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[4]

Building a Pulse EDM machine

[3]
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mark_f

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#1
I am back and starting a new project. I am building an EDM machine. I often thought it would be nice to have a version of an Electrical Discharge machine to burn out a broken tap or drill.I did a little research and found there are many "spark eroders" and EDM machines out there that are home built. My research showed me that a decent EDM machine may be worth the investment. Back in the early 80's, I set up and ran a large industrial EDM machine and know what they are capable of doing. In my research, I ran across a couple of books by Ben Fleming on building an EDM. He also has a yahoo group dedicated to building and using an EDM.
While his simpler machine would make an excellent "tap burner" and be a lot less expensive to build, I have opted to build the pulse machine as it is higher quality and more versatile.
So ....... get your popcorn and hang on.

[RSVP=55621]Click here to RSVP[/RSVP]
 

MozamPete

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#2
Welcome back - will be following.
 

mark_f

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#3
The first thing was to get a design. Ben wrote a very good book covering the building of his version of an EDM machine. I ordered the book for around $30. I was impressed when it came. It is not a pamphlet.... it is a real high quality book. He also offers a printed circuit board as an option to make construction easier.

IMG_0473.JPG

I opted to by the printed circuit board at an additional cost of about $55.
IMG_0475.JPG
This board came with a 9 pages of instructions including a complete parts list and very good instructions for building this control board. Also the list contains a source and all part numbers to order.
IMG_0474.JPG
The board instructions are very concise and step by step with instructions for testing. Ben has done an excellent job on this and has made it so almost anyone can build this.
I went online and ordered all the components to build the pulse control. The cost was about $290. With the electronics and transformers the cost to build this machine will be about $450. I feel this is reasonable considering a comparable machine commercially would cost several thousand dollars. I have materials on hand in in my scrap box to build the actual machine.
The electronics parts are supposed to arrive tomorrow.
 

savarin

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#5
Oh yeah, watching this one.
 

mark_f

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#6
This ball bearing drawer slide wil be cut down to 10 to 12 inches long. In the plans and most builds I have seen, this was cut fairly short and uses 4 of the ball bearings on each side. I intend to leave al 24 balls on each side. I picked through the slides at the store until I found one that was tight and smooth. By leaving it longer, I feel it will have better stability.
IMG_0477.JPG
The drawer slide will hold the ram assembly and let the servo motor move it as needed to keep the spark gap constant.
 

mark_f

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#7
As I scrounge for needed parts to keep from buying everything, a friend gave me a new aquarium pump to use for a dielectric pump. It has a capacity of 400 gal / hour. This should be plenty strong enough for the purpose. It is a magnetic drive so there are no seals to leak and it is submersible should I choose to go that route.
IMG_0476.JPG
It has 1/2" inlet and outlet.
 

ch2co

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#8
YES Welcome Back. Looks like a fun project. At the present time, I don't need one, but I'm sure as I follow your progress, I will absolutely
NEED to make one.
;)
CHuck the grumpy old guy
 

FLguy

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#9
I've wanted one for some time and knowing how you are soooo good at what you build I'll be watching and trying to build one from your findings.Guess this is the push I've needed. Yes Welcome back !!
 

mark_f

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Although the machine can be built in a less expensive version, I have opted to build the more expensive version. If you only want a tap burner, it would suffice to build Ben Fleming's RC version machine. However, I always want to go for better. This pulse machine will be much more versatile and has the ability to to more intricate work with better finishes.
I used the parts list from Ben and ordered ALL the control parts new from the suggested supplier. Scrounging old electronics devices such as televisions and computers, I probably could save some money but this was mush easier and I have all the correct and new parts. The electronics order came to $317 including shipping. I also ordered the three transformers at a cost of $157 including shipping.
electronics parts.JPG
This pile of bags is the close to 100 components to stuff the PC bord and build the complete control for the EDM machine.

Following the book, I listed all the controls for the machine and made a layout for the front panel.
EDM FRONT PANEL.jpg
This is a drawing of the panel with switch and control knob locations. Yhe two large boxes in the center represent the meters for volts and amps.

The following drawing is the one that will go to the engraver.
EDM FRONT PANEL5.jpg
The panel will be lasered onto an aluminum panel that is anodized black and the lines, numbers, and letters will be silver. This fancy panel comes at a price of $100 but will make a very professional looking machine. It will look "store bought" :grin:. I expect the final price of this machine to be around $600. I saved a lot of money scrounging for the materials to build the actual machine part. $475 of the cost is buying all the electronics new, which I felt was worth the time saved and the ease of building, but a good scrounger can cut this cost in half. While this sounds expensive, I looked at New comparable machines and they run close to $10,000.
 

mark_f

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#11
The recommended gear motor For the servo is made by Pittman. It is a 19.1 volt DC gearmotor with a 96:1 ratio. I will be running it on 12V DC. This motor runs between $100 and $200, depending on the supplier. I found one on eBay fr $22.
FullSizeRender.jpg This gearmotor assembly is about 1 1/2" diameter and about 3" long.
 

mark_f

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#12
I went to the local surplus supplier today and got some aluminum sheet and they cut it to size for me. $20 worth of aluminum made my control cabinet. I used the pan brake I built last year to do the bending. This job almost paid the cost of building the brake. This control cabinet to buy already made costs wel over $250.
The cabinet is 17 5/8" wide, 13" deep, and 7" high.
IMG_0481.JPG IMG_0482.JPG IMG_0483.JPG
The little right angle bent piece will hold the Bank of power resistors.
 

mark_f

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#13
IMG_0484.JPG
Mocking up the resistor bank.
 

mark_f

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#14
Today I got most of the cabinet work done. It is amazing how much work is involved in making a nice cabinet.

