OVERPRINTING OF LARGE-SCALE THERMOPLASTIC COMPOSITES IN FGF-PROCESS USING LOCAL PREHEATING

Abstract

The rise of large-scale systems for Fused Granular Fabrication (FGF) of thermoplastics opens up new possibilities for manufacturing thermoplastic composites. One promising approach is the overprinting of continuous fibre-reinforced laminates to increase complexity and functionality of highperformance structures. However, overprinting aerospace-grade materials like Polyether Ether Ketone (PEEK) requires high substrate and ambient temperatures. The large-scale systems lack the possibility to use heated build chambers and can therefore overprint only to a limited extent. This work investigates the possibility of equipping the printer system with local preheating for high-temperature substrates. Therefore, a heating concept using hot air heating is developed and evaluated regarding heating efficiency and the influence of heating on print quality. The study was performed on a modified desktop printer, with which temperature measurements and mechanical testing were carried out. Based on this study, a prototype of a local preheating for a large-scale FGF system was designed, suitable for multiaxis overprinting PEEK laminates. The heating capability of high-temperature substrates was evaluated. Results show preheating temperatures of over 200 °C and significant improvement of the material quality of printed PEEK. The developed prototype forms the basis for further process and technology development fur future composite manufacturing.