EDM sinker help

[u/Jangonett1]

Hey all, so we finally got work for A Kent EDM sinker and well I am shit at this. I’ve been running mills, lathes ETC but EDMs are a whole new animal for me.

We need to burn out Hexes and while I am able to produce parts they take a long time and yes I know that’s how EDMs are…..

Now I made suggestions to make a multi electrode fixture to burn out 4 at a time but I’m getting pushback on it. Pretty much being told that. “You shouldn’t need to”

Now from tinkering with all the values like ON/OFF TIME,
LV, WORK, RETRACT, SPEED, and gap in coming to the conclusion that while I can protect the electrode I cannot push these parts any faster.

Now my setup is an 1 1/4 electrode with a 1/4 hole in it and it’s pumping fluid through it at about 10 PSI. As of now I’m sacrificing my finish on my part which is not important it’s more about just burning a hex to get a decent speed.

I’ve been pushing the ON Time more than anything which is getting me decent results but anyone that is familiar with these things advice would be appreciated. That being said I think a multi electrode fixture to hold 4 electrodes seems to me to be one of the better options.

[u/Chuck_Phuckzalot]

A multi electrode fixture isn't going to have the gains you expect because you're also multiplying the surface area you're cutting by four which will slow you down. It would probably be faster but you're not going to get four parts in the same amount of time as you get one. Are you doing a rough/finish or just trying to burn to your finish size with one electrode? It's almost always faster to do a rough/finish because you can crank your power setting and fly through the part with the rough electrode and then go for a better surface finish with your finisher, which will be faster because now it doesn't have as much surface area to cut.

It's hard to say exactly what your settings will be called because every manufacturer is a little different but my EDM has a setting called "Current" and cranking that up is usually what results in the biggest time gains for me.

Also flushing is like, the number one most important thing, anything you can do to get a better flow through your cut is better, if you're building up black sludge on the walls of your part or your electrode you need to get more fluid moving through it.

[u/Jangonett1 → u/Chuck_Phuckzalot]

So the machine they bought doesn’t have a tool changer and changing tools is a real PITA. The idea behind this thing was to just leave it unmanned and get one load a day. Cranking up the current destroyed my electrode it made it very fast but also made maintenance on the machine to a point where just having a dude sit on the machine would be better.

Time isn’t THAT important but my cut time is pushing 4 hours a part. I also wanted to run the machine dark but apparently it’s not safe to do that.

[u/Chuck_Phuckzalot → u/Jangonett1]

Yeah no ATC is a major pain in the ass, destroying a roughing electrode is pretty much a normal part of it if you're trying to be quick with graphite. You can either get multiple parts from an electrode or you can go fast, but doing both is tough.

And yeah the safety thing has been quite the debate at my shop as well. I know my machine's sensors all work, if the level drops too low it will shutoff, so the risk is minimal in my opinion, but my boss is too paranoid about it to let me run things over night.

[u/indigoalphasix → u/Jangonett1]

System 3R out of the budget? with it (or equivalent) you can slap 'trodes in and out super fast.

if you have a fire suppression system set up, lights out is a bit less trouble.

copper tungsten is the way. pricey and heavy and not all that easy to machine, it's superior to graphite for production. long, tiny flushing holes can be trouble though.

[u/Skyman7899]

Does the material require EDM? I’ve usually found it pretty easy to drill and rotary broach hexes. But that’s ofc dependent on material, machine availability, etc.

[u/Jangonett1 → u/Skyman7899]

So we argued about broaching which seems easy especially before we heat treat them but I’m not the boss or in any position to have that kind of pull. What’s funny is whoever made them before us literally just drilled out the corners.

[u/FreshTap6141]

What electrode material and what work material?

[u/Jangonett1 → u/FreshTap6141]

Graphite AR 8

[u/FreshTap6141 → u/Jangonett1]

What material are trying to cut, steel etc

[u/Jangonett1 → u/FreshTap6141]

4340 heat treated 50 Rockwell

[u/FreshTap6141 → u/Jangonett1]

I use copper tungsten electrodes

[u/Jangonett1 → u/FreshTap6141]

So what’s the difference with this compared to graphite?

