Trying to make a homemade EDM

[ericc]

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]

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!

 

[ericc]

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.

 

[Weldingrod1]

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]

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!

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

 

[Weldingrod1]

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]

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

 

[Weldingrod1]

Yes, the hysteresis is a significant improvement.

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[GunsOfNavarone]

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

 

[Weldingrod1]

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

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