Working with expanding foam is a project I started on a few years back – it seemed to be the perfect hobby terrain solution, light and cheap. A few months ago, I was approached by Mike from Dragon-Fall asking for help in creating large terrain items for the 40K tournament. It was the perfect motivation to restart work on the project.
Masters were printed at the local library using files from Thingiverse. Three file sets were used in the project:
Files used under Creative Commons non commercial license.
Masters were gap filled with putty to prevent the mold rubber from encapsulating the cargo container.
Tried out a new Mold Max product – NV14. This rubber is super stretchy and is also super smooth. It was able to penetrate the Lego mold box at nearly every point.
First cast with Foam It 8. Its always a bit of a trial to find the right mix amount. Here the foaming resin is lifting about 30 lb of paint and rubber.
Eventually the magic number of 72g/36g was found. The final product takes detail well. You can see a few air bubbles along the back ridge. Because the rubber mold was so flexible, I was able to open the mold wide and treat with talc to fix the bubble problem.
After a fall with a stack of paint cans, it was time to get serious with the mechanical restraint. The mold is enclosed in mdf boards on all sides. Duck tape holds the sides in position. The top board is inside a plastic bag to keep the resin from sticking. Once the resin is mixed, there is about a minute of working time to get the clamps in place before the mix spills out of the box.