Subject:
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Re: Self-brew flexible bricks and silent motor for Lego NXT
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Sun, 13 Jan 2008 14:50:20 GMT
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Viewed:
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35991 times
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In lugnet.robotics.nxt, Sibrecht Bouwstra wrote:
> In the context of my study Industrial Design at the TU/e I have developed a
> 'natural animation' expansion pack for Lego® Mindstorms® NXT.
There's a simple solution to the problem you've been having with air bubbles.
Once you've got the mold filled, you need to introduce vacuum, which will pull
the bubbles right out of the material and dissipate them. Back when I was in
the thermoforming business, a company that we shared a building with used this
technique with great regularity on their poured molds because it would prevent
bubbles from breaching the mold surface just in time to be permanent.
All you'd need to do for your design is build a stiff wooden box with a
removable lid, seal the entire inside and outside with epoxy, and the opening
surface with some sort of foam tape. Stick in a nozzle of some sort that can be
hooked up to a shop-vac (preferably in the center of the top), and as soon as
you've got a mold filled and assembled, set it in the bottom, put the lid on,
and turn on the shop-vac. You'll have to experiment with it a bit to see how
long you need to run the vacuum before the bubbles will all be gone, but it
should do the trick.
Also, it might not work well with all materials. For instance, since silicone
requires oxygen to cure, sucking most of the air out will hinder the cure
process. Anything that involves a two-part mix will be unaffected, as they
would all be chemical cures that are triggered by the mixing of both halves,
regardless of what gasses surround them (or don't) at the time.
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