Building Furnace

Discussion in 'Furnaces and their construction' started by Skratch, Dec 11, 2021.

  1. Skratch

    Skratch Silver

    Yes, it's a plaster mold, don't know for sure how to melt out the wax. Thought about wife's oven,
    support mold somehow to let the wax flow out the sprue and riser holes into something to catch
    it for re-use. I'm learning as I go, any suggestions appreciated. :)

    Sorry PeTee, I miss-understood your question. :(
     
  2. Peedee

    Peedee Silver

    If it's plain POP you may have to do a re-think. Investment plasters are designed for the job, trying to get the chemically bonded water out of POP with the mould disintegrating is near impossible. POP molds and molten metal don't usually go well together

    The other guys here know more about investment.
     
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  3. mytwhyt

    mytwhyt Silver

    I'll say what no one else will say, your plaster mold will never work, even with some kind of metal frame for support. You are asking for a kind of performance that plaster is not capable of., If plaster would work, we'd all be using it instead of the expensive high temp investment we buy. I understand how a forge could be appealing, since it lets you pick up the crucible from the side... I am curious as to how a crucible will take to being direct fired, from the side, until it melts 2 kilos of copper.
    I don't know if you've been here, but there are a lot of low-cost furnace builds here.
    home and backyard metalcasting
     
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  4. Peedee

    Peedee Silver

    Thanks mywthyt, I was being too delicate.
     
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  5. Skratch

    Skratch Silver

    No worries mates, I'm old but not to old to learn, if I'm chasing a snipe just lay it on me. :)
    I appreciate any knowledge anyone wants to share, when it comes to this casting business
    I'm dumb as a day old dog. I may ask some weird questions but just consider the source. ;)
    Seriously, thanks to all for the help !

    John,,,,,
     
  6. Peedee

    Peedee Silver

    I feel bad you've got a really good wax in a plaster mold that isn't going to work.

    Please don't underestimate pouring into a POP mould that couldn't be burned out properly. I got lucky with a flash strike across my neck, my fence and garden not so much. That wasn't how I intended to learn ...

    Moving forward, can you recover the wax from the plaster? David will chime in with proper investments.

    Forges and furnaces are very different things, the build threads here are a worth reading, you will kill a crucible in short order with direct flame.
     
  7. FishbonzWV

    FishbonzWV Silver Banner Member

    For a one off, I would make life easy and go with lost foam.
     
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  8. DavidF

    DavidF Administrator Staff Member Banner Member

    There is another Dave out in California that has been working with using straight pop for his investment castings. He said the trick is to fire it extremely slowly to prevent it from cracking.
    I don't know what sort of luck he has had, but since you already have your pattern invested you might as well give it a try....
     
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  9. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Was this the one? Lost PLA/POP-Silica

    http://forums.thehomefoundry.org/index.php?threads/turbine-engine-mid-frame.2058/

    Best,
    Kelly
     
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  10. DavidF

    DavidF Administrator Staff Member Banner Member

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  11. Skratch

    Skratch Silver

    I melted the wax out by setting it over a container to catch the melt, sprue down. Set it on a hot plate to
    control the heat and covered the whole thing in alum. foil to hold the heat around the mold. Left it till
    well after no wax dripped and then let slow cool still covered, no visible cracks on mold. Kind of a Rube Goldberg
    affair but seemed to work, the wax was not recoverable. Maybe I'll just cast with some kind of low
    melt plastic as don't want to waste the mold, don't want to repeat PeeDee's experience. ;)

    Forgot to add ,,, Decided to just use the forge as intended, not casting. I'll use it to make tools
    and build a furnace in the meantime. Don't want to ruin my crucibles.
    Heck, got more time than sense, better to use it learning. :)

    Thanks, John ,,,,,
     
    Last edited: Dec 18, 2021
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  12. Skratch

    Skratch Silver

    Quick question,,, bricks delivered, planning on building the forge as depicted in video in post 8.
    I like the idea of the burner through
    the top, but question is, what is the best location , top or side or does it matter ?

    Thanks,, John,,
     
    Last edited: Dec 23, 2021
  13. Skratch

    Skratch Silver

    Well, I got my furnace fired up, not working great yet but good enough to make my first pour. It's the axe pictured above. You guys
    were right, PoP not good but I'm from MO and just like when I was told not to pee on the elec. fence I just had to see for myself,, :eek:
    Here's the result ,,,,, I'll just clean it up a bit and hang it on the wall as a reminder what NOT to do.

    Thanks to all ,,,,, John,,,
    IMG_20220110_162356.jpg IMG_20220110_162345.jpg
     

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