Hi Les, thank you again. Yeah, I guess it comes down to the old tomato/tomahto thing. I thought because the machine will never be powered down between electrode changes, and for most burns multiple electrodes are used to get a good cut, because while most of the "wear" is to the part being machined, you get ~ 20% wear on the electrode too. So it just seed like the way I did it was an easier way, instead of powering down completely after each burn. And until the bootstrap caps are charged the circuit won't work anyway. So one switch two effects seemed like the way to go.

 

Hello, Mr.Shortbus. I am also another person in rabbit hole. I have a few questions to ask you.
What do you think diesel oil as dielectric fluid.
Would it be much different between lead screw and ball screw.
I have just learned that the aluminum flexible coupling between stepper and lead screw does not work very well. To fix it, I need to put epoxy around the coupling.
So far using diesel with terrible result. I must spend at least two hours before I can put a 3/16" hole into a file. I am from Laos live in Bangkok.

 

For unknown reasons I stopped getting alerts for this thread.

I've got a Bridgeport, a 9" Southbend lathe, a 12" Logan with a 5" bed , and a Chinese 14" short bed lathe. An 18" metal cutting band saw with blade welder, a 12" homemade metal cutting band saw , a Chinese horizontal band saw. A couple of drill presses, and a life times worth of precision measuring tools and hand tools. A stick welder, Mig, small Tig and torch set up.

What the hell ... ??? I have three soldering irons.

ak

 

Hi ak,
Nice to see you back on this thread. For some time it seems that it was only SB and myself taking part.

Les.

 

... For some time it seems that it was only SB and myself taking part.

Les.

Not quite... I've been lurking in the background, as an observer. But I promise I'll break the silence when I have something relevant to say, or ask.

 

Hello, Mr.Shortbus. I am also another person in rabbit hole. I have a few questions to ask you.
What do you think diesel oil as dielectric fluid.
Would it be much different between lead screw and ball screw.
I have learned that the aluminum flexible coupling between stepper and lead screw does not work very well. To fix it, I need to put epoxy around the coupling.
So far useing diesel with terrible result. I must spend at least two hours before I can put a 3/16" hole into a file. I am from Laos live in Bangkok.

You don't say what type of EDM, and how many Amp's your transformer is putting out. The voltage will determine the spark gap distance (called "over burn"), while amperage will determine how fast it removes metal. Another factor in metal removal and the cutting process overall is the quality of the flush in the burn. Without a good flush, to get the debris out of the gap, the machine will spend a lot of it's time retracting the electrode.

Can I ask which set of plans your machine is based on? My ram uses a ball screw, but a regular thread screw should also work or even better than a "V" type thread would be one of the metric so called 'trapezoidal' Acme screws. The "V" thread needs more clearance between nut and screw to move freely, so can cause problems with the electrode feed, but a lot of DIY machines still use them. I had a small ball screw so that's what I used.

If every thing is aligned correctly, motor and lead screw, no coupling should be required. But do know that home made CNC machines try to use a steel flex coupling, because they are more robust.

Diesel fuel is something I'm not sure about, most DIY EDMer's use Kerosene. I'm not sure but think diesel has additives in it, to make the engine last longer, less wear in the cylinder, but can't really give a definite answer to that. I know though that for me at least, diesel smells worse and make my skin get a rash with long time exposure.

EDM is a slow process, it's not ever going to be as fast as regular machining with cutters. In the machine shop EDM is one if not the most expensive was of machining. Both due to time and materials used in it. But you can do things with EDM that can't be done any other way.

 

For unknown reasons I stopped getting alerts for this thread.

I thought maybe you thought my way of approaching the use of logic was just to far out there. I'm working on a redraw of the schematic now, using the better , continuous numbering system you talked about. Don't know whether to add it to this thread or start a new one called "EDM 2.0"

Hope you will continue to participate. Les has been very, very helpful in this.

 

diesel smells worse and make my skin get a rash with long time exposure.

Not to mention the fumes. I used to cut aluminum with a CNC router using Diesel as a coolant a few years ago, and it was definitely not worth the discomfort. There ought to be better dielectric fluids out there that should do the job nicely, without them being that bad for your lungs. And also less flammable.

 

There ought to be better dielectric fluids out there that should do the job nicely, without them being that bad for your lungs. And also less flammable.

