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Thread: Has anyone made an EDM/Spark Eroder?

  1. #21
    PeteF Guest

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    Quote Originally Posted by Mcgyver
    what ratio is the erosion/wear between work and electrode....the electrode must suffer some wear as they don't reuse the wire in a wire EDM...but it erodes magnitudes more slowly than the work?
    My understanding is that the electrode erodes more slowly than the work due to the polarity of the spark, if the polarity of the unit is reversed the electrode will indeed wear faster than the work. Much the same as the old points in a car.

    Pete

  2. #22
    Join Date
    Jul 2001
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    Green Bay, WI
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    3,189

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    Thanks Lazlo for the plug. Been traveling .....

    I built Flemings EDM and am very happy with it.
    I tried the old Popular Science R-C Circut and the difference is astounding
    That method took well over one hour to burn out a 1-72 tap.
    The Ben Fleming unit does it in 6 to 10 minutes.
    It cost me a $100 to build it, as I am cheap and used some WW II meters etc.
    The guys on the Yahoo Groups site now have a printed board and it has gotten streamlined. Mine was the first one built from the book according to Ben.
    Here is what the control looks like, and the voltage maximum is NOT 10 volts as the meter shows but is a percent meter of voltage applied.
    The Fleming design runs about 70 Volts DC which is full scale


    A few words.
    I tried water, Kerosene, and an EDM Fluid
    Water works, but is slow. Kero works faster, but I can't take the smell.
    EDM Fluid cuts very fast, and has no smell, but costs about 20 bucks a gallon. You can reuse it, and reuse it again. Since I do burn outs mostly I did not build a tank/filter system. I use a Cake pan as seen in the following photo, and make sure the fluid level is above the part. A turkey baster is used to flush the fluid periodically.
    A friend is building a Wright Cyclone 9 Cylinder radial aircraft engine and broke three 2-56 taps in the crankcase housing after he had 100 hours in it. We had them out in 30 minutes, and most of that was setup.
    In the following photo, I am burning through a 3/16 " thick Carbide insert, just for the fun of it , and to experiment. Using 3/16 square brass tubing (.016 WALL) I burned through in about 45 minutes, stopping several times to check the work and to move the electrode down. I burned over 6 inches of brass to 3/16" carbide. I used Kero and no circulation. Both caused me to use lots of electrode. Even when using carbon rod, such as old welding carbon rods ( carbon arc) are poor compared to commercial EDM carbon.
    So everything you do affects speed. Trying to answer 'How Fast?" is tough as home units do not cut like commercial and electrodes are subject to many variables.



    Now for those that think a carbide drill is the answer to broken taps, try this.
    I broke some stainless steel rod making a 0-80 (.060 or 1.5mm)threaded screw in a good die. Normally that means a scrap die as the stainless was locked tight .Here you see a setup with a piece of .032 (.7mm) brass rod electrode. 5 minutes later, I had a good die again. I used about an inch of rod ( 6 to 1). With carbon, it would have been insignificant in my opinion

    Rich


  3. #23
    Join Date
    Dec 2010
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    Finland
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    Rich, very nice work on the machine!

    One thing though: In EDM they don't use carbon, but graphite. Two different materials

  4. #24
    Join Date
    May 2011
    Location
    N.E. Arizona
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    Default Shop built EDM

    Hi Everyone,

    I couldnít decide if I should post this at this time Ďcuz Iím REALLY busy for the foreseeable future & my shop built EDM is buried away next to my welder where I am only using it as a cooler for my TIG torch.

    But then, I just got another argon cylinder today & had to move this stuff anyway so here goes.

    The photos are lousy & to help keep the file size down I erased as much of the background as possible. I donít have the time to setup fancy lighting - just the flash.

    About 12 years ago I was working in a university shop & built an EDM based on Ben Flemingís design. We had a 1940/50s Sears 220V AC only buzz box that we never used & lots of misc. hardware etc.

    When I first got the mechanical part finished & hooked up the welder the results were disappointing to say the least & dangerous besides. The welder was supplying about 90 open circuit volts, and Fleming recommended using rubber gloves to insulate the user because it was quite possible to get some serious shocks from the chassis. No kidding!

    The first holes tried would definitely eat out a tap, but were quite sloppy. You could actually see the arc flow outward in a bell shape as it followed the water coming out of the electrode.

