@Bogos87 While I know your no where near ready yet, have you thought about what you are going to use and how your going to make the electrode?

There has been talk in the thread and most of the Youtube videos show copper as the go to thing, but from my experience Poco graphite is a better material. Don't know if you've ever machined copper but it is gummy and prone to making burrs. While that's not the case with graphite, graphite makes a mess when machining it.
At work we made our electrodes with a surface grinder and used a vacuum type dust extractor. When they bought the CNC edm's they also bought a CNC electrode maker and tried copper and copper tungsten as a electrode material. While the CNC made fewer burrs there was still some hand work to remove them. Just the common machine shop copper while it can work is not electrode copper.

You might want to watch some Youtube videos called "learn to burn", it's sponsored mainly by Practical Machinist forum and most are done by Zero Tolerance Machine. The main guy is the only online person that has talked about how we did edm where I worked. They have at least 2 videos on graphite vs copper electrodes. Well worth the time to watch any of their videos.

https://www.practicalmachinist.com/forum/threads/everything-edm-learn-to-burn-youtube-series.396342/

https://www.youtube.com/playlist?list=PLxzIM06jyJCbWdno6Efe1AXfvRaGZhSsN

 

@Bogos87 While I know your no where near ready yet, have you thought about what you are going to use and how your going to make the electrode?

There has been talk in the thread and most of the Youtube videos show copper as the go to thing, but from my experience Poco graphite is a better material. Don't know if you've ever machined copper but it is gummy and prone to making burrs. While that's not the case with graphite, graphite makes a mess when machining it.
At work we made our electrodes with a surface grinder and used a vacuum type dust extractor. When they bought the CNC edm's they also bought a CNC electrode maker and tried copper and copper tungsten as a electrode material. While the CNC made fewer burrs there was still some hand work to remove them. Just the common machine shop copper while it can work is not electrode copper.

You might want to watch some Youtube videos called "learn to burn", it's sponsored mainly by Practical Machinist forum and most are done by Zero Tolerance Machine. The main guy is the only online person that has talked about how we did edm where I worked. They have at least 2 videos on graphite vs copper electrodes. Well worth the time to watch any of their videos.

https://www.practicalmachinist.com/forum/threads/everything-edm-learn-to-burn-youtube-series.396342/

https://www.youtube.com/playlist?list=PLxzIM06jyJCbWdno6Efe1AXfvRaGZhSsN

Amazing info, thank you!

 

@Bogos87 If your interested I have a way of making 4 burns on 1 piece of electrode material, graphite or copper. And it would be done in the lathe. If your plan is to burn one side of the block at a time.

@EdmGuru I'm getting things together to start a PM with you. But what I had as a schematic I came up with a new idea, one that will give the ionization stimulation from just one transformer/power supply. But life is getting in my way.

 

@Bogos87 If your interested I have a way of making 4 burns on 1 piece of electrode material, graphite or copper. And it would be done in the lathe. If your plan is to burn one side of the block at a time.

@EdmGuru I'm getting things together to start a PM with you. But what I had as a schematic I came up with a new idea, one that will give the ionization stimulation from just one transformer/power supply. But life is getting in my way.

Hi shortbus. Ok no problem. I don’t understand the ionisation bit unless it’s just to start the burn or possibly to get the mosfet to turn on, but there’s way round that. I can’t wait to see it.

Cheers

 

@Bogos87 If your interested I have a way of making 4 burns on 1 piece of electrode material, graphite or copper. And it would be done in the lathe. If your plan is to burn one side of the block at a time.

@EdmGuru I'm getting things together to start a PM with you. But what I had as a schematic I came up with a new idea, one that will give the ionization stimulation from just one transformer/power supply. But life is getting in my way.

Please feel free to tell me more about it. I was thinking about burning two blocks simultaneously towards the rotating electrode, but I think I don't want to make things complicated.

 

Please feel free to tell me more about it. I was thinking about burning two blocks simultaneously towards the rotating electrode, but I think I don't want to make things complicated.

