Void reduction in fused filament fabrication (FFF) through <i>in situ</i> nozzle-integrated compression rolling of deposited filaments

The rastering of discrete polymer filaments during Fused Filament Fabrication (FFF) results in the formation of voids between filaments, leading to poor properties and performance of the printed part. Minimising voids and improving filament-to-filament adhesion remains a key technological challenge for FFF. While mechanical rolling is commonly used in traditional manufacturing, its use in polymer 3D printing has not been explored much. This paper discusses the in situ compression of just-deposited filament using a roller that is integrated with the filament-dispensing nozzle. The roller travels with the filament nozzle, and compresses the filament immediately after deposition when it is still soft. The rolling process is characterised using high speed imaging and infrared (IR) thermography. The effects of compression force and roller temperature on print quality is investigated. In situ compression of the filaments is shown to result in 10X reduction in void formation. Tensile test results show 154% improvement in Ultimate Tensile Stress (UTS) and 417% improvement in material toughness due to compressive rolling. It is expected that implementation of the rolling technique discussed in this work may help print parts with improved properties and functionality.