EDM Build

[SmithDoor]

Model Engine Builder #26 has a several page article on making an electromagnetically actuated pulse mode EDM. Very simple, think door buzzer on steroids with one end of the coil connected to the electrode, the other end to a 12 volt battery. Other battery terminal connects to the work. A bit safer than the old AC line and light bulb hack, not as complicated as the sexier EDM designs that might provide sinker capabilities. I saw this being used at Cabin Fever one year, the guy showing it was poking holes that looked pretty clean. Certainly could be used as a tap / stud burner.

Cheers,
Stan

Can post a schematic?

Dave

 

[L98fiero]

Model Engine Builder #26 has a several page article on making an electromagnetically actuated pulse mode EDM. Very simple, think door buzzer on steroids with one end of the coil connected to the electrode, the other end to a 12 volt battery. Other battery terminal connects to the work. A bit safer than the old AC line and light bulb hack, not as complicated as the sexier EDM designs that might provide sinker capabilities. I saw this being used at Cabin Fever one year, the guy showing it was poking holes that looked pretty clean. Certainly could be used as a tap / stud burner.

Cheers,
Stan

Fleming's site is still up, no idea if one can order or not. Build your own HomeBuilt Electrical Discharge Machine (EDM) for machining hardened materials

 

[stanstocker]

I can't post the Model Engine Builder article as 1) it's copyrighted and 2) I like Mike and Toni (publishers/editors/the whole deal of MEB magazine) and would suggest buying the PDF back issue ($6) at:

https://www.modelenginebuilder.com/store/p29/issue-26.html
If you look around on youtube lots of folks have made cheap tap burner type EDM devices of varying quality, safety, and capacity.

Here is a link to the video of the EDM described in Model Engine Builder being demonstrated and explained by the original builder Lynn Anfinson:



For more advanced EDM projects, I think the Robert Langois book from Village Press and Brian Fleming's two books have already been mentioned.

Hopefully this gets you the info you need, sorry not to be able to provide the article, hope you understand.
Stan

 

[MrMetric]

If Fleming is still offering the items (all dates look pretty old), I have to say that I prefer 'real' books over PDF (although, it is awfully nice to be able to keep things together in a directory). I have an RC book, so a physical Pulse book is much more desirable to me.

I have a strong suspicion that only 25% of all projects (generic, not just the EDM) are ever built; heck, probably less. So, if I am able to repurpose someone's project that they don't want, it helps them, helps me, and helps reduce landfill. In the end, that is exactly what happened. That said, I think I'll contact Fleming and find out where he is with his circuit board revisions. If there are significant changes, I may opt to get one from him.

 

[MrMetric]

@stanstocker. That is a good video link demonstrating an eminently simple EDM design. Thanks for posting that. It was really quite interesting...

As for MEB... Yeah, I agree. Toni and Mike did a great job with the magazine. It seems to have pretty much ceased operation now though. Technically I still have a subscription for one more issue, but it has never been developed or sent. Given that it is about 4 years ago, I think, that I got my last issue, I think it is probably fair to say that it will not come. I am not entirely sure what happened to Toni/Mike. FWIW, though, I'm not bitter about not getting the last issue. It was a fabulous magazine that I would happily resubscribe to if it were to be resurrected.... I met Toni/Mike at the Visalia show when they first started MEB, and I signed up immediately. I lost my set of mags in a fire and bought a replacement set from an estate. I think I even got some additional partial set somewhere along the line too. I should check that out as I probably should clean them out. Anyhow, I really enjoy looking through MEB and I would highly encourage anyone interested in the articles to contact Toni/Mike. They are great people.

 

[stanstocker]

@stanstocker. That is a good video link demonstrating an eminently simple EDM design. Thanks for posting that. It was really quite interesting...

As for MEB... Yeah, I agree. Toni and Mike did a great job with the magazine. It seems to have pretty much ceased operation now though.
<trimmed>

Glad you liked the video, it was a shock to realize it was almost 11 years ago that I talked with Lynn at Cabin Fever! I think Mike and Toni were there too.

As for MEB, I know they have a lot going on in their lives, the most recent issue was #39. I missed an issue or two as my email address had changed and I didn't think to let them know. Toni sent the download links and updated my info quickly, always good folks. I hope they are able to keep the mag going. Even digital publications seem to be going the way of shows and printed pubs as our world changes. They also really need people who can write to create the content, there is only so much that Mike can write, draw, and photograph. Without new and interesting content you don't have a reader base. I know other model engineering and woodworking related mags have the same issue. There are only so many articles about silver soldering or crankshaft machining that the world can absorb

/WARNING - OT and change of direction pondering about the future and nature of model engineering follows!

