Design of a variable stiffness soft gripper for flexible manufacturing with reinforced structure by multi-material 3D printing

Driven by the mass-personalisation trend, flexibility becomes increasingly important to fulfil the requirement of customised fabrication. Traditional rigid grippers in production lines face difficulties to deal with variable products. This paper presents the design, fabrication and experiments of a novel variable stiffness soft gripper with reinforced structure. The soft gripper is constructed of three soft fingers, each finger has a soft body with rigid reinforcement and a stiffness variation unit. Rigid reinforcement in the soft finger body can increase its pressure durability and decrease the radial expansion under inflation pressure. The stiffness variation unit can ensure grasping robustness when a large reaction force occurs. Prototypes of the soft finger are directly printed out by a multi-material 3D printer in one-step printing. Grasping ability of the soft gripper is examined when the robotic arm is following a linear trajectory and a triangle path. With the help of jamming layers, the robotic arm can guarantee the grasping robustness when moving objects at acceleration up to 13.5 m/s², which is 35% higher than the traditional industrial standard of 10 m/s². The results prove that the proposed design is an effective design which can be used to perform high-speed pick-and-place task on fragile fruits.