Build an induction heater and become a metalsmith

If you’ve ever wanted to forge, cast, or smelt metal, this project is right up your alley. It’s a 30 kVA induction heater built by [bwang] over on Instructables. It gets hot enough to melt and forge steel, iron, and aluminum.

An induction heater operates by surrounding the object to be heated with a coil carrying high frequency AC current. Basically, the entire setup acts like a huge transformer with a shorted secondary. To get these currents into a workpiece, [bwang] used a TL494 PWM controller as an oscillator. The output of the TL494 is filtered and amplified a few times to generate a huge amount of AC current.

Larger versions of [bwang]‘s induction heater are found in foundries and forges all across the land; even though this small version sucks down 50 A out of a dryer or stove outlet, induction heating is very efficient. We’re actually wondering why we don’t see many home blacksmiths using induction heating, so we’ll leave that for our readers to discuss in the comments.

[sessions] reminded us of this induction heater from a few years ago. A little smaller, but still usable.

Comments

  1. Manfre says:

    We’re actually wondering why we don’t see many home blacksmiths using induction heating

    Propane is portable, relatively cheap, and has a lower start up cost.

    • Camerin says:

      Many home brew black smith shops don’t look into the current method, they look at the traditional methods of iron working. Also most people have a fear of electricity. I guess people like to see what might kill them.
      More seriously, you know that a propane torch will get hot, and it will allow you to work you piece, if someone told me to hook up some random electronics together and it will heat up my piece really quickly, and it will save me money in energy. i would be skeptical. Sounds like snake oil to me (well not really i know how it works, generating eddy currents and what not but forget all of the science for a second)

      • kc says:

        The components are not random.

        if somebody told me that masterfully crafted ceremonial sword was crafted by a guy with a hammer and a 3000 degree forge in a dirty shop somewhere in the poor side of town, or industrial park district… I’d be skeptical…!

        :-)

        I’m an EE major, network administrator, ham-radio-operator, former construction worker, who’s #1 hobby is metalworking.. that makes me about the only guy street-cred- qualified to make the aforementioned quip…! :-p

        Oh! and I’m here looking for how-to on getting started with induction furnaces for smelting steel, iron, bronze and brass for casting…

        kc
        K9SPY

    • Max says:

      And electricity is available in almost all homes these days and doesn’t need a tank to carry round, you just need a wire to move around…

      I picked up a faulty induction hob for free and it cost me a couple of quid in power transistors to fix. I did wonder if I could use it for metal melting but if there is a decent write up of how to build a melter from scratch, I could keep the hob for making dinner.

      • Bryan says:

        Despite the ubiquity of residential electrical service, there’s still a lot of issues with using it for this type of work that scares people off (namely electrical codes, homeowner’s insurance, and as others have mentioned the inability to see the thing that could fry you in an instant if you do something wrong). Plus this setup doesn’t seem like it could melt an appreciable enough amount of metal in one batch to cast anything of any significant size. Forging would probably be a bit awkward too, since the size and shape of the coil would limit the workpiece. Something like this would be fantastic for working with jewelry though, since that involves smaller amounts of metal.

        If you want to see how to build a real foundry/forge on the cheap, get a catalog from Lindsay Publications and see what they have to offer. Their offerings are much lower tech, but they definitely qualify as “really old school” hacking.

    • Kevin says:

      Propane does not burn hot enough for many flux welding applications, it will heat the metal to a malleable state without ever burning the metal but coal/coke forges allow for much higher temperatures that make flux welding much easier.
      Depending on how you do it, the start up costs of a traditional forge can actually be less than that of a propane/gas forge

      • Che says:

        Propane its self may not get too hot but a propane forge is not just propane. It is propane shot into a well insulated forge shell (ie: Kaowool). My forge is propane and it is more than capable of burning a 1095 billet into a puddle of useless slag.

    • Hackerspacer says:

      Last time I checked, blacksmiths are not known for their portability. Moving anvils isn’t easy. Last time I also checked, blacksmiths don’t exactly setup and move quickly. Most take time to learn then practice their craft. Keeping costs low is always a generally good trait to have but propane tanks cost money too as do quality blacksmith tools. I don’t buy your argument.

      • jd says:

        Blacksmiths shoe horses. Saw a guy do it out of a pick up truck. Had an anvil and everything. Couldn’t have been more than a thousand bucks worth of propane forge and tools.

