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Thread: Round and Round we go

  1. #21
    Moderator DavidF's Avatar
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    Quote Originally Posted by kcoffield View Post
    If you were in high school in the 80s and have been retired for years, Congrats and good for you! ....and whoa, those are some large lost foam castings.

    Though I believe the discovery of Polystyrene considerably predated the turn of the 20th century, I don't believe expanded polystyrene wasn't around until the 1940s. Anyone know what the earliest example of lost foam casting may be, commercial or otherwise?

    Best,
    Kelly

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    It would? How so?

    Best,
    Kelly
    Picture making all the patterns and cores for a flathead ford v8 then make the mold and assemble the cores vs just making a foam block which could be made in section, glued together, invested and poured. Maybe its just me but that certainly seems simpler in my mind.
    IIRC EPS foam was first created in Germany in the 1930's Not sure about when the first casting appeared though..
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  2. #22
    Quote Originally Posted by DavidF View Post
    Picture making all the patterns and cores for a flathead ford v8 then make the mold and assemble the cores vs just making a foam block which could be made in section, glued together, invested and poured. Maybe its just me but that certainly seems simpler in my mind.
    Ohh, agree with all that for sure....I just didn't understand how the introduction of shell to the statement made it more so......but if you just mean some sort of coating for the purpose of better finish and still loose sand, lost foam, I'm with ya. In fact, add cnc cut foam patterns and I'm really with you. I can hardly wait to get back at it this weekend.

    Best,
    Kelly
    My furnace build ----- I toil and fettle then foam turns to metal!

  3. #23
    Moderator DavidF's Avatar
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    Yes exactly!! The shell would just be to improve surface finish and allow the use of vacuum assist. Im A big big fan of using vacuum when casting. Improved surface finish, simplify gating and venting, and I would not be surprised if it has a drastic effect on the the reduction of hydrogen in aluminum castings. I cant prove the later, only speculate...
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  4. #24
    Quote Originally Posted by DavidF View Post
    ....I'm A big big fan of using vacuum when casting. Improved surface finish, simplify gating and venting
    I'm going to have to play around more with vacuum assist on my lost foam rig because it actually produces poorer finishes (in aluminum) than gravity fed and that's only at -7" Hg.

    Potential contributing factors are:


    • Limitation of drywall mud coating.
    • Unmodified or reduced pour temp from compared to gravity fed. They look a lot like a hot pour sand casting.
    • Mold temp is ambient.
    • Other unknown.



    Despite the surface finish, I either need fully coated or fine media because it also produces massive sand penetration by the metal and can tend to ingest and/or destabilize the loose sand. Lost Foam in investment or ceramic shell may be a different story.

    Best,
    Kelly
    My furnace build ----- I toil and fettle then foam turns to metal!

  5. #25
    Senior Member Tobho Mott's Avatar
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    Quote Originally Posted by DavidF View Post
    IIRC EPS foam was first created in Germany in the 1930's Not sure about when the first casting appeared though..
    Lost-foam casting was invented in the early fifties by Canadian sculptor Armand Vaillancourt. So sayeth Wikipedia, anyhow...

    Really looking forward to seeing what you do with those beads!

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  6. #26
    Moderator DavidF's Avatar
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    Good article on polystyrene and its creation...
    https://www.thoughtco.com/invention-...rofoam-1992332
    Knew germany was in there somewhere lol...
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  7. #27
    It was Harold Shroyer who patented the Full Mold or Lost Foam process in 1958: https://www.google.com/patents/US2830343

    In my files I have lots of information and photo of W.C. Grace Company experimenting with the process. My brother was in touch with the company in the early 60's and even talked with Shroyer. Shroyer got a few cents per pound when anybody used his patent, so most companies shied away from the process until the patent had expired.

    On my patterns, every time you make anything for Lost Foam it's a one shot deal. I have made multiple copies in styrofoam like those items shown in that photo.

    Or more recently, those shown below. They are different, I used ceramic slurry on those side rods. The second photo has Lost Foam Guard Rails that were molded in regular PetroBond, Lost Wax items that were invested in R&R Ultravest, and the switch frog is from a wooden pattern in PetroBond.
    Attached Images Attached Images

  8. #28
    Senior Member Tobho Mott's Avatar
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    Ok that seemed like conflicting info until I looked it up a little more:

    https://en.m.wikipedia.org/wiki/Full-mold_casting

    The first patent for an evaporative-pattern casting process was filed in April 1956, by H.F. Shroyer. He patented the use of foam patterns embedded in traditional green sand for metal casting.
    https://en.m.wikipedia.org/wiki/Lost-foam_casting

    ...Next, the foam cluster is coated with ceramic investment, also known as the refractory coating, via dipping, brushing, spraying or flow coating... After the coating dries, the cluster is placed into a flask and backed up with un-bonded sand. The sand is then compacted using a vibration table. Once compacted, the mold is ready to be poured...
    ...Lost-foam casting was invented in the early fifties by Canadian sculptor Armand Vaillancourt. Public recognition of the benefits of LFC was made by General Motors in the mid 1980s when it announced its new car line, Saturn, would utilize LFC for production of all engine blocks, cylinder heads, crankshafts, differential carriers, and transmission cases.
    Sounds like what David and Kelly have been working on is a little closer to the lost foam method attributed to Vaillancourt than Shroyer's full mold method that uses bonded sand. Except that the shell is not always used, and when shell is used it is not always ceramic.

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  9. #29
    Moderator DavidF's Avatar
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    Sounds like what David and Kelly have been working on is a little closer to the lost foam method attributed to Vaillancourt than Shroyer's full mold method that uses bonded sand. Except that the shell is not always used, and when shell is used it is not always ceramic.
    Kelly is the one piercing the waves, Im just riding in his wake

    Right now im running zero and two. The foam was a flop It didnt expand, it actually shrunk! WTH?? arrgh!! Then there is the home brew ceramic shell... I thought for sure i would have great things to report. The shell built up well and the burn out looked good. But as soon as I tried to pick it up it crumbled into pieces. Close, maybe I didnt burn it out long enough??
    foam.jpg
    shell.jpg

    Oh well better luck next time...
    A calm sea does not make a skilled sailor...
    http://thehomefoundry.org

  10. #30
    Senior Member Tobho Mott's Avatar
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    Quote Originally Posted by DavidF View Post
    ... I thought for sure i would have great things to report.
    Told ya, the best predictor of lost foam success is thinking "well there's no way THAT worked". And of course, the opposite is true as well...

    Keep it up, you'll get it all to work eventually!

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

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