Design of Compliant Mechanism Microgripper Utilizing the Hoekens Straight Line Mechanism

Precision engineering industries demand devices with high-precision motion, the manipulation of micro-objects in particular, which is a highly challenging task. The microgripper is an essential device during the micromanipulation of objects. Precision manipulations of objects entirely depend on the design of the microgripper and are complicated to achieve using the conventional rigid link mechanism. The compliant mechanism is found to overcome the complexities of the rigid link mechanism in precision applications. The micro-object may slip or slide during gripping and releasing, which can be controlled through parallel movement of the gripping jaws. This research article focuses on the design of a compliant microgripper with parallel moving jaws by employing the Hoekens straight line mechanism. The Hoekens mechanism consists of binary and ternary revolute joints, which demand a special type of flexure hinges. Hence, the article introduces the cartwheel type of flexure hinges, as cartwheel-type flexure hinges are more suitable to achieve rotational deformation, values approximating nearly to that of the traditional revolute joint when it transfers motion between fixed and moving links. The outer rim of the cartwheel is modified to allow ternary and binary joints between moving links. Cartwheel is designed with curved flexure arms that are limited to eight numbers of flexures. The structural behavior of the cartwheel is analyzed by varying numbered flexures from 1 to 8. The minimum number of flexure arms required for having better rotational performance is determined through Finite Element Analysis (FEA). An appropriate type of cartwheel is positioned in the mechanism. The structural performance of the designed microgripper is carried out through FEA, and its parallel movement is verified. The microgripper is fabricated from structural steel through wire Electrical Discharge Machining (EDM) technique and actuated using Shape Memory Alloy wire. The displacement of the microgripper jaw is experimentally measured, and the results show a promising improvement.