Additively manufactured foamed polylactic acid for lightweight structures

Purpose: This study aims to make foamed polylactic acid (PLA) structures with different densities by varying deposition temperatures using the material extrusion (MEX) additive manufacturing process.

Design/methodology/approach: The extrusion multiplier (EM) was calibrated for each deposition temperature to control foaming expansion. Material density was determined using extruded cubes with the optimal EM value for each deposition temperature. The influence of deposition temperature on the tensile, compression and flexure characteristics of the foamable filament was studied experimentally.

Findings: The foaming expansion ratio, the consistency of the raster width and the raster gap significantly affect the surface roughness of the printed samples. Regardless of the loading conditions, the maximum stiffness and yield strength were achieved at a deposition temperature of 200°C when the PLA specimens had no foam. When the maximum foaming occurred (220°C deposition temperature), the stiffness and yield strength of the PLA specimens were significantly reduced.

Practical implications: The obvious benefit of using foamed materials is that they are lighter and consume less material than bulky polymers. Injection or compression moulding is the most commonly used method for creating foamed products. However, these technologies require tooling to fabricate complicated parts, which may be costly and time-consuming. Conversely, the MEX process can produce extremely complex parts with less tooling expense, reduction in energy use and optimised material consumption.

Originality/value: This study investigates the possibility of stiff, lightweight structures with low fractions of interconnected porosity using foamable filament.