# Electrical Discharge Machine Version 2 (edmv2)



## brino

Hi All!

My first attempt at a home-built Electrical-Discharge Machine was posted here: 
http://www.hobby-machinist.com/threads/my-edm-project.41481/

It obviously did work, but was really just meant as a "proof of concept". 

The short comings: 
1) it had no vertical feed. Whenever the vibrating head had "cut" as deep as it could, I had to adjust the two pieces of angle iron that were clamped together to move the head down. Of course in doing so the entire thing also moved sideways and changed angles. So not only was it a two person job, it took multiple attempts to get the spindle realigned with the first hole. 
2) the entire machine was energized to the discharge voltage 
3) there was no control for angling the head to get into more awkward locations. 

I considered just adding a lead-screw feed mechanism to the original design, but that would mean that I still need to "babysit" the machine and turn a feed handle when it stopped cutting. I would rather have one I could ignore for a while while it worked away. 

I am currently working on EDMv2, it should overcome the problems above by: 
1) using a stepper motor and lead screw arrangement for vertical feed. 
2) having an insulator in the head so that only the chuck and tool are energized 
3) using some extruded aluminum supports with t-slots to give better adjustment 

All the stepper motor designs I found in my initial research (see part one linked above) used large single-purpose driver boards. I did not want to get into building a large circuit either on a bin-board or making my own PCB. Instead, I decided to use a small arduino board and pre-built motor driver board both from ebay. In the arduino code it is easy to instantiate a stepper motor and send up/down step commands.

link to arduino "pro-mini": 
http://www.ebay.ca/itm/130977194597?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

a little USB programming dongle for it:
http://www.ebay.ca/itm/141150349286?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

link to stepper motor driver: 
http://www.ebay.ca/itm/281551893660?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

The machine support arm will be built such that gross positioning is done manually with handles to lock parts in the t-slots. 

When using the machine to remove a broken drill bit or tap only around 1 inch of total vertical feed is needed. Making a hex recess for an Allan key would need even less, maybe only 1/4 or 3/8 inch. Therefore an automatic feed range of only a few inches is required. 

Using a stepper motor with 200 steps per revolution means I can have rotational steps as small as 1.8 deg. 
Combine that with a lead-screw and we're talking about minuscule feed steps.
For a 1/2-13 lead screw one full rotation is 0.077 linear inch, so one motor step is 0.000382 inch!
For a 5/16-18 lead screw one full rotation is 0.056 linear inch, so one motor step is 0.000278 inch!

However, since the lead-screw mechanism is simply a piece of all-thread rod and a nut from the bin, I am under no delusions that the amount of slop would allow such tiny steps. In fact since the feed may be constantly switching direction(see below), backlash will likely be a major limit to minimum step size.

In the code for the arduino I will easily be able to control the minimum step size. It may turn out that I use say 10 stepper motor steps as the minimum step size for my vertical feed. 

For controls I am planning to have one switch that chooses between automatic and manual mode. 

In auto mode the processor will measure the discharge voltage and extend the head one step if the voltage is above a threshold. If the discharge voltage is below the threshold, then the head will be withdrawn one step from the work. The discharge voltage will be reduced thru a resistor divider, limited by some diode/zener circuit, and then finally capacitor filtered before being run into an arduino analog input for sensing. 

In manual mode, another "centre-off" toggle switch will allow me to extend or retract the head for positioning the tool and work. 

In either mode limit switches will set the end of travel in both directions. When these microswitches are operated, further movement in that direction will be disabled. If I have spare digital output pins of the arduino, I might hang an LED near each switch to indicate when it has been tripped. 

All switches will be "debounced" in the arduino code to limit motor chatter due to mechanical contact bounce. 

The power supply for the discharge voltage will initially be the same one I used before. However, having automatic vertical feed will allow me to run better A/B comparisons to try different voltages, discharge capacitors and even reverse polarity. 

For the dielectric fluid I see no reason to move away from the distilled water that worked well in the first installment. I may however, add a filter and recirculating pump as I get further down the road. 

Some parts are already complete: the insulator, a plastic slider block for the spindle, motor mount and lead screw. I have basically just started writing code for the arduino, and have a bunch of assembly and debug ahead.

-brino


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## brino

The stepper motor I am using was from the junk bin, likely removed from a printer, scanner, or photocopier.

It is marked:
Step-Syn stepping motor
type 103-718-0340
DC 4.2V 1.5A
1.8 deg. per step
Sanyo Denki Co.
Made in Japan

The motor originally had the gold-coloured mount you see below.
That mount did not suit my purpose, so I sketched, cut and bent a new one and welded the corners.




more to come......
-brino


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## brino

I decided to re-use the 1/4 inch spindle and drill chuck from my version 1 machine, but since I did not want the entire machine at the discharge voltage, I needed to put an insulator in the spindle.
I found some clear plastic rod kicking around and made this:






-brino


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## JimDawson

brino said:


> In auto mode the processor will measure the discharge voltage and extend the head one step if the voltage is above a threshold. If the discharge voltage is below the threshold, then the head will be withdrawn one step from the work. The discharge voltage will be reduced thru a resistor divider, limited by some diode/zener circuit, and then finally capacitor filtered before being run into an arduino analog input for sensing.



I love it!


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## brino

The lead screw is a 4" piece of 5/16-18 all thread I found in my bolt bin.
The black tube was (I think) from one of those folding camp chairs.

I found some steel bar stock and made a shouldered bushing; the big end will go on the motor shaft with a set-screw, the small end is a tight fit into the tube.
From the same stock I also made a 5/16-18 nut with a plain cylindrical outside. It is also a tight fit into the other end of the tube.

The motor will spin the tube, the tube will drive the nut, extending or retracting the screw.

Both friction fits will get a spot of thread-lock on final assembly.
The hex nut will be used as a jam nut to lock the lead screw to the next part of the spindle.





-brino


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## RJSakowski

brino,  it sounds like an interesting project.  I am looking forward to seeing the completed project and a report on its use.


