Wire EDM'ing Molybdenum????

CPM2014 · Jul 16, 2015

Does anyone have experience wiring Moly? Trying to cut 4" tall Moly461 and having no luck. Charmilles said to use steel technology with some slight changes but still nothing. We have tried Tungsten Tech as well with same results (or lack there of). Wire is just bouncing then breaks. Please help! :confused:

Sybilsurf · Jul 16, 2015

Was your starting point from a hole popped hole? The reason I ask is that I had a job where the exotic metal (I forget what alloy) became contaminated with the standard brass tubing and I couldn't pass through the nonconductive layer. I asked an old coworker (it was a repeat job) and he said that a copper tubing was the ticket. I had to run a drill through the piece to clean out the brass and it was fine.

CPM2014 · Jul 16, 2015

Entering from the outside of part. No contamination.

KilrB · Jul 16, 2015

CPM2014 said:
Does anyone have experience wiring Moly? Trying to cut 4" tall Moly461 and having no luck. Charmilles said to use steel technology with some slight changes but still nothing. We have tried Tungsten Tech as well with same results (or lack there of). Wire is just bouncing then breaks. Please help!

What machine, wire, and diameter of said wire?

CPM2014 · Jul 16, 2015

KilrB said:
What machine, wire, and diameter of said wire?

Tried both, Charmilles 4020, and a Cut200. .012" Brass wire

KilrB · Jul 16, 2015

CPM2014 said:
Tried both, Charmilles 4020, and a Cut200. .012" Brass wire

First, check you FF setting, I don't know about the 4020 but I have had our 200/400 both inexplicably set FF to 1.

Now, can you tell what is causing the break? Is it burning it in two or wearing?

Where is it breaking? Above, below, or at the part?

You probably have but, have you turned FF way down (50-60) to get it started and then cranked back up?

Have you taken the front off the lower head to make sure everything is alright in there?

CPM2014 · Jul 16, 2015

KilrB said:
First, check you FF setting, I don't know about the 4020 but I have had our 200/400 both inexplicably set FF to 1.

Now, can you tell what is causing the break? Is it burning it in two or wearing?

Where is it breaking? Above, below, or at the part?

You probably have but, have you turned FF way down (50-60) to get it started and then cranked back up?

Have you taken the front off the lower head to make sure everything is alright in there?

Wire is breaking at part. I have tried all the usual setting variables. Moly has a very high melt temp (5000deg) and I am wondering if the high temp has something to do with it. The machine just flat out doesn't want to burn it. I had to back the wire speed back to .1/hr just to get it to cut at all. Cut just will not stabilize. Have you cut Moly before? Part also discolors quit a bit as if it were heating up

KilrB · Jul 16, 2015

CPM2014 said:
Wire is breaking at part. I have tried all the usual setting variables. Moly has a very high melt temp (5000deg) and I am wondering if the high temp has something to do with it. The machine just flat out doesn't want to burn it. I had to back the wire speed back to .1/hr just to get it to cut at all. Cut just will not stabilize. Have you cut Moly before? Part also discolors quit a bit as if it were heating up

Long ago on the old Andrew-Charmilles machines.

Not recently on any of the newer machines though.

Because of the density and high melt point it was very slow cutting, like tantalum.

Will it require skim cuts?

Might be a high B, mild FF, and lower tension with some follow up skims is the ticket.

Hope some of our sages show up soon to help figure this out.

EDM JOE · Jul 16, 2015

I've seen wire breaks at the entry cut when wire cutting Moly with .010 wire in the past. All I can offer is (if possible) I have removed the outer skin on the Moly (by milling). That allowed the wire to start cutting from the outside of the raw stock.

Also, I hate to be that guy, but... Are your upper and lower power contacts, contact blocks, and so on, worn, dirty, or otherwise compromised? Have you checked your power and ground cables for contamination or other defects?

Lastly, if brass/hard metal .tec files exist for .012 wire, maybe you could try that. The melting point of Moly is closer to tungsten than the melting point of steel.

rwbaldwin · Jul 16, 2015

EDM JOE said:
...I have removed the outer skin on the Moly (by milling)...

+1
Sometimes the recast layer can really cause problems. We used zinc coated wire and an oil dielectric (as moly is soluble in water.)

Sybilsurf · Jul 16, 2015

If you get one spark and the wire breaks then I would say you have some surface layer that is nonconductive. If so then I would try EDMJOE's suggestion of milling (or filing) the entry point.

EDM JOE · Jul 16, 2015

Sybilsurf said:
If you get one spark and the wire breaks then I would say you have some surface layer that is nonconductive. If so then I would try EDMJOE's suggestion of milling (or filing) the entry point.

Just before setting the part in the tank, I'd scuff the entry area with Scotch Brite (for luck). I'm not sure if Mo oxidizes in a normal shop atmosphere. I'm not looking it up because I have no desire to burn it again. Molybdenum is hazardous. This will contaminate your dielectric reservoir. See www.molybdenum.com/health.pdf

Morali · Jun 18, 2018

Contaminated DI reservoir

I have been cutting some Moly plates in my wire, and we are not even getting a couple hours out of the DI bottles before we have to change them out. I was wondering if I am hurting my machine by running Resistivity so low for so long, we are trying to cut about linear 200in at 2" thick plates. I am seeing some dark coloring on my table, that which I have never seen before.
Thanks for any suggestions you can offer.

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