The usual route to a foam wing is buying sheet stock or large blanks, so watching a stack of slabs get sliced out of throwaway cooler boxes is a genuine treat. Nathan Knight rescues white expanded polystyrene coolers and their lids and turns them into smooth flat sheets, and the stated goal of keeping foam out of the bin is one I wholeheartedly back.
The machine behind it is a 4 axis CNC hot wire cutter, built around an Arduino Uno with a CNC shield and driven by DevCNC software. The cooler is first cut into sections, box and lid both, then the foam is positioned beneath an automated horizontal hot wire that slices along programmed paths. A Harbor Freight hot foam knife is on hand as well, and small metal weights and heatsinks sit on the blocks during cutting.
The tensioning is the detail that stands out for me. The wire runs across a large aluminum bow with a rigid spring on one side, while three zip ties pull it tight on the other side, and that pairing is what keeps the wire tensioned for a straight cut. The results back it up: clean, flat rectangular slabs with every molded contour, bevel and edge shaved away, ending in a tall tower of stacked polystyrene sheets. The digital readouts on the power supply held around 24.0 and 24.1 during the runs.
The clear trade-off is waste. Slicing off all the molded contours, bevels and edges means a fair share of each cooler becomes offcuts before a usable slab appears. When the raw material costs nothing, though, that seems a very fair price for flat, even wing stock.
Project by Nathan Knight. Watch it on their YouTube channel: