My brother collects diving equipment. For some of his collection items, spare parts are hard to find or not available at all. This is also true for his Spinnaker regulator. The mouthpiece is crumbling to dust.
I therefore took measurements and modelled the mouthpiece in 3D-CAD. Then, I designed a mould from that data. The mould was printed in 3D on my Ultimaker² printer. A prototype was then cast in silicon. Casting was done in vacuum to avoid gas bubbles in the material.
The mould is well suited for casting silicon parts and will stand a small batch for sure.
Casting at temperatures above 50°C is not possible with 3D printed moulds made from PLA. The mold gets too soft at that temperatures.