These photos show the progress so far. Now it is time to start building.

The first photo shows the major component layout.
component layout.jpg
You may notice the cooling fan is going to mount inside the cabinet at the end of the "tunnel" that will house the power resistors.This fan will essentially be blowing air through the enclosed "tunnel" and directly out the back. This will most likely give the best cooling. It is more efficient than drawing the air through.
the vent hole in the back.


fan and vent holes.jpg
The same size vent "in" is needed to support the air flow out. There will be a filter with low air flow resistance to keep dust out of the cabinet and a wire guard on the outlet hole.


meter holes in cabinet.jpg
The meter holes are cut in the center of the cabinet front.


meters.jpg
I purchased a matching set of meters for the front.


power plugs.jpg
The AC inlet Plug and the Gap Power outlet plug are mounted in the rear of the cabinet.
I will now get to mounting the parts and begin wiring. I will also begin stuffing the PC board.

Mark Frazier
 

FOMOGO

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#15
Looks like your doing it right, as usual. good to have you back Mark. Cheers, Mike
 

BRIAN

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#17
Just booking in Mark .
Got my peanuts and popcorn.
Brian.
 

ch2co

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#18
I could use a cold beer along with the peanuts and popcorn.
But I too am watching this impressive forum with anticipation.

CHuck the grumpy old guy
 

mark_f

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#19
Thank you Guys. I always wanted to build an EDM machine.
 

mark_f

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#20
I got the fan structure finished and the fan mounted.
fan mounted 2.jpg

The fan essentially will blow through a box to cool the resisters. The fan is 100 CFM. I think it should do the trick. I have designed a bracket to hold the resistors in front of the fan. It will be next on my list.
fan mounted.jpg The "box" is completed when the cover is on.


A friend spent a lot of time making me an aluminum work tank from .085" thick aluminum. It is 18" X 12" X 8"
work tank.jpg
He cut it, bent it and then tried to weld it on the corners. No matter what we did we could not weld this aluminum. We called the supplier and found it it is not weldable. This aluminum is a cheap grade from china and it will not weld. They said it has to be epoxied, but the epoxy is horrendously expensive. So ...... I am going to pop rivet angles on the corners and seal the inside of the corners wit fiberglass if it will stand up to the dielectric or kerosene.... I think it will, but if anyone knows different, let me know. I hate to waste a nice tank.
work tank 2.jpg

Time to start wiring the control.
 

chips&more

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#21
I was going to say 100% Silicone Sealant. But then I just looked up its properties and found out it does not like prolong periods of exposure to solvents? Maybe try a test piece first, if you go that route. Or get a plastic tub. You can repurpose a HF coolant tank from one of their saws in the parts list.
 
Last edited:

ch2co

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#23
Hey RR cool table of compatibility. Its huge.
Thanks
 

mark_f

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#24
I have been informed that fiberglass works just fine.
 

f350ca

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Just to be on the safe side I'd use epoxy resin rather than the polyester. My boat from the 60's has fibreglass fuel tanks, an testament to fibreglass.

Greg
 

mark_f

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Just to be on the safe side I'd use epoxy resin rather than the polyester. My boat from the 60's has fibreglass fuel tanks, an testament to fibreglass.

Greg
Dielectric fluid is pretty harmless, but I will probably use kerosene for the dielectric. I think the fiberglass will hold up to that.
 

rwm

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#27
Welcome back Mark! Great looking project so far!
Robert
 

mark_f

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#28
I started working on the ram today.
leadscrew bearing.jpg
I made an aluminum block and bored each side for a ball bearing. This will hold the lead screw that moves the electrode up and down. It will mount to the aluminum bar that serves as the ram base.

ram parts.jpg The drawer slide has been cut down to length and will also mount on the base bar. It now has 4 inches of travel. You can also see the brass lead screw nut in the photo.
threading leadscrew.jpg I am single point threading the 3/8-24 lead screw in the lathe to get a good fit on the brass nut. It cannot have any backlash.
 

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#29
GREAT TO KNOW ALL THE PRAYER'S WORKED, Your prior memo did not sound very promising, looking enthusiastically to your current project.
 

mark_f

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GREAT TO KNOW ALL THE PRAYER'S WORKED, Your prior memo did not sound very promising, looking enthusiastically to your current project.
Yes, I am pretty much back to normal (whatever that is). The infection is gone and my incision on my spine closed up completely about a week ago. The only problem or danger right now is the high risk of a major stroke, but I am not letting that hold me back.
 
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