Exploiting flexi-rigid behaviour for complex insertion in limited spaces: Towards a flexi-gripper for heavy objects

This paper introduces a novel two-phase gripper that exploits a flexible be-haviour during actuation and is rigid during grasping and handling. It uses form closure but keeps the footprint at the minimum, thus allowing complex insertions in limited spaces. The main advantages of the gripper are its capability of grasping fragile objects with different shapes, sizes and weights, its low footprint and simple architecture (low number of degrees of freedom), as well as the easy actuation. The gripper has been designed as the end effector of a robot for cores manipulation in casting moulds in steel industry. Indeed, in foundry the casting operation takes place pouring steel in a mould where fragile sand cores plugs are delicately and precisely placed. The gripper is based on a rigid flexible beam, that is flexible in one direction and becomes rigid in the opposite one, so it bends and curves with almost no force in a direction but behaves like a beam in the other one. When approaching it exploits the flexibility to wrap the core, then, thanks to an engagement and by exploiting the weight of the object, it acts as a rigid beam. The paper illustrates how the gripper is conceived and modelled, and a prototype developed, tested and evaluated. The prototype showed a very good adaptability to different object shapes and sizes.