I have wanted to make my self a precision 4 axis WEDM for about 12 years now (ever since I heard of them), now I think I am ready mentally to attack the project. I have questions about them and hope the plethora of collective knowledge demonstrated by this forum can help me in my terrible quest!

So to start off!

I know that the key to a good EDM is the power supply, in your experience what makes the perfect setup? Will a quick discharge like a capacitor discharge suffice? Or would it require a constant arcing that which can be found with a current controlled square wave?

Is there more to an EDM power supply then frequency control, voltage control, and current control?

I was thinking of making a power supply that can go to 100 KHz PWM voltage control and capacitive current control. I would like to use a variety of wire but preferred .003" I am not sure about the optimum power but would build it to 1000 watts, is this enough?

a diagram of the power supply:

220V filtered DC
|
V
Switch <--- Square Wave generator 0 - 100Khz PWM V control
|
V
Switched Capacitor Bank <---- Digital Bank control for power of spark
|
V
Wire Cutter

Any help would be great! Thanks!

Cheers!

I had built one about 10 years back, real basic unit that I used to remove broken taps and such...
No longer have it, but I found a surplus power supply that was relatively high voltage [I think over 200v], and used manual feed with a current meter for monitoring, don't remember current draw anymore.
For a wash fluid I used plain diesel fuel, low pressure with relatively large volume to carry away the dust..not real safe, but was real handy and worked well enough..
I do remember that indicated current [and resulting arc size] would make quite a difference on the actual diameter of the cut, mine wasn't a wire style, just plain ground to shape carbon electrodes [arc-air rods]..

enjoy...:)

If I were going to do a WEDM, I'd want a square wav power supply that would allow you to set on and off times. This ability smooths out the cuts and allows you to machine at a faster pace.

camtronics has plans......maybe you might look at them . i am intersested but it is the unknown...........if it could work i am in.

I've been putting it off for years.
New years resolution! Time for me to have a go too.

Hi,
Happy new year to all.
I'm working on an small homemade EDM switched mode pulse generator. I'm aiming for 0-15A (maybe more), 0 - 150V and 0 - 100kHz pulses (isofrequent and isoenergetic). The unit should be able to work at will in a pulse or relaxation mode). The electronic project is already in an advanced fase, but for the moment I'm lacking expensive measuring equipment for making good relevent load measurements, snubber adjustment and calibration of current limiters/controllers. The whole thing will be controlled with a microcontroller to set all kind of parameters for finishing result and speed optimizations. And above all it should be affordable for a simple student as me. The primary objective is to use it for a zinc EDM, but later on I plan another version for wire EDM.

1000W is way more than enough for .003 wire. Our big machines only have a 60 amp power supply and i havent ever seen it maxed out on .01 wire and i have cut things 15 inches in height before. I would think that you would want to Square wave to be able to control the cut more. A big factor in EDM is being about to control the curf of the cut(the with of the cut overburn ect) so you should be able to control that a little better.

camtronics has plans......maybe you might look at them ..

are those the ones with the draw slides? struck me as a joke, i might be wrong but i'd want to hear of someone's success with it before i purchased draw slide plans. jim glass @ the chaski forum has built a wire edm and there's some good content on this site on the challenges of doing so.

I've want to make one as well, cost of the brass wire is the current excuse :D

I am still doing allot of research right now as to determine the operational requirements for the power supply. Yea 1000W is allot, and I still am not sure on the power range that I am looking for. I am fixing to make a test circuit with a TIP121 transistor as a switch, it will do about 6A at 70V (I think) still trying to figure a scheme to measure discharge voltage to determine gap width. The microcontroller I am using is the 18F1220 running at 40Mhz or 10 million instructions per second. I should be able to capture the voltage and current with its AD converter but if it will not work for this app. I will use a 18F4431 a bit of an overkill but it should work. it should also serve as a controller for the switching power supply.

