The extrusion-based additive manufacturing of moisture-cured silicone elastomer with minimal void for pneumatic actuators

The extrusion-based additive manufacturing (AM) of moisture-cured silicone elastomer with minimal voids and high strength, elongation, and fatigue life is presented. Due to the soft nature and extended cure time of moisture-cured silicone, AM is technically challenging. When each layer is deposited, it can compress and deform previous layers. This compression is exploited to prevent void formation in silicone AM. This research aims to explore process parameters for voidless silicone AM of solid and thin-wall structures for pneumatic actuators. Experiments were performed to study effects of flowrate, layer height, and distance between adjacent silicone lines on the solid and thin-wall vertical layer deformation and void generation. The results were then applied in AM of two thin-walled hollow silicone pneumatic parts: the sphere-like balloons and finger pneumatic actuators. The sphere-like balloons exhibited diametric expansion between 152 and 207% with burst stress between 1.46 and 2.55 MPa (which is comparable to the base material properties) while the pneumatic finger actuators were able to fully articulate over 30,000 cycles before failure.