Semi-analytical and numerical models to predict the extrusion force for silicone additive manufacturing, as a function of the process parameters

Material extrusion (MEX) has become a highly desirable additive manufacturing technology for creating silicone-based structures in the biomedical and soft robotics fields due to its ease of fabrication of complex structure without molding or casting. However, the lack of models for the MEX process when extruding silicone has limited its application. This study seeks to bridge this gap by introducing semi-analytical and numerical models of the MEX process that can predict the extrusion force in practical scenarios, accounting the counterpressure force from the deposited silicone beads on a substrate. Using a custom-made MEX setup capable of extruding silicone, the two proposed models were validated through experimental tests. The models, semi analytical and numerical models, demonstrated maximum accuracy of 99.7% and 99.3% respectively in predicting the extrusion force based on the process parameters such as layer thickness, nozzle size and flow rate. The development of a tool capable of predicting the silicone printing force, such as the one proposed in this paper, can expand the role of MEX in the fabrication of silicone structures beyond the current limitations by improving the manufacturing process control, enabling the creation of thin-walled structures, and enhancing accuracy.