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## brino

In the first version I made two brass bushings to hold the "spindle"*. Due to the welded frame of that version I ended up with some misalignment between the two bushings causing the spindle to bind if I tightly mounted both bushings. At that time, I simply let one bushing "float" to test the EDM concept. The spindle was guided by the one bushing and the solenoid. (two points enough to define a straight line!)

In V2 I decided that to avoid some misalignment issues I would do two things:

make a single long bearing block with a drilled and reamed hole for the spindle, and
make all the mounts as adjustable as I could.
The spindle was reused from the first version. It is just a 1/4-inch steel rod. It was cut to insert the clear insulator rod to isolate the rest of the machine from the discharge voltage at the head. The flat that was used for the solenoid on V1 is now used for a set screw to lock on a collar. This collar is threaded in the other end for the lead-screw.




I used a block of white plastic for the bearing/slider block. Note that I do not need the insulating plastic here, it was just the material I found that looked suitable. The slider block is mounted on a aluminum angle with slots in two directions for adjustability.

Milling the mount slots:



Here's how the plastic bearing/slider block mounts:







The long slot on the "front" of the bearing block will be used for a small (#4-40) pin to stop the spindle from rotating. 
I have yet to drill and tap that hole in the spindle.

-brino

*-Really the word "spindle" is wrong here as it will not "spin". Instead it will have an oscillatory motion.


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## brino

For the sake of maximum adjustability, I decided to use some aluminum t-slot extrusions that I found at my local used tool store.

These will be used for the EDM motor and head mounting:




So here is everything except the lead-screw test fit on the extrusion:






The lead-screw will go in the gap between the motor and the spindle. It's a good thing that gap is adjustable!

I will try to get some shots with the lead screw installed uploaded soon.....and perhaps some video of the head moving in manual mode.

-brino


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## brino

Sorry for the delay, I got distracted by a couple auto repairs; exhaust on my wife's vehicle and coolant leak on mine. Now after a replacement coupler & clamps and a new radiator I had time to get back to this.
Also, up 'til now the programming was being done at the computer desk in the basement office space. Now with getting ready for higher voltage and a bucket of water I had to make room in the shop.
Currently it's on my welding bench, but I need to move it over to the bench where the shop PC is for program debug. So I need to move my sons project over to the welding bench. I need a bigger shop!

Progress since last update:
-I got the spindle drilled and tapped for the anti-rotation pin that rides in the slot of the white plastic slider block
(it is tapped #4-40 and of course I broke a tap on the first hole....if only I had some kinda machine to deal with that.........)
-I threw together a temporary stand, welded out of an old bed frame (the final frame will be manually adjustable)
-I used another piece of aluminum angle for a temporary switch mount (the top switch is auto/manual, the bottom switch is manual up/down)


So here's the latest:







more to come....

-brino


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## brino

I am currently using a two-output power supply. Each half running at 5V, but I wanted to separate any electrical noise of the motor pulses from the arduino supply.



okay...it is still a bit of a rats nest......the arduino pro mini is plugged into a bin board for testing. That is mounted to a piece of mechano from an earlier robot project. I made up a couple supports that are repositionable within the t-track slots to mount the mechano and the motor driver:














-brino


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## brino

So far my arduino code only supports manual mode, the auto mode is like an "off" setting.
I think the manual mode speed is waaaaay too slow, it might be nice for fine adjustment, but it's way too slow for rough set-up.
Perhaps I need both a slow and fast manual traverse, like a "jog" position for rough setting.
In the code I have control over both the speed and the number of steps to take, so I just need to play with the values some.

Below is a short video clip of manual mode, it is very hard to see any vertical movement, but it should be great for "auto" mode......

It does make some noise, but was nearly drowned out in the video by a plane overhead, the shop door was open.

-brino


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## brino

Hi All!

This post is just to show how I approached this project. It is sorta a "inside my brain" view. 
I am sure everyone has their own approach to both the design and build phases, but I don't see "the process" discussed much. 

Feel free to skip ahead to more interesting posts(coming soon!)
Also, feel free to chip in about how you approach a new design.

I had meant to upload along the way some of the design sketches I made of the various parts.
No deep design, no math (until I got to the electronics).
I did not use any CAD, CAM, g-code, or cnc.
I used paper and pencil first, then manual mill and lathe later.

Much of my research about EDM was done earlier with my first version of the machine (see post #1).
This design was mainly about the new vertical feed mechanism and learning about arduino.

I tend to do sketches of the various ways it _COULD_ go together, kinda a "brainstorm" of random ideas. In this step I may think about particular tricky bits for days, and then have it come to me when I'm driving to work. I might also present a small problem part of it to my wife or my sons to get me out of an idea rut and to see new perspectives.

Often I change the design between the drawings and the making. Once I have it in my head, I can bring the raw materials to the bench and try fitting things to see how they go. Look for interferences, different/better ways, and look for problems (will all adjustment screws be accessible?, will the chosen parts take the forces involved, etc.). Sometimes this spurs new sketches and finding new stock for parts. Sometimes it also means new tools, if I can justify a different way of doing something.

Enough "talk" below are a few of my early sketches. Some will look like the parts above, some were changed along the way with no new sketches made.....

Stay tuned for some real project related updates.

-brino


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## rwm

Very impressive so far!
Check out this use of EDM:
https://gallery.autodesk.com/fusion...an-inconel-718-miniature-gas-turbine-vane-set

R


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## brino

rwm said:


> Check out this use of EDM:



That is very impressive, thanks for sharing the link!!
In a discussion with a friend this week he suggested mine needs an X-Y table for making it into an engraving machine. I told him basically "baby steps!"

-brino


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## brino

okay, progress continues.

I changed the manual feed to be 200 motor steps, that's 1 revolution per "step" of the lead-screw.
Now you can see it move!
This looks good for the manual positioning of the head.

-brino


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## brino

Now some electrical design......

As mentioned I wanted the arduino processor to monitor the discharge voltage and drive the head accordingly; drive down when the voltage was high and retract the head when the voltage was low.

I am reusing my original power supply that looks like this:



Out of the transformer I see ~84 V AC.
After the diode bridge and filter capacitor I see ~114 VDC.

