Homemade electric furnace

Discussion in 'Furnaces and their construction' started by Scott K., Sep 16, 2017.

  1. Scott K.

    Scott K. Copper

    I get the impression that most people use gas, but for a few reasons I chose electric.
    For starters, I just do small hobby stuff, so I don't plan on doing really large castings. So I bought a bread maker, but that didn't get hot enough, (I'm joking, I'm not that stupid). I did use a bread maker though. But I basically gutted it to get the box. I got an element from Euclids.com. And installed a PID controller, solid state relay, and a cooling fan. And a lot of insulation. I also had to remake the plastic top and lid out of steel.

    My first test fire didn't go so well. It kinda got away from me. It actually melted the insulation, and the relay. So I cut it in half to give more area between the hot side and the electrics. I also used better, ceramic insulation. It doesn't look as good, but it works.

    It can hold up to an A4 crucible, but I could build it bigger in the future if I need to. The whole project cost me about $120. If anybody is interested, I can post something that resembles a how-to article with schematics.

    At the moment, I'm working on a burnout oven. And no, it's not from a bread maker. It's from a microwave. It will be big enough I should be able to burn out 4 - 6 flasks at once.
     

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    Al2O3 likes this.
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    Thats fricken awesome!! Yes please do a build thread! clever as all hell, you sir can open alot of doors for people wanting to get started.
     
  3. Scott K.

    Scott K. Copper

    Thanks. I'll try to get a new thread started soon.
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I like it. My furnace is electric with Kanthal coils and I built it to have the maximum recommended coil and wall loading. It's just simple TC, PiD, and SSR controlled but I'm very happy with how well it works for melting aluminum. It was an involved build that has several furnace sizes, electric and fuel fired, burn out and heat treat, etc, etc. There is a build link in my signature below.

    Here is a direct link to the electrical controls portion.

    http://www.alloyavenue.com/vb/showt...nace-Build-Log&p=187793&viewfull=1#post187793

    One feature I included during the build was the ability to shut down the electrical coils leaving all else operational. This was just low voltage toggle switches that opened up the SSR control circuit. I also included indicator lights to display whether the coils were active and they are powered directly from the coil circuit. This allowed the PiD and temp display to remain operational and not have to re-boot after shut down. I could also see the duty cycle of the heating elements and also insure the coils were shut down before I opened the furnace to skim, flux, extract crucible etc. I considered an interlock to do so but decided against it because it was needed for both the furnace body and lid, and if either one failed, it actually could increase the chance of electrical shock if I relied upon it.

    The other thing I'd mention is it's actually pretty easy to build and wind your own resistive heating elements and this allows you to build exactly what you want in respect to power and dimensions.

    Best,
    Kelly
     
    Scott K. likes this.
  5. Scott K.

    Scott K. Copper

    Dude, that thing is awesome! I'm at a loss for words, 'good job' just doesn't cut it.

    I also have a switch to cut of power to just the coil, a switch to turn off the cooling fan (which is turned on by the pid), and a switch for the whole thing. They are lighted switches so I can tell when they're powered.

    If I get more involved with casting, or need to do bigger parts, and am able to expand, I may base my new design from yours. With your permission of course.

    I did think about winding my own coils. I made a vacuum forming machine many years ago, and wound the coils for that. But that is a much lower temp. I am not perfectly clear on how to figure out how many watts are needed to get to a particular temperature. So I didn't want to take any chances, I found someone online who specializes in coils. Euclids.com was more than helpful and I got two coils for less than $50 each.
     
  6. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Thanks Scott. That is very kind of you to say. Anything I post is meant to be helpful and available to all who wish to do the same. -No permission required.

    This is good, but I must confess, I still need to be very deliberate to make sure I shut down the coils before I open the furnace and I have on occasion lapsed.

    You might consider downloading and reviewing this:

    http://www.hi-tempproducts.com/pdf/the-kanthal-furnace-mini-handbook.pdf

    You can buy the wire on eBay for about 20% of that and when/if, you get into higher power, you basically buy the wire by the pound from the Kiln and pottery supply stores. I made four 4kw 220vac Kanthal A-1, 14 ga coils for about $25 each and there's two of them in my furnace.

    Best,
    Kelly
     
    Last edited: Sep 17, 2017
  7. Scott K.

    Scott K. Copper

    I will definitely keep that in mind. Thanks.
     

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