The material extrusion process using a heated syringe in additive manufacturing offers the advantage of fabricating various materials with a single device while being cost-effective due to the ease of material storage and management. Additionally, since the material is sealed inside the syringe, it is isolated from external contamination, allowing for the processing of materials sensitive to environmental exposure. To optimize this process, this study aimed to identify the most effective material geometry and corresponding extrusion parameters. Thermoplastic polymers (PLA, TPU, ABS) were processed into chunk, disk, and pellet geometries, and extrusion experiments were conducted. The optimal parameters, determined through preliminary experiments, included extrusion temperatures of 200 °C, 207 °C, and 240 °C, and air pressures of 300 kPa, 550 kPa, and 550 kPa for PLA, TPU, and ABS, respectively. Experimental results demonstrated that chunk geometry achieved the highest extrusion ratio and the best quality of fabricated structures, with fewer defects such as bubbles. These findings highlight the importance of maximizing the material's contact area with the syringe wall while minimizing air exposure, providing a practical pathway to improve extrusion quality in the heated syringe additive manufacturing process.

This study explores the feasibility of creating a pneumatically driven soft gripper using Thermoplastic Polyurethane (TPU) through Direct Ink Writing (DIW) technology via a heated syringe extrusion process. Unlike traditional DIW methods that do not involve heating, this approach allows for the extrusion of heat-sensitive materials like TPU, thereby broadening the potential applications of additive manufacturing. The soft gripper was designed based on prior research, and key fabrication parameters—such as temperature, pneumatic pressure, and nozzle diameter—were optimized. The resulting soft gripper was assessed for its mass, surface quality, and bending performance. The findings indicated that the soft gripper produced through heated syringe extrusion exhibited surface characteristics and mass comparable to those made using conventional Fused Filament Fabrication (FFF) techniques. Additionally, bending performance tests demonstrated that the gripper could be predictably controlled through pneumatic pressure, achieving bending angles consistent with previous studies. These results suggest that heated syringe extrusion is a viable method for producing high-quality TPU-based soft robotic devices, providing a cost-effective and versatile solution within flexible manufacturing systems.