Homemade plasma, crazy?

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I have been doing a lot more fabrication lately and a plasma would really be nice but not in the budget right now.  I have bought a bunch of new tools lately and probably not going to be able to make any more big purchases for a while!  I've been trying to make some of my own tools(rim clamp and spring compressor) lately for a fraction of what they cost to buy.  So I got to thinking what would it take to make a plasma cutter?  I've been doing some googling and research tonight and it seems that a lot of others have made their own plasma cutter.  Most of the home made ones say they cost 200-300 bucks and can cut 1/2" according to the inventors.  This would be plenty for me and think I can come up with 300 bucks for the parts to make one.  Just wondering if anyone has ever made one or if this is a crazy idea.  I'm going to look into it more and get a parts list together and start sourcing the electrical components to see how much it will cost to build.  So if anyone has any suggestions/advice/experience with home made plasma cutters feel free to share it.  Thanks, Scott
Reply:Its a crazy idea. If you want something that is safe and will actually work....then spend a few more bucks and buy a low cost chinese plasma. It will get you started cutting metal. Or buy an older, broken down commercially built unit to tinker with.....at least the engineering has been done...it just may need some duct tape and tye wraps to get it working again!Those that have built their own plasma....at least all that I have seen....have built units that are very dangerous....due to the open circuit voltage levels required for plasma arc cutting.....and generally get very poor performance in terms of cut quality and consumable life.Jim
Reply:There are a few EBay auctions featuring customer returned Chinese plasma cutters. Generally they are selling for less than 200 dollars. As Jim said the engineering is already done and you'll be able to get some tinkering fun while trying to repair it. http://www.PlasmaMetalCutter.comGiantTech Cut40DGiantTech Cut50DGiantTech CT520DGiantTech Tig200sGiantTech Arc200GiantTech Tig200PACDCMiller MM210No Brand Chinese Chop SawNo Brand Chinese 4" Angle Grinder
Reply:Thanks for the replies guys.  I don't have any experience in trouble shooting and repairing electronics so don't think buying a broken machine is the way to go for me.  Well I guess I got a little excited when I read about others making thier own.  Thought I could copy thire plans and come up with something that works for a decent price but looks like it was to good to be true!Guess I'll just wait till I can afford a decent used one sometime down the road.  Thanks for the advice guys.
Reply:I hope you were not thinking of designing your own torch.When I was a welding engineer at Linde/L-Tech - which is now ESAB, we had a Phd who did nothing but design plasma torches.  The physics is insanely complicated.  You have to have a solid theoretical understanding of plasma physics, gas dynamics, and thermodynamics.  Then there is the trial and error process in the lab where you get the gas flows right and burn up a lot of torches in the process.Then too, the control electronics and power supply of most good plasma units differ from that of a conventional TIG system.
Reply:Well I was just considering the thought of building a unit.  Never even got around to the torch part!  During my searching there was others that built the torch.  I posted this to see if it was even posible to do something like this before I started getting a parts list together.  Seems like this isn't a diy project for many reasons so pretty sure I'll just live without a plasma cutter for now.
Reply:If your in the market for a low cost plasma cutter, you can check out GiantTech plasma cutters.  They have two models; the Cut 40D which is 40amps, and the Cut 50D which is 50amp rated.  Both units are dual voltage; 110-220.  These are Chinese made units but are relatively inexpensive and from what I understand fairly reliable.  I am in the market for a new plasma cutter and probably will purchase one of these units which will suit my personal needs.A few of my toys !LinuxMintManjaroMiller Roughneck 2E Lincoln WeldPak 100HTP MTS 160 Chicago Electric 80amp Inverter   Victor O/A
Reply:Surprisingly, I didn't find this thread through the forum, but through google.  I really dislike being told my ideas are crazy and unattainable.  How did anything get invented or made in the first place?  The guy making the combustion engine probably wasn't doing things deemed safe, but look at our world today.  Combustion engines everywhere.Personally, I wouldn't try and make a plasma torch, that can be afforded, the device itself is likely the most expensive part.I don't know where you all live, but I live in the United States of America, I don't believe in slavery.  When you buy chinese stuff, not only are you not aiding your brothers and sisters, but you are also enabling and aiding the slave owners of asia.It's gonna be used, DIY or American made for me.  I vote that you try and make a plasma cutter, that is what I aim to do.  I was considering using an altenator to make a TIG, but the high frequency portion doesn't seem like something I could figure out, so a used miller is real nice for me.  As for the plasma cutter, perhaps you could figure out some designs online and expand upon them.  Create where others won't.  Those who would sacrifice freedom for security deserve neither.Miller 330 a/bp water cooledI believe in gun control, I hold my gun with two hands.  If you want to know why, click here.Buy American or bye America.
