Sharp corners on EDM

Hi all!
New to the forum, new to EDM too
Can anybody tell me which parameter to adjust to protect the sharp corners of electrodes? I am working on Agie EDM sinker with copper electrode on steel, thanks all for your inputs
Allen

Since you are new to the process, copper electrodes are going to wear faster than graphite. So you might have better luck switching to graphite material. I think you will achieve faster results to finished cavity. I don't know if you have a quick change chuck with changeable pallets and a matching machining fixture, but having the ability to machine multiple and re-machine/redress worn electrodes and precisely re-insert them into the EDM machine is essential. Though I personally use an alternative, 3R Macro System is probably the most popular chuck for EDM. It is definitely worth the investment and you can find them on the second hand market quite readily.

Additionally, there is the so called "No Wear" setting which I believe can only be implemented using graphite electrodes. This setting essentially makes the polarity of the electrode positive. Maybe your Agie calls it something like positive electrode polarity. In practice I have only used it for roughing with my equipment as I don't think it produces a good surface finish for me.

If you don't need to wire EDM your electrodes, I would recommend you give graphite a try. There are various particle sizes of graphite depending on the fineness required in the application. Poco graphite has some good resources available to you and can recommend proper grades to use.

Thanks so much for your quick reply. I ran into the article about Graphite electrode, I will give it a try, the problem is I do not have the vacuum in place to machine graphite yet. I use HIRSCHMANN system 5000 electrode holder, The Agie Mondo 50 has tool changer....but I can barely run it now! Everything is new to me. once again thanks for your helps.
Allen

AllenT said:

Thanks so much for your quick reply. I ran into the article about Graphite electrode, I will give it a try, the problem is I do not have the vacuum in place to machine graphite yet. I use HIRSCHMANN system 5000 electrode holder, The Agie Mondo 50 has tool changer....but I can barely run it now! Everything is new to me. once again thanks for your helps.
Allen

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Nice to see a new member take the time to thank the ones that gave answers. Welcome to PM, Allen... Hope you become a regular..

Hirschmann makes great stuff too. I don't sink enough to justify better and dedicated equipment, but I've been known to hold a Craftsman shop vac hose near the cutter. Don't be tempted to use coolant though it might sink into the graphite pores, and I recommend baking the graphite blank out in a warm oven prior to machining to remove any moisture from storage. The Poco tech people are really good at helping you choose the proper grades, there are several, and proper machining parameters.

Ill add that it depends on how deep you are burning as well as material and current. Any time I burn something I use multiple electrode. The electrodes are a consumable, every time it sparks material is eroded from the part and the electrode. Multiple roughers and a finish is the way to go. Through coolant will help with the efficiency of the burn by ensuring the burnt material is evacuated and not causing a buffer.

Excellent point plastikdreams...
While a fine grade graphite is definitely the right move over copper, there are also processing methods that need to be considered.
Multiple electrodes and burn tool paths.
I would recommend straight -Z roughing under-size on all sides and bottom (example: -.025" electrode leaving .005" stock per side), and then using an under-size (-.035") second electrode to burn into the corners in X, Y, and -Z.
What this does is disburse the energy (heat) over three faces of the electrode instead of concentrating the energy (heat) on the easily eroded sharp corners of the electrode.

Jay Crumb
Advanced EDM, LLC
440-567-5808

JayCrumb said:

Excellent point plastikdreams...
While a fine grade graphite is definitely the right move over copper, there are also processing methods that need to be considered.
Multiple electrodes and burn tool paths.
I would recommend straight -Z roughing under-size on all sides and bottom (example: -.025" electrode leaving .005" stock per side), and then using an under-size (-.035") second electrode to burn into the corners in X, Y, and -Z.
What this does is disburse the energy (heat) over three faces of the electrode instead of concentrating the energy (heat) on the easily eroded sharp corners of the electrode.

Jay Crumb
Advanced EDM, LLC
440-567-5808

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And we haven't even touched on orbit/vectoring lol

When it is not possible to put the electrode in a no-wear condition, the selection of the proper grade of graphite can reduce the amount of wear. Since each manufacturer produces many grades in a number of classifications, it is important to understand the characteristics of the graphite. I will prefer Graphite. 3r Tooling is the latest technique used, we have to be much creful when using this.

3r stuff is nice but insanely overpriced and parts are scarce...plus their macro pallet quality has gone down.

The first question ought to be ... "Why does your pocket need sharp corners?"

Internal sharp corners are an invitation to cracking.

If you cannot radius the corners, can you relieve them?

AllenT said:

... the problem is I do not have the vacuum in place to machine graphite yet. ....
Allen

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This is why the good lord invented cheap shop vacs sold at the big box stores. Along with cardboard and duct tape collectors.
Bob

Thanks for all, Vacs from big box stores would work, it's time to switch to Graphite, hope it's not to late:-) once again thanks all for your inputs
Allen

If it’s the same agies that I’ve used, it’s ACO- 4 which enables the current to active work surface protection. Which simply cuts down Amps in relation to the variation of surface contact over the course of an erosion

I'm puzzled that nobody has talked about spark gap. If the op is concerned about wear, maximizing spark gap will greatly decrease wear. Finer graphics increases strength drastically and reduces wear somewhat the down powerline controls most of the wear. A .010 sg down powerline has significantly less wear than a .005 sg down.

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Im using Copper electrodes only on my Mitsu. AE12v Advance. Edge on electrodes by my knowlege are far better with using copper electrodes than graphite. Also if electrodes are simple, just make them few, put them in toolchanger and use correct offset and orbit. Its no problem to get to VDI0 on new Mits.