I have been reading allot of specks on machines and put there current rating to about 20A this is max current to the work right? That should not be a problem to achieve for my circuit topology.

I could find no info on frequency or pulse width and timing though… not yet anyway!

Have a look at the UC3842/3/4/5 switchmode driver family.
Very simple to use, quite flexible.
Drive power devices directly.
Current limiting cycle by cycle.
Built in oscilator and 5v reference.
Easy to use opto isolator in feed back loop, cycle by cycle.
If they use them set top boxes, they don't cost much.

neilw20, never used that one before, but I have used the MAXIM version of a SMPS, it worked very well, I might use something like this, I dunno. It depends on how ambitious I am. Thanks for the suggestion.

Here is my sketch of the power supply.

In this setup I have a transistor (Q1) connecting the wire tool to ground through an inductor (L1) and a current sense resistor (R1). The current is fed to an accumulating filter which "averages" the current reading to make it more suitable for my A to D in the microcontroller. this is where I will at least chop the current to the wire but hope to do a pwm current control, (L1) will add reactance to the circuit an allow a smooth current control. As you can see the power for the spark is supplied by a buck SMPS of a standard implementation and is also controlled by the uC, the uC also turns the high voltage on with the relays. I don’t have some of the circuitry modeled in this sketch, such as the clock circuit for the uC, and the idle resistor on the load side of the buck converter. You might notice that for the voltage references and dividers, there are additional capacitors, well that is because the AD converter in the uC likes a low impedance source, the caps help provide it, and also they help smooth irregularities so the program does not chase its tale. They also reduce the parts count by a huge amount as they are replacing opamp buffing circuits.

This is what I am thinking now anyway. But I think I may need to start with the machine or I will have no way to test the Power supply (nuts)

Also can anyone tell me what (I'm with stupid) is supposed to mean? It has been driving me nuts for a while.

He's my cousin.

Hi
I have a Chinese Pc driven WEDM machine this thing is 15 years old and I have been doing all its repairs for a long time. So I know a little bit about wire cutting machines. I cannot speak for the new machines many of them now use Ac current for the spark. My machine the maximum current you can use is 3 amps and that cut 120mm of steel I normally cut around 40mm steel and then I use around 1.5 amps at 25volts the transformer is rated at 90volts. The cutting current is not the problem the problem is with the software. One needs to reverse the motors if the voltage goes below 5volts and again when the voltage is up. You should first speak to some one like EMC and see if they have a solution for that problem. I would not recommend you go for 4 axis I do all my cutting in 2 axis its faster. My machine use a 0.2 steel wire on a drum that changes direction, it would be possible to fit something like that to a CNC mill.

The cutting current is not the problem the problem is with the software. One needs to reverse the motors if the voltage goes below 5volts and again when the voltage is up. .

that's the reason i tout the newall encoders for this project, not because I have aspirations of machining to a few millionths but because of the resolution it would give on the distance the wire travels toward or away from the work....I speculate that a lower frequency, lower wattage diy WEDM would benefit from a very fine control this distance.

Hi
The cutting current is not the problem the problem is with the software. One needs to reverse the motors if the voltage goes below 5volts and again when the voltage is up.


Ahh, the challenges! Actually where I am at right now is trying to come up with an elegant circuit to measure the breakdown voltage of the gap, I am thinking about using a capacitor that will add reactance without significantly changing the properties of the cut. That way the gap breakdown voltage is a function of time and can be measure that way. This can be used to add a feedback loop to the control circuitry, which I think I am going to build a dedicated uC unit for that and interpret the G-code directly. I am also going to add AC capability to minimize electrolysis.

I like the Idea of a 4-Axis but I must admit I don’t know much about it. I know that x,y are the cartisan movements and the u,v are the offsets, however are these absolute measurements? or are they based on a virtual plane at the top and bottom of the parts? If so that means I have to calculate the real points in real time off of the G-code representing virtual points! Oh the drama!

And about the 5th axis! is this just the x,y plane moving in the z axis or is it both x,y and u,v moving at the same time.

