# Trying to make a homemade EDM



## ericc (Jan 11, 2021)

Hi.  I tried to make a homemade EDM.  This is inspired by savarin and brino, who appear to have made some successful ones.  I wanted to start with the solenoid actuated design because it is simple and it would make a good foundation for a proof of concept.  The starting point was the circuit that savarin posted.  I tried it out, and it did not work so well with my available components.  I think that the problem is that all the charging current must go entirely through the solenoid.  This results in the solenoid being engaged too much of the time, and also it restricts the total amount of power that can get into the circuit.  My initial machine was able to make a hole in a 1.5 mm piece of steel sheet in about 10 hours.  It was very fiddly and jammed or stuck continually.  Part of the problem was the top of the shaft getting distorted where it attached to the solenoid, but even with that addressed, it still seemed kind of anemic.

One thing that really helped was changing the circuit diagram.  The original diagram is posted for reference.  If you run the resistor directly to the capacitor and connect the solenoid across the resistor, the operation becomes quite a bit more aggressive.  In this case, the capacitor is being charged through the resistor and the solenoid in parallel instead of in series.  When the voltage drop across the resistor becomes too high, presumably due to the electrode being stuck, the solenoid will actuate, pulling it free.  Now the problem became that flimsy chemistry lab stand.  The support rod is anchored in plastic, and the retainer screw is also threaded in the plastic.  That makes it very floppy, and causes the electrode to jam in the hole once it has been drilled a bit.  Still, it reduced the time to get a hole considerably.  A hole appeared in 1 hour in the same piece of metal.  It seems that this small change is a major improvement.  The stand should probably be replaced with something custom fabricated.  Even a wood setup with a piece of square tubing like savarin posted would be much more solid.  Any amount of slop causes movement which wallows and binds the hole, which will be especially deleterious for tapping.

I will post a picture of the original circuit and the first prototype.


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## Shotgun (Jan 13, 2021)

I will be watching your progress very closely.  I have a CNC gantry mill that I build a long time ago that would convert very easily to EDM.


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## ericc (Jan 13, 2021)

The proof of concept works, but it is just too slow.  A CNC gantry mill should be really rigid in comparison to EDM requirements.  Probably nothing to worry about there.  I am building a more rigid frame for the mechanism to see if it helps.  There is not too much on Youtube to look at.  There is just that one guy with the desk lamp stand.  It is clear that this is too wobbly.  Maybe the problem is that the capacitor is too large and sticking causes everything to be pulled out of line.  I'll need to experiment more.


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## Weldingrod1 (Jan 13, 2021)

I used a stepper motor and leadscrew on mine. You need really slow feed and a tiny gap! Plus, the electrode wears quite a lot.

Sent from my SM-G892A using Tapatalk


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## ericc (Jan 13, 2021)

Hi Weldingrod1.  I am planning that when/if the next step (more sturdy frame) doesn't produce results.  It seems that @savarin has good results with his setup.  Maybe it is just a rigidity problem.


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## brino (Feb 5, 2021)

@ericc, I am following. Thanks for sharing this!

@Weldingrod1 , have you posted any photos (or better) a build thread?

Thanks,
-brino


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## RJSakowski (Feb 5, 2021)

I have been thinking about a sinker edm for some time.  My thought was to use my CNC mill as a driver for the electrode.  I have .0001 positioning capability with exquisite control over feed rates.  This would remove the need for the solenoid.   Thoughts?


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## ericc (Feb 6, 2021)

RJSakowski said:


> I have been thinking about a sinker edm for some time.  My thought was to use my CNC mill as a driver for the electrode.  I have .0001 positioning capability with exquisite control over feed rates.  This would remove the need for the solenoid.   Thoughts?


The position control is far superior for energy utilization than the stupid solenoid.  Much of the time with the solenoid is spent either stuck and shorted or retracted and doing nothing.

Here is my new frame to replace the chemistry ring stand.  I have also rigged up a leadscrew based positioning system, which I will try later after exhausting a few more possibilities.

Hmmm.  I can't seem to rotate it into a vertical orientation.


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## RJSakowski (Feb 6, 2021)

I like to look at additional ways to utilize the CNC capability.  So far, I have added a USB microscope for use as an optical comparator and a diode laser for low power tasks like cutting gaskets, and resist prior to chemical etching.  

