Capacitors for home made EDM?

[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?

[macona]

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.

[Dawai]

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.

[macona]

AC capacitors will have no problem with DC.

I think....

-Jerry

[dr pepper]

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.

[davidfe]

What type of EDM??

Wire-Cutting or what??

[Dawai]

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..

[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.

[dr pepper]

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.

[davidfe]

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.

[Dawai]

Actually, I got a miller 35amp, the one that looks just alike the hobart, dragon, lincoln for a while.. OLD, but still works. And I will get every penny out of it.

No, not looked how it works except the current "forward" board which lights it up with HF, then keeps the current on. I have to take it and blow the grinding crap out of it every few months. I have had it apart, I am a electrician. I see nothing really complicated there. Like my first mig, it was really simpler than I realized. Not a CC_CV like all the new ones, but I did pay a premium price for it way back then, but then again, nothing to break in it.

I need a new torch for the old miller, the one has home machined parts in it holding the consumable switch in place. Crappy thing has been dropped a million times evidently. Once too many. Consumables, right now for what three costs? I can buy 100 off ebay.

I just got in from Ace Hardware where I bought two 6/32 taps and one drill bit to start mounting the controls which are wired in place. They sent a young girl to follow me and watch me in the store. I am not that ugly?? I'm Not a thief.. I am pretty angry.. I found the old man in the hardware-tool section and Let him help me instead of helping myself there. I'll calm down before I complain online about spending $16 on $8 of three small items and being insulted by the staff there.

That ain't the only store around, it was on the way to haul the garbage off thou. $8 would have bought a lot of gas.

[Dawai]

DavidFE:

http://www.youtube.com/watch?v=6W3tLDBdPQQ

Yeah, it is dangerous.. all plasma cutters throw sparks, use electricity, welders, ever lay on a concrete floor and drop the ground clamp and get on the stinger? I thought I was dying. Ground the stinger and pick up a ground clamp? yeah.. I saw colors.

Working on junk out in the driveway is a good way to die.

It'll all work out. As I desire. Brute force with resistors or transistor pulse drive? I got the rig working. Now to fine tune it with a controlled axis. I ruined about $500 in parts just the other day on the milling machine. Drilling a super-hard bolt out of a softer casting.. it wanders.. a pilot hole to keep it on track would be worth a lot.

[davidfe]

Thank you for the link.

[dr pepper]

Here you go then.

http://www.metacafe.com/watch/982092/how_to_build_a_homemade_diy_plasma_cutter/

DO NOT BUILD THIS, it'll probably kill you, this machine is not safe.

Just realised same vid as above, same applies though.

[Dawai]

This the Westinghouse welder box, I cut it in half in length to house all the parts needed for the capacitor welder, spot welder, edm, and tiny tig welder. It has two seperated compartments which I like, the cpu and other parts can be away from the high voltage and spark gap.

http://img.photobucket.com/albums/v85/ibewgypsie/PICT0860.jpg
This is the magic box that used to run my gantry robot for the castings, also, it ran the cnc bender 3 axis. Madman took the other inverter out of it back to Canada. About all the good stuff is now gone.. ran off a remote 422 com link to the house computer. IP Camera monitor never did work right.

http://img.photobucket.com/albums/v85/ibewgypsie/PICT0863.jpg
Would not fit.. so.. had to alter the other box
http://img.photobucket.com/albums/v85/ibewgypsie/PICT0865.jpg

[Dawai]

I pulled a bit of hair out, but.. I got about five of them lil Synchronous 120 volt stepper motors left the crack heads didn't steal.

Using a pair of current relays, a voltage divider circuit and a "deadband" pot between it and the HI voltage circuit? well.. I can use a master control relay (MCR), and that lil motor to step up and down according to current or "bottom set limit"..

this frees up about $200 in stepper motor and drive. And I don't have to worry about the mosfets in the geckodrive dying from the hi voltage cleaning of the electrode. I think, no real reason to install the cpu and lcd till I go to expand it to the other functions either.

