EDM Sinker with an open door?

Hi, we have a long pipe about 38" that we need to trim a few mm on each end, and then add a small interlock on it. It obviously does not fit in our sinker. My question is: can we run the sinker with an open door? Is it safe? This would mean that we can only use flushing to remove the scrap, since there will be no oil bath. Has anyone done it? Has anyone done the same thing on the Wire EDM?

Yes... it can be done rather easily.
Just make sure your flushing completely engulfs the spark area or else there is potential for fire.
I have even used tupperware to give me a submerged effect around the spark area.

yes... I have also run WEDM in this manner.

Jay Crumb

I agree with Jay Cee it can indeed be done but here are some other things to consider before you quote:
First; make sure you have a REALLY GOOD dam inside the pipe.
Siphoning all your dielectric oil through the pipe and onto the floor is considered bad form.
Water from a wire EDM; perhaps not quite so bad but still not fun.
The best kind of dam has Orings in it...nice big soft squishy orings to seal really really well. especially if the pipe is not DOM and has a weld seam in it!!

As Jay Cee says, make a mini tank inside the main tank.
Use a cheap plastic bucket and cut a hole in the side of it you can shove the pipe through.
Make the fit of the hole good enough that your inflow from the flushing wands is bigger than the outflow from the leaks around the hole.
As long as you can keep the bucket full, leaks won't matter because they'll all go back into the main tank.
The full bucket is what makes the fire hazard go down.

Resist the temptation to plug the leaks with plasticene...it'll dissolve in the expensive dielectric and wreck it along with the filters and maybe the pumps too.
(Rustlick 250 dissolves plasticene: I don't know about other brands)

Resist also, the temptation to just point a couple of flushing wands at the burn zone and call it good.
Again as Jay Cee points out, it's a pretty severe fire hazard if you get too cocky with this.
You can get away with it for a 2 amp burn, but for an 8 amp burn maybe not so much, and for a 20 amp burn...forget it.

You'll probably need to bypass the float switch and maybe a door interlock to make this work.
Make sure OSHA and your insurance company are nowhere near when you do this and don't run the burn unattended.

Also watch the loads on the machine; if you hang a gazillion tons of steel several feet out from the edge of the machine your ballscrews and linear rails will never be the same again.
Ditto if you just park a sawhorse out on the outboard end of a heavy workpiece and expect the machine servos to drag it around in X and Y.
So no orbiting unless your machine has a ram mounted orbiter or the part is really light and needs no outboard support.
That's about it...oh yeah; don't forget to charge through the nose for all the extra risk and hassle!!
Cheers

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

I do surface flushing all the time, workpiece not submerged, no problem, but my burns are mostly in the 2A and less range, not 8A. I've also found that cardboard boxes make excellent temporary coffer dams for submerging just a spot, at least in a sinker; the oil has no effect on the cardboard or glue. Not sure how it would work on a wire machine, though.

The fact that the workpiece is a pipe rings a warning bell, however. If you are burning through the wall, or accidentally might, you have to be sure the pipe is flooded full... you can't surface flush the inside of a pipe and you'll get hydrogen burning in there, or worse yet an explosion. Reminds me of a story told me years ago... the shop had a large (several square feet) mold cavity block in the tank, cavity facing down. Since there was no vent from the cavity, it didn't fill with oil when the tank filled. When the burn broke into the cavity, it started to fill with hydrogen until the mixture became critical, and then the ensuing WHOOMF blew all the oil in the tank out onto the floor.

Dennis

Here are general tips that may help... when I burn unsubmerged I always get one of my bosses to man a fire extinguisher right next to the machine. No joke. If the machine catches on fire, it is not my investment. By the way, very small flare-ups can be extinguished by spraying them with dielectric oil... no oxygen, no flame. Run a box fan toward the machine to help disperse the vapor layer that forms above the dielectric. I've extinguished many flare-ups with Ionoplus 3000 synthetic dielectric oil. Also, leave yourself a clear path to the door, and hit the E-stop while your running away if things get out of hand.

Two things learned in this thread -

1. - the answer to the OP's question.

2. - there are more people as foolish as I am than might be imagined at first blush...

Thanks guys. At least I know I'm not the only one.

Just adding this since there seems to be so much concern about fire...
Killing the power puts out the fire 9 times out of 10.
It's the unattended job that continues to spark and continues to feed the fire that is the one that burns down the shop.
In fact, ONA's new fire detection system does just that...and only that...

A good point was brought up Model man.
Be ready for the break-through spark.
Especially if it goes into a closed (non-vented) cavity.
I also have a story of a guy who had a cupped shaped electrode that wasn't vented.
He called me over to the machine and said, "Listen to this...it's making a funny noise.
I leaned in closer and heard one smaller "boom" right before the bigger boom broke his electrode in half.
Through electrode flushing (either out or in) would have saved his day.

Jay Crumb

I run my machine without the tank flooded all the time. My parts are small and the machine is big, so waiting for the tank to fill is a pita. Mainly less than 10 amps if just flushing with the pipes and no dam, and never when I'm not around. I just want to add one other thing to watch for, make sure your flushing pipes are not atomising the fluid. eg, hi flow though small nozzle. Remember the liquid does not burn, only when it is heated enough to evaporate into a gas is it flammable, or as I found out once, if the fluid is being atomised by the nozzle.

So I was working at my desk, damn, flame detector has alarmed out the machine again, (somtimes happens from reflected sunlight), oh well I'll wander out and reset it, hey what are all those flames... The detector had shut off the machine, and like jaycee said, main fire was out when pump stopped, but not before setting alight some of the microswitches on the head. Blew out the flames like birthday candles (made a wish... no serious damage) That was close.

Well this is an old topic, but I figured I post a picture I made when I had to deal with oversized parts, in case someone having hard time visualizing said suggestions, about making a little tank around the burn area. The clear plastic I used is a plastic cover of a spiral bound exercise book. I had to burn out a broken tool.

I like the girly poster in the back with the guy striking the same pose next to her.