      • gpav says:

        Regarding the comment that blacksmiths shoe horses: Wrong. Farriers shoe horses. They have (or should have) special training in a very technical subject — the anatomy of various animal hooves, and the injuries and diseases thereof, and the modes of treatment that can be applied through specially constructed shoes. Blacksmiths may sometimes make horseshoes, but they are more likely to make many other things as well. Farriers, not so much in my experience.

        It’s kind of like the difference between a gunsmith and a machinist. Different specializations and knowledge domains, similar skills and tools.

        I was a working blacksmith for a while some years ago (at a local historical park and for a summer at a nearby Renaissance Fair — I spent that year commuting between 1562, 1845, and 1992. Hard to keep the accents straight.)

        The man I learned from spent twenty or so years as a machinist before he retired and became a farrier, and then did that for a bunch of years until he got tired of looking at horses’ hooves so he focused on blacksmithing and training blacksmiths.

    • canid says:

      Way, way lower. I use propane and charcoal. cost me about $40. I definitely want to build an induction heater one day, but that day is not here yet.

    • The cheapest Chinese machines of a suitable size for blacksmithing are $2,000. American are about 2 times that. I am a hobby smith in Washington State. Grant Sarver, a noted smith and tool maker in our the Northwest Blacksmith Association, started selling and promoting these machines years ago. They are fairly commonly used by professional smiths here.
      They lend themselves to specific purposes related to the size and shape of the piece of stock being heated. Well equipped smiths who can afford extensive tooling use induction heaters as part of several other heating methods. Propane forges can and do reach welding temperatures, but are limited by chamber and burner size as well. Coal definitely reaches weld temperature easily, but forge welding is not exclusively or perhaps even frequently used. It requires more skill than arc welding, and a heated and hammered arc weld is almost indistinguishable from a forge weld.
      As a hobby smith I would like to have an induction heater, but I will have to build it for expense reasons alone. That’s fine because it’s bound to be an interesting, exciting, educational experience.

  2. Andrew Hooper says:

    From memory electrical heating metal has been around for many years and I remember reading an article where it was used in a workshop. I don’t recall the exact method used but I do remember it employed an oak barrel and a high current.

    As a blacksmith I see issues with induction heating firstly in many cases your steel is not straight. in addition I have to wonder what heating the in a strong magnetic field is like to do the the grain of the metal.

    Something to ask yourself is “Why has the traditions not changed much over thousands of years” in addition much of the hand forged work using traditional methods tends to last a lot longer sue to the introduction of silicates and carbon as part of the forging process and using induction you would not get this.

    We dug up some tram parts and blacksmith tools that were burred for 60 odd years. these were pulled out, cleaned up and are almost as good as new. The same went for the Mastermyr find.
    http://netlabs.net/~osan/Mastermyr/

    Items made even in propane forges do not tend to last as long or exhibit the same quality as those made using traditional methods.

    However these types of devices would be perfect for some of the forging process such as rivet making, bolt making etc.

  3. happyhotfurnace says:

    The neat thing about this is being able to do it in an apartment.

    Anyone have any induction korean bbq tips?

    • craig says:

      korean bbq, use a hair dryer for blower with hunk of exhaust pipe to kingsford (or other) charcoal. YES, it works. still need the anvil and quench, but five gallon bucket should work for quench. kids play pool with play sand to catch slag on your patio to house the anvil area. fire extinguisher available ‘just in case’ and a 12 pack of beer for the nosey neighbor with a cell phone on his hip. VIOLA!

  4. Lord Binky says:

    The use of coal adds carbon into the metalworking process which controls a few factors in the end product. You would lose a lot of control with the use of other methods of heating.

  5. Jinx says:

    I’m friends with quite a few art knife makers who specialize in damascus and there are more professionals who own inductive forges than this article implies. Cost isn’t usually an issue for the big guys, they have huge write offs each year. The big issue is relearning the forging process on these inductive units. These guys have grown accustomed to using fired forges over years of work and have a developed feel for their equipment. I would prefer induction hands down…gas forges are loud, hot, and bright. When I’m over at my friends forging, it takes me quite a while to get over the vision issue alone.

  6. Drew says:

    I would love one of these for heat treating watchmaking parts- but I fear it would be overkill! Can anyone tell me if it is all out heating, or can you control the power output- so say, I could heat up a screw or barrel arbor to cherry red, and keep it there with a constant power output for a couple minutes?