Reply:If the reasoning behind building your own plasma cutter is lack of money to buy one, you would be alot better off just buying an oxy/acet torch rig instead.  Now if you're a real brainiac with an electrical engineering degree and just want to fool around and see if you can build one, that's something different.  Could be fun!MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:HI Here are a set of schematics for a Plasma cutter.  By the time you buy a torch and the componants you will have a few hundred bucks in it. So the buy used is better.Good luckTom Attached Images
Reply:This schematic is for a drooper style power supply....the current is limited by the size of the input isolation transformer.....the current is not constant...it will vary depending on arc voltage, which is controlled by the effective length of the arc and the nozzle orifice size as well as gas flow rate and type of gas used to create the plasma arc.There are no safety features......in fact with this schematic the only way to extinguish the arc is to pull the torch away from the plate......and then there will still be lethal DC voltage present between the electrode and nozzle.This circuit would be fun to experiment with....but will not likely produce a plasma system that is either safe or productive. Just be careful with this kind of open circuit voltage (200 to 400 vdc) ...Jim
Reply:This has peeked my interest. Fortunately I understand the deadly nature of electricity and have a friend who is an electrical engineer. He is the one who helped me adapt that Miller spoolmatic 30A to my Hobart Beta MIG 250. Google, here I come. I will post my progress.I truly believe that where there's a Bill, there's a way.Bill LambertArgon WeldingABQ NMSic gorgiamus allos subjectatos nunc
Reply:Item # 130341714062 on eBay is an ebook with the plans for making a home made plasma cutter. A video is also on the page to watch it work. Buy It Now price is $9.99 for the plans. Should be worth that to satisfy curiosity if nothing else.Only when the last tree has died and the last river has been poisoned and the last fish has been caught will we realize we cannot eat money.                                         -Cree Indian ProverbSA 200 LincolnVictor Torches
Reply:Originally Posted by jimcoltThis schematic is for a drooper style power supply....the current is limited by the size of the input isolation transformer.....the current is not constant...it will vary depending on arc voltage, which is controlled by the effective length of the arc and the nozzle orifice size as well as gas flow rate and type of gas used to create the plasma arc.There are no safety features......in fact with this schematic the only way to extinguish the arc is to pull the torch away from the plate......and then there will still be lethal DC voltage present between the electrode and nozzle.This circuit would be fun to experiment with....but will not likely produce a plasma system that is either safe or productive. Just be careful with this kind of open circuit voltage (200 to 400 vdc) ...Jim
Reply:Originally Posted by ponch37300I have been doing a lot more fabrication lately and a plasma would really be nice but not in the budget right now.  I have bought a bunch of new tools lately and probably not going to be able to make any more big purchases for a while!  I've been trying to make some of my own tools(rim clamp and spring compressor) lately for a fraction of what they cost to buy.  So I got to thinking what would it take to make a plasma cutter?  I've been doing some googling and research tonight and it seems that a lot of others have made their own plasma cutter.  Most of the home made ones say they cost 200-300 bucks and can cut 1/2" according to the inventors.  This would be plenty for me and think I can come up with 300 bucks for the parts to make one.  Just wondering if anyone has ever made one or if this is a crazy idea.  I'm going to look into it more and get a parts list together and start sourcing the electrical components to see how much it will cost to build.  So if anyone has any suggestions/advice/experience with home made plasma cutters feel free to share it.  Thanks, Scott
Reply:Video of a homemade plasma maybe hit this guy up for plan's
Reply:It would be nice to see pictures of the actual power supply......every video of a "home made" plasma cutter that I have seen to date shows a torch that was not home made! This one looks like a chinese copy of an old Esab or Thermal high frequency start 30 amp torch. Jim
Reply:Originally Posted by tnjind Originally Posted by jimcoltThis schematic is for a drooper style power supply....the current is limited by the size of the input isolation transformer.....the current is not constant...it will vary depending on arc voltage, which is controlled by the effective length of the arc and the nozzle orifice size as well as gas flow rate and type of gas used to create the plasma arc.There are no safety features......in fact with this schematic the only way to extinguish the arc is to pull the torch away from the plate......and then there will still be lethal DC voltage present between the electrode and nozzle.This circuit would be fun to experiment with....but will not likely produce a plasma system that is either safe or productive. Just be careful with this kind of open circuit voltage (200 to 400 vdc) ...Jim
Reply:You are correct that the schematic is not complete. I stand corrected.....it just plain won't work as drawn!Jim
Reply:Jim Besides, a 50amp mains isolation (1:1) transformer is not a commonly available thing (that I know of).