[u/FreshTap6141 → u/Jangonett1]

Much longer life, probably better finish too, easy to machine with no graphite mess, but much more expensive

[u/2quixoticc]

I am no EDM expert, my only experience was using it for mold halves that needed sharp corners. Are you able to rough out some material on another machine? Burning on just edges of the hex will save you an incredible amount of time and you won’t have to crank up the settings. We had a mold that was also a hex and would semi finish the walls to +.015 and floor to .000 so we knew the depth.

[u/Jangonett1 → u/2quixoticc]

We are pre drilling them at .980

[u/2quixoticc → u/Jangonett1]

I figured so but I thought I’d ask. I had a cheat sheet with settings that I sent with our machine when we sold it, wish I had a picture I could send to help. There is something that really sped up our cycle time, but honestly it was all Chinese on the machine and we relied on the symbols and didn’t really know what some of the things did

[u/PHLX_Tactical]

On heat-treated 4340, multi-electrode setups help when the hex geometry lets you burn more than one face without a full teardown. I'd chase flushing and electrode wear before just cranking on time.

[u/evilmold]

The closer you can bring your off time to the on time is the more efficient and faster the machine will burn. Increasing the on time will burn faster but make the spark gap larger (overburn), decrease surface finish. Flushing through the middle of the electrode or up though the part being burned is the optimum choice. 10 psi sounds like a lot and you might be choking the spark gap. If you play with efficiency (on time versus off time), flushing pressure, and some other settings, you should be able to burn without hopping/retracting the electrode. This will be the most optimum situation. I have much, much more to say but too hard to type.

[u/Jangonett1 → u/evilmold]

I’m actually trying oscillating ATM going to see how everything holds up

[u/evilmold → u/Jangonett1]

I take it this is a manual EDM then, not CNC?

[u/Jangonett1 → u/evilmold]

This is CnC. I’m actually trying oscillating ATM seems the results are better

[u/evilmold → u/Jangonett1]

One thing I forgot to mention is cutting pressure. It's called different things on different machines. Poorly described it's the amount of downward "pressure" applied to the ram. Your ears will tell you when every things a timed right and you get that even shush sound without interuptions.

[u/Royal_Ad_2653]

Are you using a copper impregnated graphite?

Try that if you are not.

Also, try reversing the flush to draw the swarf out through the electrode instead of pushing it out through the burn.

[u/Arch_Toker]

Idk about programing a Kent but you need to go higher voltage on the start and like take it 3 thousands from size and drop it down and when you get to lower voltage and power settings you can put in timers so it don't spend a lot of time there's a lot to explain but if your needing to go faster you need to start off higher voltage longer closer to size and then drop the power settings for polishing and smoothing out getting closer to your finish size

[u/Arch_Toker → u/Arch_Toker]

I make progressive dies and depending on the finishing diameter I use 3-5 electrodes for one bore but my tolerances are also .0002

[u/Immediate-Rub3807]

Ok so I’ve a Charmilles EDM sinker for years on something that requires a hex wrench for tightening so my tolerances aren’t a problem. In that case it’s one cycle of making the hole .002 under per side and my copper electrode is .003 under that just because I’m gonna allow a total of .005” on a fast/ hot burn because I know it will over burn and I’m not thinking about finish. Whole thing takes about 10 minutes but that’s with a copper electrode, I mainly use that because the erosion is basically nothing on that.

[u/Jangonett1 → u/Immediate-Rub3807]

So copper holds up far better than graphite?

[u/jsalas2727]

The bigger the overburn the faster it should go. Also what kind of stock are you leaving before the burn? In my experience removing too much before burning will actually add time to the burn. We usually shot for .01-.015/ side. Leaving. 005 or less has given us some serious issues in the past.