My friend, @twin.koi, commissioned a prop replica for a cosplay they were putting together for Pax East 2025. For this project the design focus was on aesthetics and weight. The sword had to match the reference in both scale and color, while being light and ergonomic enough to be carried around the convention hall for a prolonged period. This was especially relevant because the prop was a longsword, so printing at default infill would make for a very heavy prop.
After looking at reference photos of the original prop, as well as other cosplayer's attempts at making this prop, I made a prototype on Onshape. My friend supplied the driving dimensions for the sword so that it would scale with their cosplay, and I printed out the sword on a Bambulabs P1S, so that portions of the sword could be printed with multiple filaments, simplifying postprossesing and assembly of multi-colored sections.
The sword was too large to be printed in a single pass, so I split it into 4 sections with large, flat interfaces. To get the sections to connect together, I placed two locating pins between each section, so that the sword would be optimally constrained. To find the best fit for my printer's tolerance, I printed out several different hole and pin test fits, and recorded the best interference fit.
After the parts were printed at a minimum infill, I assembled the sections with the pins to test the final alignment, and after verifying everything fit together nicely the interfaces were glued. The interfacing surfaces were intentionally as wide as possible, for a maximum effect from the glue.
The prop held up for the entire convention without failing, fulfilling the design goal. For a future attempt of this project, I would improve the pins and infill of the plastic. Shortly after the convention, several pins snapped, and because the pin fragments were still glued into the holes the prop was not recoverable. Upon investigation it was found that the pins had been mistakenly printed at 20% infill, and were much weaker than they were intended to be. In the future the pins should be either printed at 100% infill, or ordered out of a stronger material. I would also change how the main sections were printed, with a thicker outer shell and sparser infill. Because the prop was a sword, there were several sharp edges that were quickly deformed when the prop was dropped or bumped into objects. I think a thicker shell and lighter inside would both make the prop lighter overall and also make it more resistant to those deformations. Additionally, changing the material to ABS instead of PLA would help with this.