There are far more folks doing 3D printers and routers these days, with some coming over into our weird little world as they discover needs or desires that they can't meet with additive or lighter duty cutting machines.

The huge increase in interest and enjoyment of tabletop gaming has created a resurgence in model and figure making, some of which we see drifting over into machining, often in the smaller scale range such as Sherline sized machines. A different focus than many here have, but lots of CAD or modeling software being used to create files to print or cut. I know more people who are making belt buckles, knives, gaming stuff, jewelery, and special tools to support other hobbies than I know who make engines. It's interesting, it's similar, but is it model engineering? Does it matter? From the articles in Model Engineering Mag in the UK apparently I'm not even a model engineering guy as I don't build steam locomotives and didn't discover that CAD might be useful just last week.

It will be interesting to see how things shape up at Cabin Fever 25, hopefully there will be some fresh faces as well as folks known a long time. I'm pretty sure it won't be the same, it will either be a freshly invigorated event or one that is fading into the past. I hope for invigorated.

Several groups I've been associated with for a number of years are slowly turning into the old guys piss and moan about how nobody is coming into the hobby coffee club while spending two weeks debating the benefit/risk of using grease on auto wheel studs, living in the past, and wondering why that kid who seemed pretty skilled never came back. I'm a 63 year old kid, and I've given up or dropped to lurk mode on several groups I really used to enjoy. Looking at youtube, there are plenty of new faces doing interesting things, perhaps we'll see some of them at Cabin Fever.

Take care,
Stan

 

[bengt-olausson]

Fleming's site is still up, no idea if one can order or not. Build your own HomeBuilt Electrical Discharge Machine (EDM) for machining hardened materials

Hi
I orderered the digital book and recieved a day later.
Regards Bengt

 

[MrMetric]

I got my book and board from a member here on MEM. He was no longer interested in pursing the idea, I have a strong interest in it, he offered at a very reasonable price, and voila! Everyone is happy....

The reason I'm posting now, however, is an update on the board... The one I got was a pulse 2.0. I figured I should contact Ben Fleming before I started collecting parts and assembling a board that may be obsolete (the current version is a Pulse 2.0B). Even if I had to get a new board, I would still have been happy with my purchase as I really preferred having a physical book copy. The 2.0 and 2.0A pictured on Fleming's website are very similar. The biggest difference I can see is that there is a clear pad problem on one of the diodes as it encroaches into the MOSFET heatsink area. OK, that is a layout screw-up but easily resolved. There are also some added ground pins next to test points, etc, but those are also not that important.

Fleming was pretty quick to respond and said that there really haven't been any significant design changes between 2.0 and 2.0B; he recommended that I just go with the board I got... One thing I thought was odd when I looked at the board is that it is setup so that the MOSFET pads are mirror images. This means that they MOSFETs have to be mounted on opposite sides of the boards. This, it turns out, was by design, to help assist in heat dissipation. One other thing that Fleming said that might be of interest to people here is that on the newest version of the board, he recommends only 2 of the 4 MOSFETs. Apparently that provides adequate power.

Fleming did say that there have been significant changes to the different generations of the RC boards. As such, you may want to obtain a new version of those should you decide you want to go down the RC route instead of pulse. Frankly, I haven't completely decided which I want to do yet. I have both the RC book and the pulse book, so I have to cost them out. The big expense seems to be in transformers, but there are some surplus places around where I might be able to pick something up.... We'll see.

 

[EDMGuru]

Sorry, I don’t wish to throw a spanner in the works at this stage of your builds but actually a commercial grade EDM machine is easy and cheap to build, the problem is there is a misconception that there’s some sort of manufacturer’s design secret to these machines which makes people overcomplicate their home build designs usually by using some sort of code to control the actual burn. There's no need to buy a book or anything like that, the electronics are simple and mainly use "off the shelf" parts and the resulting machine performs, in my opinion, better than any DIY build I've ever seen online.
I've posted this comment on other forums lately and it has received mixed results but let's see how it goes on here.
It might be worth you having a look at the video that I posted on YouTube a few weeks ago in response to other people having design problems, showing a simple machine that I built a few years ago, which I think you will agree proves my point

 

[SmithDoor]

It looks like a solenoid pulling up after sparks on object.
The hard part is DC power supply a DC welder is big enough to do the job.
Some day I will try that but been 20 years since last time I need to remove a broken tap.

