For most of us, Spot Welders would fall into this category. [mrjohngoh] had the need to join two pieces of sheet metal. Instead of purchasing a commercial unit, he set out to make his own spot welder.

Unfortunately, early attempts failed quickly as the heat from the welding nozzle melted the adapter. However, with a new design that held the nozzle handle far from the hot end, the ersatz metal ...

and flexible medical equipment. Interestingly, there are actually a few different subsets of plastic welding. Since you don't need to reach temperatures as high as you would for metal, you can get ...