The CNC is a great choice because of the ability to control motion via software vs. hardware.  Especially so because of using G code as the operational language.  Aside from that though, it shouldn't take too much effort to combine a lead screw/stepper with an Arduino controller or the like as Weldindrod1 has done to accomplish what the solenoid is trying to do.


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## savarin (Feb 6, 2021)

Mine works but I wouldnt call it fast, when I reduced the shaft inside the solonoid for a looser fit and rewound the coil to give the correct 26mh it worked much better. it does get hot so I cant run it unnattended.
I also run a little aquarium pump squirting directle at the hole.


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## ericc (Feb 8, 2021)

I have finished with attaching an acme leadscrew to a ball bearing drawer slide.  It will fit in the frame I showed earlier.  I scrounged a couple of gears, and an Arduino.  I will have to find a geared stepper motor or something like that to drive the screw.  This is starting to take up some time.  But it seems that is what is helpful during this stay-at-home era.  It is getting kind of tiring.  Recently, I received an advertisement pushed to me on the web news.  It promised a good four hours of tinkering time and four stars of difficulty.  It was difficult for me to get past the Chinglish.  It was annoying, but the news is pretty annoying too.

Look at this silly stuff.  I think the anti-rotation slide is worth 5 stars at least.  Even with only a circular electrode, it seems to be required.

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## hman (Feb 8, 2021)

Somehow, none of your links came through, and only 1 of 3 images.  From your description, both items sound worthwhile.  Please try sending again.  Thanks!


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## ericc (Feb 8, 2021)

hman said:


> Somehow, none of your links came through, and only 1 of 3 images.  From your description, both items sound worthwhile.  Please try sending again.  Thanks!


Hi hman.  This was just a junk ad that popped up on Yahoo News.  It is probably against the terms of service to duplicate everything here in the forum.  I just copied a bit of it over to illustrate how desperate everyone is getting for a little bit of tinkering time.  This spam advertisement shows a product which is kind of spoon-fed making, not really machining or design in a real sense.  I am trying to reassure myself that my string of poor results are just the kind of forward progress that is giving me a worthy task to occupy myself with during the isolation of the pandemic.

I just glued the anti rotation guide in place.  Laying it out and centering it turned out to be a lot easier than I feared.  It is a huge improvement in the stability and smoothness of the solenoid retraction action, and should help improve the speed of erosion.  I still need to adapt the ram assembly to the new slide, then there are a few more circuit modifications for the next iteration.  Bit by bit, and tiny but hopeful increments in effectiveness.


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## Weldingrod1 (Feb 8, 2021)

I built mine at least 25 years ago. I might have internal photos somewhere, and I think I scanned the schematics recently. 
Key stuff:
Pulsed current output switching power supply for the arc
Comparator based feedback to control the stepper motor going up and down
Electrode rotator with a motor brush on the shaft and a fluid swivel 

Pro tip: add a copper sleeve to the shaft for the bush to run on. :-(

Erosion rate is a function of current times time. High peak current destroys your electrode faster and gives a rough surface.
	

	
	
		
		

		
		
	


	







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## brino (Feb 10, 2021)

ericc said:


> The mechanical mechanism is extremely presented, and the clear transmission process is clear at a glance,



Are they trying to say that the instructions in the kit are clear?............because they failed, and that does NOT bode well for the actual instructions!



ericc said:


> I am trying to reassure myself that my string of poor results are just the kind of forward progress that is giving me a worthy task to occupy myself with during the isolation of the pandemic.



Eric, My EDM builds (both the first version and the second version) were a lot of trial and error.

I believe the type with the head oscillation controlled by solenoid whose current also affects the spark to be one where you'd really have to invest a bunch of time to tune it. The inductance of the solenoid, the current/voltage characteristics of the spark power supply, and the weight of the head would all need to be in careful balance.....and then if you changed the head weight you'd have to tune it again.

I found using the arduino controlled stepper motor was a great way to decouple the feed from the spark power supply. It really made the system an assembled collection of "blocks", where each can be changed in isolation to see the affect on the system. I have found it a real ongoing project with so many tweaks and upgrades possible.

I have used it a couple times for real work and it does work okay....although much slower than desired.
I still want to spend a bunch of time trying different spark power supplies. I just do NOT have the time.

I see that you are making progress. Please don't give up!

