Multi-material FDM 3D Printed Arm with Integrated Pneumatic Actuator

One approach to realize more life-like soft robots is the use of pneumatically contracting structures, acting as muscles. Fabricating such systems usually requires manual assembly or molding steps, which extend the time between designing and testing of a new concept. In order to streamline rapid prototyping this study used a multi-material FDM 3D printer for producing a simplified robotic arm with an integrated pneumatic muscle. The actuator working as a pneumatic bicep is printed from thermoplastic polyurethane with a shore hardness of A70, while the arm itself is made of rigid polylactic acid. During the printing process the muscle is, while being printed itself, embedded into the arm by a physical joint, through which the arm assembly can change its angle according to the actuation. In this work, we describe the challenges appearing in such a combined processing of two different materials and how they are addressed. Through its design the resulting soft robotic arm is printed without the need of any support material inside its hollow structures and is ready for testing right after the printing finished. By applying negative pressure to the actuator's inlet, the arm was able to lift up to 270 g load.