Hello all, new user here.
For a few years I've been willing to build a simple sinker EDM machine. I stumbled upon the design and circuit from the user 'Awake' and am in the process of building it (with a few modifications so far, and likely more modifications to follow. Still, the starting point is his circuit, for which I'm very grateful.)
The input section and stepperboard have been built and works excellently. Picture is below in the attachments.
As stated, I've made a few modifications to Awake's design. First of all, I wanted to have a manual override function of the electrode (manual up/down). Also, I wanted an automatic flushing function that every 4-35 seconds pulls the electrode back for a user settable time of .2-4 seconds. These modifications also work well, at least, when testing the board on the desk.
The next step is building the power section, using 2 pcs. of 24Vac transformers (450W each). It's all supposed to end up in a scrounged Rittal cabinet.
Been playing around in CAD to layout the front, how it will have to end up like. I've decided to add a voltmeter and current meter to get more feedback of the process, as I've never used EDM myself before. Added a few more switches to select capacity in smaller steps, not sure if that will be useful in the end but better to have it and not use than the reverse. Only thing that's still missing is an emergency stop button, have to find a place for that somewhere yet.
No real work has been done on the mechanical part, apart from digging up the linear bearing from the attic. Runs very smoothly and has no detectable play, so should fit the purpose just fine, I expect.
Ok, sorry for the long story and show & tell, but the reason I'm posting here is that I have a few questions that I hope someone in this forum would have an answer to.
First of all, I notice in the youtube video of Awake (
http://www.youtube.com/watch?v=1MtOfzxMnEI) that the wires to the electrode and workpiece are pretty thin; is this ok? I'd expect that the thinner the wires, the more resistance and thus the less powerful the arcing will be. Am I right in worrying about resistance in the wires, or is it a non-issue?
(in the past I've built a spotwelder based on a microwave transformer that was useless because of a few milli-ohm resistance; (I also built the milli-ohm meter I measured it with:
http://picasaweb.google.com/motorcon...MilliOhmMeter#))
Secondly, I noticed others are using electrolytic capacitors to store the arc energy; as I have a large bunch of 4.7uF/100V non-electrolytic caps, I intend to build a capacitor bank from those. Am I right in thinking that these should stand up to this kind of use (abuse...) better than the electrolytic caps? On thinking about it, maybe the fact that others have so much resistance in the lines is a helpful factor in limiting currents and keeping the electrolytic caps happy?
Thirdly, I intend to use a higher voltage, 2 pcs. of 24Vac transformers with secondaries in series for 48Vac, which should yield about 70Vdc after rectification. (old transformers from UPS-es, 450W each; I expect these will be big enough?). Am I right in thinking that by using a higher voltage, my EDM would be more effective and faster in removing material?
Looking forward to your input, or hearing anything I may have overlooked or improvements upon my ideas.
Peter,
The Netherlands.
(For those interested, higher resolution images and more of my projects can be found here:
http://picasaweb.google.com/motorconversion)
I started over on the one in the middle, with the result that it is not quite as crisp. The one on the right is nice and crisp (more so than it looks in the picture -- I'm not sure what sort of reflection I got in the picture. The best result so far was about .100" depth in 5 minutes. I'm sure that is pitiful compared to commercial units, but it is fast enough for my current limited needs (pun intended! 
Linear Mode
