wire overburn

[bamavick]

Using a Charmilles Robofil Wire machine, I am having a problem with the wire overburning where I lead into the profile and it only seems to happen on round holes where we have a cnc hole which we use to centerfind. It leaves just a small mark in the profile. I only use one cut (E2) setting. On occasion our operators run the machine wide open (150" hr) until it meets steel and breaks the wire. Could this be this problem? Or does anybody else have a solution or idea? Thanks

[Del.]

ALL wire machines will leave some kind of a mark, especially if you are only taking 1 pass. I would advise taking some skim cuts to reduce the size of the mark.

[Matt Berube at Ferron Mold]

I don't know Charmilles wire EDMs at all but if you want a nice finish with no blemishes you should be using more than one pass. 1 Rough and 3 Skims is what I normally use.

 

Another thing that comes to mind would be that if you're drilling a "start hole" very close to the finished wire contour size and the wire never gets buried in the steel (i.e. you're not dropping a slug) you need to turn down the flushing pressure because full flush without burying the wire=wire bouncing around and leaving blemishes on the part.

 

What size is your start hole and what size is the finish wire contour ?

[bamavick]

The size of our start hole varies, but I do know that the wire does cut in enough to bury. We do use more cuts on certain parts, but economically we can't on these parts that I am having problems with.

[gavetta]

Are you leading in on a straight line move or arcing in?

[CAM-mando]

Agree with previous posters that adding skims is the only way to remove the entry / exit marks completely but as Gavetta suggests arc on your lead in could help. If operators are jacking up parameters it will probably increase the mark.

 

I'm curious What kind of tolerance are you dealing, what's the material and how big is the hole?

[John White WLM&T]

Kinda hard to explain but we will add an extra little bump on the surface that we lead in and out off of right where we lead in. After we remove the slug we go back and trim the lump off. You may have to experiment a little with the power settings a little to get the blend right so the lump is gone and you can't see it.

 

John

[BF]

Feather in, feather out.

[peon]

If allowed, create a half moon on the round geometry beyond the circle. Lead in and out on center of that arc. I have done that for years on dowel holes on our Charmilles machines WITHOUT skimming. The Charmilles rough cuts (E2) are much more accurate and cleaner than the Mitsubishi, Agie and old Elox wire machines. I don't believe in skimming everything if your rough cut can do the job within tolerance.