-brino


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## Weldingrod1 (Feb 10, 2021)

If you have the ability to do it, I strongly suggest the stepper motor control method. There's two important levels. Too low a voltage means move up. In the window, leave it alone. Too high a voltage, go down.

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## brino (Feb 10, 2021)

Weldingrod1 said:


> If you have the ability to do it, I strongly suggest the stepper motor control method. There's two important levels. Too low a voltage means move up. In the window, leave it alone. Too high a voltage, go down.



You are saying two different thresholds so that there is some hysteresis built in........
I did NOT do that with my implementation. That would be another interesting idea to explore.

Thanks,
-brino


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## Weldingrod1 (Feb 12, 2021)

Yes, the hysteresis is a significant improvement.

Sent from my SM-G892A using Tapatalk


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## GunsOfNavarone (Feb 13, 2021)

I'd really like to see one of the home made EDM working...definitely interesting.


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## Weldingrod1 (Feb 14, 2021)

Mine needs a tear down for fresh power transistors, so not any time soon. Sorry!

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## brino (Feb 14, 2021)

GunsOfNavarone said:


> I'd really like to see one of the home made EDM working...definitely interesting.



I posted some short videos in my EDM threads.....

Version 1:
https://www.hobby-machinist.com/threads/my-edm-project.41481/post-356086
https://www.hobby-machinist.com/threads/my-edm-project.41481/post-356099

Version 2:
https://www.hobby-machinist.com/thr...rge-machine-version-2-edmv2.49689/post-421580
https://www.hobby-machinist.com/thr...rge-machine-version-2-edmv2.49689/post-421587
https://www.hobby-machinist.com/thr...rge-machine-version-2-edmv2.49689/post-731963

-brino


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## Bentley18 (Mar 9, 2021)

Hi Guys,
I saw this thread on EDM's so I'll share my EDM project. I was given a Andrews moving wire machine by my shop landlord. I've been eyeing it since I started renting space from him. He said he just shut it down a long long time ago and there it sat. It is totally intact and needs cleaning up than moved to my side of the shop. I'm not sure how to proceed, maybe get the controls fired up then address the hardware side. The documentation is long gone so I'm going to contact the company to see if they still have any material for it. I do have a person who has been really good with working with these old machines so I'll pick his brain, he's going to come over once it's moved and wired up.  I'll get photo's to post.


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## brino (Mar 9, 2021)

Oh boy, oh boy!
I welcome any input from someone with a production-level machine.



Bentley18 said:


> I'm not sure how to proceed, maybe get the controls fired up then address the hardware side.



Just be aware of the voltages used, there can be an open circuit voltage of around 100VDC.
There can also be pulsed high currents.

Photos would be fantastic!

Thanks,
-brino


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## Bentley18 (Mar 10, 2021)

Good evening. Yes Brino, thanks for the advice. You can't be too careful. This is what I've got, I hope to get it moved soon. It's will be a work in progress.


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## brino (Mar 10, 2021)

Oh Wow!

That's a wire-EDM system.......like an EDM "bandsaw".
That's a specialty item, used for cutting very hard steels to very close tolerances.
They require such fine controlled feeds that they often need CNC to move the work-piece around the wire.
Not sure if yours moves the wire or the work.

Perhaps you should start a new thread for this beast, so we don't hi-jack @ericc 's thread any further.
Feel free to start a new thread, and add a pointer to it from here.

So many questions........
Is that one of the cutting wire spools behind the open cabinet door?
What kind of wire does it use? (material and diameter)
Can you supply some internal photos too? I'd love to see how it's built!

That is quite a unit that will take some deep understanding to use properly.
Now that's a project!

-brino


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## ericc (Mar 11, 2021)

Go ahead.  Don't worry.  I'm still chugging along.  I have made the second prototype with leadscrew and ball bearing slide.  It still needs a stepper motor drive and computer control.


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## Bentley18 (Mar 11, 2021)

Hey there. maybe I should start a new one. I'm new here and I don't want to "high jack" a thread. But for now, I'll at least respond. That spool is the exec tape for the operating sys. The kind with the holes it(old, old school). As far as wire goes, you can use brass and the dia. is .005". I will get some photos when I get a chance. Working for a living is getting in the way of fun. I will admit I have worked with EDM's in the past, just 2D cutting PCD, CBN tips for brazed tool and also carbide.


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