molds and casting

Discussion in 'Scratchin' & Bashin'' started by davidbross, Dec 20, 2004.

  1. davidbross

    davidbross New Member

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    I am trying to reproduce a cruved, brick building. I plan to use rtv rubber for the mold. My question is once I make the mold how can I, using either plastic or plaster, reproduce the item? It seems like I will end up with some very thick sections where the model curves?
  2. TrainClown

    TrainClown Member

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    I would try using auto body filler, like Bondo fiberglass filler. Get the feather-weight stuff as it is easyer to sand, but most any will work. They are mixed from 2 parts and you can trowel it into the mold and it stays put without pooling from gravity. A small can will go a ling way for modeling.

    TrainClown ;)
  3. davidbross

    davidbross New Member

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    would that be appropriate and cost effective on a commercial model? I am thinking of releasing my first kit.
  4. Bill Stone

    Bill Stone Member

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    I've seen (haven't tried it myself) molded resin retaining walls molded flat and then the molded piece is bent into a curve by demolding it before it is totally cured and just bending it to the desired shape. Worked slick. Of course the mold has to be made on the flat to start with.....
    Bill S
  5. TrainClown

    TrainClown Member

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    It's worth an experiment! I think bondo would be cost efective and work well. It's just another kind of polyester rezin type plastic.

    TrainClown
  6. philip

    philip Guest

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    David,

    as Bill suggested curve the mold. I guess the 100 dollar question is...What exactly are you wanting to reproduce? Post a picture or e-mail it to me & I'll post it up. If the master is already made, glue it down and pour your rubber around it. that way your radius reproductions will all be alike. Still TC's method would be the most cost effective depending on what scale is involved.

    philip
  7. Muddy Creek

    Muddy Creek Member

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    I'd do some experimenting with a variety of materials. Some of the finest brick casting I've seen was Hydrocal wall castings in an N Scale kit by Downtown Deco. I've never seen Bondo used so don't know how it compares for detail quality but nothing looks worse than poorly cast brick work.

    I'd also try using a two part mold to keep the curve and the thickness uniform. Properly constructed, I think this would be your most cost effective method, reducing your labor, material and the inaccuracies in bending a panel to the correct radius after the fact.

    Casting isn't rocket science but it takes a bit of practice to get it right. (I'm still practicing and hoping to get it right someday.) I've been selling some laser-cut wood kits and the main thing I've learned in the process is that people who pay cash for your product rightfully expect the parts to be perfect.

    Wayne
  8. CalFlash

    CalFlash Member

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    If it's small enough and there is no need for access to the inside (like a brick base to a watertower) I'd just make the mold from a master and pour it solid with hydrocal or other plaster. If larger or hollow is needed, how about an interior plug. Think of an angle food baking pan but with a larger center.