Development of new formulation for soft material in paste extrusion-based 3D Printer

Fused Deposition Modelling is a form of additive manufacturing where solid filament is heated into molten state and deposited onto a heating platform to create three-dimensional objects layer-by-layer. Since heating and cooling processes are involved in Fused Deposition Modelling (FDM), this restricts the use of thermoplastic polymers such Room Temperature Vulcanizing (RTV) silicones and gels. Others concern are with the right rheological properties for extrusion and the ability to provide desired mechanical qualities upon quick solidification. To develop a suitable silicone printing technology, it is crucial to understand the silicone polymerization mechanism in terms of its rheological and mechanical characteristics. Due to the numerous factors that can influence silicone paste mixtures, this study utilized the Taguchi method to design experiments, optimize factors, and predict properties, thereby avoiding extensive and resource-intensive experimental work. The study specifically considered the factors of curing method, mass ratio of silicone thinner, and fumed-silica in the silicone paste formulation. Among the 9 samples generated through the Taguchi method, only one sample demonstrated favourable results in terms of mechanical properties and the curing process, with a mixture ratio of base silicone, silicone thinner, and fumed-silica at 15g, <1g, 0.1g; respectively. However, further investigation into the fixed amount of silicone and fumed silica in the selected mixture ratio indicate that the amount of silicone thinner must be less than 1g or can be omitted as the silicone paste can be used as printing ink for the extruder. The shore hardness testing for the silicone samples revealed with zero percent silicone thinner exhibited a hardness value of 21.5 HA (Shore A) while the sample obtained less than 1g displayed a significantly lower hardness value of 10.5 HA. These findings indicate that the addition of silicone thinner in the silicone paste formulation, as optimized through the Taguchi method, contributed to a reduction in the hardness of the material for shore A scale. This suggests that the presence of silicone thinner affects the elasticity and flexibility of the silicone paste, resulting in a lower Shore hardness value. The discrepancy in hardness values between the samples further highlights the significance of formulation optimization to achieve desired material properties for silicone paste-based applications in 3D printing.