Balloon Banjo: 3D-Printed Instrument Turns Party Balloon into a Sound Box

The Balloon Banjo, a novel musical instrument created by Co:Creation Lab, is a 3D-printed design that utilizes a replaceable party balloon as its sound box to investigate the impact of air volume on resonance. This DIY banjo is composed of seven printed parts, along with fishing line or nylon strings and a standard round balloon, enabling sound modulation through balloon inflation and string tension adjustments. In total, the instrument comprises 19 components, including a neck, two bridge pieces, left and right flanges, seven pegs, and peg sockets, all assembled without metal hardware or glue using hand-turned plastic screws. It promotes experimentation by allowing users to interchange balloons and strings of varying thicknesses. Technical details include PLA printing with a 0.4 mm nozzle, a layer height of 0.2 mm, and 15 percent infill, with an estimated print duration of about 11 hours. The pegs and sockets are crafted with a finer 0.16 mm layer height for better fit, while the designer recommends a 0.15 mm clearance for PLA and an additional 0.05 mm for PETG. The neck is printed flat to enhance durability, as vertical printing could lead to breakage along layer lines under tension. Serving as both a playable instrument and an educational tool in acoustics, the Balloon Banjo illustrates the relationship between air volume, string tension, and tone. This project was highlighted on designboom, with all images provided by Co:Creation Lab.