AC vs DC current?

Sorry for making so many posts lately, I just have so many questions, and in this case both google and books available are falling short in the answer.

I am mainly burning tungsten carbide, PCD, and some steel (though I am unaware of what type of steel) as I make cutting tools. My mentor has recently told me that we have had "no good luck" in using AC current on our tools, claiming issues with wire breaks and poor surface finish. Therefore we have been using DC currents when burning.

I feel that AC current would be more beneficial in the long run, especially as we are looking into cutting high volumes of PCD pucks in the near future, but I don't know enough about the application of AC vs DC to fix the issues they've had in the past.

The manuals I have on hand are not being incredibly helpful to me, as the technology manual we have does not cover the materials we use, and the operator's manual does not explain the difference in currents. I have attempted to google the difference between AC and DC currents in the application of EDM machines, but I'm finding either completely irrelevant information, or perhaps one or two articles that are a little too dense for me to comprehend.

Can someone help explain in laymens terms the impact these two currents make on tools, so that I can make more educated decisions when switching between the two?

And yes yes I know, if DC current is working for us I probably shouldn't mess around with it, but just because we've been stuck in our ways for the past decade doesn't mean innovation is out of the question, ya know?

Hi again Ishira:
AC vs DC current...well there are theories, and there are theories about which is better and why.
AC generators were developed (so far as I understand) to reduce electrolysis of susceptible materials; titanium and tungsten carbide spring to mind.

However, the better strategy for both carbide and for PCD apparently, is to use an oil dielectric rather than water in the machine.
But you cannot just dump in a bucket of oil...you need the correct generator.

Makino makes a line of machines specifically for carbide and PCD...others probably do so too.
They use oil dielectric specifically to eliminate the cobalt leaching that occurs with water dielectric and to enable finer finishing than can be done with water..

So far as I know, cobalt is the most common binder for tungsten carbide and is also present in PCD...something to do with promotion of the diamond crystal growth when the material is made.
So these oil dielectric machines have been specifically marketed to makers of edged tooling...form cutters, punch dies etc etc.

So is AC better than DC...theoretically it's supposed to be, but whether that's actually true is anyone's guess, especially since your results will probably vary from machine to machine.

If Brian Pfluger from Makino sees this thread, he can probably chime in in much more detail about which is the best way to cut carbide and PCD and why.
You may want to knock on his door anyway, and see what he says.

But so far as I know, the biggest and best respected cutting tool manufacturers pretty much all use these special machines for wire cutting carbide and PCD.
Whether their generators are AC or DC, I have no idea!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

If only I could convince the higher ups to invest in oil dielectric or Makino machinery. They're stuck on Fanuc brand, and water dielectric. They're wanting to buy two "new" (used) machines, and both of those are Fanuc as well. Unfortunately I think I'm stuck with what I've got, haha!

Cobalt leeching is the main issue they've been discussing, it would be great to have some new information to bring to the table about how to manage it.

I hate EDMs and I should start with that.
Cobalt leaching due to the water. Everyone's favorite go to excuse and so misunderstood.
And then go to oil and the problems do not go away.
Water is bad for carbide and PCD yet many machine tools work just fine in water based coolant.
Hmmm.
But I do have to say cobalt leaching is a real thing in carbide, CBN, and PCD work.
You need a SEM or outside use of one if this a concern.
PCD has a cobalt binder. The EDM process eats the binder not the PCD. This is why some high performance PCD grades really do like EDM and are laser cut.
Slicing and dicing PCD dics for tips is not a easy world to get into. Yes I know full discs are so cheap as base material but this is so full of things.
Bob

(All this just a guess from out there and I've been proven wrong so many times here so this just an opinion. I know just enough to be dangerous.)

CarbideBob said:

You need a SEM or outside use of one if this a concern.

Click to expand...

What is a SEM?

As I said in the other thread, you really need to speak with application engineers at fanuc for this. We can give you info and direction, but they will be able to give you solid info on their specific machines.

You said you started 6 months ago, this is an opportunity to really get a good foothold in the company.

Plastikdreams;

How would I go about getting in touch with those specific people? I'd definitely like to. Every part of this is pretty new to me, including reaching out to people and finding resources, so forgive me for being a bit naive.

It's no problem, you are just looking for some very application specific questions. Their contact info should be with the books. Otherwise call the fanuc dealer and start tbere.

Ishira said:

What is a SEM?

Click to expand...

Scanning electron microscope.
One step past normal optical stuff on seeing edges and cracks. Expensive stuff and a pain in the ass to use.