We're big fans of building your own tools to solve a particular problem rather than reaching for an off-the-shelf solution, and we're hardly alone. The OpenBuilds website is filled with users who design and build everything from hand tools to laser cutters, and user Mohsen Abbasi recently published a neat little creation of his own: a portable hot-wire cutter for foam. Using some wood, wire, a spring and a lithium-polymer battery, Mohsen's creation allows him to quickly cut and shape modelling foam for a radio controlled boat he is building at a fraction of the cost of an off-the-shelf mains-tethered equivalent.
I needed a foam cutter to cut Polystyrol for a self-built boat. I did not want to pay a lot of money and could not find a portable cutter. That's why I built it myself.