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Difficulty Keeping a Mold Water Tight

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Difficulty Keeping a Mold Water Tight

Postby JLeague » Fri Jul 10, 2015 12:14 am

I have a 8"x6" Mold Max 30 mold that I recently finished, and upon filling it with water to approximate the amount of resin needed I noticed it leaks a bit at the bottom seam.

The gate I created at the bottom of the mold is only about 1/4" from the edge and I'm concerned that might be part of the problem. I also use rubber bands (size 64) against a cardboard backing, and while they stretch fairly well they don't seem to be as tight as I would like. Doubling the bands creates a bit more stress and I'm worried about warping the casts or damaging the mold. ...I never anticipated researching rubber band sizes, but here I am.

I'm curious if this is as simple as getting the right size rubber band or if I'm in trouble as a result of my gate distance to the edge? I'm also curious if the slightly higher viscosity of Smooth Cast might prevent it from leaking versus water? If it's the gate distance to the edge, I'm wondering if anyone has any suggestions? I'm willing to add a little to the bottom but I'm not sure it will work.

Thanks for reading, and any help would be greatly appreciated.
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Re: Difficulty Keeping a Mold Water Tight

Postby RageofAchilles » Fri Jul 10, 2015 4:12 am

This sometimes happens with two part moulds. Soft rubber compresses when banded causing the centre to loosen up. I sometimes put a band vertically to pull the centre in tight.

for best results you need very rigid boards that are custom cut to the size of the mould, this will alleviate the warping effect altogether. I brace my larger moulds with wooden planks cut to the size of the mould.

it does sound like your channel is too close to that edge though, resin will not leak as much as the water, but it will cause a bit of a mess with the channel so close to the edge.
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Re: Difficulty Keeping a Mold Water Tight

Postby mangozac » Fri Jul 10, 2015 7:42 am

Yeah 1/4" is probably a little close, but shouldn't be a massive issue. Resin is much thicker than water so won't leak as much (if at all). You'll probably just get a bit of flash there.

Note that there is an ideal clamping force when using rubber bands - too tight and you can warp the mould, causing these kind of issues. And as RoA mentions, always use some boards on either size. These evenly distribute the clamping force and minimise warping.
Oh yeah I can make that....
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Re: Difficulty Keeping a Mold Water Tight

Postby JLeague » Fri Jul 10, 2015 10:35 am

Thanks for the advice guys, I really appreciate it!
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