Here’s an industrial job I did for Polyfoam, Inc. Lots of interesting uses for expanded polystyrene foam on their site, as well as some impressive recycling stats. They were working with a window manufacturer to design packaging material for windows and needed 200 sets of prototype parts to test the design. They provided blanks and I cut the recesses in them. Here’s the before and after:
This foam is a bit different to work with from the sheets of pink or blue foam you get at the big box lumberyard, which has a smooth skin on it. That smooth skin is pretty impermeable, so when you apply a vacuum to the bottom to hold it down it pulls down tight. The white foam allows some air to move through it, so in order to hold it down securely you have to move a lot of air away from the bottom side, which required building a special vacuum fixture. Here it is with the parts in it after machining:
Wow, is that stuff white! It’s hard to take a good picture of it. Here’s the board without parts:
The blotchy orange stuff is some thick shellac to seal up the MDF material the fixture is made of to prevent air leakage, and make sure all the air is pulling down the parts.
Here’s a closer shot showing the rubber gaskets:
The black rectangles are pieces of foam which push the parts into place to make sure they are accurately positioned.