The switches and LED above are still TBD. I want them in the completed unit, but so far have not implemented them.

The LED is meant to be a warning of high voltage present at the head.
The second part of the switch and the resistor marked "Rdisc" would be for discharging the capacitors when the power is turned off. This should reduce the number of shocks I get when fiddling with it.

-brino


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## brino

In order to protect the arduino processor from the high voltage I needed to reduce it for sensing.
My 5V arduino cannot accept a voltage above ~5VDC.

This is what I came up with:



Resistors R1, R2 and R3 provide a voltage divider to scale the voltage down. R1 and R2 are in series and so the values simply add together. They could be one resistor, but since I am dropping significant voltage I thought two discrete parts would give more options for part selection.

D1 is a 5.1V zener diode for protection. Typically, zener diodes are used in voltage regulator/reference circuits. If the
voltage across it goes above 5.1V it "turns on" and conducts. R4 adds some series resistance to limit the current thru the zener. I am using R4=1k-ohm.

The capacitor shown above is meant to stabilize the sense voltage to the processor. I chose 100nF (based on past experience).

D2 and D3 provide more "safety".
D2 conducts if the input voltage gets once Vfwd higher than Vcc.
D3 conducts if the input voltage gets one Vfwd less than GND.
I choose 1n4148 fast switching diodes because I had a drawer full of them. 

-brino


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## brino

Details of the voltage divider resistor selection are below.....







Although today's power supply generates around 114VDC, I decided to design the resistor divider able to handle a higher voltage. I decided on 200VDC as the maximum, that should give me plenty of headroom to play with discharge voltage sources.

I chose R1=R2=100k-ohm as a standard value and worked out R3 to be 5.128k-ohm.
I had a 5.1k-ohm resistor so "good enough".

Based on those values the current thru the resistors is low so 1/4 watt thru-hole resistors were used.

-brino


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## brino

I wrote the arduino code to support these electrical design decisions.

I found that the arduino already supported a great way to debug programs.
The serial port used to program the arduino pro mini could also be used for status updates from the running program. Much like  the venerable "printf" statements in other high-level languages.

So in the automatic mode I had it sense the analog input voltage, "math" it into real values, and print it out. The code was:

    case Auto:

      Asamp = analogRead(PIN_VDISC_SENSE);
      Vsamp = (float) Asamp*5/1023;
      Vdisc = Vsamp/0.0249;

      Serial.begin(9600);      // open the serial port at 9600 bps:
      Serial.print("A0 reads:"); Serial.print(Asamp); Serial.print("\t");
      Serial.print("Pin Voltage="); Serial.print(Vsamp,2); Serial.print("\t");
      Serial.print("Discharge Voltage="); Serial.print(Vdisc); Serial.print("\r\n");

      Serial.end();

      Next_State = Start;
    break;

the screen shot showed:



okay so a little more coding and I can make some sparks.....

-brino


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## rwm

Very interesting. What is the typical voltage/current of a commercial machine and what do you expect from yours? I assume you could get a resistance of 0 at the work head so how do you limit the current? Should you consider having your discharge resistor permanently in the circuit rather than switched? That seems safer. You could use a high resistance value and still discharge the cap pretty quickly.
Robert


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## brino

@rwm

Thanks for pointing out something I left out of my recent posts.

Here I had not mentioned the series resistor I used.
In the "version one" thread I mentioned the 10-ohm 50 watt resistor that is in series.
Like this:




This is also a great opportunity to point out:

Do this only at your own risk!
I am (and this site! are) not responsible if you hurt yourself, someone else or any property by doing this.
Electricity and fluids can be a bad combination.
This is from the internet -do your own research, understand what your doing, etc. etc.
Note: Since my workshop is a two-car garage attached to my house, I chose to use a non-flammable dielectric fluid.  Distilled water is my dielectric rather than the typical kerosene, varsol, etc.
This build should also allow me to experiment with various fluids for wetting, cooling, etc

With all that said, I should actually be able to try this machine in auto mode this weekend.

-brino

!!!!EDIT!!!!!
Please see post #37 of this thread for an updated drawing!
Above I forgot the discharge or spark capacitor!


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## rwm

OK. That makes sense. So at max it pulls about 14 Amps? Must be a big transformer. Can't wait to see it run! I have some questions:
I see you have a constant power supply. Does the EDM power need to cycle on and off to work? Does it make a spark when operating? Is this process kind of like super-electrolysis? Or is there some other destructive mechanism as work? 
Robert


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## brino

Today was full of software frustration!!

After having the USB-serial port work okay up 'til know I ran into a blue screen of death (BSOD) whenever I let the arduino monitor window run for very long. This put a big wrinkle into my debug plans.

The USB-to-serial converter I was using (link above somewhere) uses a "Prolific" device so I had installed version 1.12 of the prolific driver, initially it worked okay....but that was only for short periods. When I started seeing the repeated BSODs I went searching for a solution and found people recommending an older version 1.10 driver:
http://superuser.com/questions/680737/bluescreen-when-putty-reads-from-serial-port

I could not find the older driver, so I tried a newer one version 1.14. That one showed BSODs as well. CRAP!

I never did find an old version of the Prolific driver online, but luckily stumbled across a copy I used years ago.
I found version 1.1.0 from 2009 (the one I expect they meant in the link above).
I installed it and I no longer see the BSODs. I have attached it here.

However, now after a short time of using the monitor window, Win7 sees the string of data on the serial port and assumes it's some kind of mouse and installs a driver for a "Microsoft Serial Ballpoint Mouse". This seems to disable my real mouse and really screw with the system. Sigh.

After searching, I tried a number of things from here:
http://answers.microsoft.com/en-us/...e/e0e03b9b-e9ae-4645-8b3c-5754f06ec3b5?auth=1

So far the only work-around is to let it start the "Ballpoint" install and then in Win7 Device Manager disable that device.

What a pain!

However, I did eventually have some progress. I will try to post it later.....

-brino


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## brino

EDM_V2 is alive!

