Effects of Material Extrusion Printing Parameters on the Foaming Behavior and Properties of Foaming Agent Modified Polypropylene: A Taguchi Based Investigation

Foam 3D printing offers a promising route for producing lightweight structures, although the cell morphology and mechanical performance of printed polypropylene remain highly sensitive to processing conditions. This study investigates the effects of printing temperature, printing speed, and nozzle diameter on the foaming behavior and property retention of polypropylene containing a chemical foaming agent using a Taguchi L9 design. Printing temperatures of 220°C–240°C, speeds of 40– 80 mm/s, and nozzle diameters of 0.4–0.8 mm were evaluated through density, hardness, tensile, and flexural testing, scanning electron microscopy, and differential scanning calorimetry. Printing temperature had the greatest influence on density, contributing 34% of the observed variation, and affected hardness and cell morphology. Nozzle diameter was the dominant factor affecting mechanical performance and contributed 59.1% to flexural strength variation. The 0.8 mm nozzle was associated with a more stable cellular structure at high temperatures, while printing speed showed a smaller overall contribution. The preferred conditions identified from the main effect analysis provide practical guidance for selecting printing parameters within the ranges investigated. These findings provide a quantitative basis for balancing lightweight design and mechanical performance.