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Pressure Tank

A project log for Moldmaking and casting

A recent project involved making one mold and 2 castings with LEDs inside

Sophi KravitzSophi Kravitz 07/31/2015 at 14:113 Comments

Once the silicone is mixed, it must be degassed. The yellow bell jar connected to the blue vacuum tank is what we use for degassing. You put your mixed silicone in the jar and crank up the vacuum. It's pretty fun to watch the air (bubbles) being pulled out of the mixed rubber. Once the rubber is mixed, it's time to pour.

We are located in NY, and it's July- so it is really hot and humid. We're not doing this in a temperature controlled environment as we should be. Water (humidity) getting into the silicone can cause it to not cure, and heat can cause the silicone to kick (cure) faster than is optimal, trapping bubbles.

The pressure tank to the right is what the mold is placed in to further draw bubbles out of the casting.

Discussions

Jarrett wrote 07/31/2015 at 15:00 point

They're mixing up silicone with a curing agent, and then using the vacuum chamber to remove all of the air bubbles. After that, they will pour all of the newly degassed silicon into a box with the model master to create the mould. More air bubbles will be introduced in that pouring process, of course, but it's still a lot better than the freshly mixed silicone.

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esot.eric wrote 07/31/2015 at 15:54 point

oh, wow... glad I asked, not at all what I imagined.

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esot.eric wrote 07/31/2015 at 14:30 point

the vaccuum pump/tank takes air out of the jar, first, then (or simultaneously) out of the mold-chamber? So when the bubbling stops in the sample-jar, it indicates that it's out of the mold as well?

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