I had picked up a cheap, used drill-press vise for this project. I drilled and tapped a hole for a stainless bolt to connect the positive lead to the vise.
So far I am just re-using the original electrode from version 1, it is just a piece of 1/4" copper tube.
I had a 1/4" thick, by 1" wide by 3" long piece of mild steel as my first test piece.
I started with clean distilled water as the dielectric fluid.

Here are a few short video clips showing the machine in action.
You can hear the stepper motor, it is sort of a tapping noise.

movies1-3 are just different views of it running. 
movie4 is a close-up
movie 5 is a view of the "spindle", I added some red and black sharpie lines so you can tell which way it's moving.

Here the machine is running in auto mode. One step in my code is equal to 10 stepper motor steps. I am using a threshold voltage of 50V.....if the discharge voltage is above 50V the arduino drives the head down, if it is below 50V the head is driven up.

-brino


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## brino

Here's the dimple left after a few hours of running

Just out of the tank:




and after wire brushing:



I measured it at about 50 thou. deep.

-brino

I have added thumbnail views below.


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## brino

It occurred to me that this machine was not working very fast.

I have a finite-state machine running on the arduino that samples the three switch, debounces them to eliminate mechanical noise, eventually gets to the "Auto" state, measures the discharge voltage, outputs some debug info on the serial port (state transitions and voltage readings) and then finally drives the head accordingly.

I decided to make a new arduino sketch with just the bare minimum code.
It simply measures the voltage and drives the head; no switch reads, no debug info, no other state changes.
I also made the step size equal to one motor step.

That sure changed things......see movie6 below.

-brino


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## brino

I still have a number of system improvements to make:

I need to make my temporary machine stand much more sturdy. When the motor is moving fast it sets up a little wobble in the machine. I expected this, I have seen twisting in the upright spine. Currently I believe the cut is wide and removing more metal than necessary. Perhaps I need to bite the bullet and start construction of the final, adjustable stand.

I need some kind of filter and pump system. I am amazed at the amount of reddish, magnetic debris left in the water. I believe it would also help the cutting progress to wash this debris from the cutting area. Currently I am flushing it using a syringe every once in a while.

In the code I already have ideas about:

re-writing the state machine such that the "auto" state is a single tight loop.
the switch debounce time could likely be shortened significantly 

I still want to add limit switches to disable the motor at end of stroke.

I still have many variables to look at:

I can adjust the number of motor steps per machine step taken in auto mode
I can adjust the motor speed (separately)

I can adjust the voltage threshold
I can play with various high-voltage power supply options, including adding more discharge capacitance.

That's all for tonight.

-brino


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## John Hasler

Use interrupts to handle the switches.


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## brino

@rwm , sorry Robert I missed your questions......'til now......



rwm said:


> Does the EDM power need to cycle on and off to work?


The EDM high-voltage supply does not need to cycle on/off. Basically when the electrode gets close enough to the work that the arc jumps the discharge capacitor dumps it's entire load and erodes a little bit off the work piece. There is a high-wattage series that drops the entire voltage if the electrode contacts the work piece. Either way, the power supply will need some time to recover the output voltage for the next spark.



rwm said:


> Does it make a spark when operating?


Yes! These things are also called "spark erosion machines". All the action takes place under a dielectric fluid....basically an insulating fluid but with a polar molecule. Many systems use parafin. I am using distilled water, since parafin is flammable. (and my workshop is attached to my house!)



rwm said:


> Is this process kind of like super-electrolysis? Or is there some other destructive mechanism as work?


It is really just the jump of electrons from the negatively charged electrode to the positively charged work piece that erodes off the "high-spot", then the next high-spot, etc.

-brino


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## brino

John Hasler said:


> Use interrupts to handle the switches.



Hi John,
I believe from other posts that you have done many microcontroller projects.
But your comment confuses me.

An interrupt is for something that needs immediate service.
I WANT to debounce the switches as mechanical contacts are notoriously "noisy", there could be dozens of contact bounce events per switch operation.....that would drive an interrupt handler crazy!

-brino


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## John Hasler

You won't get an event on a limit swtich unless you've hit a limit: that's something that needs immediate service.    Interrupts will be disabled in the ISR.  You can handle the debouncing there or disable interrupts globally and set a volatile variable to tell the main loop it has a limit switch event to deal with.  Better, though, would be to use optical interrupters (or SR FFs and SPDT switches) and eliminate bounce.

Use a timer interrupt to poll the manual switch every 100ms.  Only run the debounce code if it shows a change of state.


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## brino

@John Hasler ....ahhhh I see, your comment was meant for the limit switches. Yes they could be interrupts and not debounced.
and yes, optical sensors would be great, I had not thought of that...probably because I had already pictured mounts for some microswitches I have.
But I may rethink that now.......
One big plus for me using the arduino was to not need external flip-flops for switch debounce (......and the easy stepper interface, of course).
Thanks for your comments.

In my head I was thinking about the auto/manual switch and the up/down switch that only operates in manual mode. For those switches I originally had the code checking the auto/manual state every loop (with debounce) before entering the "Auto" state. I already proved that is a waste of time. I have plans to rewrite the state machine to stay in the "Auto" state until a single "Manual" switch event is seen, then go out of auto and debounce it. That way there is no switch debounce in the main "Auto" state, only on a change of state.

What I have found useful when debugging is pulling out the power plug for the high voltage supply -that causes the auto mode to lift the head, then I can squirt some water in to clean-out the debris and plug it back in to continue the "cut". This helps because I do not have to touch the switches mounted on the head and induce more motion in that wimpy (temporary!) column.

So many improvements are possible.....so little free time!

-brino


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## brino

....anyone have ideas for a small pump and/or filter system for the water?

For the pump:

it could be 5VDC, 12VDC or even 120VAC
I would prefer to have an adjustable flow rate

unfortunately I do not have an idea of range for flow rates
I could seeing using those adjustable, segmented/articulated plastic coolant lines for aim-ability.

For the filter, 

I suppose a small aquarium filter could work?!?
would automotive fuel or oil filters work okay with water?
I could also see using some magnets in the system to grab the conductive debris
Thanks for any ideas!

