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Post by Tommy on Dec 25, 2016 20:16:43 GMT -5
I am wanting to build a mold out of a alumilite Rubber,resin or etc. So I can pour expandable foam in the mold. To make a few foam parts. And the mold will still hold its shape and size. Most of my foam parts will be less then 12"X12"X12" inches in size. And The outside of the mold will be boxed in on all sides with wood if necessary. To give the casting mold more support. I know expandable foam does produce pressure. but I do not think It is a lot. We also know from building expandable foam parts. very seldom do they come out perfect. They always need a little light sanding here and there, but that is expected.. Thanks For any ideas or suggestions you may offer us. Or if other members build expandable foam parts. What material do you use ?
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Post by carol - Alumilite Corp on Dec 29, 2016 13:48:17 GMT -5
Tommy,
Shake both the A & B side. Alumilite Rigid Foams are 1:1 by weight or volume, make sure you mix thoroughly.
Scrape both the sides and bottom well to ensure a complete mix. Pour the resin down the sides of the mold wetting out as much as possible. The foams will start to rise about the 60 second mark. If you are going to “pack” the foam, mold release a piece of non porous plastic, glass, or metal. Leaving one small corner of the mold open as a breather hole to allow the pressure to release. Allow to cure for a minimum of 30 min
ensuring the skin has cured enough to safely remove it from your mold. Release is also recommended but not required when using silicone rubber molds.
To produce the best skin possible, mix long into the open time and pour as late as possible to fill the mold cavity.
This late pour technique allows for a tighter surface quality. If the part is to detailed or large and you can't wait or lose open time make sure to tilt, rotate and coat the entire mold surface with mixed foams before it starts to rise/set. It does create quite a bit of pressure when expanding, a mother mold (by wood as you suggested around the silicone mold) will help hold it in place. If you are packing the foam it could change the density with the top on the mold (make sure to use release on top piece).
Alumilite Rigid Foams have an Open Time of 45 seconds at 75 Degrees F (100g mass)
your work time. Warmer ambient room temperature will also shorten work time. To increase the open time of Alumilite resins, simply
chill the “A” & “B” sides of the Alumilite in the refrigerator increase the open time of the Alumilite Foams by 30 to 40 seconds. If you are going to chill resin, make sure you preheat molds prior to pouring 120F for a more even and consistent cure.
Regards,
Carol
Happy New Year
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