There are. But most DIYer's won't spend the money on them. I know I can't justify it for my home use. The one we used at work when I retired was IonoPlus 3000 http://advancedcnctechnologies.com/nodeorder/term/280/all
$225 plus shipping for 5Gal. The one they used when I first started running EDM was a Mobil oil product, the labels on it said, "this product contains materials known to cause cancer". Not the normal California warning, that says everything causes it, but a warning with no state listed. Couldn't wear gloves because the parts and electrodes were too small to feel with rubber gloves. Just ate right through regular medical/latex gloves . And we had our hands covered in it for hours a day. And it still wasn't flame proof, just flame resistant.

 

I used to cut aluminum with a CNC router using Diesel as a coolant a few years ago, and it was definitely not worth the discomfort

We used water soluble oil for machining and in the wet surface grinder. Actually works better than cutting oil.

 

Thanks for answers Mr. shortbus. Mine is ram type. It is palse EDM using SG3525.
The transformer is 70vac weight around 6pounds, I dont know the amps. I also use a little 110 vac in pararell to higher the voltage to ease sensing circuit . Mine circuit is originally base on a book I found on ebay seven years ago. As far as I can remember. It was by Amsterdam press as it was the cheapest I could find. At the time, I needed something to start up with. It was RC type and had basic sensing circuit with only one transistor. Also interface with pararell port to a note book. And supply with the book was a small program in assembly language. Turn out that the first time I tried it burnt out my notebook' s pararell port. As now I have more experience and thinking back. The book probably never work. The nice samples on the book must be done on real machine. After that I' v spent my lisure time for last five years to make it my own. Mine is just like your.
It is just logic board to control. But instead 40xxx series. I use 74xxx. .... and instead of using window comparator. I use zenor diode to detect voltage. The only downside is that it is not easy to adjust gap voltage. May be something else I dont know.

 

and instead of using window comparator. I use zenor diode to detect voltage. The only downside is that it is not easy to adjust gap voltage. May be something else I dont know.

Hi, sounds like me, what was in a book/plan wasn't good enough. Yes a window comparator is needed for the ram 'servo control', since the motor needs to retract when gap conditions aren't right. Your transformer also sound similar to mine, mine came from an old servo motor drive control.

While not sold by Amsterdam Press the book sounds similar to one I have, called, "S-EDM for the home shop", by Proved by Practice Publications. Does your books plans call for the tank to be made from perspex/acrylic sheet cut and glued together?

 

Yes, That book was the one. Have you tried it, Did it work for you. They suggested using vegetable oil which I also tried, the oil is quite good for erosion. But it has down side. It trends to become sticky ,gummie after being kept expose to air for a month. So far Iv found that kerosine is the best for erosion. But Bad part is, It need to be submerged, it is volatile and a system to handle the liquid needs a big engineering project. Not suitible for home shop at all. I need small footprint ,slow is OK.The only thing iv got from that book is using fuel pump. But when use to pump diesel it not so reliable. Many time it need a blow from a hammer to start. I am now thinking how to convert a shock absorber to a pump. I think this weekend I will try water as a dielectric. (Diesel is bad dielectric because it is not break down easy, made so difficult for your sensing circuit to detect and slow down or stop just before hit the target. )
But it cheap and easy to handle, Diesel is good for making experiment.
Many people on internet choose go for wire EDM. I guess those people need challenge by extend their knowledge of Arduino or homemade CNC rather than need to develop a really usful machine. Why do you want wire EDM for ,now we have laser or water jet which replace 80% of job used to be monopolised by the wire machine. Unless you can make machine half as good as Makino, Sodick or Mitsubishi then it will be useful.
For you and I sinker is the real challenge, am I right.

 

I haven't and wouldn't try the way that book says to do an EDM. While the ram it's self in that book is pretty good, the rest is way, way 'old school'. Using light bulbs for resistors is how it was done in the experimental stages of EDM they know now how to do it. And using any plastic for the work tank I disagree with, a fire and they can happen, and the plastic tank starts to melt is asking for a disaster. You're right about vegetable oil too.