-brino


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## JimDawson

brino said:


> For the filter,
> 
> I suppose a small aquarium filter could work?!?
> would automotive fuel or oil filters work okay with water?
> I could also see using some magnets in the system to grab the conductive debris



Maybe an inline water filter from your local big box store?

I don't think a fuel or oil filter would well, I think they're designed to reject water.

Magnets are good, maybe in the filter canister?

Princess Auto has a number of small submersible pumps, some have adjustable flow.
http://www.princessauto.com/en/detail/300-gph-statuary-fountain-pump/A-p8317513e


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## brino

JimDawson said:


> Maybe an inline water filter from your local big box store?



I dunno using a water filter to filter water?!?!?
Jim you come up with some crazy ideas sometimes......

-brino


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## rwm

I have a little giant pump and it has run for a long time. Amazon has some pumps for less than $15. I love the magnetic filtration idea.
R


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## brino

It has been bothering me for a couple days that the machine just did not have the ooomph that the previous one did.
Yeah there were some sparks and some metal removal, but not the aggressive rate as before....and no aggressive sound.
One of the books described it as a "bacon frying" sound with lotsa little pops.
Also when I had tried to get some still photos of the sparks I tried several times and didn't get any.

I am using the exact same high-voltage supply what's up? 

Then I reread my post #27 above about one option being to play with the discharge(or spark) capacitor......hhhhmmmmm.
The spark capacitor.....I FORGOT THE SPARK CAPACITOR!!!!  

I show it in the version one thread here: http://www.hobby-machinist.com/threads/my-edm-project.41481/#post-356086
But I forgot to install it here and left it out of the drawing in post #21 above.
It should be "downstream" of the big series resistor.

Here is an updated version:


(I will also go back and add a note in that post to refer to this one.)
(clickable, resizable thumbnail version below)

I am currently using a 680uF, 200V capacitor for the the discharge(or spark) capacitor.
Most of the versions I saw during my research had a bank of switches to select different caps and add them in parallel.

Now I cannot get pictures because there is so many black debris plumes being ejected from the hole!
Right now it looks like Coke.

-brino


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## brino

Based on the location of the anti-rotation pin in the slot, adding the missing capacitor has  meant more progress in the last hour than the previous several hours of running!

It makes sense too. Without the spark cap right across the work/electrode gap it was the energy stored in the capacitor beside the diode bridge doing the work.......and it had to work thru that big 10-ohm 50-Watt series resistor.

Now there is nothing in the way of dumping a whack of energy when it sparks.

Leave it with me and I'll figure it out eventually!

-brino


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## brino

It's been a little while since I updated this thread.
The project has been a little slow......but NOT stopped.

First I stiffened up the mount. The problem was this temporary mount was put together to be well, temporary. So I added a couple diagonal braces of 1" angle iron. Sorry no pictures. Now the head doesn't wiggle in an arc around the upright. (Long term I want to use a couple of aluminum extrusions I picked up. I just need to find ways to have them quickly adjustable ad lockable.)

With that done, I fired up the machine to finish the test hole in that scrap of 1/4" thick steel bar.

In post #27 above, I showed how it looked about 0.050 of the way thru.

Here it is a little deeper:





and finally a thru hole:
(the little nugget was the centre of the hole cut out by my hollow 1/4" copper tube electrode)






and from the back the hole looks cleaner since the head wasn't vibrating around (I fixed that before cutting all the way thru):



Once I figured out that spark capacitor blunder, it went much quicker.

-brino


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## brino

Second I worked on a filter system.

During operation, the water in my tank changed from clear to this:



I have NOT figured out a great way to use magnets in the filter system.

As proof of concept I tried one rare-earth magnet in a zip-lock bag just thrown into the tank. I'm calling it a "bagnet".
Here's one bagnet in the bin:



Here's what it picked up:



and then I wiped the bagnet onto a tissue:



Sure it got some out, but how do I use it in a "continuous flow" manner. Still need some thought here.

I tried a simple coffee filter in a funnel and it did a great job.
Look at the muck it pulled out:



and the water looked clear.

Next I bought a water filter with replaceable cartridges, like this:



I had originally picked up one of the spare filters and a handful of ABS parts to make my own, but at the checkout realized that the parts cost as much as the filter off the shelf (about $31 CAD). Back I went. Plus this filter has a see-thru chamber for the filter.

I bought the one with a 5 micron filter cartridge and it pulled almost nothing out of the dirty water.
When I swapped it to the 1 micron cartridge the filtered water looked clear.

Oh, and I am using a pump like this:
https://www.amazon.com/500-Universa...402&sr=8-15&keywords=swimming+pool+cover+pump

That's it for tonight. I gotta get up early for car pool with my son.

-brino


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## brino

okay, it's waaaaay past time that I updated this thread.

The pump and filtration system is working great (even if I couldn't find a way to incorporate magnets!).
After a number of test cuts I could see the water flow slowing down, so I took the filter to the laundry sink and ran water thru backwards and it immediately restored the good flow.

What have I cut?

After adding a diagonal brace to stop the EDM head from swinging around I cut a new thru hole in that same 1/4" thick scrap steel bar using the same copper tube electrode.
I must not have dried it off after removal from the tank....it got kinda rusty.
However, it showed: i) the hole was much more round as the head did not bounce around, ii) the new nugget is cylindrical (the first one was a cone from the head swing).









still more to come.......some spoilers........I tried a brass tube instead of a copper tube electrode, I have tried reverse polarity, and I tried a pencil "lead" electrode.......and more

-brino


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## brino

......ohh and here is the copper tube electrode after the cut above......






-brino


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## brino

I also tested a 5/32" brass tube electrode.
I switched back to utility knife blades as my target metal, mine measure 0.025" thick.

The holes I cut are marked with red circles in the photos below.
(click for larger picture!)

With electrode negative it took 6 minutes to cut a thru hole:





With electrode positive it 20 minutes to cut thru the blade:




Interestingly, the electrode positive threw up a burr around the hole but *on the top side*!

Both left a slight ring visible around the hole, but it does not show up in the photos above.
(if I was cutting with oxy-acetylene I'd call it a "heat affected zone", here I dunno.......)