Adjust welding current rheostat, adjust deadband there on front.. push the MCR latch circuit (broken by lower limit) and it should bounce up and down till it settles in the sweet spot between hi voltage and low voltage settings. Once it reaches bottom, it will shut off unlatch MCR , cycle back to top limit.

All for less than $10 or so, from junk. NOW common sense tells me to move that 1800's drill press with the "already mounted" 120 volt stepper quill feed out there. Most everything I have to burn out will fit on the table on it. Room for a wash tub pan on the table too.

Of course, if I drink the electrofied water, It may make me sick. Teach me a new way to break-dance? there will be shiny circles on the floor where I be spinning?

There is nothing funny about risky tools. The best things are made in China with a imitation UL label, I got a food processor that has knocked me silly twice now. Shame on me. A bubble membrane over that switch would have prevented it.

[lazlo]

DavidFE:

http://www.youtube.com/watch?v=6W3tLDBdPQQ

Among the major flaws in that design, its not isolated -- you're connected directly to the mains! At least put a isolation transformer inline. A fuse would be nice :)

If you're using an old welder as a starting point, you already have those...

David, if you're already burning metal, you may have realized by now that the magic is in the pulse width and duty cycle: the bigger, and less frequent, the pulse, the larger the crater. So it eats metal faster, but the surface finish sucks.

Small pulse width @ high frequency cuts slower, but leaves a much nicer surface finish.

Robert Langlois's EDM book/articles from HSM Magazine goes into a lot of detail on capacitor selection and sizing.

[Dawai]

Hey Lazlo:

Still playing sick here. I got the box cut up, and redrilled. Laid the hobart battery charger transformer into it, the 3phase bridge, the other small things. It needs painting. ugly as sin.

It has turned cold, rainy today, I was standing on the old cinncinatti lathe trying to dig through a box of old robotic parts (opto22) and there about two feet in front of my face was a huge brown snake crawling off slowly, 55 degrees.. I was in a spot where I could not run, could not fight, just had to stand there wobbly and let it crawl off the shelf and disappear. Copper head or corn snake, no clue. My vision was blurry and I was in no mood to fight with it.

No headway today. Yeah, I had it temp wired, using the 100 amp transformer, the "fine current" control off the welder and the next step.. 20 amps. NO mosfets to play with. So far I have just blowed chunks of metal out like you describe.. but fine tuning is coming.
I smoked one of them old opto22 boards, new it was $560.. not a good day. I had it wired into the 5vdc on the pc.. yep.. was a jumper tying it into the 12 volt yellow.. but the wire coming out was red.. so.. I took it for granted it was 5volt.. fried.. no smoke, just dead.
You rarely see that opto22 stuff on ebay these days. replacements?? no clue.. I'll run it as long as I got parts thou.. I found out with a basic stamp you can trigger a waveform or timed pulse, as for a capacitor welder, or hi frequency drive.. run till you tell it to stop or for a timer period. It runs via 422 serial com link..

I got a usb-232 adapter tied into a 232-422 convertor box w/terminals tied into the B100 pb16hc brain board and backplane. OLD junk obselete, but still working for me.

I had a book, it used a vibrating engraver pen, and a dc arc welder to burn out bolts.. you got it into the sweet-arc spot and the pen kept jiggling the electrode till it burned it out.
Mine is nearly as crude. At the moment.

[Dawai]

I'm still scratching my head trying to figure out how to read the current back into the cpu..

I got a voltage divider circuit drawed up, got the zener diodes found, a opto22 isolator card.. It is digital, hi voltage indicator, and low voltage indicator.

Motor-relays will follow bus voltage, low voltage causes motor to go up, hi voltage advances toward stock. A deadband pot will hopefully slow bouncing. The motor I have chosen is a 120 volt stepper-synchronous motor that can stall or instant reverse without heating up. (JUNK) It will be running the quill on the old drill press.

