Fused deposition modeling printing is a material extrusion (MEX) process that has gained popularity over the years due to its increased affordability and greater versatility. There is a wide variety of MEX printing technologies and a broad spectrum of materials that can be 3D printed, ranging from metallic to non-metallic materials. MEX has emerged as the most common technology in consumer-grade, desktop 3D printers for printing thermoplastics, such as acrylonitrile butadiene styrene (ABS) and polylactic acid. High-density polyethylene (HDPE) is a widely used thermoplastic material for product packaging. The sheer availability of recyclable or recycled HDPE (rHDPE) from used packaging has led to efforts to apply it in MEX printing. However, rHDPE presents challenges as a filament material, including issues such as part detachment from the print bed and high warpage. The focus of this study is to determine the optimal conditions that can mitigate, if not eliminate, the print bed adhesion problems associated with printing rHDPE filaments. This was achieved by conducting a series of tests to address these challenges, including part removability relating to the shear strength of print bed adhesion to identify the necessary range of print bed adhesion and corresponding parameters.

Ankle braces typically restrict the functional range of motion. Braces should preferably allow a free functional range of motion during sport while protecting the foot at high-risk positions beyond that range. This could be achieved with 3D printed metamaterial structures that could have varying properties throughout an individual’s ankle range of motion. This paper aims to illustrate an exploratory methodology of using an affordable Fused Deposition Modelling 3D printing technology to develop an ankle brace using metamaterial structures. It also showcases the design, manufacturing processes and testing of 3D printed customised ankle brace prototype designs that incorporated metamaterial structures. Initial tests showed that as designed, the prototype braces maintained the full range of motion for plantar flexion angles. Results also showed that the prototypes required one of the lowest moments during functional range of motion while achieving almost twice to thrice the moment required beyond the functional range of motion.