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doctor demo
12-25-2009, 03:23 PM
I just rec'd My Village Press copy of ''Build an E D M'' and was wondering if any one has built or is building one.

Merry Christmas!


Steve

Evan
12-25-2009, 05:05 PM
I want to make some holes in solid carbide tooling so I will be doing some experiments with a sinker in the near future. Something very simple, suitable for making holes and removing broken tools like taps.

Evan
12-25-2009, 05:11 PM
Here is some very useful looking information on the process.

http://dspace.mit.edu/bitstream/handle/1721.1/32827/57615823.pdf?sequence=1

John Stevenson
12-25-2009, 05:11 PM
May be wrong on this but I'm sure i have seen references on t'internet about the design using some voltages generated direct from 110v mains and not from an isolated supply.

Imay be wrong but there are one / some Yaho groups on this subject.

.

lazlo
12-25-2009, 05:24 PM
May be wrong on this but I'm sure i have seen references on t'internet about the design using some voltages generated direct from 110v mains and not from an isolated supply.

There's a primitive EDM in an old Popular Science that uses mains power directly -- stuff like that would never be published today :)

The C.R. Amsbury/Robert Langlois/Ben Fleming designs are all fundamentally the same -- a step-down transformer feeding a DC rectifier which powers a relaxation oscillator. It's an easy thing to cobble-up in an afternoon with junk from the shop -- David Cofer has a video he posted in the Welding forum where he's just manually holding the electrode.

Robert Langlois' book (a collection of the articles published in HSM) is excellent -- it explains all the EDM concepts and how to calculate the values for the power resistor, the various RC settings (for speed versus surface finish burns). Ben Fleming's design is very heavily based on Robert Langlois', but he adds a very clever design to pump and filter the dielectric fluid.

Like David, I've had the electrical section working for awhile, but I haven't gotten around to making a stepper or servo-based electrode ram. On my Tuit list...

Dawai
12-25-2009, 05:28 PM
Mine, Lazlo was a terrible dissapointment on the cnc bridgeport.

I do however have a tim-the-tool man fix.. laying in the floor waiting on too-cold to work on the streetrod weather..

It's a 2hp motor coupled to a 5hp dc motor-now generator I will tie in on top of the lil tiny transformer to produce some sparks..

Sparken-die deutsche?? ha.. had to..

I also have the transformers saved from the huge plasma cutter I demo'ed... 180 volts.. lost the schematics thou.. it is a current control transformer..

Evan
12-25-2009, 05:35 PM
If you have a pair of heavy duty transformers meant for 117 vac input you can connect the secondaries to each other to make an isolation transformer and remove the power to ground hazard. Of course a purpose made isolation transformer will do also. I have one rated at about 1000 watts so I am good to go in that respect.

outback
12-25-2009, 08:08 PM
Below is the Sinking EDM made from Langlois book. I did not make the stepper motor control. My downfeed motor is a 90VDC gearmotor. I use a programmable controller to monitor the spark voltage and it runs the gearmotor forward, stop, reverse. I can also retract the electrode at the end of the run and stop it at the top the the stroke.

I'll offer one tip. Use regular EDM oil as a dielectric fluid. It works the best.

http://img.photobucket.com/albums/v30/jglass/Automation%20Projects/sinkingEDM.jpg

Outback

doctor demo
12-25-2009, 11:34 PM
Thanks Guys, for the input. I'm thinking a simple sinker for broken taps etc. much like Evans idea. I have not had a chance to dig into this yet with today being Christmas and all, but I did flip through the book and was surprised to see that Bob is running 60 volt @ 5 amp for the secondary....seems a little wimpy.

Steve

chipmaker4130
12-25-2009, 11:57 PM
Steve, I don't think you need a huge supply for most applications. I've started one designed by Ben Fleming, and it is really simple. He provides an inexpensive book and circuit board if you want to go that route. From what I've read, high current just makes a crummy cut. You can check him out at: http://tech.groups.yahoo.com/group/EDMHomeBuilders/
The design is very simple, no steppers or the associated controllers and it seems to work .