Dave

I can't post the Model Engine Builder article as 1) it's copyrighted and 2) I like Mike and Toni (publishers/editors/the whole deal of MEB magazine) and would suggest buying the PDF back issue ($6) at:

https://www.modelenginebuilder.com/store/p29/issue-26.html
If you look around on youtube lots of folks have made cheap tap burner type EDM devices of varying quality, safety, and capacity.

Here is a link to the video of the EDM described in Model Engine Builder being demonstrated and explained by the original builder Lynn Anfinson:



For more advanced EDM projects, I think the Robert Langois book from Village Press and Brian Fleming's two books have already been mentioned.

Hopefully this gets you the info you need, sorry not to be able to provide the article, hope you understand.
Stan

 

[SmithDoor]

Here is one from the internet
https://www.instructables.com/EDM-Electrical-Discharge-Machining/I have not built this one.

Dave

 

[stanstocker]

Sorry, I don’t wish to throw a spanner in the works at this stage of your builds but actually a commercial grade EDM machine is easy and cheap to build, the problem is there is a misconception that there’s some sort of manufacturer’s design secret to these machines which makes people overcomplicate their home build designs usually by using some sort of code to control the actual burn. There's no need to buy a book or anything like that, the electronics are simple and mainly use "off the shelf" parts and the resulting machine performs, in my opinion, better than any DIY build I've ever seen online.
I've posted this comment on other forums lately and it has received mixed results but let's see how it goes on here.
It might be worth you having a look at the video that I posted on YouTube a few weeks ago in response to other people having design problems, showing a simple machine that I built a few years ago, which I think you will agree proves my point

I very much like the results shown in the video. I understand the off the shelf square wave generator just fine. I've looked at several designs over the years, from the scary line voltage through a diode and lamp/capacitor flavor to some fairly complex designs. What you have shown in the video seems to be a very effective while still reasonable to build option. Pretty hazy on the 100V power supply and motor driving aspects though. From the pictures I can make at best some ballpark guesses at your general approach, but not enough to whip up the power supply/controller. Are you considering making schematics available (free or paid), or is this sort of a prototype for the basics and the stepper based new machine? If so, are you going to be offering a plan set, even at a minimal level, so others can build the upcoming machine?

Thanks,
Stan

 

[L98fiero]

Sorry, I don’t wish to throw a spanner in the works at this stage of your builds but actually a commercial grade EDM machine is easy and cheap to build, the problem is there is a misconception that there’s some sort of manufacturer’s design secret to these machines which makes people overcomplicate their home build designs usually by using some sort of code to control the actual burn. There's no need to buy a book or anything like that, the electronics are simple and mainly use "off the shelf" parts and the resulting machine performs, in my opinion, better than any DIY build I've ever seen online.
I've posted this comment on other forums lately and it has received mixed results but let's see how it goes on here.
It might be worth you having a look at the video that I posted on YouTube a few weeks ago in response to other people having design problems, showing a simple machine that I built a few years ago, which I think you will agree proves my point

That's interesting but he doesn't provide even a simple schematic for the 'electrically challenged' like myself. Anyone up for the challenge?

 

[EDMGuru]

Hi stanstoker,

The power supply to the power generator is via an isolation transformer (not shown in the video) which has an output of 70 volts ac. Once rectified this gives the 100 volt dc supply for the power generator which is just a basic amplifier design with 3 (could be more depending the number of power settings you require up to the output power of your transformer) individually switched on power outputs through separate high wattage resistors and their value determines the output Amps. The total output Amps is therefore just a resistor in parallel calculation as each stage is switched on if that makes sense.

The speed controller is as it is with no modifications. It’s an off the shelf part and it controls the z axis position via a voltage divider from the power generator output using Ohm’s law. Basically as the required burn plasma level is reached, the output voltage from the power generator (which is shunted through the high wattage output resistor) drops, which also causes the speed controllers built in speed control to change its voltage control reference point, and so the speed and direction of the dc motor changes.

The stepper motor version machine uses my own custom design controller which is not like anything else online as it doesn’t use a comparator as such it’s more of a cascade voltage control which allows the provision to build in an anti arc circuit (basically it turns off the power generator on the very low potential arc forming pulses) it’s burn is very stable and once finished looks like it could be a real game changer for the home EDM builder.

Getting back to the dc motor version I’ve always said that you don’t need to use code or EDM design’s from a book or anything like that to build an EDM but it looks now like I should maybe put this machine design in a book as it’s simple and can have other uses.

