This is a simple 3D model to 3D print a "glue stick" out of plastic. The idea is to use a glue gun to extrude molten plastic instead of hot glue.
See https://wp.me/pk3lN-1dUM for the full story. In short, I used a high temperature glue gun with a "glue stick" 3D printed from PLA instead of a real glue stick. As a result, the glue gun uses PLA instead of hot glue. This file is the 3D model I used to print the "glue stick" out of PLA.
This 3D model has notches in it to engage the feed arm on my glue gun, an 80W "Surebonder" high temperature gun from Amazon. However, different gun models may have different feed systems. YMMV. I printed mine at 75% infill, oriented with the ramps of the notches pointing "down" so that supports aren't needed.
This is the inside view of a model assembled using the PLA glue gun. It is very convenient to do these seams while holding pieces in place because 1) the glue gun is ergonomic and easy to handle, and 2) it bonds and cools quickly so you don't sit waiting for glue to dry/cure/etc.
This is the outside. The seams are lined up, and not filled with glue. Much easier to sand and fill with bondo or something prior to gettting a nice presentation finish. (Ever tried to sand a seam filled with glue? Ughh...) Also the seam is rigid and inflexible, it has no "bend" to it like most glues do.