Here's how the electrode looked when finished:





-brino


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## brino

....after seeing that last post again I thought I could do better (brighter) pictures

Here's the electrode negative:




and the electrode positive:




-brino


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## brino

I had read in one of the references about using graphite electrodes.

Well I do NOT have any of those, but I did find some cheap pencil "lead" refills.
Made of 100% unknownium!
What have I got to lose by trying it?

The green circle shows an attempt with electrode negative.
The red circle shows the electrode positive attempt.




I gave each attempt over 7 minutes, and basically used up the entire electrode in that time.
It did almost nothing except leave a bunch of grey floating crap in the water and make a smell like some brushes on an old motor I remember.

Here's the pencil lead refills I tried:



Full images attached below.

-brino


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## dieselshadow

This is a pretty cool science experiment. I'm enjoying this thread. Thanks Brino.


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## brino

A little info on dielectric fluids..... @mephits asked some questions here:
http://www.hobby-machinist.com/threads/goofs-blunders-you-should-avoid.49036/page-11#post-443219

In order to keep that thread on topic, I'll tell what I know here.......



mephits said:


> Interesting. So the EDM doesn't push enough wattage to crack the water into free hydrogen and oxygen? That would create a whole new set of flammability issues!



I suspect there is some electrolysis going on, I do see bubble formation when the high voltage supply is turned on.
However, I believe there is so little H2 and O2 produced that is is rapidly diluted in the shop air.
I suppose I could try catching some in an inverted test tube and running a few tests.



mephits said:


> So as a question to all and sundry who actually have EDMs. What about standard cutting fluids like emulsified synthetics makes them less desirable here? Conductivity issues? Cost?



Dielectric strength is the biggest concern, ideally you want the electrode close to the work before the break-down and the spark occurs.
Other considerations are flammability, performance, health affects of the fluid (both vapour and liquid), and of course cost.

In my research into home shop EDM, kerosene is used most of the time.

In "Build an EDM" by Robert Langlois, he says he started with varsol, then kerosene but was concerned with flammability of both. He also relates a story of hand wounds taking longer to heal after exposure to a commercial dielectric oil. He tried water, but suggests it should only be distilled water and that it should not be recycled (like I'm doing!). He also suggest plain water is not "wet" enough due to the surface tension. He ends the chapter with "_I now use an ethylene glycol, soluble oil and water mix of 5:5:90. This works but my research on this continues...._"

In the EDM How-To book by Ben Fleming he also mentions kerosene and a commercial fluid: Rustlick EDM-30.

-brino


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## brino

I had promised some pictures of ball bearings that I attacked with EDM.
Here's the first installment.

I tried to hold this ball in the recess of the vise jaws where the bolt head is for mounting the jaws.
I thought it was tight enough, but the ball spun leaving some strange craters.





-brino


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## Subwayrocket

Someone else mentioned little giant , i've used a Little Giant 500203 pump for a few things. It's a good little pump , won't do higher pressure thru long thin lines but it works well. If u need something a little beefier, I've got over a hundred hours on a Shurflo 8000-912-288 on demand pump in a 50psi application thru long thin hose , my TIG cooler . I've also got the same pump (12V version) running about 10 years as the "on demand" water supply for my off grid cabin .  It's a pretty cool project you've got there Brino , you should shoot some video of it in action !


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## brino

I tried another ball bearing.
This is an old 1/2" bearing from the bin.

Just as before it was held in the old drill press vise. The fluid used is distilled water.
The electrode was a bare 14 AWG copper wire, it had to be replaced a couple times due to wear.
That's why the entrance hole is larger than the exit hole, either the work moved, the head still has some jiggle, or one of the electrodes was bent.
This burn took 3-1/2 hours. 
I really need to get limit switches mounted so I do not have to babysit it.

Here's a shot of the bearing and used electrodes:



The entrance hole:




and the exit hole:




I am a little disappointed at the (lack of) speed.

But I am not done I want to try:
-copper-clad, carbon-core welding electrodes,
-different spark power supplies,
-different spark capacitors,
-different arduino software with different motor step sizes,
-whatever else I can tweak

-brino


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## f350ca

very cool project brino. Would the tungsten for tig welding work as an electrode?

Greg


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## brino

f350ca said:


> Would the tungsten for tig welding work as an electrode?



You know what? I thought of that one night in passing, but did not write it down.
I'll add it to the list.

Thanks Greg!

-brino


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## eugene13

Very impressive project.


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## brino

Hi All,

I got some time to try some other electrode types.

Theory says to use graphite electrodes. Not having any of those on hand, and continuing in the experimental ways of this project I tried carbon-cored, copper-clad electrodes. I have these on hand as my first welder was a home-made unit using an old electric space heater I got at a yard sale. That unit was based on one my Dad made, and I believe his was roughly modeled after an old popular mechanics article where they removed the carbon rods from alkaline D-cells. My 120V welder basically has a high-current heater element in series with an insulating handle that allows you to bring two of these electrodes together (the heater element would glow) then separate them and a beautiful purple arc would form between them. It was mostly used to braze, but could get hot enough to weld thin steel parts.

Here's the package from the last set of these electrodes I bought along with some random electrodes:



Here are four holes and the electrode used:



It took only 6 minutes to puncture the utility knife blade.
It took about 8 minutes to produce a clean thru-hole............This surprised me!

The previous tests with hollow copper and brass tube electrodes removed (burned, disintegrated, eroded?) only a thin ring of material.
This solid electrode had to "process" a much larger volume of material so I expected it to take longer.
Maybe that's why it is preferred.

Full sized pictures below.

-brino


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## brino

....also, as Greg (@f350ca) suggested I tried a tungsten TIG electrode.

It made a clean hole thru the utility knife blade in 6 minutes (see the orange circle):



I need to measure the consumption rate of the electrodes to make this a more scientific dissertation, but I want to keep this fun, not work.....

Once again full sized images are below.

Be well!
-brino


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## brino

It has been a while since my last update, but recently I had to fire the machine up for more than just testing.
I snapped off a 6-32 tap in a workpiece!

