Machine tools often have powerful drive motors, allowing them to work quickly and accurately to get the job done fast. However, this can cause major damage if the tool head collides with an unexpected object. To protect against such occurances, [Xnaron] developed a simple system to shut down his plasma cutter in the event of a crash.

The system consists of a 3D printed collar that fits around the plasma cutting torch. The collar has two mating parts, which are held together with three magnets and three ball bearings to act as a key, maintaining the correct orientation. Three limit switches are then fitted, held closed by the two mating halves. When the torch collides with an object, this causes the magnetic coupling to seperate, triggering one or more of the limit switches, and shutting down the machine safely.

Video of an unplanned collision shows the device working well. It’s a neat solution that could probably be adapted to other types of machine tool that don’t experience high lateral forces. Of course, if you don’t yet have a plasma cutter, you can always make your own. Video after the break.