Reply:The ones we used to use when we built smaller transformer based plasma systems were not 1:1 typically. If we had a 240 volt single phase input the transformer secondary was around 280 to 300 volts. From there it was rectified.....then switched with a pulse width modulator (with a current feedback loop).....The isolation transformer was tightly wound for excellent voltage amperage characteristics.....so we could maintain constant current for better consumable life and cut quality. The design in the schamatic is going to create a current spike on arc initiation that will seriously shorten the life of the torch nozzle. Been there, done that.....about 30 years ago. It will work....but you could probably search and find an old Thermal Dynamics Pac5xr or Pac3xr that is an almost identical circuit......and buy it for scrap value....and get it into working condition. There are thousands of them out there! Hypertherm never built a drooper power supply with a hand torch......we had one with a machine torch (40 Amp) but it was short lived back in the early 80's.....Jim Colt
Reply:Jim,Where would the current spike you're referring to in this schematic come from?(I'm genuinely curious because I don't know why/where it would)  My thinking is that while, yes, it will have a much higher OCV than CCV, (since no regulation), it has quite a bit of inductance that should keep dampen any abrupt changes from 0 amps (OCV) to large amps (CCV).  My understanding/analysis of the circuit is probably insufficient.Also; Obviously, because of what a transformer is, you will get a higher OCV than CCV; but is this somehow necessary for the operation of a PAC, or a byproduct of how it was done with models having no active regulation?My assumption so far, from an electrical standpoint, has been that a PAC is basically a triggered spark gap.  The two ways of triggering the gap being a third electrode, or superimposing HF/HV onto it to breakdown the dielectric in the gap (in this case fast moving air).Suppose one had a regulated DC supply that could supply the necessary current, and maintained a voltage on the torch that is what the CCV would be when cutting.  Would it not be possible to superimpose HF onto the cable, or use a torch with a second electrode to initialize the arc?  Also; what is the typical CCV of a PAC?Thanks.
Reply:The starting mechanism is high frequency (10 to 15kv @ 10 mghz) coupled through an air core transformer onto the electrode with a return path through the nozzle. Once gas flow (air) is established through the torch, exiting out the nozzle orifice...the DC Power is activated between the electrode and the nozzle, and also on the plate. With DC in the torch...and air flowing...now the high frequency is activated.....this energy ionizes the air passing between the negative electrode and the positive nozzle...creating a current path from electrode to nozzle for the DC.....the DC now adds energy to this plasma jet and the high frequency can be deactivated. This DC /ionized air arc is forced by air pressure through the nozzle orifice...this is the pilot arc. If the plate...which is at positive potential...is in close proximity to the arc....some of the current will split and create current flow from the plate through the work lead...back to positive in the power supply.....a current sensor senses this current and opens the pilot arc relay.....disconnecting the nozzle from the positive side of the power supply....all of the current now flows from electrode, through the nozzle orifice and to the plate.The momemt the high frequency ionizes the air inside the torch (with the DC on)......a current surge ocurrs with DC current trying to satisfy the apparent short circuit between the electrode and nozzle....this creates a high inrush for a few miliseconds.....which is followed by a droop in voltage.......which can cause the pilot arc to extinguish a few seconds later....normally a capacitor (surge injection capacitor) is also in the circuit between the electrode and nozzle to inject current to maintain the pilot arc until the main transformer can recover from the initial inrush. The short term initial inrush is often damaging to the nozzle orifice.Newer technology used PWM current control technology to gradually ramp up the pilot current...increasing consumable life dramatically during the starting sequence.Jim
Reply:Wow 1st time I have seen this one about someone thinking of building their own Plasma Cutter. Unless the person is an electronics wizard and has the available parts it would be far safer in the long run to buy a used one or buy a Cheaper Non brand name one. Just buying the electronic components,circuit boards, wiring, torch and consumables is cost prohibitive.BUILD YOUR OWN PLASMA CUTTER Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:Originally Posted by specterWow 1st time I have seen this one about someone thinking of building their own Plasma Cutter. Unless the person is an electronics wizard and has the available parts it would be far safer in the long run to buy a used one or buy a Cheaper Non brand name one. Just buying the electronic components,circuit boards, wiring, torch and consumables is cost prohibitive.At then end of the day i think we can thank mass production for ppl even being able to afford a plasma so i doubt you would be able to make a decent duty cycle one for the same or less then a one you can buy
Reply:you cant beat machine mass production than a personal try that uses try n error... more error in that sense... upgrading a used machine is another ball game...Unit in my fab shop dept:my good hand and team that trust me...A lone welder make art... a village full of welder make Miracles...