Gordon

Evan
12-26-2009, 12:35 AM
I am surprised at how high the average current is. I think you can gett by with much less if speed isn't so important. You can melt the tip of a screwdriver with a 9 volt battery if you use it to charge a big capacitor.

For a sinker the control system can be very simple. What I have in mind is something entirely self regulating such as using the current flow when contact is made to energise a solenoid that pulls back the electrode. The current that charges the main capacitor will keep the solenoid energised until the capacitor is mostly charged. Then the tool drops back into contact, rinse and repeat. It should stutter along nicely all by itself.

John Stevenson
12-26-2009, 06:50 AM
I have one here, a commercial one that Charles P gave me, supposedly not working but I'm told they are that simple that they are easy to fix.

I think they are called a tap out or something ? looks very simple, a bit like a tool setter for a CNC and you lower it onto the tap, switch on and the water container provides the weight to drive the electrode into the tap.

I can take some pics if anyone is interested, might help to get it working again.
probably won't use it because firm across the road has professional die sinkers and if I break a tap they take it out for free as we work closely together swapping and borrowing tools / materials

David Powell
12-26-2009, 10:16 AM
Robert Langlois is a member of our society, ( Toronto Society of Model Engineers). He has very kindly and at great effort brought several of his machines to our meetings on completion and demonstrated them running. While time constraints didnt always allow him to complete the job the machines were doing in front of the audience he passed around sample parts for the audience to examine. The power supply in our lecture theater is 110 v 20 amp. A few of our members have begun to build similar machines and Robert has been able to offer much helpful advice.I hope this is reassuring. regards David Powell.

Dawai
12-26-2009, 10:21 AM
YES< John.. send pictures.. I love taking things apart to see how they work.. even better when I don't have to.

MAKING IT FOLLOW THE CURRENT.. well if you have a cpu, or computer.. a opto22 isolator board, dc in put modules plug into the board, convert INPUT voltages to ttl Optically isolated voltage signals..

On the input side.. figure the open voltage level, buy a zener diode for that voltage.. figure a voltage below that.. buy a zener diode for that voltage.. this gives you TWO levels of signal.. one voltage bus is high, advance cutter, voltage is low, back up.. or hold.. (for you non-technical people.. a zener diode is a diode with a gap, it takes a certain "forward" voltage to "turn on" and bridge that engineered gap.. example.. a 5 volt zener will not turn on at 3 volts.. but will at greater than 5volts dc).. I had one 70 volt zener tied into a SSR relay to dump "generated" voltage from a robotic supply.. it'd dump till voltage came below the 70 volts, then turn back off.

Simple?? well so simple I have not done it yet.. My Langlois version is so weak, I became annoyed.. http://smg.photobucket.com/albums/v85/ibewgypsie/?action=view&current=vibratingedmtest.flv

On the very last page, it states that it does not work without edm fluid.. one sentence warning.. of course..

Using the Vibrating pen.. well it wiggles the end of the electrode allowing a continous burn.. it will burn out taps then or broken bolts.. providing you have some way of lowering it into the part.. it took about a minute to eat a hole in a 1/8" piece of steel.

I want... perfect holes in extreme hard steel.
I want... engraving in extreme hard steel
I want... to deposit carbide on tool jaws.

I need to learn more.. this was just a exercise in building one.

Evan
12-26-2009, 11:01 AM
A quick bit of research shows that the brand name EDM fluids are registered under CAS# 64742-53-6.

The description of that CAS is "MINERAL OIL, PETROLEUM DISTILLATES, HYDROTREATED, LIGHT"

That is the same thing you buy at the drug store to rub on a baby's butt. It's also known as transformer oil as well as a wide range of common hydraulic oils.

Peter N
12-26-2009, 02:16 PM
A quick bit of research shows that the brand name EDM fluids are registered under CAS# 64742-53-6.

The description of that CAS is "MINERAL OIL, PETROLEUM DISTILLATES, HYDROTREATED, LIGHT"

That is the same thing you buy at the drug store to rub on a baby's butt. It's also known as transformer oil as well as a wide range of common hydraulic oils.