Hi Bogos87. That does sound a bit complicated but having said that a unique feature of the Easy-Peasy EDM is that having a DC motor to drive the Z axis you can spark in the up direction as well as the normal down direction by simply reversing the two wires to the motor. I’ve done this myself when making press tools on the EDM you can spark erode in the up direction in order to back off the bottom tool once the electrode has gone through the bottom tool half.

Cheers.

 

Hi Bogos87. That does sound a bit complicated but having said that a unique feature of the Easy-Peasy EDM is that having a DC motor to drive the Z axis you can spark in the up direction as well as the normal down direction by simply reversing the two wires to the motor. I’ve done this myself when making press tools on the EDM you can spark erode in the up direction in order to back off the bottom tool once the electrode has gone through the bottom tool half.

Cheers.

I guess if the Z axis is modified to let's say X axis (I mean horizontal), then electrode can burn one block in one direction of the motor and changing the direction can erode the second half, right?

 

I was thinking about burning two blocks simultaneously

That would work with my idea, but then you would only get 2 burns from 1 electrode.

 

I don’t understand the ionisation bit unless it’s just to start the burn

Exactly, you talked earlier about a high voltage to get the burn to start, getting the burn to start means ionization of the dielectric fluid. Giving it a pre-start/kick start then allows all of the burn voltage to remove metal, instead of using part of the time/voltage to get the ionization needed. Any spark has to ionize the gap and then the energy follows.

 

That would work with my idea, but then you would only get 2 burns from 1 electrode.

I guess it's the best for me to go one step at the time- so, I need to build a EDM first, and maybe later will complicate it more with unusual upgrades.

 

I guess if the Z axis is modified to let's say X axis (I mean horizontal), then electrode can burn one block in one direction of the motor and changing the direction can erode the second half, right?

Hi Bogos87. Yes it could be done that way but it would be a complicated build as you would have to make sure that the DC motor was clear of the dielectric fluid. It maybe easier just to hold each mold half one above the other?
Cheers.

 

Hi Bogos87. Yes it could be done that way but it would be a complicated build as you would have to make sure that the DC motor was clear of the dielectric fluid. It maybe easier just to hold each mold half one above the other?
Cheers.

Something like that, yes.
I guess, when the time for it comes, it will be a matter of trial and error. Concentricity of the both closed parts is the key here, so, I might need some good optical measuring unit for quality control, as well.

 

Exactly, you talked earlier about a high voltage to get the burn to start, getting the burn to start means ionization of the dielectric fluid. Giving it a pre-start/kick start then allows all of the burn voltage to remove metal, instead of using part of the time/voltage to get the ionization needed. Any spark has to ionize the gap and then the energy follows.

Hi shortbus. Yes I agree about the ionisation is needed to start the burn but the spark pulse voltage already present at the electrode will start the burn , that's how I do it and it works fine, the mosfet doesn't have to see a ground connection at the source (output) in order to switch on, a modern mosfet driver chip will do that and my bootstrap design also does just that and I've checked the output voltage and pulse on my oscilloscope and it's good.
Cheers.

 

my bootstrap design also does just that and I've checked the output voltage and pulse on my oscilloscope

I know we agreed not to take over Bogos thread but it's hard not to. Have you ever used an isolated DC-DC converter instead of a boot strap?

 

I know we agreed not to take over Bogos thread but it's hard not to. Have you ever used an isolated DC-DC converter instead of a boot strap?

After some time I realized that just 3 of us making conversation about the same subject, so going sligthly offtopic is not the problem for moderators, I guess. It's allright with me, btw, because the infos are interesting.

 

I know we agreed not to take over Bogos thread but it's hard not to. Have you ever used an isolated DC-DC converter instead of a boot strap?

Hi shortbus. No I’ve never used an isolated DC-Dc converter instead of a bootstrap circuit but isn’t that how a mosfet driver IC works only they call it a charge pump circuit? The idea behind my new mosfet power generator was to make a simple way to create a pulse EDM power generator but it’s probably easier to just use a mosfet driver IC, the only problem being the physical size of the IC when it comes to soldering it to the PCB. I had in mind using an LTC7001 driver IC but its only 3mm square!

Cheers.

 

I had in mind using an LTC7001 driver IC but its only 3mm square!