    Thatís when I started working with an electronics wizard from one of the other departments. As we tried different ideas & learned as much as we could about commercial EDMs the solution hit me that we needed to keep the voltage low so that the arc would only come off the end of the electrode & not the sides.

    Once we went in this direction the results finally and quickly started looking good.

    This is a VERY short description of what we went through over a year of on & off work. Plus lots of transistors. We got teased by the others in the shop that we were building a transistor tester not an EDM.

    The enlarged bottom view shows the first ragged holes and the clean hex shape on the right once we got everything sorted out. These holes are on a 3/8 HSS lathe bit & the top item is a carbide blank, just for fun.



    I can now put a 1/16 hole through 3/8 HSS in less than a minute. As the diameter of the electrode increases so does the cutting time.

    We found that 12 to 15 volts is ideal for clean cutting but once above 15 volts, the arc becomes much harder to control & so does the hole size and shape.

    The tall rectangular box on the bottom of the chassis takes the welder input & changes it to DC. The blue capacitors in the rear view store the DC charge from this box & are triggered by the vibrating electrode.

    The welder operates on 110 volts to cut itís output in half, making it easier to reduce the electrode voltage to 12 to 15. Another trick is to run the vibrating engraver on 110 volt DC to cut itís vibrating cycle in half, giving the capacitors more time to charge.







    Now hereís my problem.

    I know I have all the schematics & even an Auto Cad file for cutting the circuit board that you can see in the back view of the electronics.

    Getting the time to review all of this & play around w/the machine again is the difficulty.

    I can probably answer questions easily that you might have from looking at the photos, but the electronic details are a bit fuzzy for me after 12 years.

    Iím not trying to blow anyone off, or to throw something out there that I canít/wonít back up. Iíll do all that I can to help out, but you have to understand that I have deadlines etc. to meet. OK?

    Ask all you want & I promise Iíll do my best/fastest. You wonít hurt my feelings & I hope that I donít hurt any of yours.
    Last edited by jhe.1973; 07-26-2017 at 02:09 AM. Reason: Replace photos
    Best wishes to yaíll.

    Sincerely,

    Jim

    "To invent you need a good imagination and a pile of junk" - Thomas Edison

    "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

  5. #25
    Join Date
    May 2011
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    N.E. Arizona
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    Default Additional photos

    Here are the views of the back.

    I was limited to 4 photos in the above post.



    Last edited by jhe.1973; 07-26-2017 at 02:14 AM.
    Best wishes to yaíll.

    Sincerely,

    Jim

    "To invent you need a good imagination and a pile of junk" - Thomas Edison

    "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

  6. #26
    PeteF Guest

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    Thanks for that Jim, the results of that hex shape are extremely good. Do you recall just how much you deviated from the original design (electronics wise) fro Ben Flemming's design?

    Pete

  7. #27
    Join Date
    Jun 2008
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    Yorkshire, Centre of the known Universe
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    Only take a few pulleys and an electric motor to convert the last one into a full blown wire erroder.

    Wish we'd had that in our toolroom forty years ago, would have saved about 10 sq inches of floorspace, such a simple design.

    Regards Ian.
    You might not like what I say,but that doesn't mean I'm wrong.

  8. #28
    Join Date
    Apr 2010
    Location
    Canada
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    2,502

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    Quote Originally Posted by jhe.1973

    I know I have all the schematics & even an Auto Cad file for cutting the circuit board that you can see in the back view of the electronics.

    Jim
    Would you have a chance to post the files in whatever format here, if only the schematic?
    Max.

  9. #29
    Join Date
    Dec 2010
    Location
    Finland
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    If someone is going to build an EDM, remember to use a transformer between mains voltage and the machine! This isolates the voltage from mains. Now add grounding wire to the chassis of the machine (table). This way you can't get shocked from touching the machine unless you grab the electrode.

  10. #30
    Join Date
    Mar 2005
    Location
    Toronto
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    Quote Originally Posted by Circlip
    Only take a few pulleys and an electric motor to convert the last one into a full blown wire erroder.
    .
    cnc has become so accessible, cheap drives steppers and software, hopefully some diy wire versions will appear.

    Jaakko, two questions; what is accomplished with all the bells and whistles your modern design has? Faster cutting, more accurate etc? low cost build? Just wondering what the incremental benefit is over the other designs using more modern electronics. Secondly, could what you're building be easily adapted to a drive a wire version?

    I really like seeing all the machines you guys have built, great stuff!
    .

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