The project is a custom drill extension for a friend. He's making wooden salt shakers and pepper mills. For deep drilling of the bodies he needs to run his current forstner bits deeper than the shanks allow. Some off the shelf drill bit extenders are available, but all the ones we saw had heads bigger than the 1" minimum size hole he wanted.

I came up with this:



The idea behind the double-ended split clamp is to allow use of various shank lengths, or even to allow stepping the length up but retain minimum tool stick out at each step.

It's a 4-1/2" long piece of 7/8" dia. steel bar drill 2" deep at each end for a 3/8" shank. (The hole does not go thru.) The side is slit along the entire length, but I still need to slit half way thru the bar 1-1/2" from each end to provide a split clamp. I was going to do the last slits after tapping the holes for four 6-32 socket-head cap screws.

Of course I broke a tap.......Bugger!

the tap:




the plugged hole:





My EDM machine is not exactly finished.....I still need to incorporate an arduino power supply and a stepper motor power supply (still using a bench supply for both), I want to try different spark power supplies, I need to package it all up, I'd like to make a more adjustable head, etc.

I tried to just pick and punch the broken tap tip out, but it would have none of it......so EDM it is.

I used a piece of 14AWG house wire as the electrode and lined it up in the plugged hole:



After only a few minutes I could tell by the rhythm of the machine that it was thru!




Then just a small punch got out the rest of the debris from the broken tap. I followed that with the tap drill to be sure it was all out.












It worked!
I had to buy a new tap and have not had a chance to try again. Hopefully the hole wall is still "soft" and normal.

I'll try to post back with a video of it working too.

-brino


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## ch2co

Come on, you broke that tap on purpose because you were tired of burning holed in knife blades.

Seriously folks, this is really cool, congrats! The beast is alive.


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## brino

ch2co said:


> Come on, you broke that tap on purpose



Ha, nope! I would *never *break a tool intentionally.
....but I have had enough accidents that I knew an EDM would be worth it!

-brino


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## Turnaround

Back in the day, our automobile oriented machine shop used hex shaped carbon rods, submerged in a jury rigged puddle of kerosene to erode hex shaped holes through whatever was broken off inside some threaded holes of very expensive parts. Once the hex hole was developed, an Allen wrench would unwind the stub. Problem was, someone "borrowed" our EDM for an emergency job, and that was the last we saw of that beloved EDM.


Sent from my iPhone using Tapatalk


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## rwm

Nice work! I bought some nitric acid for this purpose but it would not have worked given the steel workpiece. 
Robert


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## brino

Turnaround said:


> our automobile oriented machine shop used hex shaped carbon rods, submerged in a jury rigged puddle of kerosene to erode hex shaped holes through whatever was broken off inside some threaded holes of very expensive parts. Once the hex hole was developed, an Allen wrench would unwind the stub.



Hi Turnaround,
How long did the machine take to make a hex socket deep enough for an allen wrench? we're talking hours, right?
Oh and how big of hex?

Thanks!
-brino


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## Turnaround

brino said:


> Hi Turnaround,
> How long did the machine take to make a hex socket deep enough for an allen wrench? we're talking hours, right?
> Oh and how big of hex?
> 
> Thanks!
> -brino



Our Store bought EDM had a little "drill press" type arrangement, that allowed the operator to turn a crank and push the shaped carbon down towards the hole. Your senses told you how much and when to feed the carbon to erode a hole in a broken tap or drill bit. It took five to ten minutes to erode through something like the remnants of a 3/8" - 16 tap. The dam and kerosene was a necessary part of the equation.


Sent from my iPhone using Tapatalk


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## Mark_f

Brino,

I am finding this thread fascinating as I am waiting to finish and try the EDM machine that I built earlier this year.


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## brino

Hi Mark,

I am trying to find the time to do a bunch of experiments with different power supplies. I want to try a beefier (higher-current) supply with a bank of capacitors to switch in/out to adjust things.

I'd also like to try a pulsed power supply, so I am very interested in your build too. 

-brino


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## Mark_f

Mine has a 2000 mfd capacitor on the output and switches in power resistors to regulate the current. The output is about 80 VDC and around 10 Amps.


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## cs900

wow, what a great project. Subscribing for future updates!


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## brino

Okay, it's hard to believe that I started this thread about four years ago.......and the V2 EDM machine is still NOT DONE!!!!
I have NOT built or bought a dedicated power supply for it
I have NOT hardwired the circuit around the arduino controller
I have NOT played with the high-voltage supplies
I have NOT added a bank of spark capacitors that are easily switch in/out
I have NOT put all the above in a case

I did just use it though....and the sketch here in post #37 came in real handy when setting it back up.
Once I literally blew the dust off the arduino circuit in the "bin board" it worked great!

I picked up these partially built lathe tool holders at the local used tool place for $10.



The one with the red X's already has the dovetail cut too big for my tool post.
The nearest one has the tap broken off in the right-most hole.....
My guess is that's when the builder gave up and sold all his tools! 
(we all know the feeling, right?)

I thought I'd let the EDM work on it while I did something else....(I still don't have end-of-stroke limit switches installed either)

Here it is being lined up in the vise:



...and a short video clip of it running:
View attachment short_clip.mp4


















After a few hours and one electrode change, the broken tap was just about cut thru and I picked out the bits with tweezers.
The cylinder in the middle is the centre of the tap, and around it are the tap flutes:




You can see how the brass tube electrode got eroded too and became form-fit to the tap flutes.....







It did work, but I think the copper electrodes lasted longer and cut faster.
Too bad as I now have a small bundle; brass was recommended in one of the books, and I had been picking up pieces when I saw it.
Oh well. It will get used somewhere.

Here's how the threaded hole turned out (I have not yet run a wire brush and tap thru it...):



At this rate I should have the project complete sometime within the next 30 years or so.....

-brino


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## francist

Hah, I was just thinking about this yesterday and whether you’d done any more on it! John Saunders of NYC-CNC has a fairly recent (last week or so) video exclusively on EDM. I think the place was Spectre EDM (?)