Hi edm, I hear you on the small surface mount stuff, they are making things hard on us old guys. They do make some thing called "surf boards" that you solder the surface mount part on then it has pins that you can put in a regular through hole IC holder. That way the whole PCB doesn't have to be surface mount. A link to one of the many being made and sold. https://www.capitaladvanced.com/6000ser.htm

With a standard half bridge driver you need to use 2 mosfets, some one years ago (who has since passed away) told me to use the isolated DC-DC convertors but didn't explain how.

 

"EdmGuru, post: 1861367, member: 565586"]
Hi Bogos67


Yes if you use Dominik’s design of EDM but it wont do what you want it to do unfortunately as it’s a pulsed RC design which by design have high electrode wear rates also there is no provision to change the pulse frequency and current output which is necessary for the finishing stages and even then you will still need some electrical knowledge to build it. Do you have a machine frame built or in mind already? Have you thought about the dielectric system for a pulse EDM? They use an oil based dielectric which is a fire hazard so your machine will have to be sited in an out building or such (not made of wood) to be safe. It may be possible to use deionised water successfully at low Amps on a pulsed EDM but I’ve never heard of anybody doing this due to the increased voltage, pulse frequency, duty cycle and the electrical conductivity of water compared to a wire EDM which typically only work at approx 15v due to only a 20% duty cycle at the wire, so this could be a first for you if it works!

The Easy-Peasy design of EDM has probably 95% of it’s parts available “off the shelf” but you’ll need to take some voltage measurements from the speed controller etc to get the right balance for the voltage divider feedback to the speed controller which controls the Z axis during the erosion process so again some electrical knowledge and equipment (multi meter) will be required. The pulse power generator is the only part that’s not available “off the shelf” (apart from the designs online that don’t really work all that well) so you will need to build one but I can help you there. Maybe I should start selling my pulse power generator online? The first thing I would do is build a good machine frame and go from there, you’ll enjoy the journey.

Cheers.

 

Install GoogleDoc and follow this link for a free book on my Generator " https://docs.google.com/document/d/1In0B1h1-_mlV5twyFxUpd_1IikoQJgToKDnoxyyx9tQ/edit?usp=sharing " Once reading it do not forget to comment, Please!

 

Hi Roong, I hope you are well.

I’ve read through your eBook and recommend the following, also no offense is intended:

The first part about safe practise when using a high D.C. voltage is okay but a bit lengthy, maybe it’s better to just use a more standard disclaimer and avoid the effects descriptions of D.C. verses A.C. voltage on the human body.

In chapter 1 you state that you have not found anyone on YouTube using a stepper motor successfully for an EDM sinker? My stepper motor EDM on YouTube works well, It has a fast stable burn, with low electrode wear and also has anti arc function and auto Z axis retract when the depth limit switch or stop switch is tripped. Part 1

Part 2

Anti arc

My EDM has been further improved since the making these videos. Also My Engines on YouTube successfully redesigned the Ben Fleming EDM to get a stable machine with low electrode wear.

Also you state that your machine has the smallest footprint on Earth? My Easy-Peasy D.C. motor version of an EDM is only the size of a standard PC case and a small drill stand, which is maybe a bit smaller than your machines footprint?

The next part about using transistors as a switch etc is a bit overcomplicated for this machine build and should be shortened and reworded as most people, in my opinion, who are interested in building a sinker EDM will either be confused by the description or already know how a transistor works and disagree with your circuit design etc suggesting different ways or even using an ic type solution. It’s much better to just state that “this is the way I designed the circuitry for this EDM to work” and leave it at that.

Chapter 2 and 3 are largely good but I would never use any P channel transistor or mosfet in any of my circuit designs, especially in a push pull circuit as they don’t give a true output square wave form on their output, which leads to increased electrode wear. I’m interested in your design of current limiting in the power generator. I’ll model a simulation in LTspice to check the output wave form etc.

Chapter 4 is also basically good but again a bit overcomplicated for the beginner, also your stepper motor sense and hold circuit, I feel is not necessary, if you use an op amp instead of the LM393 comparator, I know an op amp doesn’t switch as fast as a comparator ic but they will still switch faster than your max pulse frequency so are okay to use.

I hope that you find my comments on your machine helpful and I wish you every success in the future with it.

Cheers.