METAL MELTER!

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About: Random Weekend Projects

Here's a microwave oven transformer that's been modified into a dangerous little device. Now it can pump out 800 amps of electrical current, so let's use it to melt some metal!

http://www.thekingofrandom.com

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    78 Discussions

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    DavidW785

    Question 8 months ago on Introduction

    Can you tell me what power supply is needed to run this unit? thanks, it's the only thing i am not sure of.

    2 answers
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    StephenA21DavidW785

    Answer 6 weeks ago

    @DavidW785 - You said, "Can you tell me what power supply is needed to run this unit? thanks, it's the only thing i am not sure of." Look up Transformer on wikipedia, then understand that the primary of this MOT (Microwave Oven Transformer) is DIRECTLY connected to house current. The secondary is removed and replaced with a few windings of thick copper wire. I build this. Use a three-prong plug (the one that came with the microwave oven should be perfect). and take the ground from the plug and firmly attach it via lock-nut screw to the steel part of the transformer. If the primary develops a short through to the steel, this might save your life! Better yet, I am a fellow maker and not an electrician, and it would be best to get professional advice from a licensed electrician, since house current is involved, and lives are at stake. Please be careful!

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    DavidW785StephenA21

    Reply 6 weeks ago

    thyanks for the info, i be very careful using 240V

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    Is it just mine, or does you transformer also make a vibrating humming noise? I used two gauge wire as you did, and mine makes a loud humming/vibrating noise. Is that suppose to happen?

    3 replies
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    StephenA21RocketPenguin

    Reply 6 weeks ago

    That humming sound I consider to be an awesome feature, not a bug. That humming sound is to be expected -- that is the sound of a LOT of energy going through your transformer, and it is a symptom of things going RIGHT!

    Ok. Thanks, just wanted to make sure. Mine doesnt seem to work as fast as yours. The voltage rating is 1.5 volt output, and i dont want to screw up a volt meter measuring amps...

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    StephenA21crazy-blender

    Reply 6 weeks ago

    No. Don't do this. Your circuit breaker should trip, but you could cause a fire. If you really want to know for sure, go to electrical engineering stack exchange and ask your question again.

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    Norway1973

    5 years ago on Introduction

    Could you add a clamp on one cord like the one welding machines and some sort of tip on the other cord so this could work like a plasma cutter? :-)

    1 reply
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    StephenA21Norway1973

    Reply 6 weeks ago

    Did this with vise-grips and it worked really well.

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    herpingdo

    5 years ago on Introduction

    I browse Instructables quite a bit, but I've never bothered to make an account. I made one though, just to comment here.

    I saw this project, and remembered I had a MOT somewhere. I found it the other day, and I decided to modify it. The only tools I had to work with were a 10 year old hacksaw with a dulled blade, and a hammer. 6 hours of intermittent hacksawing and bashing later, and the weld was finally broken! I tapped the primary out with ease, but the secondary was a different story. I sawed and bashed and did everything I could with my tools to it. No luck whatsoever with getting that out. All I managed to do was wedge it in a bit better. I decided to make a trip to the hardware store, and pick up some cable and some tools. I got a chisel, a new blade, and a rubber mallet. That still wasn't enough to bash out the secondary though. I even tried drilling it out a bit, but that was useless. So I decided to bake it at 250 for about an hour, When it came out, I slowly chiseled and hammered and pried away at the secondary, until finally it was all gone. I now wish I had taken a picture of the huge pile of copper strands all over my workbench. From there, it was an extremely easy build. I cable-tied the transformer back together once I was done, and I was ready. At that point it was about midnight, so I figured I would have to wait until the morning. Morning's soon, so I'll let you know if it works or not once I test it! Wow, I've just written a bit of a novel here.

    tl;dr: It is extremely difficult to build one of these without the proper tools. Buy the right tools, and bake the MOT in an oven for a bit if the secondary is stuck.

    1 reply
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    StephenA21herpingdo

    Reply 6 weeks ago

    I made one of these, and it works, so I know what I'm talking about -- don't remove the primary (the thicker wire). Remove the secondary (the much thinner wire), and replace with a few turns of really thick copper wire -- I used the thickest jumper cables I could find at walmart, and that worked very well.

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    Mich63

    4 years ago on Introduction

    Would this work as a smelter for iron? I have a bunch of rebar lying around, and I'm thinking of trying to melt it down into blocks, then forge them into swords.

    1 reply
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    StephenA21Mich63

    Reply 6 weeks ago

    It can melt rebar, but only a small amount, as it heats up very quickly. More turns might be better. (I made this and used 4 turns of jumper cable from Wal-Mart, and mine heats up in about 15-25 minutes of use).

    I once worked at a powder metal plant, where they would actually melt the iron (I estimate swimming-pool size pool of iron) this way. It was called an induction furnace, but it seemed to work by conduction, because they had two huge electrodes that they would plunge into the ladle, but I am not sure. All I AM sure of was the awesome humming sound as they pumped energy into the thing, and my metal melter makes a similarly satisfying hum. Oh, yes, and the last day I was there, the molten steel worked its way through the fire brick and contacted the underlying water jacket, resulting in a powerful explosion, and molten steel on floor of the plant, which they later had to jack-hammer out. They would create steel powder by taking a stream of steel pouring out the bottom, and having a stream of water intersecting it at right angles, for a sustained explosion that created an iron powder that they later added different things to (copper powder, nickel powder, graphite or carbon, and sometimes other things like chromium, molybdenum, and manganese, along with a binder, a kind of glue, that kept things from separating out.) We would use tons of hydraulic pressure on the powder poured into a die to press out a metal part, that then went through a sintering furnace to produce the finished part. I was on university co-operative education assignment as a Research and Development technician, and we were trying to develop better binders (glues). I would test the hardness, toughness of small bricks (2" x 0.25" x 1").

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    Bowtie41

    4 years ago on Introduction

    Would more turns on the secondary give more current?What about more turns in the primary?Can the core be solid steel instead of laminated?Lotsa questions,but I'm looking for more amps,and since I have a mill,thinking of scaling up the MOT to 2x size with a custom core if possible or feasible.

    3 replies
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    StephenA21Bowtie41

    Reply 6 weeks ago

    Max current would be achieved by a single turn.

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    PlasmaGuy101Bowtie41

    Reply 3 years ago on Introduction

    keep the primary the same, if you want a higher current ( at lower voltage ) output then reduce the secondary winds. NOOOOO! if you use a solid steel core than you'd be wasting half the energy by inducing eddy current which generate heat in the core.

    The way I understand transformers, it's all about the ratio of the windings (primary to secondary). So if you maintain the amount of windings on the primary and increase the windings on the secondary, then yes, the current increases. In terms of the core, solid steel becomes permanently magnetized if exposed to a powerful enough magnetic field.

    Hello Wildfire Phoenix here. This looks really cool and is something that I will do with microwave transformers (definitely an array of them).

    I was wondering could someone, swap the plug for a light switch attached to a powerful car battery for this amazing metal melter?