    If not, the idea that I could melt STEEL in my apartment is f*ing incredible. Not everyone wants to deal with expensive propane or dedicate an entire side of their house to a huge propane forge grill or something like a blacksmithy to melt steel.

    I have a guy right now with a Levin instrument lathe and full watchmaker’s workshop in his kitchen- he would kill for one of these for small quantity metal melting in a compact form. This is awesome! Totally why I come to hackaday multiple times a day for years now.

    • Hackerspacer says:

      From the perspective of an apartment owner or even neighbor, the concept of my tenants melting steel INSIDE THEIR APARTMENT seems somewhat terrifying at first glance.

      • matt says:

        You forgot that for all intents and purposes it becomes their apartment when you sign the lease, what they do inside is their business. If they cause damage, then take it out of their deposit. And how about all the fires started every year from deep frying, cooking, cigarettes, etc?

    • Malikaii says:

      Since it’s electrical, I imagine you could use some PWM to control the temperature.

  7. George says:

    Snap-On sells little portable induction heaters to make the removal of bolts easier than using a torch in tight spaces(I.E. – under the hood of a car or inside the car even.) It’s called the Mini-Ductor II:

    http://blog.toolsource.com/index.php/2010/07/mini-ductor-ii-magnetic-induction-heater-kit/

  8. jedi says:

    14 oz of propane cost me less than ~2oz of butane.. gets me a few days of playing with melting glass being very wasteful. still, for metal, playing with dangerous voltages and eddy currents piques my interest. i think i will build one of these sometime. i’d like to see just how small I could reproduce this, retaining the functionality.

  9. I just wish I didn’t live in an apartment so I could use ANY method available to melt aluminium for casting. :|

    As it is, I’m saving all my scraps and stuff from my beginner’s practice with turning and milling, so I can one day melt them down. :o

  10. sessions says:

    two years ago we had a similar post.

    http://hackaday.com/2010/06/04/1000w-induction-heater/

    could you add a link to the article in the post?

  11. drdog09 says:

    Induction forging and melting got its foothold in the speciality metals market where the presence of the exit gases from coal/coke/Nat Gas would effect the characteristics of the metal. If you want to melt large gobs of metal quickly and still use juice, then electric arc furnaces are the ticket.

  12. Anthony says:

    In the US, not all houses/apartments have 220v 50w outlets, and getting an electrician to install them can be absurdly expensive. Also, if you want to be portable, nothing beats a nice cylinder of propane or acetylene for making heat, though if someone could do a hack using a Prius to power a portable induction heater…

  13. John says:

    will this incuction heater ,melt platnium?

  14. John says:

    will this particulat induction furnace melt platnium?

  15. DogLaw says:

    So… Induction heating is broadly used in foundries. So if the metal you are using came from a modern foundry, it probably already has any inherent issues that might be imbued upon it present when you buy it. Granted, these are generally at melt point temperatures. I can see some concern with this, but have never seen any issues. To be honest, what are you forging that this could be an issue?… As far as electrical shock goes, high current, high frequency low voltage has the same dangers as arc welding. If you aren’t comfortable with the electrical apparatus in the cabinet, then don’t build it. Size limitations, yes. But to forge something small, why waste the resources firing up the furnace. You can use it for smelting, annealing, and forging. The coil to induce the current is easy to make, so to be somewhat malleable in respect to application. As far as not adding carbon to the metal, this should be an advantage to controlling the addition of carbon. Adding carbon should be done in the hardening process. You should heat the part of the work you are not putting the hammer to, in order to maintain an even heat in the work…. For several reasons. I think it is a good addition to a shop. I’m a machinist by trade, and induction annealing is a great tool for us. Beats the pants off of a MAP gas torch.

  16. tivnan.m says:

    Correct me if I’m wrong, but this works by inducing an electric current in the conducting metal causing what is essentially, a short circuit. I don’t think it would have the same effect on biological tissue. So, if the conductors are properly insulated, this might also be more touch-safe than a propane torch.

    • luke says:

      The long term effects of living in strong magnetic fields is not well known. But there is much evidence to suggest that high tension power lines are detrimental physiologically. Induction furnaces run at a similar hertz, but much higher strength.

      I wouldn’t be worried using one occasionally, but it may cause problems for someone who uses it every day for a living.

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