Development of Functionality-Graded Materials (FGM) component via spur gear system in Material Extrusion (MEX) technique

Additive manufacturing (AM) is a means of production by building up material, layer upon layer, with Material Extrusion (MEX) being the most common system owing to its simplicity. Functionality-graded materials (FGM) are composite materials, created to achieve spatial variation of their properties by forming a compound of two materials whose volume fraction is changed across a certain direction. A method to develop and fabricate FGM by mixing and varying materials using MEX was designed employing a spur-gear driven delivery system comprising a hopper-based feed utilising granules of different materials, melted and mixed at point-of-use before being fed to the gear system, which controls the ratio. The pre-mixed materials are delivered to the print head to print the desired FGM component. The mixing system flow-channel model was extracted and simplified for simulation, and the flow field simulated by Ansys software, with complex viscosity of Poly (Lactic Acid) (PLA) set at 600 Pa.s at 200°C. PLA was selected as the base material due its biodegradability and biocompatibility. The simulation result demonstrated that the spur-gear system fails to deliver the PLA base material due to lack of downforce, with a positive drive with greater downforce being required to deposit the molten PLA.