming so figure I'll give it a try, the good thing is I also have a set of .008 guides...might have some wire too!