Extrusion Mechanisms for Printing Thermosetting Prepolymers

Abstract The Direct Ink Writing (DIW) additive manufacturing method has been widely used in advanced printing applications, although it is often considered a complex and expensive system to construct. This study investigated two extrusion mechanisms that can be integrated with a gantry system for printing functional thermosetting inks. The first mechanism employs a lead screw directly connected to a bipolar stepper motor, which converts the rotary motion of the motor shaft into a linear motion. The lead screw is used to push the plunger of a syringe loaded with viscous thermosetting prepolymers. The second mechanism employs a gear system to transmit the motion from the motor shaft to the lead screw. The mechanical fixtures to hold the motor, lead screw, gears, and other components were designed and fabricated via 3D printing. Different gear ratios were examined for the gear-based system. An acrylate-based photocurable resin was thickened using fumed silica to induce non-Newtonian shear-thinning property. The study focused on various print parameters, including print speed, extrusion rate, linewidth, and ink viscosity, and tailored G-code commands were used to print different inks. The printed structures were photopolymerized using ultraviolet (UV) light. The printed outcomes were evaluated, and two extrusion mechanisms yielded comparable results. It is believed that the proposed system will make 3D printing of functional inks more accessible.