[Malcolm] was having a grand time with his new 3D printer. He was getting tired of monochromatic prints, though. Not having a machine with multiple extruders, he went looking for a way to join pieces of filament. There were a few designs on Thingiverse, but they required milled parts that he didn’t have the tools to recreate. Rather than invest in a mill, [Malcolm] decided to build his own filament joiner. He started by raiding his wife’s hair care tools. His first test was a curling iron. It had the heat, but lacked a good surface to join the filament. [Malcolm's] next test was a ceramic hair straightener, which he found to be the perfect tool.
The splicing process is simple. Start with a hot iron, then lay two pieces of filament on top of the short end of the iron. They soften quickly and melt together. [Malcolm's] real trick is to slightly pull the joint once the two pieces have joined. Pulling causes the filament to stretch, slightly reducing the diameter of the joint. A thinner joint helps prevent extruder jams as the joint passes through. This method works great for PLA. We’d love to see if it works for ABS as well.
Click past the break for an example piece and for [Malcom's] instructional video.