EDM Drilling Machine

[Industrial Toys]

The most amazing thing I have seen in a little while.

Drill through anything (conductive) with Electrical Discharge Machining - YouTube

Man, Some people are SMART! It makes me feel like anything I do is like a kid with glue and sparkly bits.

Many years ago, a friends brother had a company making moulds for the auto industry amoung other tools, using EDM. That's the last I ever heard of the technology.

 

[BukitCase]

Those've been around for awhile - from about 1982 to 1990 I was the guy who got called to repair/tune an archaic version of that (rare metals plant) - needed a high voltage power supply (in this case, around 1200 volts), and got the needed current by using 24 big fat metal-capped tetrode tubes wired in series parallel - the "drill" was basically an electrically driven small drill press that was controlled by a servo drive system -the "bit" was a piece of copper rod, with a cross-section of whatever shape was needed to be drilled - one common shape was a sort of triangle, but with its sides "pushed in" (concave) - that one was used to "arc drill" the balls out of ball valves, so that their flow response became LINEAR instead of "little-most-little" as they were rotated.

The other main use was drilling 4 3/8" mounting holes along one side of a cast solid tungsten triangle. The part's function was as one of the internal steering vanes in the exhaust stream of missiles (hence the tungsten)

In each operation, the part was mounted in an immersion tank and submerged in a really low viscosity cutting oil during the entire "drilling" operation -

I got so tired of working on that cantankerous yesteryear beast, that was 30 years ago and I can't remember the brand name of it to save my sorry butt... Steve

 

[Industrial Toys]

Interesting. I don't understand how precision drilling can be achieved using that basically wet noodle of a drill rod..

 

[gsganzer]

That's pretty cool. The tolerances are amazing!

We had a waterjet machine at one of the places I worked. It was pretty cool and typically operated at 90,000 PSI spraying a garnet cutting media. It could cut though a piece of fabric, foam, leather, stone, all the way to 8" thick titanium. One of the largest users of the waterjet technology is Kimberly Clark, making diapers, because there's no chance of small metal cuttings from mechanical cutting blades.

 

[BukitCase]

"basically wet noodle of a drill rod"

There's essentially ZERO physical pressure applied, all "drilling" is really just the arc "blowing away" anything in the path of the "drill", which is maybe better described as an electrode. The one I worked on would take about 1/2 hour to "drill" a 3/8" hole thru 1" of tungsten. When the cutting oil bath was new/clear, all you could see was a tiny ring of fire right around the electrode.

Oops, forgot to mention - the electrodes are hollow, and the same coolant the work piece is submerged in is ALSO pumped thru the electrode - it's a good thing, because Tungsten's melting point is over 3400 degrees Celsius - without the forced cooling, it'd probably take a couple hundred electrodes to drill one hole. WITH the cooling, one electrode typically got maybe a dozen 3/8" holes before it was out of spec.

That "servo drive system" I mentioned looked at arc voltage to control the down travel, and adjusted vertical position based on (preset) arc length.

That function worked exactly the same as the up to 50,000 amp vacuum arc melt furnaces I also worked on at the same company(s)... Steve

 

[Industrial Toys]

I guess the neat part is that the electrode does not have to blast away material that will hurt your tolerances, but kind of just nibbles away at the material, burning it away. Basically, like using a stick welder as a cutting tool.

 

[dstig1]

EDM is used all the time in the Mold and die making industry. And it's been around forever... but if you don't have exposure to those industries, or other high precision industries like medical devices, then you would probably not be aware of them. It is much more expensive than hard milling so it is only done as a last resort for things that can't be made another way. What is shown is wire EDM. there is also sinker EDM where you start by machining an electrode out of graphite that is the reverse of the shape you want to make. Then you burn it right into the steel..slowly...

 

[5030]

The most amazing thing I have seen in a little while.

Drill through anything (conductive) with Electrical Discharge Machining - YouTube

Man, Some people are SMART! It makes me feel like anything I do is like a kid with glue and sparkly bits.

Many years ago, a friends brother had a company making moulds for the auto industry amoung other tools, using EDM. That's the last I ever heard of the technology.

The Remington clone receivers on both my hunting rifles are made from solid titanium and wire EDM cut. So are the bolt faces and charging handles. Actually, the common machine shop name for electrical discharge machines are 'die sinkers'. Wire EDM machine are very precise, cut exceptionally clean and burr free and you can engrave in metal with them as well. My titanium receivers not only have the builders name in them but my initials as well.

 

[npalen]

We used EDM back in the sixties to "drill" out broken taps. The electrode would take out the center of the tap and the rest could be chipped out with a small punch. Very useful on expensive workpieces.
Another method used on larger taps, say 1/2" diameter, was to heat red hot with a cutting torch and then briefly "hit the oxygen". The tap would disintegrate and the hole could then be cleaned out with a fresh tap, if you were lucky.

Edit: A variation of EDM machining is with a stretched wire passed thru the workpiece.

Edit: Example of tap burner: https://www.ebay.com/i/142810091094...JG9lbeZQYSH85jIfkKkvn1e_gt2eqyQBoCv5IQAvD_BwE

 

[Tonyinohio]

I was a design engineer for a high precision plastic injection mold building shop. Coke bottle molds are insanely precise for a one and done product. I recall the spark gap for an EDM electrode was 0.0015 per side.the "trode"would oscillate to burn the hardened steel and the flush holes built into the carbon trode would flush the debris away from the work piece. Neat technology and I'm sure today it's way more awesome.

 

[Alan W.]

Worked at an auto parts manufacturer that made high pressure gas fuel pumps.
They were EDM machined in a saline solution. That created immense amounts of hexavalent chromium contaminated fluid.
The parts were very well finished

 

[mark02tj]

Back in the early 80's I worked in tool and die. One place I worked at we made molds for plastic sanding blocks. The blocks were different shapes (rounded, triangles, etc.) sold in a blister pack to consumers. The mold maker would create the desired shape in carbide and use that for the electrode. When the EDM process was done, there was a perfect impression of the electrode in the block of steel that would eventually become the mold.

The next place I worked was a more traditional tool & die shop. We had an entire "EDM Department" there that included machines that were stationary as well as early CAD/CAM wire EDM machines that could cut radiuses in the parts. Also cool, but a slow process. The operator had one of the best - and highest paying - jobs in the shop. He would set up the machines, push a button and then read a book. No standing at a mill or drill press for him!! I don't know if being the son of one of the upper management guys is what landed him in that position or not!

I went back to school in '83 and got an accounting degree. I went into public accounting and had several clients that were in the tooling industry. Touring their shops they were always amazed/amused that their accountant knew what most of their equipment was, knew how to use some of it and could also read a set of mics! :laughing:

 

[dfkrug]

A local friend is a machinist who owns an older wire EDM. He has been trying to give it away for years. Problem is, it is heavy (several tons), and you have to pick it up. So far, several people have said they want it, but have never followed through. "Free" is a dangerous word.

This machine was used to make prototype implantable devices for some medical company here in the Silicon Valley. It seems to be a lot like a slow, precision plasma cutter.

It may be worth a couple of hundred $ in scrap, but it has to be hauled to the recycler to get paid.