Adventure Time: The Finn Sword

The Finn sword, full size at about 65cm from pommel to tip, shaped to the show's proportions rather than a toy's — the wide leaf-shaped blade and the blocky hilt with its inset gem all read right in photos, which is what you want from a convention prop.

The gem is the centrepiece: translucent, with an LED behind it (5050 chip) that genuinely lights up in a dim room, not just a highlight you hope for in daylight. It's the sort of detail that gets stopped for at every convention. The switch hiding in the grip means there's no obvious button breaking the lines of the hilt, and the lithium-ion battery charges over USB-C through a port tucked into the pommel — no batteries to swap, and charging from a power bank in your bag while you're on the floor.

Printed in PLA+ and PETG: light enough to wear for a day, sturdy enough for the wear that comes with it. Like any prop, it's built for looks and handling, not for hitting anything.

Each sword is printed and assembled one at a time, so small variations from the photos come with the territory.

Development

This project began with extensive research and design planning to ensure the Finn Sword replica would be as accurate as possible. Multiple screenshots and artwork from the Adventure Time series were collected to replicate the scale and shape of the sword accurately. Using Blender, I created a precise 3D model of the Finn Sword, capturing every curve of the leaf-shaped blade and the distinctive hilt with its embedded gem.

Initial prototypes were printed using standard PLA material to test the fit and accuracy of the design. These iterations helped refine the model through several versions until we achieved the final product shown here.

Final Production

To ensure the sword was both durable and visually appealing, a blend of PLA+ and PETG materials was selected. These materials provided the necessary strength and a smooth finish, ideal for a high-quality prop. Once printed, the components were carefully assembled.

The electronic components were fixed into place inside the hilt and handle sections, hidden away behind the translucent gem embedded into the hilt. Any seams were smoothed out to ensure a seamless appearance. The LED light-up feature was a critical aspect of the project. High-quality 5050 chip LEDs were installed behind the gem, with the wiring neatly routed through the hilt.

To ensure convenience and longevity, a rechargeable lithium-ion battery was integrated into the grip. The battery setup included a USB-C charging port, discreetly hidden in the pommel, providing an unobtrusive and practical solution for recharging.

Gallery

Shop this build

• The Finn Sword — £99.00, Full size, approx. 65cm long, 5-7 days