I want to add a b axis but that is trivial compared to the others

Baby steps. Start with two axis and go for more in round two. This would keep the learning curve to something with possibilities of success.

MrWild, you are right, baby steps are best, however if I eventually wanted a 4-axis as apposed to a 2-axis, the structure would be vastly different so if I don’t want to build two machines of this magnitude I will need to bite the bullet and go for the 4-axis. I will not likely build another WEDM after this one (too many other projects on the list).

Besides it will be a 2-axis until I figure out the programming to make it a 4-axis. ;)

Cheers!

llilrex, curious if you developed an opinion on what frequency would be most practical.

On four axis, if i owned a job shop and bought a WEDM, yup I'd want it. but as a home shop guy I'm not coming up with a lot reasons to...isn't the most common use for four axis WEDM to create draft angles on stamping dies? so far at home haven't need that, but maybe i'm stuck thinking inside the box. adds a lot of complexity.

what!!!!!!!! are you not feeling well?????? if i had a 4 axes i would sit up thinking of things to do. even it was just to cut the morning butter for toast!!!!!!:-)

what would I do with it? hmm...
Jet engine parts: diffusers, NGVs, turbine blades. I also experiment with nozzles, and high pressure equipment that use carbide parts. Other things are special gearing in robotics using hard material and slight helix. man I dunno maybe other things too. who knows but for the most part I want it because of the complexity. like my good German friend said to me one time "why make it simple when you can do it complex?" I think he was quoting someone else but anyway. a good challenge to hone my skills and give something useful to me in the end. If I crash and burn, it will only make me stronger in the end.

oh yea, the frequency is still up for grabs, I haven’t found any definite data on it yet. I have been researching allot of machines, patents ect. But mostly they talk about wave form. I think the there needs to be time for the arc to extinguish which in my other projects having to do with high power High voltage discharges it would be somewhere around 20Khz but like I said I don’t know yet. Anyone able to lend an opinion on that is welcome. But on other facets of the issue the speed of cut would be theoretically proportionate to the frequency, the more sparks the more cut the more specific power. but there has to be a happy medium and since my hardware at the moment will do 100Khz with out to much of a problem I might just make it adjustable to that.

like my good German friend said to me one time "why make it simple when you can do it complex?" .

one analysis has them loosing war because of that

you could do interesting shapes, not sure how many of those example would work....ie a helical tooth pattern doesn't have straight line to its form afaik. If you really wanted to push the envelope build a rotary electronic erosion machine like they use for PCD and run hobs on it. :D :D for me, a 2 axis wire and a sinker would capture 99.99% of it and be way down the curve from a 4 axis, but the fun of it we can build what ever the hell we want, right?

keep posting on it, I'm interested to learn of your discoveries...i'm not as committed to a build yet but am enjoying learning and thinking about it

PS, oh yeah, you can control up to 100kHz? doesn't the PC controller poop out before that?

After allot of research I found that 100Khz is the low end of the spectrum. but before I reveal what I have found a word about the controller, yes I can control 100khz and with PWM my current max with this controller I am working on is about 410khz and the transistor switch is capable to much more then that. However I may have to abandon my current strategy, like I said I want a good power supply and here is where I found the modern standards to be.

The generator voltage is 20 to 150V

The generator frequency is 100Khz to 10Mhz

The sense technology is separated and often even timed meaning the power is not monitored directly but rather as an observer. And often alternately used I.E. a cutting pulse of oscillations and a measuring period fallowed by a cutting pulse and so on.

Now my current design cannot do this so I will have to try again. Fortunately I have a bit of experience in high power high frequency oscillators and with various coupling techniques. Heck the first time I witness electrical discharge machining was a continues breakdown in a 45,000 volt capacitor connection (that was cool... and very loud!).

