It's been a long time since I posted here. I'm still building carbon frames but making a big change in direction. Below is one of many steps towards molding tubes and frame components in-house.
In order to create molded carbon tubes and frame parts I needed to be able to mold silicone bladders that fit the inside shape of the final carbon parts. I didn't want to use wrinkle prone sleeves or other methods. I want to use shaped bladders. In order to make molds I purchased a 3D printer. I chose an Atom 2.0 Printer for the accuracy and print volume (particularly print height). Now, each iteration of a mold costs about $10 worth of ABS filament.
Here are mold components for a bottom bracket bladder being printed.
I lightly sanded the parts, smoothed them with acetone and covered them in mold release.
I mixed up the two part silicone and attempted to degas it prior to injecting into the mold.
I used an empty caulking tube and caulking gun to inject the silicone into the mold. It started to pop open (the end cap) so I had to clamp it shut during the injection phase. Having made the mold parts out of "clear" ABS I could tell the mold was filling well.
After letting it cure overnight I trimmed the excess silicone and opened the mold.
It was a bit of a struggle to get the core part of the mold out of the bladder. Luckily the silicone stretches a long way. The finished bladder has some flash and a few bubbles in it but it holds air which is the important part. The flash trimmed of easily leaving a smooth outer surface.
I've also been using the printer to make models of each tube I intend to mold. More to come...