Screw extrusion fused granulate fabrication : trends, materials, extruder classification and future development

Abstract

This paper presents a systematic review of fused granulate fabrication (FGF), focusing on the classification of FGF extruders, the determination of materials used, and an analysis of past and present trends to forecast future developments. As a rapidly growing field, FGF is increasingly relevant for advancing a circular economy, making it essential to understand the current level of technological achievement from an academic perspective. This review also aims to identify the research hotspots to facilitate future collaborations and classify existing systems to better guide further developments, highlighting gaps in the literature and emerging trends. The review was conducted following the PRISMA guidelines, ensuring a comprehensive and methodologically sound analysis. FGF extruders were classified based on screw length and diameter, identifying small-scale extruders (up to 100 mm in length), medium-scale extruders (100–200 mm), and large-scale extruders (over 200 mm). Additionally, we categorized powder-only extruders, which are typically under 7 mm in diameter, specialized for heat-sensitive materials, and predominantly applied in personalized medicine and scaffold production. Our findings reveal that a wide variety of materials, including high-performance polymers, fibre-reinforced composites, elastomers, and direct regrind materials, are being utilized in FGF. Novel designs, such as in-process material mixing, are also emerging. These findings provide an updated overview of the current state of FGF technology, offering valuable insights for policymakers and research groups. By understanding which class of extruders is suitable for specific applications, stakeholders can make more informed decisions, guiding future research and development in the field.