Anyway I am thinking of using a capacitively coupled class E oscillator running at about 2.4 Kw at 4Mhz up to maybe 8Mhz.

or

4Mhz @ 7micro amps, I would have to shield the thing so it didn’t create allot of interference but it is totally doable. Actually it would be a circuit very similar to a induction furnace I built a few years back.

With that frequency capability very fine finishes are possible.

One more thing… is it me or are EDM companies very secretive?

Cheers!

you could do interesting shapes, not sure how many of those example would work....ie a helical tooth pattern doesn't have straight line to its form afaik.

It is true that you cannot reproduce a helical tooth pattern with a WEDM however but you can produce a pseudo-helical gear; it will not do some of the nifty things that a true helical will but it will get you a quiet-running gear. With the NGV and turbine blades I would not actually machine the blade profile but it will allow me to remove 90% or better of the material in a roughing cut, then I can profile the blades with a sinker or machining center. Otherwise that stuff is real painful to machine with the equipment I have.

I am actually thinking of making a edm end mill like machine that I can use to produce more complicate profiles but I have to keep the simultaneous project count down.

cheers!

Here is an experimental circuit. Rated at about 400W for this version.

Here is the circuit theory:

Stage 1. 4 MHz crystal oscillator provides a square wave.

Stage 2. the 4Mhz get fed into a line driver buffer where it will get much more current capability to drive the next stage.

Stage 3. the square wave gets fed to a push pull amp

Stage 4. Through an isolation transformer and a DC blocking capacitor the 12V amplified current gets fed to a MOSFET that is the switch for the class E power amplifier. the principle for the Class E is understood and if anyone has any questions about it I will post what answers I can come up with. now the 400W rated 4Mhz current limited (through the DC blocking Cap) is delivered to the work.

I will think some more on how to put a state sense circuit into it for "intelligent control"

not really sure where you get your generator info from, but all of the edms that i service do not run above about 50khz....never heard of anything running in the megahertz range......

although the chinese have been making an edm system using low voltage and low current, (which may use higher frewuency) with a wire that spins back and forth off a steel drum. and it just flies back and forth....

they call it fastwire edm

what we normally think of wire edm they call slow wire edm.

the machine does not cut in di water, rather some synthetic oil mixed with water....

I got my information from patents, actually quite a few of them are high frequency, I just assumed that this is where the industry is at right now. It is nice to know however that the WEDMs that you worked on only went to 50Khz, this make things allot easier. But the Generator that I researched was and Agia unit.

The patent used the term "prior art" to describe 100Khz to 10Mhz implying that their Generator is improving on others in a specific way, which was not in the frequency of it.

But if you have more info for me I would appreciate it, like a manual or spec sheet... anything like that. it sounds like you have allot more experience in this field then I do

I got my information from patents, actually quite a few of them are high frequency, I just assumed that this is where the industry is at right now. It is nice to know however that the WEDMs that you worked on only went to 50Khz, this make things allot easier. But the Generator that I researched was and Agia unit.

The patent used the term "prior art" to describe 100Khz to 10Mhz implying that their Generator is improving on others in a specific way, which was not in the frequency of it.

But if you have more info for me I would appreciate it, like a manual or spec sheet... anything like that. it sounds like you have allot more experience in this field then I do



well i have never heard of an "Agia" edm machine.....you might mean agie...and specifically what model generator???? or are these "textbook" circuits...patents that will never be used...

as far as genberators go, a simple 555 timer (or two) can be used to generate a pulse
no secrets here just plain old electronic design.

most taiwan machines do......now they use an atmel.....

here is a typical generator spec:

output voltage -200vdc yes that means wire negative and table at ground.

variable ON TIME : 750ns to 2.25 us (use 100ns increments)

variable PULSE RATE: 5khz to 52khz (variable with potentiometer)

rise time < 20ns ("secrets" of edm...)

