Modelling Heat Transfer in an Extruder for Recycling Plastics into Filaments for Use in Additive Manufacturing

Global production of plastic increased by 500% over the last 30 years and it is expected to continue to grow to 850 million tons/year by 2050. Plastic use results in a substantial environmental burden due to both land and water pollution as plastics take 10 to 450 years to decompose in landfills. This has resulted in increased calls for innovative ways to recycle plastics, one of which is a decentralised solution where wasted plastics are recycled into filaments for 3D printing. This has been identified as a promising solution, especially for low-income communities in the global south where waste management infrastructure is inadequate. However, studies have highlighted the need for more research and development in the extruder design and operation, especially in terms of optimising temperature distribution and the cooling rate in order to prevent poor filament quality and inconsistent filament diameter. This paper describes the modelling of the temperature distribution and cooling rate of an extruder. The innovation is that the extruder is designed to be built and operated in low-income settings of the global south using locally available materials and skills. The aim of the work is to develop a mathematical model for evaluating the thermal distribution in the extruder as well as optimise the cooling rate conditions. The model is useful for optimising the operating conditions such as ambient temperature, extrusion temperature, extrusion speed, cooling rate and spooling mechanism.