[macona]

What opto22 board did you kill? There are a lot of modules up there, is it a motherboard or something else?

[Dawai]

Hi.

Well.. I fried a B100, Possibly blew the fuse on a rack. No modules were sticking in the brand new board, I was working on the com link here.

Funny thing about them old boards, if it is not between 5.0 and 5.1 volts they never will talk.

The pattern tufting machines I built for Queen Carpet used a parallel DMA kinda of board, Opto22-Pamux, those are much better at rapid changes. I have one pc board left with a isa bus, I had it on a robotic creeler in 1989.. I bought these serial boards off ebay about ten years ago, I had envisioned a robotic casting system where I could sit in the house and just take a wheelbarrow and bring up the casted parts to ebay. Well, when a gearbox got busted cause I pushed a limit over ride in a moment of confusion? It was several thousand dollars I did not have in pocket to replace. The remote camera never worked correctly. I went from one to another. The last one, a gadspot lays here on the bench taunting me. I had it working with the surveillance system for a week.. quit again. It loses it's static set ip address and you have to go hunt it. Battery? or however it keeps it in memory. It is dynamic ip when you push the reset and you "find" it.. other than that? it took some excellent green glow pictures where you could not see what was going on. THE newest $25 chinese BNC connected cameras are much better. I ran conduits in the ground, never had help here to pull the cable.

You might remember the "hot Liquid metal" water-pistol topic where people said I was insane? Thrud was around then.

Surface finish on this contraption can "suck" for a while, as long as it burns bolts out as I ask.
http://img.photobucket.com/albums/v85/ibewgypsie/EDMprimarydrive.jpg

The antique 300 amp westinghouse welder had inline resistors and a HUGE rheostat for fine current adjustment. I moved the two base resistors over into this can, the rheostat will probably give me more than enough power. THE big can-capacitor is off a oxygen generator supply, the breaker-switches are from the westinghouse welder, how they switched in the resistors. Transformer is from a hobart battery charger, modified, I did one of these with a loop of welding cable as a secondary for a spot welder.. I may move that over to this one and just leave that circuit open.
The 120 volt superior synch stepper, once you push the go button and latch Mcr, it runs down till it breaks hi voltage relay circuit, if it breaks low voltage circuit it runs back up. It bounces up and down charging circuit, deadband pot adjusts that, the other pot in the voltage divider circuit just tunes it in. I plan on putting test points out where I can adjust it too thou.

The lil block where the zener feeds is actually two modules, a idc5 opto22, and a oac5 module. THE bus circuit feeds into the high voltage side and triggers the ttl side, the input will power the input on the ac module.. a way of keep a bit of simplicity in the circuitry.. all on a 4 position pbr4 opto22 backplane board.

It seems to work while wired on the table. I had on saftey glasses while working since lately I have been known to make mistakes.

[Dawai]

Happy day? the toshiba Mosfets from the current line of Chinese plasma cutter-welders are being sold on ebay.

Too bad I've not made enough money here in a while to buy some to play with.

Like Lazlo said, hi frequency is a cleaner burn.

brute power RESISTORS, heat made up, fan blowing directly on them... Can't find any replacements at Radio Shack??

http://img.photobucket.com/albums/v85/ibewgypsie/PICT0866.jpg

http://img.photobucket.com/albums/v85/ibewgypsie/PICT0867.jpg

Like Dolly Parton's bra? ten pounds of tators in a five pound sack?? ha.. I love her.. The 3phase 300 amp bridge rectifier has two spare diodes.. or some for the spot welder??

[Dawai]

I just got a offer of $500 for this rig. He wants it as a chrome plating supply? Never thought about it.

Two wires change and it becomes a 12 volt dc, swap two, 24, swap two 48.

That'd let me buy them Toshiba FET's to play with.

Edit: October 21st, 2009.. this build has ended here.. I will complete it as a dc supply for a buddy, the goof ball in Atlanta has not called me back. He can make a living derusting and powdercoating with it.