It could be used as a small attachment for a mill or drill press and by using the dc motor to drive a threaded copper bar through a nut instead of a slide you can create internal or even by using a copper “die” external threads in hard materials.

Another simple use I’m looking at working on doesn’t require a power generator and so long as your pattern is, or could be made, conductive is a copy mill or copy lathe attachment. What do you think?

 

[stanstocker]

Thank you for adding some information. I'll need to contemplate and digest a bit on this. Other than some high power linear regulators in hybrid packages back in the early 1980's I've never been involved in the power electronics side of things other than repairing some amplifiers over the years, so although all the words are known to me the relationships will need some thought.

I'm assuming you are switching the power resistors with FETs driven by the square wave generator? My guess is the small relays on the power controller are for the fluid pump and feed motor control. Am I at least somewhere close to right, or as Pauli said so well at one physics seminar "Not even wrong!"...

I'll go back and read over Langois and Flemings stuff and try to get back up to speed, it's been quite a few years since I did electronics work for a real living. Once I get a bit more up to speed I will probably have some questions, but I don't want to waste folks time on things that should be apparent

I will ask one more though: Are you running the electrode at ground or power supply level? Your coin example showed very little if any electrode wear, and I've read in several places that running the electrode at ground and the work hot reduces electrode wear a lot.

EDM is sort of like tool and cutter grinders for me, an interesting itch I'd like to scratch although odds are there are already more projects around here than I'll ever get done before my best by date wanders around.

As for your copy lathe / mill idea, it's so far past where I am with EDM I can't even really grasp just how it all would work, but if you decide to follow up on it I'll be sure to pay attention.

Thanks again,
Stan

 

[EDMGuru]

Hi stanstocker,

The square wave frequency amplifiers output is amplified by the power generator, so basically you’re just changing a square wave output of say 5 volts @ 10 mA to an exact copy of the square wave but at a voltage of 100 volts @ 10 A (or what ever the output Amps is that is set by your output high wattage resistor value) although the output amps on an EDM should be calculated at the working voltage so at half the open voltage.

The power generator in its most basic form (1 power output) can be made by using only 3 transistors and is very simple in design (the audio industry have been doing this type of thing for years).

If you are referring to the 3 small blue relays on the power generator board in the video they’re actually what is used to switch in 3 outputs which go via 3 separate high wattage resistors and it’s just a resistor in parallel calculation for the power output which in my case was 3.5 A, 7 A and 10 A.

Most of the time when using a copper electrode the polarity on a sink type EDM is kept positive, the only main exceptions are when eroding carbide (with tungsten copper) and using a graphite electrode for maximum material removal (normally a graphite electrode is kept positive but running it at negative polarity removes material 4x faster but with high electrode wear). Wire EDM machines normally run with the wire at negative polarity for faster metal removal (electrode wear isn’t an issue as it’s constantly being replaced) and they use a different type of power generator which is more like a pulsed RC type of machine.

I have compiled over 45 years of working on these machines, mainly as a business, a lot of technical information, which you won’t find anywhere online, for different electrode and work piece material at different Amp, pulse frequency and duty factor settings for spark gap sizes, metal removal rates, electrode wear, surface finish etc. Maybe this information should go in a book too?

 

[ajoeiam]

Hi stanstocker,

The square wave frequency amplifiers output is amplified by the power generator, so basically you’re just changing a square wave output of say 5 volts @ 10 mA to an exact copy of the square wave but at a voltage of 100 volts @ 10 A (or what ever the output Amps is that is set by your output high wattage resistor value) although the output amps on an EDM should be calculated at the working voltage so at half the open voltage.

The power generator in its most basic form (1 power output) can be made by using only 3 transistors and is very simple in design (the audio industry have been doing this type of thing for years).

If you are referring to the 3 small blue relays on the power generator board in the video they’re actually what is used to switch in 3 outputs which go via 3 separate high wattage resistors and it’s just a resistor in parallel calculation for the power output which in my case was 3.5 A, 7 A and 10 A.

Most of the time when using a copper electrode the polarity on a sink type EDM is kept positive, the only main exceptions are when eroding carbide (with tungsten copper) and using a graphite electrode for maximum material removal (normally a graphite electrode is kept positive but running it at negative polarity removes material 4x faster but with high electrode wear). Wire EDM machines normally run with the wire at negative polarity for faster metal removal (electrode wear isn’t an issue as it’s constantly being replaced) and they use a different type of power generator which is more like a pulsed RC type of machine.

