Sinker EDM cutting steel against steel; what generator settings work for you?

[implmex]

The title kind of says it all; I'm sinker EDM matching a super complex parting line on a mold, with five tapered shutoffs.
I burned it as close as I dared to go and now I'm burning the hotside core against the coldside core to match the corner rads and bring the parting line together the last 0.010" (these are side shutoffs, so I'm only actually removing about 0.001" of material to close the mold by 0.010")

Problem is, I have no generator settings for steel on steel burning, so the burn is going slow as molasses on a cold day.
I'm running a Hansvedt MS4 Foreman sinker.
I have been playing around by trial and error, trying to find better settings than what I have been using; (I started from my settings for copper tungsten against steel, and I'm putting 4 amps into a burn whose surface area is about .0625 square inches. (1/4 x 1/4")
I'm unconcerned about wear of the half that's the "electrode" for this burn; it matters much more that they match, than that they be a specific shape.

Can any of you provide some guidance on good pulse duration, on-time/off-time ratios and anything else you can think of to give me a better starting point than simply guessing at it?
I am assuming, I don't want a "no wear" setting; it seems kind of pointless to be eroding the workpiece half while plating onto the electrode half, but other than that, I have no theoretical basis to help me find a good starting point, or what parameters to adjust from there to optimize the burn.

Cheers

Marcus
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining

 

[Matt_W]

I've had no experience of steel on steel, but would be very interested to hear if anyone has.

 

[implmex]

Hi All:
So, for those who are interested in this subject; I got a very generous private message this morning from Bud Guitrau, inviting me to call him to go over the problems and solutions to steel on steel sinker EDM.
For those who don't know his name, Bud is the author of The EDM Handbook, and is currently working for Makino I believe.

Here's a distillation of his wisdom:
1) Set the total pulse duration to a relatively small value to keep the burn fine and the overcut down.
We settled on a start point of 40 microseconds.
2) Keep the % on time at 50% or below to avoid plating the positive side of the electrode/workpiece pair.
3) Generous high volume low pressure flushing is crucial
4) Keep the trode in the burn as long as the cut remains stable (the cut is intrinsically inefficient with such a conservative duty cycle and short pulse duration that it pays dividends to keep the trode in the burn as long as possible before cycling the ram.
5) Clean the burn often; soot will accumulate quite quickly, inhibiting the burn.
6) Change polarity of the burn fairly often to distribute the wear evenly between the parts.
7) Be patient; this will never be a fast process.

Bud's recommendations are suitable for any situation in which the trode material is the same as the workpiece material, and gives a good starting point.
The burn is doing better than it was (still pretty slow, but that's a part of doing this technique)

Bud, thank you most kindly; I really appreciate your willingness to share your expertise this way!!
Cheers

Marcus
Implant Mechanix – Design & Innovation - home
Vancouver Wire EDM -- Wire EDM Machining

 

[Zahnrad Kopf]

Class act. And just reminded me to buy his book. Thanks to both of ya.

 

[EDM JOE]

Hi All:
For those who don't know his name, Bud is the author of The EDM Handbook, and is currently working for Makino I believe.

Bud also publishes great technical articles in EDM Today magazine frequently...

A lot of the advice on generator settings matches up with the steel on steel technology that came with Charmilles X0 and X00 series machines, though point #6 might make you question why you did not think of it first.

 

[Bud Guitrau]

Just came across this... thanks for the kind words.
I've had a fabulous career and need to guide anyone who follows. Happy to help.
Bud

 

[implmex]

Hi Bud:
Your generosity with your wisdom and your willingness to bail my ass out of a hole resonated with me and will do so forever.
Even though this thread is pretty ancient, I appreciated it greatly and continue to do so.

I do what I can too, trying to guide those who come with questions...it's the thing that keeps me coming here even in spite of the occasional loud and rude.

I've received priceless stuff from so many of those generous souls who hang out here, and I've saved myself countless hours of head scratching, so giving back what we can, when we can, is what makes the forum as good as it is and I'd really like to keep it going in that spirit.

So thanks Milacron, for setting it up, and thanks to all who participate constructively, including your generous contributions Bud!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[Bud Guitrau]

To Marcus,

You do a yeoman's work here yourself, sharing your daily, real-world experiences with us and I have learned many strategies from you. Thanks for your generous contributions here and I urge you to continue to do so and for others to join in, whether learning or teaching.

To All,

Don't be shy... join in the Q & A conversations. This is a fun, chummy, well-behaved place to hang out with many EDM Brothers.
All we need is pizza and beer. Could you imagine what a hoot that would be?

Bud Guitrau