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Thread: Improving Rigidity in Resin Casting

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    Default Improving Rigidity in Resin Casting

    So, thanks to a generous donation of mold-making materials, I've been doing a lot of thinking about what I'd like to make and how I want to go about it. One of the things I've heard through the years is that for several reasons, resin-cast parts can warp. Since one of the things I'd like to do is make resin wall sections, has anyone tried embedding rigid materials like, perhaps, metal rods, plastic or metal channel (u-channel, I-beam, box-channel, etc.), or the like into the resin while it's curing to firm-up the parts? I did some searching and haven't found evidence of this being done, though it's late and I haven't searched very thoroughly yet, so who knows. That's why I'm asking you people.

    Anyway, what say ye, NSNers?
    PW&NJ Railroad

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    @PW&NJ

    I haven't heard of resin castings warping but that isn't to say it can't happen. That being said, I cannot see any logical reason why you couldn't embed something into the mold to give structural stability to the cast. I probably wouldn't use plastic as it is pliable; however, perhaps small gauge brass tubing or similar?

    Obviously, whatever you used would effect the thickness of the wall sections being cast, which could be the only down side perhaps.
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    Not too worried about thickness, especially if I could use whatever I embedded for a dual purpose. Like if I used some brass or aluminum box channel across close to the top, that could be used to hold the roof. Lots of options here, just thinking out loud. I have an older resin cast shell for a locomotive that has warped, which is why I got to thinking about this (still need to straighten that up some day). Anyway, I guess I'll continue my research and do some experimentation. :spy:
    PW&NJ Railroad

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    @PW&NJ

    Depending on the type of Mold Material you have, you may need to get some Mold Release if using Resin for your casts. I use Smooth On Universal Mold Release if that helps at all
    Cheers Tony

    "Knowing what to do is one thing ... being able to do it is another"
    "It is easy to criticize ... a lot harder when you have to justify it"

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    Hi PW&NJ,

    Regarding the casting warpage...if you heat the casting in boiling water for a few minutes...you can place it on a flat surface, weight it down and it should remain straight once it cools.

    If the warpage is the result of gravity and time...consider imbedding steel wire(coat hanger, piano wire, finishing nail, etc.) in the casting.

    Given the low cost of resin, consider adding reinforcing ribs or make the master casting thicker.
    Happy Modeling

    Bruce

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    My experience with resin warping is limited. I am not aware how much of an issue it is out there and have done a fair amount of casting in my time. I have seen some cast loads that did not stand the test of time. But since I do not know what they were exposed to before I got them used, I assumed it was heat due to storage in an attic or hot car.

    If your cast shell had had the support of a mechanism, do you think it would have still warped? (Warped? or sagged?)

    Before I would take the time to solve the embedding issue, I might consider how to give the part more strength, as @BruceNscale mentioned - thicker walls, ribs, etc. Even if you found a convenient way to embed support, (open back, 1-part mold, lay it in?) if the warping was really an issue from shrinkage over time(?) or something, it may still exert force on an embedded part, and still warp...(?)

    What about adding rigid support after the part is cast a cured? Like what we might do to a warped wood or plastic kit?
    Another consideration is to cast the structure in solid parts, if you don't need interiors...

    Food for thought. Not sure what you are planning. Resin casting products have come a long way in last 10-20 years. Early resin products definitely had some issues, UV, shrinking and cracking, oily residues, etc.

    Let us know where you go with this. Good luck.
    Steve - Jugtown Modeler..............Don't know enough about railroading yet, but scale modeling is my life..............Web-Folio

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    Thanks Bruce and Jug! I guess my issue probably isn't as much of an issue as I'd thought, and is only coming to light because I'm getting closer to actually being able to cast anything. The locomotive shell I have that was warped was from about 9 years ago (and not sure how long before that it was cast, nor how it was stored) and it had a slight sag and some wavy warping. I was able to correct it slightly by putting it into very hot water and sticking Legos built up on the inside to get it flatter. I think if I can do that more precisely, I can bring it back pretty close to normal. I just wanted to make sure the wall castings I made didn't end up the same way. I plan to build some sections with DPM wall components, then cast those larger sections to build larger structures more easily. Anyway, I'm going to start by tinkering and seeing how it turns out, and I'll definitely be posting my results.

    Next step, see what I can dig up to trade for some resin so I can actually do any of this.
    PW&NJ Railroad

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    Hi PW&NJ,

    I've been using Alumilite for vehicles and small detail parts for about 15 years.

    The only issues I've had were due to incomplete mixing or rubber molds that were not straight. Both of which were my fault.
    Happy Modeling

    Bruce

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    Thanks Bruce! That looks like some good stuff.
    PW&NJ Railroad

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