Electrical Discharge Machine Version 2 (edmv2)

[brino]

our automobile oriented machine shop used hex shaped carbon rods, submerged in a jury rigged puddle of kerosene to erode hex shaped holes through whatever was broken off inside some threaded holes of very expensive parts. Once the hex hole was developed, an Allen wrench would unwind the stub.

Hi Turnaround,
How long did the machine take to make a hex socket deep enough for an allen wrench? we're talking hours, right?
Oh and how big of hex?

Thanks!
-brino

 

[Turnaround]

Hi Turnaround,
How long did the machine take to make a hex socket deep enough for an allen wrench? we're talking hours, right?
Oh and how big of hex?

Thanks!
-brino

Our Store bought EDM had a little "drill press" type arrangement, that allowed the operator to turn a crank and push the shaped carbon down towards the hole. Your senses told you how much and when to feed the carbon to erode a hole in a broken tap or drill bit. It took five to ten minutes to erode through something like the remnants of a 3/8" - 16 tap. The dam and kerosene was a necessary part of the equation.


Sent from my iPhone using Tapatalk

 

[Mark_f]

Brino,

I am finding this thread fascinating as I am waiting to finish and try the EDM machine that I built earlier this year.

 

[brino]

Hi Mark,

I am trying to find the time to do a bunch of experiments with different power supplies. I want to try a beefier (higher-current) supply with a bank of capacitors to switch in/out to adjust things.

I'd also like to try a pulsed power supply, so I am very interested in your build too.

-brino

 

[Mark_f]

Mine has a 2000 mfd capacitor on the output and switches in power resistors to regulate the current. The output is about 80 VDC and around 10 Amps.

 

[cs900]

wow, what a great project. Subscribing for future updates!

 

[brino]

Okay, it's hard to believe that I started this thread about four years ago.......and the V2 EDM machine is still NOT DONE!!!!
I have NOT built or bought a dedicated power supply for it
I have NOT hardwired the circuit around the arduino controller
I have NOT played with the high-voltage supplies
I have NOT added a bank of spark capacitors that are easily switch in/out
I have NOT put all the above in a case

I did just use it though....and the sketch here in post #37 came in real handy when setting it back up.
Once I literally blew the dust off the arduino circuit in the "bin board" it worked great!

I picked up these partially built lathe tool holders at the local used tool place for $10.


The one with the red X's already has the dovetail cut too big for my tool post.
The nearest one has the tap broken off in the right-most hole.....
My guess is that's when the builder gave up and sold all his tools!
(we all know the feeling, right?)

I thought I'd let the EDM work on it while I did something else....(I still don't have end-of-stroke limit switches installed either)

Here it is being lined up in the vise:


...and a short video clip of it running:
View attachment short_clip.mp4

















After a few hours and one electrode change, the broken tap was just about cut thru and I picked out the bits with tweezers.
The cylinder in the middle is the centre of the tap, and around it are the tap flutes:



You can see how the brass tube electrode got eroded too and became form-fit to the tap flutes.....





It did work, but I think the copper electrodes lasted longer and cut faster.
Too bad as I now have a small bundle; brass was recommended in one of the books, and I had been picking up pieces when I saw it.
Oh well. It will get used somewhere.

Here's how the threaded hole turned out (I have not yet run a wire brush and tap thru it...):


At this rate I should have the project complete sometime within the next 30 years or so.....

-brino

 

[francist]

Hah, I was just thinking about this yesterday and whether you’d done any more on it! John Saunders of NYC-CNC has a fairly recent (last week or so) video exclusively on EDM. I think the place was Spectre EDM (?)

I’m not really up on the process but it was interesting nonetheless. Might want to check it out on YouTube.

-frank

 

[savarin]

Awesome project Brino, I know where your coming from with the 30 years, just look how long my bino is taking.

I havnt been able to touch it since well before christmas.
The pair of us need a gee up.

 

[brino]

@savarin
Charles, you helped get me started on EDM.
What's the best electrode that you've used?
Thanks!
-brino