GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: OTmachine on October 30, 2022, 01:29:43 AM
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I have run sinker type EDM’s and have found references to DIY ones. Would like to build one for my home shop. Just checking to see if anyone had come up with a good set of plans.
TIA, Keith
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Lots of info and builds, of varying quality:
https://www.youtube.com/watch?v=MZm-mvxa2qo (https://www.youtube.com/watch?v=MZm-mvxa2qo)
https://www.youtube.com/watch?v=AQCpueMkZ6o (https://www.youtube.com/watch?v=AQCpueMkZ6o)
https://www.youtube.com/watch?v=kRc1NFO8uwo (https://www.youtube.com/watch?v=kRc1NFO8uwo)
https://www.youtube.com/watch?v=SWy3Dgn7_aw (https://www.youtube.com/watch?v=SWy3Dgn7_aw)
https://www.youtube.com/watch?v=8jMz8i1d_OI (https://www.youtube.com/watch?v=8jMz8i1d_OI)
https://www.youtube.com/watch?v=2ewSbI52ICc (https://www.youtube.com/watch?v=2ewSbI52ICc)
https://www.youtube.com/watch?v=ZtzwGIv5adk (https://www.youtube.com/watch?v=ZtzwGIv5adk)
https://www.youtube.com/watch?v=6Jt08F1HOiU (https://www.youtube.com/watch?v=6Jt08F1HOiU)
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Working on it off and on as time allows. Arduino control, have the code part to where it will advance and retract due to differential to a reference voltage, stepper driven actuator essentially done, mounts on a magnetic indicator base. Power supply is essentially a switch mode power supply (166VDC @ 10A) and a power transistor actuated by the arduino to supply adjustable pulse.
Has the capacity to kill...no plans will be forthcoming.
Some pics;
(https://i.imgur.com/PMInz11l.jpg)
(http://i.imgur.com/mKbbFDhl.jpg) (https://imgur.com/mKbbFDh)
(http://i.imgur.com/d297Vhel.jpg) (https://imgur.com/d297Vhe)
Al
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Watching, interesting relevant link added:
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html (http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html)
Jesse
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An EDM would be excellent for burning small cavities in an airgun mold, for casting slugs or pellets.
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I’ve got most of the parts gathered for the mechanism but haven’t settled on how I want to supply the erosion circuit.
I too will use arduino for control because I’m familiar with the platform and it can be easily programmed.
Dave
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Thanks for the replies. An Electro-Arc came up for sale on facebook and kind of renewed my interest. It was cheap, but from what I recall caps and such seem to fizzle after so many years and repair parts were not cheap. And the Electro-Arc has a larger footprint than I care to dedicate space to. I had started researching in the past, but like a lot of things, it got put on the back burner. I am retiring at the end of the year, so I should finally have some time. A home made sinker type of EDM would do a Lot for me. Carbon electrodes are really easy to machine and produce pretty close tolerance features. When I get it together, I will post.
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For sure share it here. Sounds like there is definitely interest.
Dave
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Watching, interesting relevant link added:
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html (http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html)
Jesse
Jesse, That is a good basic one. I had saved that link back in May. But I am looking at ones with vibratory feed, which can be accomplished pretty easily. I have some old industrial battery charger transformers which I was saving for this. Lots to research. Thanks again!
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So I threw some stuff together. It looks unsanitary as hel but is working as planned (sort of).
Of course I’m controlling the stepper with arduino. It monitors voltage between the workpiece and electrode. Really simple program. I have a potentiometer to adjust the max voltage the arduino sees (5v) and a smoothing cap. It handy to be able to adjust that quickly without having to adjust your program.
The erosion circuit starts with a variac to a bridge rectifier through a current limit bulb. Then two larger caps. Then a 200v mosfet driven by a cheap pwm generator. I can adjust duty and frequency on the fly.
It works but it needs a bit of refinement, lol. And it was reasonably cheap to build. The only expensive item is the variac that I have for other stuff as well.
I want to try a different (carbon) electrode (in the video I’m just using some solid copper wire). I also will play with the freq/duty as well as input voltage.
Anyway, initial testing has went well.
Dave
https://youtu.be/i0IVm89hB2E
And a picture of the hole in the aluminum, I may need to turn it down some…not sure. Looks like it is pretty rough. You can’t tell from the picture but the holes are about 3/16” deep.
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Cut a notch from a piece of file using a brush from electric motor. I tweaked my arduino program and got a pass through without backing out. Started sizzling and eased through in about 2 minutes.
Still rough looking, hoping a pump to keep cut clear helps. Along with tweaking the voltage, duty and frequency.
I sketched up the erosion circuit so y’all have an idea what is there. Pretty simple. I’ll sketch the depth controller later.
Dave
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And the depth control circuit. Arduino only wants to see 5v max so the resistor/ potentiometer scales the voltage back.
To move tool up, turn pot to zero. To stop, turn pot up until tool stops. To set to cut, turn pot up until tool starts to move down.
Dave
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Looks like progress! Burn should be cleaner. From the video, I can say that the oscillation is too slow and looks like the amperage is too high. I will have to dig out my notes. I believe that I wrote down all of the parameters from back in 1980. Thanks for sharing.
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My brother retired as a journeyman mold maker leader who's got access to a mold shop that he helped one our friends build from modified older machines with modern equipment added.
Our friend builds prototypes for mold shops and also repairs some of the cheap Asian built plastic injection molds for what little is left in our industry these days. When I was being shipped
off to the Viet war my brother was still in high school in a trade class through high school to be a mold maker. Our friend did buy an EDM for his shop as well and those machines can
really be complicated from what my brother has told me but, if a person knows what he's doing with an EDM he can really do some amazing things with one. My brother when he was
still in the working force use to give me those MX wheels for polishing and they sure were nice to use but they do wear out fast. I used those MX wheels a lot when I was building
muzzle loader kits, and those really do a great job when it comes to polishing steel, brass, aluminum etc. The crazy thing is I always wanted to get into machine tool technology big time
when I was in high school and did plan on going into the trade after high school but uncle sam nabbed me up first. I ended up retiring from the electronics business but it sure never payed
like that business that my brother was in. Oh by the way those MX polishing wheels aren't cheap either because a while back I asked my brother about them and he said they're really
expensive if you have to buy them.