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Thread: Capacitors for home made EDM?

  1. #1
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    Dec 2005
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    Default Capacitors for home made EDM?

    Hi. Well.. I guess I have not found the answer I wanted to hear?

    What kind of capacitors stand up well to the edm discharge. I have two industrial welders here in bits and pieces. Two transformers I can get 48 volts x 100amps from.. center tapped, with a triac in the middle..

    The lil lcd and basic stamp is the controls I did six or so months back.. but.. what kind of capacitors are best? Electrolytic is what they use in the "kit" plans sold by HSM..

    I need a bolt burner in the worst way here. Also, to go into the spindle hole on the cnc. A simple bolt burner can be just a vibrating pen a brass rod and a welder.. reverse polarity..

    I have talked to several people with factory edm's they have mineral oil-wound capacitor banks. I did that once in a tesla coil.. in a five gallon bucket.. so the explosion would be contained.. I used to travel and replace electrolytic capacitors in the 4 way motor valves.. seemed the plc reset the output every six scans.. turned them on and off till they blew..

    Anybody got a part number or "type" of capacitor that can stand up to the heating of continous charge-discharge?
    Excuse me, I farted.

  2. #2
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    Beaverton, OR
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    Default

    Quote Originally Posted by Dawai
    Hi. Well.. I guess I have not found the answer I wanted to hear?

    What kind of capacitors stand up well to the edm discharge. I have two industrial welders here in bits and pieces. Two transformers I can get 48 volts x 100amps from.. center tapped, with a triac in the middle..

    The lil lcd and basic stamp is the controls I did six or so months back.. but.. what kind of capacitors are best? Electrolytic is what they use in the "kit" plans sold by HSM..

    I need a bolt burner in the worst way here. Also, to go into the spindle hole on the cnc. A simple bolt burner can be just a vibrating pen a brass rod and a welder.. reverse polarity..

    I have talked to several people with factory edm's they have mineral oil-wound capacitor banks. I did that once in a tesla coil.. in a five gallon bucket.. so the explosion would be contained.. I used to travel and replace electrolytic capacitors in the 4 way motor valves.. seemed the plc reset the output every six scans.. turned them on and off till they blew..

    Anybody got a part number or "type" of capacitor that can stand up to the heating of continous charge-discharge?
    They are caps available specifically designed for pulse discharge. Usually oil filled caps. Look for a cap with a low ESR, high ESR limits max current.

  3. #3
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    Default

    Pre-discharge bus... well I been hunting some huge dc tank capacitors from old inverter drives.

    Out board.. well. I got a box full of old motor start type capacitors.

    I am still tinkering with the design, as normal, I made it too large to fit onto my one ton flatbed. I got it all crammed into a box, need to drill mount holes.. Tempted to lay it all out on the table and wire it as is. I ran a temperature controller for metal melting for a year like that thou.. some of it in a cardboard box. THE com link in a plastic baggie.

    Capacitors, well.. I am still hesitant about using a ac quick discharge capacitor on a dc circuit. Not much to lose, they are free and here in a box.
    Excuse me, I farted.

  4. #4
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    Default

    AC capacitors will have no problem with DC.

    I think....

    -Jerry

  5. #5
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    Default

    Thermatool do a EDm which uses paper type caps as part of the supply, dont have a part number however I seem tor recall they are made by draloric, in what was west Germany.

  6. #6
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    Default Mr. Cofer,

    What type of EDM??

    Wire-Cutting or what??

  7. #7
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    Ignition cleansing circuitry.. ok? THE drill drive is the hold up.. it all works.

    New, A hand wound coupling coil tying 6000 volt ignition transformer from a boiler into the output from the 45 volt converted hobart battery charger transformer fed 300 amp diode bridge rectified circuitry.. using a bank of breakers and steel wound resistors up to the 100amp output on the xfrmer. This is great for making sparks fly out from under your fingernails. I am just going to pulse it to clean the electrode.

    Problems? you bet.. smoky in the shop?, you bet.. no problem. I got on saftey glasses and standing on a rubber mat. A water hose is standing by.

    Next level.. well.. I will be cutting some copper tube for electrodes.. ok? bore a hole that is a hole. Mounting the stepper on the old craftsman drill press, it is the DOWN right now till I get all the bugs worked out.. the lcd kicked my butt for a few days.. only talks in ascii transmitted characters.. not line chatter rs232..

    Well... up one more.. a plasma cutter.. ignites the same way.. need a torch head to play.. they are $40 off ebay. I don't think I will need the guy on youtube's water resistor thou, I got current control. Question? with a ceramic nozzle and orifice? would it not work to "FEED" a copper wire in as the sacrificial copper -cutter plasma stream instead of using them expendables?

    Up one more.. the incorporated homebuilt spot welder needs the HF to clean oil as it lights the fire.. I had gotten into a habit of rocking the part if it don't light right up.. ON the bottom of that transformer is a loop and half of welding cable around the primarys. I need to build a stud gun too off those 1.5 volt coils.. do body work with.

    It make sparks.. hums.. controls the power. I am working right now on a voltage divider circuit to tell the stepper when to back off and build power.. peck.. peck.. peck.. And am upgrading to a gecko drive and larger motor nixing unipolar brute resistor force and heat without a chopper drive.

    I gutted two industrial welders for parts. Gotta love re-purposing junk. (look eastward for the glow in the sky?)

    I am still anxious about them ac capacitors. I have saw them blow up like a slinky before. Will take pictures.. let er blow..
    Last edited by Dawai; 10-14-2009 at 10:05 PM.
    Excuse me, I farted.

  8. #8
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    Default

    That guy on youtube should have his video yanked. What he is doing is so incredibly dangerous its not funny.

    I have posted in the past here and over on PM exactly how the different types of plasma cutting torches work. If you are asking what you are asking you dont have a clue about how they work.

  9. #9
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    Default

    There are people here in the uk building those things and using our 240v supply for them, really dodgy.

    I'm fairy sure the thermatool I was thinking of was a electrode type, as it was used to remove broken studs etc.

    The same place had cloos welding robots, and the weld sets were high frequency switchers and had sprague capacitors in them, I procured a couple and connected them to a crappy SIP mig welder I used to have, which just had a rectifier - no smoothing, and it was definately not so crappy afterwards.
    Last edited by dr pepper; 10-14-2009 at 11:47 PM.
    Build it, bodge it, but dont buy it.

  10. #10
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    Default Macona

    Quote Originally Posted by macona
    That guy on youtube should have his video yanked. What he is doing is so incredibly dangerous its not funny.

    I have posted in the past here and over on PM exactly how the different types of plasma cutting torches work. If you are asking what you are asking you dont have a clue about how they work.
    What video??

    Please.

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