For years we always used paraffin as the dielectric fluid for the sparkers in the toolroom.
Quite a few years back the HSE said this wasn't safe any more, so now we use a 'proper' dielectric fluid that smells just like paraffin, but apparently isn't paraffin, and is apparently safer :rolleyes:
Still flammable though.

Peter

Evan
12-26-2009, 02:37 PM
What you are using now is probably "Highly hydro treated deodorized low volatility paraffinic fractions", otherwise known as Lamp Oil.

John Stevenson
12-26-2009, 03:42 PM
Bloody hell Peter, first thing next week go and rub the wire eroder with your sleeve and make a wish.

.

lazlo
12-26-2009, 06:43 PM
Paraffin to Brits is kerosene. Kerosene is a common EDM fluid, although there are obvious issues with the flash point, and you're plunging a spark gap generator into it ;)

Decent dielectric, but it's tough on your skin.

Dawai
12-26-2009, 09:07 PM
I can tell you, heat kerosene to 100 degrees or so, it will flash and burn like gasoline.

People used to use it in tractors and cars, low compression ones of course, but.. they'd run a copper line around the exhaust manifold and then to the fuel line, a t and two valves.. crank it and heat it up on gas, then switch it over to kerosene, then before you shut it down, switch it back to gasoline..

Innovative farmers.

What would happen to a EDM if the fluid got to flash temperature?

Parrifin? people add Parrifin to mineral oil, to increase the viscosity and "weight" of the oil.. I think.. old quaker state oil, the thick congealed JUNK in the bottom of the metal can was solidified parrifin.. NOW adding it to a mineral oil would slow the flash point of it while allowing it to be used as a edm fluid.. is this what they do??

Evan
12-26-2009, 09:17 PM
No worries with mineral oil. You would have a tough time lighting it with anything less than a propane torch.

doctor demo
12-26-2009, 10:30 PM
Well I've stumbled around My junk collection and came up with a 1KVA transformer with two primary and two secondary windings 240-480 primary ,240-120 secondary.
If I hook up the primaries in paralell and the secondaries in paralell and connect to 120V to the primary side, I get 60V output.
Now the question, KVA times 1000 devided by the voltage =amps 16 roughly....is that correct?:confused:
Also is it a reasonable size to start with (Bob uses 60V in the book) I don't want tap burning to be like watching grass grow.
More questions to come, I'm sure.:)
Steve

jeremy13
12-26-2009, 11:47 PM
I also want to make one. Wire cuter and CNC controlled. I think the planes I looked at used a large battery charger for the transformer.

Mcruff
12-27-2009, 12:31 AM
16 amp output would burn large taps pretty fast in a commercial machine.

I have run industrial EDM machines alot, as in 1000's of hours over an 18 year period. I know that most of these homebuilt sinkers like most of the modern commercial machines use servo or stepper motors to run the rams up and down but I never liked them, the older hydraulic rams are more sensitive, faster and faster cutting but cost more to build. As far as capacitors they work fine on the machines up to a point, in most machines caps are a last resort due to the fact they are slower and offer less control over the spark and gap.

doctor demo
12-27-2009, 01:02 AM
Well I'm no electrical engineer so I don't know that it will be 16 amp out for sure but I'm hoping that someone will clarify befor I start wiring stuff together:D

I remember seeing an old edm awaiting an auction about thirty years ago and the controll/power cabinet was about the size of a VW buss and the machine was the size of a small bench top mill. Never thought I'd be thinking of building one.

Steve

Evan
12-27-2009, 04:35 AM
16 amps at 60 volts you can weld with. Not very well but I know I could strike an arc and hold it with that. It darn well should be good enough to burn out taps.

Here is welding with a car battery using 1/16 rod.

http://ixian.ca/pics7/weldbatt.jpg


Now, you might say that the car battery has a lot more current available but not really because the EDM is storing energy in a large capacitor and dumping it all at once giving a momentary current much higher than the average current.

Dawai
12-27-2009, 08:59 AM
Watching mine work??

