Fused filament fabrication (FFF) of bio-based low-density polymer foams

In a world in which lightweight construction is playing an increasingly important role due to the need to conserve re-sources and lower the greenhouse gas emissions, it is important to develop new technologies that enable lighter products. Additive manufacturing offers a high lightweight potential due to its freedom of design by realising low part densities, but it is not yet possible to print low-density polymer foams to achieve even lighter parts. Therefore, this paper presents a novel, extrusion-based additive manufacturing process that uses a bio-based polymer filament loaded with a physical blowing agent to manufacture foam parts. An extrusion test setup allows the analysis of foam extrusion boundary condi-tions, i.e. the relationship between feeding velocity, heater temperature, extruded material diameter, extrusion force and extruded material density. Lowest densities can be achieved by using low temperatures and fastest at this temperature possible feeding velocities. A comprehensive parameter study on the additive manufacturing of a simple foam test part shows continuous low densities of nearly 100 kg/m3 with an adequate print quality. The analysis of the foam mechanisms of three selected scenarios demonstrates that the calculation method used has adequate predictive power for print results. With the characterisation used, correlations of the expansion velocity and time of the polymer while printing can be reasonably well mapped after the printing process.

Presentation language: ENG