OUTPUT CURRENT: 288 amps (peak current) variable in 16 increments
hope you have a current probe handy, we must measure current peaks.....(more "secrets" of edm)

why so much current, these are instantaenous currents, your front panel meter usually reads the straight line dc current, which will be quite smaller, say, several amps

we would like to generate lots of very narrow(with lots of time in between) high current pulses....

now i would build me a nice power switch circuit to switch -200v to the above specs.

then only make them like 15 amp modules or so, and just using your favorie logic, t switch them in and out (parallel) (even more "secrets" of edm)
try some IRF450 's

but hey, if ya wanna build an rf machine, go right ahead, but i think the FCC would have something to say about that.....

and cheap brass .010" wire will run fine on it, with properly desighed heads and flushing, i see 12 square an hour....

Yea I did mean Agie sorry about the typo.

This is all good news to me; I have found it very hard to track down the specs that you mentioned.

If you would like to know about the patents hear is one of them "Method and apparatus for machining, 6,252,191"

There are more but this is the only one I have handy

So you are changing my mind yet again!
Regardless I have resolved my self to making the machine first and then the generator after.

And since I am argumentative I must rebuttal that an RF generator and work need only to be contained in a faraday cage and it will not radiate energy thus the FCC will have no problem with it. I have a RF switching power supply that produced 60,000VDC that runs at about 8Mhz. it uses air core transformers and hydrogen flooded gaps and a faraday cage is how I make it not radiate power. oh yea and good line filters.

Hi,
Happy new year to all.
I'm working on an small homemade EDM switched mode pulse generator. I'm aiming for 0-15A (maybe more), 0 - 150V and 0 - 100kHz pulses (isofrequent and isoenergetic). The unit should be able to work at will in a pulse or relaxation mode). The electronic project is already in an advanced fase, but for the moment I'm lacking expensive measuring equipment for making good relevent load measurements, snubber adjustment and calibration of current limiters/controllers. The whole thing will be controlled with a microcontroller to set all kind of parameters for finishing result and speed optimizations. And above all it should be affordable for a simple student as me. The primary objective is to use it for a zinc EDM, but later on I plan another version for wire EDM.

Dear Sir,
Do we have the plans available for interested members. Please let us know.

I would like to see your plans.

jsologuren

Dear Sir,
Do we have the plans available for interested members. Please let us know.

Dear Sir,
I would like to have the plans for my hobby shop.
Regards
kulk_sd

I have basic circuit plans but I want to see different Project in order to add a bit more and the share my experience.
My Yahho Mail is sologurenjulio@yahoo.com

...Julio

Dear Sir,
Please let us know when you have completed your trials
Regards
S. D. Kulkarni

I have been working on my circuit, found a good microcontroller, and good sampling circuits.

I will keep it simple, but sophisticated. My prototype board has a RS232 connection and so I will use that for real time monitoring. It will stream things like the current sampled with a basic differential amplifier, average current, voltage and waveform; it has a maximum of 4 channels that are set up in this way. Because it is a microcontroller it will have the capability to change allot of parameters on the fly, with a connection to a PC, and also through simple voltage control via potentiometers.

Although I have not been able to get the power end components together I think I am on the right track, thanks to the people here in this forum.

I think that will be an interesting project to follow.
Regards
S. D. Kulkarni

Although I sill have to program it, I have the pulse controller completed. I designed the board to be a universal controller CPU, complete with free bias resistors for switched inputs, and differential instrumentation amplifiers suitable for current measurement and thermocouples alike. It should work well. I am using a IGBT to drive the cutting element directly for now.

Please keep on updating so that we are aware of the progress. I am very much interested in making a really good WIRE EDM machine.

Please let us know the present status of the project.

As you might know, this is a big project. I am working on other components at this time. Such as the XY UV table, power supplies, motor controllers. When I get something more relevant to the EDM process its self I will be sure to post it.

The X-Y table is about to hit fabrication. I will start there and add UV to it later. I might use a sinker tool first and a Wire later, depends on what’s going on at the time I get there. So I hate to be a slow DIY but there are things that one cannot help without therapy!