They release HUNDREDS Of amps, in milleseconds. Then charge at (mine is 10 amps).. one reason the di-electric fluid is a higher resistance than water. It creates a semi-fluid capacitor that releases in a rush, vaporizing the metal.

Note the cloud of vaporized black metal around the spark, why I took note of it in the video.

One thing to note, capacitors, they hold energy, higher voltages mean higher chances of getting fried. Note the "black taped" electrode I am holding in my hand? one layer of black tape is good for 600 volts di-electric.. unless wet..

Rock on dudes.. teach me more..

A real good toy? some of them transistors off ebay that they use in chinese plasma cutters-welders and a computer "stutter control" making the fluid less important. buy me some- somebody..

Dawai
12-27-2009, 09:08 AM
http://cgi.ebay.com/CHINESE-PLASMA-CUTTER-TOSHIBA-K2837-MOSFETS_W0QQitemZ230404984170QQcmdZViewItemQQptZBI _Welders?hash=item35a5350d6a

Mosfets.. off ebay.. currently $13??

this would work as a exit power control on a proper heatsink.

lazlo
12-27-2009, 09:24 AM
16 amps at 60 volts you can weld with. Not very well but I know I could strike an arc and hold it with that.

To put Dr. Demo's transformer in perspective, Ben Fleming's design uses a pair of 25V, 2 A transformers in series = 50V @ 2A = 100 Watts. In other words, Ben's design is a 100 Watt EDM.

Several people here, including Rich Carlstadt, have built Ben's design according to the book, and it works great, albeit slow: roughly 0.1" per hour.

Robert Langlois' design uses a pair of 30V, 5 A transformers in series = 60V @ 5A = 300 Watts (i.e., 3 times the power of Ben's).

But as I mentioned earlier, these designs are all nearly identical, so you can size the transformer as big as you want. But you'll need to also resize everything downstream: the current-limiting power resistor, the filtering cap, the burning caps...

lazlo
12-27-2009, 09:27 AM
Mosfets.. off ebay.. currently $13??

this would work as a exit power control on a proper heatsink.

But now you're talking about a pulsed power supply, like commercial EDM's. That's the Holy Grail for the home-shop EDM'ers :)
Cuts much faster, and wears the electrode way less...

Dawai
12-27-2009, 09:28 AM
I have been hunting large capacity capacitors for a while now. Seems I used to use them as shot-puts to throw at squirrels.

They just don't seem as prevalent as they used to be. Used to be they were in every AC VFD drive I worked on.

I charged one of them 1000vdc capacitors up with a megger-ohmer once and was going to throw it into my driving apprentice's lap.. I thought better of it and stuck it to the door handle where it blowed a chunk as big as a pencil eraser out.. It would have hurt him. Deadly voltage possible.

Dawai
12-27-2009, 09:33 AM
That would allow, for the SPARK welder, the tiny tig, and edm to work from the same power sources.

Also not mentioned is multiple current supplies.. if you take 10 amp 30 volts, add 1 amp 60 volts to it, you have 60 volts. but as the voltage decays, the heavier supply picks up and holds the "exit wave form" longer.. Make sure you have a bridge rectifier behind each transformer to isolate them.

Weston Bye
12-27-2009, 07:49 PM
I built an EDM from the Langois book. Used a 220/480 to 120V 1kva machine tool control transformer - 1000 watts available, never had to use it all. Wired the 120v line to the 220 side of the transformer to get 60vac out to a bridge rectifier, then through a couple of huge wirewound resistors to the capacitor bank.

So far, have only had to use it to make a very special shaped hole: 270 of a circle about 3/16" diameter with a 90 sector remaining. Used a brass electrode machined to the shape I needed and plunged it in about 3/4" deep.

