1. Home
  2. ⏣ General Metalworking
  3. Ram EDM troubles

Ram EDM troubles

I was trying to use my Southbend/Ingersoll/Hansvedt 150B Ram EDM over the weekend and ran into some difficulty. Maybe someone can spot what went wrong.

I was trying to burn a .125 hole through a piece of HSS. Things started out ok, but towards the end things kinda went astray. I was using a .125 graphite electrode that I had drilled a .062 core hole for dielectric flushing. I used a small diameter trode since I wanted the test to progress quickly, therefore less material removal.

First problem I had was with the work tank. My system uses compressed air to move the fluid from the holding tank to the work tank. As the work tank filled to 3/4 capacity, if I kept applying air, the air started bubbling though the line causing fluid to geyser out of the work tank and all over the floor. This required that I clean the shop floor several times. I found it easier to shut off the air at 3/4 and submerge the work using the recirc pump.

Once I got going things went slow but smooth until the end. The ram kept oscillating up and down about 1/32" and the volts and amps swung wildly. Then it looks like the end of the electrode melted and it messed up the mouth of the hole. How that happened I don't know. I never broke through the hole. Perhaps if I undercut the electrode that would have been better (wafer type). That means I couldn't core the trode though.

My fluid is old, it came with the machine so it's history in unknown. It is dark amber color, but doen't appear to have suspended particles that could be causing shorts, as least as far as I can tell. I could look at a sample under magnification. I plan on eventually changing it along with the filter but its a messy job.

I posted the pics to the dropbox if it worked.

formatting link
Ed, are you out there?

Reply to
Tony
Loading thread data ...

You're arcing. Why, I haven't a clue.

Check the bent-over end of that electrode and see if it isn't steel. Graphite doesn't melt. Assuming it's steel, that's further confirmation that you're arcing.

The first thing I'd check is to see if you have polarity set right. After that, punt...

Is the machine otherwise working OK?

Good luck.

Ed Huntress

Reply to
Ed Huntress

Oh, another likely thing: amps set too high? This varies with the machine, of course, but a starting point is 30A/in.^2 of the electrode's projected area. That works out to something like 0.28A for this electrode. Are you set at that order of magnitude, at least?

Ed Huntress

Reply to
Ed Huntress

your tank is probably low on fluid & whenthe level gets below the out line in the tank, air gets mixed with it.

Either the fault of poor flush thru the electrode or sometimes while breaking thru with a cored electrode, there is a small pin left over in the middle of the hole. as you get close to the end , the pin starts tipping over & touching the inside of the electrode causing a short. The best thing to do now is break the pin off as far down as you can & clean out the hole with alcohol, air & a pik. redress electrode & go back in with around 5# of flush pressure. It sounds like the condition that you have encountered is "DC arcing", which leaves an almost nonconductable surface on the subject metal.

Reply to
Wwj2110

After looking at your pictures it appears that there was no flush coming thru the electrode at all. With proper flush you can pop a .125 hole thru a .25 toolbit in 15 minutes or less.

Reply to
Wwj2110

Ed,

My machine doesn't have an amp setting per se. It does have servo speed, freq, duty cycle, sensitivity, and gap spacing. So I guess by adjust those the end result changes the amps. The meters were running from 5 ~10 amps at

40 volts. Trouble is adjusting those controls involves a lot of guess work.

Tony

Reply to
Tony

I think thats what happened. Now that I look at it again, the pin was there when things were going ok, and now after the arcing the pin is missing. It must of caused the short circuit like you said. I came real close to burning through because I can see a ring on the underside of the work.

So I guess standard procedure is to break out the pin as the work progresses to avoid disaster?

This EDM isn't as easy as they make it sound!

Tony

Reply to
Tony

I had a decent flush coming through the hole, although after the arcing the end of the electrode got buggered up.

Reply to
Tony

The polarity is set to normal, which the manual indicates electrode negative.

Also, I was operating in the pulse mode, without capacitance. Maybe next time I will try capacitance mode.

Tony

Reply to
Tony

What those meters actually read is a little problematic, but that 5 - 10 A for a cored electrode of 0.125" can't be right. Maybe that's the current when you were actually arcing? That would be another indication of arcing.

As for the voltage, we'd have to know what's normal for a Hansvedt, and, again, what its meter is actually reading. That can't be the actual voltage during an arc. It *can* be the average voltage during normal sparking.

Keep fiddling. Something is bound to turn up.

Ed Huntress

Reply to
Ed Huntress

Leave the pin in place until you start to break through and the cut becomes unstable. Then stop the cycle. In a hardened steel, you only have a thin bridge of metal holding the slug in and it can easily be broken off. Less chance of disturbing position on your workpiece. You probably want to change your dielectric and make sure your filtration system is working properly and you see the correct pressures from the circulation pump. We just had to replace ours due to wear.

Rich Williams

Reply to
Rich Williams

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.