Custom 3D-Printing Pen was Designed to Weld Plastic Parts Together

Half-Baked Research created a handheld tool that takes the concept of a 3D pen and supercharges it into a gadget designed to do more than simply slap some molten plastic in the air, resulting in a real plastic welder for the makers. Standard 3D pens just draw a line of melted filament, which is ideal for casual drawings or simple repairs.

We’ve seen makers use them as glorified glue guns, filling gaps with PLA or PETG and holding things together with a few tacks. However, welding is a very different beast. It entails heating both the base material and the filler until they melt and fuse together at a deep level, allowing the bond to withstand stress and strain. Glue holds surfaces together, whereas welding fuses them together. There are industrial plastic welders, but they are typically bulky hot-air guns or fussy torches. This invention puts serious welding power into a tiny small pen.

Half-Baked Research begins with a rather easy problem: most off-the-shelf 3D pens have poor ceramic tips that do not effectively transfer heat to the workpiece. Welding is a time-consuming and incorrect process that necessitates holding down the trigger for extended periods of time or risk completely damaging the part. The remedy is simple: replace the ordinary 3D printer hot-end with its trusty brass nozzle. Brass is excellent at conduction heat, resulting in a pleasant, targeted warmth just where the joint needs it. To make matters even better, they improved the extruder, which now pumps filament quicker and hotter than most regular pens.

The ultimate result resembles a slightly beefed up up hot glue gun, rather than the slim doodling pen you might imagine, earning it the nickname “plastic extrusion gun”. They spent some time in OnShape, a free CAD tool, building a housing for the thing, which would house the hot-end, extruder, bearings, and electronics in the proper locations. They used a tiny little DC motor from AliExpress to drive the filament feed, as well as a microcontroller, some motor drivers, a display, and a DC-DC converter all connected neatly on custom PCBs, eliminating the need for messy hand wiring.

Assembly was a nightmare, as he had to solder some boards, press some bearings into holders, tidy up cables, and ensure the hot-end was correctly fastened. He turned out some JLC CNC pieces for increased strength and heat resistance around the important sections, while leaving the nozzle metal for good old-fashioned direct contact and rapid heating. Users simply load a spool of 1.75mm or 3mm PLA or PETG, adjust the temperature to their preference, and regulate the speed manually or via a fancy pulse mode activated by buttons.

Demonstrations show the tool melting the edges of two plastic pieces with the heated nozzle, pumping out new material to fill the seam, and then fusing the entire thing together into a single solid piece. Another way for creating plastic rivets is to just put the nozzle in, start squirting material while pulling it back, and then hammer that hot glob flat with the head of this machined aluminum tool, and you’ve got yourself a clean, embedded fastener.
[Source]