Rich Carlstedt
12-27-2009, 11:17 PM
I built Ben Flemings outfit, and it works fine for tap busring and general shop stuff. It will not do wire EDM, and is not as powerful as the Langois unit.
The unit is small and compact, without taking up a lot of room.
I did not build the tank and filters as that needs shop space i do not have
Most setups are on the mill or Drill press and use manual pumping with rubber bulbs providing the flow. I find this works for my work.
It has 3 power settings and I seldom use max power
I used kerosene for quite a while and did not find it to be a hazard.
Remember (!) if you are putting 200 watts of power, that it is heat, and must be dissapated. I am running maybe 40 watts, and the metal cake pan can
handle the load. The problem with kero is the smell.
I switched to EDM fluid (crystal ?) and the smell was gone and production went up 30-50% . The cost is worth the effort
http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/EDMControl.jpg

Here is Flemings Servo drive I built, but added ball screws and an over-running clutch, which is really needed, as a stalled servo could blow a Chip.
Plans are on the Yahoo EDM website

http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/EDMServoDrive.jpg

Here is an action photo.
I burned through a commercial carbide insert (.188" thick 4.5mm) just for laughs.
I consumed about 8 inches of brass tube and it took almost an hour to make the square 3/16 hole.
I now use carbon rod, and it works 3 times faster than brass tube (Tube requires lower watts)
If i did it again I think it would take 15 minutes or less

http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/CarbideBurnout.jpg

Here is a fantastic use of EDM. If you break a piece of Stainless Steel .060 (1.5mm) in diameter and less than 1/8 inch long in a 0-80 die...how do you remove it and yet not damage the threads.
Simple, burn it out with a 1/32(.8mm) brass rod
The setup took about 5 minutes and saved an expensive die.
The cost, was about 1 inch of 1/32 rod from a hobby shop
I am showing the setup, before the fluid is added.
The vise in inside the cake pan
http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/Burningabroken0-80stud.jpg

Lots of new avenues can be taken.
As a post note, I built the Popular Science or Mechanics unit from the 1950's
and got it to work to remove some broken taps. this unit is so superior, and well worth the less than $ 100 I have invested in it.

Rich

doctor demo
12-27-2009, 11:58 PM
I built an EDM from the Langois book. Used a 220/480 to 120V 1kva machine tool control transformer - 1000 watts available, never had to use it all. Wired the 120v line to the 220 side of the transformer to get 60vac out to a bridge rectifier, then through a couple of huge wirewound resistors to the capacitor bank.

.
Weston, that sounds quite like the transformer that I have.
Would You mind sharing the resistor and capacitor set up You used?

Steve

Weston Bye
12-28-2009, 08:43 AM
Weston, that sounds quite like the transformer that I have.
Would You mind sharing the resistor and capacitor set up You used?

Steve

The resistor (only used 1, I had to go look) is an Ohmite 300W, 16 Ohm wirewound ceramic, similar to this.

http://www.smcelectronics.com/AUDRES.JPG

THe capacitors were just ordinary electrolytics that satisfied the capacitance and working voltage requirements specified in Langois' book.

Dawai
12-28-2009, 11:22 AM
I had in my hand.. I think it is in a bucket somewhere now.

A auto-electric antenna.. it has a linear drive, a small dc motor.. and?? anybody took one apart? it says not to "hook" power to the motor.. sticker on the motor that reads that..

It would be of course the perfect tap burner already made extender.. just add power control..

A dodge car.. well it had two window door motors that were servo drives.. feedback and all.. two of them would be a plasma cutter or torch cnc drive.. Nothing to make.. just use.

doctor demo
12-31-2009, 10:14 PM
Update to the lack of forward progress.
I picked up 9 new 250V caps. yesterday at a surpluss place along with some other misc. stuff for other projects $40 total, not bad.
Here is the rub, I was sure that the box they were in was marked 100mfd and in reality they are 1000mfd. So now I have 8 spares for the big one and no small ones, I could have taken them back and exchanged them for the right ones but EVERYBODY closed early today:mad: .
So now I'll have to wait till next week:( .

Steve

Evan
01-01-2010, 12:10 AM
To heck with the EDM. 9000 mfd at 250 volts and you can do underwater spark discharge forming. It's similar to explosive forming on a small scale. That's 280 joules delivered in a millisecond, a peak power of 375 horsepower if it were continuous.