I don't know what your part of the world has available in the stores. But if I was going to start over in my build I would look for something like this - https://www.ebay.com/itm/3-1-2-Gallon-Electric-Parts-Washer-Solvent-Pump-Portable-New-/182043654705 For one price you get a metal tank and a pump made for petroleum fluid. The pump should be a centrifugal type - https://en.wikipedia.org/wiki/Centrifugal_pump, which the parts washer comes with. You don't need much pressure, like you would get from a fuel pump or a piston pump. 3 to 5 PSI is enough, and with a centrifugal pump they self regulate, meaning if the out put of the pump is choked down with a valve, they will not try to build more pressure, the impeller will just spin without putting a high load on the motor.

Where I worked they tried to use water when they bought some new sinker machines. Spent a lot of money on a deionizing system and the tanks used in it. Doesn't work for sinker EDM. Works for wire EDM because it doesn't make any way near as much debris when cutting. A 1/2" square electrode removes much more metal into the fluid than a 0.010" diameter wire does.

Wire is also the most expensive to run of the EDM types. The wire can only be run through the cut once, it's then scrap. Wire can't make a pocketed hole, one that doesn't go all the way through the part. I never got to run a wire machine, but to me a sinker is more of a home shop type machine, it's more versatile for most things. While it looks better in a Youtube video because it's moving and looks like it's doing something and a sinker is kind of like watching paint dry or concrete harden.

 

The wire can only be run through the cut once, it's then scrap.

I've seen wire being reused a couple of times more. But the cut is nowhere near as precise as the first time it's used. And the wire is at risk of breaking when it's reused, which is quite an annoyance. You're quite right about sinkers producing a huge amount of debris.

 

I've seen wire being reused a couple of times more. But the cut is nowhere near as precise as the first time it's used. And the wire is at risk of breaking when it's reused, which is quite an annoyance. You're quite right about sinkers producing a huge amount of debris.

They tried it at work, had two machines set up back to back one was doing the first or rough cut and using the wire from another machine that was doing finishing cuts. It wasted more time than it saved in money. Two different set up times cost, and usually they did 3 passes on a part, a rough, a first finish and final size. The last two use a faster wire speed and more wire, and the machine doing the roughing runs slower speed, so then they had a bunch of wire that got tangled and still was scrap.

Both using the wire twice and water for sinker were thought up by bean counters and engineers that didn't understand the process. And ended up costing the company money in the long run.

 

Two fuel pumps, I have are for motorcycle. One is 13.5V axial flow type. The other is mix between centrifugal and Tesla type. It wont give much pressure because it isn't designed for thicker diesel. And I put a PWM I made from 555 in middle between power supply and pump. No problem once it run but to make it run. The red tank in the picture, I made one similar to that using fuel pump and I use an auto oil filter as a filter. I found out (but not so sure) that auto oil filter clog easily because it too fine and to make good spark I think we need oil with suspended graphite, oil should not be thoroughly clean (unless we use synthesis oil then graphite is not to be needed). So I switch back to use my old sock.

 

to make good spark I think we need oil with suspended graphite, oil should not be thoroughly clean

Never heard of that. Do know though they make a special dielectric oil for finishing, but it has powdered aluminum in it.

 

they make a special dielectric oil for finishing, but it has powdered aluminum in it.

. Isn't that confirm my hypothesis. But I still have little experience because my machine just slowly mature. Also i notice using too strong flush not give good result, I guess because graphite that is newly generated is scattering away. Once the flush is slower some remaining of the graphite can help sparking , am I right.
Normally EDM oil is something opposite to transformer oil. EDM oil needs to breakdown easily otherwise it be useless. In vegetable oil there are a lot of place hydrogen is replaced by oxygen make vegetable oil polar and shorter distance for electron to jump. Synthetic oil I think is made by embed some weird atom to hydrocarbon chain to make it polar. But aluminim powder, I wonder how to prevent it from not being oxidized. Aluminum oxide is perfect insulator. It must be some mechanism I still don't understand.

 

Also i notice using too strong flush not give good result,

Earlier in this thread I kind of hinted at the flush problem. When first learning to run an EDM I was having problems getting a good burn. It ended up being my flush pressure was too high. Volume not pressure is the key to a good burn.

The powder in the dielectric is only there to reduce the distance that the spark has to travel. That is why it is only used for fine finish work. And even though the powder would be oxidized to a certain extent it is still conductive. Because it isn't actually part of the metal being removed, the spark jumps to a bit of the powder then jumps to the actual work. I have never used this finishing dielectric, this is just from reading about it.