I have compiled over 45 years of working on these machines, mainly as a business, a lot of technical information, which you won’t find anywhere online, for different electrode and work piece material at different Amp, pulse frequency and duty factor settings for spark gap sizes, metal removal rates, electrode wear, surface finish etc. Maybe this information should go in a book too?

If not a formal book - - - maybe an e-book written by chapter or article - - - - maybe here or a blog or some such.

This bunch here would likely stick a special sign on any serious of posts doing what you are talking about.
(Its a really good bunch imo - - - - I'm still quite a 'new guy' here yet though - - - grin!!!)

Technical books I find sorta frustrating.
Example - - - - 20 years previous 2nd edition - - - still costs $460 usd for a copy. (If not more)
Can't get it any which way - - - scarce as hen's teeth in libraries (research ones) and then too much of the information isn't really useful.
Can't figure that last part out until you read the book thoroughly AND work through it (that all doesn't happen in a short period of time!).

Publisher doesn't give a rip though.
Authors mostly long dead (articles written while they were in the later stages of their careers) and the area has evolved in a different direction.

Me - - - if I've got something that is useful for others - - - I'll likely just open source it.

 

[stanstocker]

I know that EDM is one of the those areas that most of the hobby folks seem to perk up and listen when it comes up. I also know that most "That would be really great, I'd buy plans or I'd build one!" in reality never get off the ground or are overcome by events. The world is full of partially completed Quorn / Tinker / Bonelle tool and cutter grinders I think. I'll admit my mostly done Quorn is out in the shop waiting for me to get a few weeks to go play with it, rather than dealing with all the things that seem more pressing.

I'd love to see a schematic for your amp/power switcher. Although as you say odds are a suitable circuit can be conjured, the fact is your circuit works well. Many almost work, you tube is full of machines that are only a wee bit past being tap burners if that. If you chose to invest the time though, it's unlikely to get you much more than thanks even if you were to sell a plan set for $25 or $40. I know a few people who have published some plans, and they haven't managed to retire early on the proceeds...

So thanks for what you have shared, and if you choose to share more I'll be reading!
Stan

 

[desbromilow]

Stan, FWIW I built one off the Fleming design a while ago for the express purpose of "drilling" holes in HSS sheet. If you want to see some video of it running, go to:
It cost me about $100 to build, but I was lucky that I had some salvage transformers which were "close enough" for the build. It's a pulse type (RC) and the capacitors are ones taken from disposable film cameras which the local photo processing lab gave me free for asking.

Since the video was taken I've built a tank from a plastic food container, with a modular aluminium frame which drops inside for clamping the workpiece in place - the big problem in the video is the work piece moving.
My electrodes are turned from carbon arc-gouge electrodes. I can use the same arc-gouge electrodes and cut any shape using files, etc.

Des in West Oz

 

[aeroHAWK]

Hi stanstocker,

The square wave frequency amplifiers output is amplified by the power generator, so basically you’re just changing a square wave output of say 5 volts @ 10 mA to an exact copy of the square wave but at a voltage of 100 volts @ 10 A (or what ever the output Amps is that is set by your output high wattage resistor value) although the output amps on an EDM should be calculated at the working voltage so at half the open voltage.

The power generator in its most basic form (1 power output) can be made by using only 3 transistors and is very simple in design (the audio industry have been doing this type of thing for years).

If you are referring to the 3 small blue relays on the power generator board in the video they’re actually what is used to switch in 3 outputs which go via 3 separate high wattage resistors and it’s just a resistor in parallel calculation for the power output which in my case was 3.5 A, 7 A and 10 A.

Most of the time when using a copper electrode the polarity on a sink type EDM is kept positive, the only main exceptions are when eroding carbide (with tungsten copper) and using a graphite electrode for maximum material removal (normally a graphite electrode is kept positive but running it at negative polarity removes material 4x faster but with high electrode wear). Wire EDM machines normally run with the wire at negative polarity for faster metal removal (electrode wear isn’t an issue as it’s constantly being replaced) and they use a different type of power generator which is more like a pulsed RC type of machine.

I have compiled over 45 years of working on these machines, mainly as a business, a lot of technical information, which you won’t find anywhere online, for different electrode and work piece material at different Amp, pulse frequency and duty factor settings for spark gap sizes, metal removal rates, electrode wear, surface finish etc. Maybe this information should go in a book too?

I am VERY MUCH interested in building a machine like yours. I saw your video and became intrigued. I operated an EDM nearly 30 years ago and the machine was old then. I suspect its electronics were quite basic, similar to what you have described. After studying what you have posted, I am getting an idea of your circuit. Is this close?