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aluminum casting problems

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  • matus1976
    Hello, for some time I have poured and cast small aluminum C clamps. The past two weeks I have tried to make more of them and my pours keep failing, they do
    Message 1 of 4 , Jan 3, 2007
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      Hello, for some time I have poured and cast small aluminum C clamps.
      The past two weeks I have tried to make more of them and my pours keep
      failing, they do not fill out entirely. I have made over a dozen of
      these succesfully, now I can't seem to make even one. I dont get it.

      I am making a C clamp that is about 4" long and 3" tall out of 3/4"
      pink polystyrene foam, then buyring it horizontally in sand with a
      pour spout sticking up out of the sand. I have tried short wide
      spouts, long tall wide spouts, tall narrow spouts, tilting the clamp
      at a slight down angle. Waiting until the aluminum is really hot and
      pouring right after it has melted. The only thing I can think is that
      my garage is not heated, and it's colder lately and the other clamps I
      did were in the summer.

      Any suggestions?

      Thanks

      Michael
    • Lyle
      I pour in an unheated garage every weekend. Usually 6 to 10 molds and sometimes it s below zero (not this year yet though) Your pouring temp won t be affected
      Message 2 of 4 , Jan 3, 2007
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        I pour in an unheated garage every weekend. Usually 6 to 10 molds and
        sometimes it's below zero (not this year yet though) Your pouring
        temp won't be affected but if your running a small crucible, it'll
        cool off faster. I would venture to guess your pouring them too cold.
        If your not running a pyromter, you might have to let the melt "cook"
        a little longer as the propane isn't getting to your burner as fast
        as it does in warmer weather due to the lower vapor pressure and
        tendancy to freeze up the tank. I have the same problem with bronze
        in cold weather due to the propane tank freezing up. Aluminum seems
        OK for me but I get a melt in just a few minutes. Why lost foam for
        such a simple part?
        LL

        --- In hobbicast@yahoogroups.com, "matus1976" <matus@...> wrote:
        >
        > Hello, for some time I have poured and cast small aluminum C
        clamps.
        > The past two weeks I have tried to make more of them and my pours
        keep
        > failing, they do not fill out entirely. I have made over a dozen of
        > these succesfully, now I can't seem to make even one. I dont get
        it.
        >
        > I am making a C clamp that is about 4" long and 3" tall out of 3/4"
        > pink polystyrene foam, then buyring it horizontally in sand with a
        > pour spout sticking up out of the sand. I have tried short wide
        > spouts, long tall wide spouts, tall narrow spouts, tilting the clamp
        > at a slight down angle. Waiting until the aluminum is really hot
        and
        > pouring right after it has melted. The only thing I can think is
        that
        > my garage is not heated, and it's colder lately and the other
        clamps I
        > did were in the summer.
        >
        > Any suggestions?
        >
        > Thanks
        >
        > Michael
        >
      • Scott Trostel
        I pour castings outside in Ohio and this time of year I can plan on an extra 100 to 200 degrees of heat in gaining successful pours because the sand is colder
        Message 3 of 4 , Jan 3, 2007
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          I pour castings outside in Ohio and this time of year I can plan on an extra 100 to 200 degrees of heat in gaining successful pours because the sand is colder than in the summer and it is going to draw the heat from the metal before it can flow into the cavity as we hope..

          One foundryman I know who pours in an unheated shop tells me that on Monday morning until the shop warms up they pour at 1,600 degrees. As the shop warms and the sand warms they cut back on the pouring temp. By Tuesday they can pour at about 1,350 degrees.

          matus1976 <matus@...> wrote:
          Hello, for some time I have poured and cast small aluminum C clamps.
          The past two weeks I have tried to make more of them and my pours keep
          failing, they do not fill out entirely. I have made over a dozen of
          these succesfully, now I can't seem to make even one. I dont get it.

          I am making a C clamp that is about 4" long and 3" tall out of 3/4"
          pink polystyrene foam, then buyring it horizontally in sand with a
          pour spout sticking up out of the sand. I have tried short wide
          spouts, long tall wide spouts, tall narrow spouts, tilting the clamp
          at a slight down angle. Waiting until the aluminum is really hot and
          pouring right after it has melted. The only thing I can think is that
          my garage is not heated, and it's colder lately and the other clamps I
          did were in the summer.

          Any suggestions?

          Thanks

          Michael





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        • matus1976
          Thanks, I will try that. My propane tank did cool significantly and freeze to the ground yesterday. My crucible takes about 20 minutes to heat up enough and
          Message 4 of 4 , Jan 3, 2007
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            Thanks, I will try that. My propane tank did cool significantly and
            freeze to the ground yesterday. My crucible takes about 20 minutes to
            heat up enough and melt the aluminum in it when I cold start it. The
            crucible is just a 1/8" walled steel pipe about 4" in diameter with a
            3/16" plate welded at its base, could the crucible be too thin? I
            havent got around to making a steel mold for the clamp yet, and I can
            make the foam clamp in just about a minute with a hot wire cutter. I
            want to figure this out because I want to start doing more complex
            parts, but if I cant get such a simple shape to fill I got issues! I
            am going to try pouring the clamp vertically and see if that works.
            But I'll definately try letting it cook for a while. I have a bunch
            of 4" pulleys I want to pour as well.

            Michael

            --- In hobbicast@yahoogroups.com, "Lyle" <creepinogie@...> wrote:
            >
            > I pour in an unheated garage every weekend. Usually 6 to 10 molds and
            > sometimes it's below zero (not this year yet though) Your pouring
            > temp won't be affected but if your running a small crucible, it'll
            > cool off faster. I would venture to guess your pouring them too cold.
            > If your not running a pyromter, you might have to let the melt "cook"
            > a little longer as the propane isn't getting to your burner as fast
            > as it does in warmer weather due to the lower vapor pressure and
            > tendancy to freeze up the tank. I have the same problem with bronze
            > in cold weather due to the propane tank freezing up. Aluminum seems
            > OK for me but I get a melt in just a few minutes. Why lost foam for
            > such a simple part?
            > LL
            >
            > --- In hobbicast@yahoogroups.com, "matus1976" <matus@> wrote:
            > >
            > > Hello, for some time I have poured and cast small aluminum C
            > clamps.
            > > The past two weeks I have tried to make more of them and my pours
            > keep
            > > failing, they do not fill out entirely. I have made over a dozen of
            > > these succesfully, now I can't seem to make even one. I dont get
            > it.
            > >
            > > I am making a C clamp that is about 4" long and 3" tall out of 3/4"
            > > pink polystyrene foam, then buyring it horizontally in sand with a
            > > pour spout sticking up out of the sand. I have tried short wide
            > > spouts, long tall wide spouts, tall narrow spouts, tilting the clamp
            > > at a slight down angle. Waiting until the aluminum is really hot
            > and
            > > pouring right after it has melted. The only thing I can think is
            > that
            > > my garage is not heated, and it's colder lately and the other
            > clamps I
            > > did were in the summer.
            > >
            > > Any suggestions?
            > >
            > > Thanks
            > >
            > > Michael
            > >
            >
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