Design and Simulation of a New Concentric Gripper with Two-Finger and Support Bar Driven by a Wedge Cam

A mechanical gripper is end effectors that use mechanical fingers actuated by a mechanism to grasp an object. The fingers are the most important part of the gripper that actually make contact with the object either by physically constraining the object with the fingers or by retaining the object with the help of friction between the fingers. Driving the finger movements can be done by linkage, screw, gear and rack, rope and pulley, or cam actuation. A wedge cam is now mainly used to drive a two-finger gripper. Two-finger gripper is generally not suitable to grip cylindrical objects. When gripping a cylindrical object, gripping object must be centered by fingers. Fingers are closing toward a central axis to squeeze the gripping object at the very center of this axis. This paper will design a new concentric gripper with two-finger and support bar, which is driven by a wedge cam. The geometrical method design is used to find out the cam curve and the curved slots of the new gripper. In addition, velocities and accelerations of the cam follower, curved slots are determined by kinematic simulation to check, whether there is a jump in the speed curve and a jerk in the acceleration or not. In the mechanical gripper design, calculation of gripping forces and reaction forces, acting on the joints of the gripper according to the finger stroke, must be carried out. These forces will be determined by dynamic simulation of multibody system. The results of this paper show the cam curve, curved slots, graphs of gripping force and reaction forces. They are the basis for determining the dimensions of the parts and making the new gripper.