I’m not really up on the process but it was interesting nonetheless. Might want to check it out on YouTube.

-frank


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## savarin

Awesome project Brino, I know where your coming from with the 30 years, just look how long my bino is taking.

I havnt been able to touch it since well before christmas.
The pair of us need a gee up.


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## brino

@savarin 
Charles, you helped get me started on EDM.
What's the best electrode that you've used?
Thanks!
-brino


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## petcnc

brino said:


> At this rate I should have the project complete sometime within the next 30 years or so.....


Well, I can wait to see it finished as I will build mine then!!


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## brino

petcnc said:


> Well, I can wait to see it finished as I will build mine then!!



Petros, You might just lap me on this build!
-brino


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## savarin

Hi Brino, I've only used copper and brass but I think the copper works better.
I found the small copper electrode I used to burn out all those 4mm taps used to burn itself to a sharp point but still did the job.


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## rwm

I broke a tap off yesterday. I immediately thought of this thread as I took the part out of the lathe! I almost researched postage to Ontario, but I got creative with a carbide end mill instead. Cost of the end mill was probably about the same as shipping!
Robert


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## JohnnyTK

Found this after watching 



 looks interesting you can get the drill head for $63. USD on AlliExpress. The more and more I look at this, it might be my next rabbit hole.


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## GunsOfNavarone

The drilling/straight hole application is no doubt awesome, what about cutting across (almost like a CNC plasma table)..Is that possible with this sort of setup?


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## savarin

Electrical discharge machining - Wikipedia
					






					en.wikipedia.org


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## brino

GunsOfNavarone said:


> The drilling/straight hole application is no doubt awesome, what about cutting across (almost like a CNC plasma table)..Is that possible with this sort of setup?




I have never used one, or even seen one live, but I  think you want something called "wire-EDM".
It's like an EDM bandsaw, but way faster than mine, and typically CNC-type control.

I'll find some links.
-brino


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## brino

Here's a 2 minute video on basics of wire-EDM:


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## GunsOfNavarone

So, long story short, it's a different machine? Seems very similar, could it be a fairly straight forward conversion? Or is the power needs vastly different?


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## brino

Yes, in industry it is a different machine.
Exactly why, or if there are any "combination" machines is beyond me.

-brino


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## middle.road

Rabbit Hole *WARNING* !
OK, now I'm remembering a misc. box of 'junque' from an auction 5+ years ago with some electrodes in it. 
The question is can I find it? or better yet do I still have it?
(Too many boxes of junque around here...)


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## ch2co

DAN
It's right there in that closet in the drawer right behind the box that's  right behind that other box but underneath that sheet of copper that you were looking for last year.


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## Tim9

kind of old thread... but -
Just a thought. Would silicone bronze Tig filler work. You know, that 1/16 inch bronze filler. I only scanned throughout this so I forgot the thickness of the lead pencils mentioned. And not sure if the silicone is a problem. Anyway, just thought I’d throw that out there.
Broken tap removers are really cool. I bought that book and read up and was planning on a build.... but life got in the way.
Anyway, cool stuff Brino.


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## Hawkeye

Yesterday, I got pulled into a rabbit hole about a shop-made wire EDM. Extremely cool, but by the end of the day I realized it would cost more than I can commit to it right now. (Check out videos by BaxEDM; follow at your own risk.) I decided to stick to a plunge-type unit for now. I have a doorbell EDM, but I feel the need for something more impressive. Plus, I'm between rabbit holes ... I mean projects ... right now.

This morning, I found this thread. I'm amazed at how close all of your thinking is to my own - right down to sizing the LED resistors. I'm planning on reworking a microwave transformer for my power supply. I figured I could fit 33 turns of the wire I want to use into the secondary slots. Based on the open-circuit voltage my spot welder puts out,the open-circuit voltage with 33 turns will be (wait for it) 84 volts. [Edit: Just wound the secondary - only got 30 VAC out of it. Guess I'll be shopping for a roll of wire.]

Has anyone tried tungsten electrodes for small diameter holes? Just wondering.


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## brino

Hawkeye said:


> Yesterday, I got pulled into a rabbit hole about a shop-made wire EDM. Extremely cool, but by the end of the day I realized it would cost more than I can commit to it right now. (Check out videos by BaxEDM; follow at your own risk.) I decided to stick to a plunge-type unit for now. I have a doorbell EDM, but I feel the need for something more impressive. Plus, I'm between rabbit holes ... I mean projects ... right now.


Mike, I hope you share your build too!
I figure it we could save each-other some time with lessons learned along the way.



Hawkeye said:


> Has anyone tried tungsten electrodes for small diameter holes? Just wondering.



I did in this very thread.
I'll see if I can find a link to it......

-brino

EDIT:
@f350ca asked about TIG electrodes here:
https://www.hobby-machinist.com/thr...rge-machine-version-2-edmv2.49689/post-447011

...and I tried them and posted results here:
https://www.hobby-machinist.com/thr...rge-machine-version-2-edmv2.49689/post-449538


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## Hawkeye

Thanks, Brino. I had skipped ahead yesterday to see how the story ended. I went back today and found your mention of tungsten.

I have a spare drill chuck, which I will use to hold some electrodes, but I'm also planning to use some plastic or brass "endmill holders" so that I can send some dielectric through the tubular electrodes, when I use them. Just to improve particle removal. So many little side details we can get into as we go along. First, I need to rewire the power supply transformer. It's getting hard to find copper wire these days. Most of what Amazon and eBay sell now are CCA (Copper Clad Aluminum). Guaranteed not to last very long.


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## markba633csi

Hi Brino: Back in the 70s I built an EDM from an article in either Popular Science or Popular Mechanics- simple, ran off the mains.  Voltage doubler, a couple caps and a couple incandescent bulbs for ballast instead of big resistors. Hand feed, with a crank.  Kerosene, never had a fire.  I remember graphite made the best tool, from carbon zinc batteries.  Lasted the longest. I think pencil lead isn't conductive enough, or something.  I also remember the kerosene would get black very quickly,  never did build a filter system but it needed one
Great job on yours! 
-Mark


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