Infill Density in Additive Manufacturing and Application to the DFMA of an Iron Man Helmet

Additive manufacturing has become increasingly popular for rapid prototyping and industrial applications, particularly in the context of Industry 4.0. However, given the vast design parameter space, there remains a lack of characterisation of the mechanical properties for varying design parameters. Consequently, flexural tests are undertaken following the ISO 178:2019 for fused deposition modelling (FDM) samples, with three infill patterns (lines, gyroid and triangles), four thermoplastic materials, namely acrylonitrile butadiene styrene (ABS), polylactic acid (PLA and PLA+), and polyethylene terephthalate glycol (PETG), and infill densities (print material to part volume ratio) ranging from 0.10 to 1.00. Here we show that (i) the modulus and strength are independent of the tested infill types; (ii) the mechanical properties increase linearly with infill density; and (iii) considering mechanical properties, mass and cost, PLA+ appears as the most suitable overall material choice, with PETG appropriate for strength-driven, low-cost applications. Ultimately, PLA+ is applied to the design for manufacturing and assembly (DFMA) case study of an Iron Man helmet. These findings provide novel insights into the variations of mechanical properties with infill type, density and material for 3D printing applications and may contribute to future development in lightweight and cost-effective additive manufacturing.