Design for Assembly Guidelines for High-Performance Compliant Mechanisms

Abstract

Compliant mechanisms with ultrahigh precision motion are being increasingly used for several applications including micromeasurement, micro/nanomanipulation, microfabrication, and so on. Flexure linkages offer inherent advantages of being frictionless, highly repeatable, and having great design flexibility. Monolithic fabrication of these mechanisms limits the use of multiple materials for optimized design and is expensive or infeasible especially for three-dimensional mechanisms. An alternative method of assembling components of a compliant mechanism is considered in this paper and design for assembly guidelines are put forth. It is found that if each of the connections of a compliant mechanism is constrained exactly using two pins as per the traditional practice, internal stresses are generated in the links and their warping does not allow the desired operation of the mechanism. The proposed guidelines, which are based on Grubler’s criteria, include a simple formulation to determine number of locating pins to be used in the entire assembly. Further, these guidelines also determine the locations of these pins. Several compliant mechanisms were fabricated and assembled using these guidelines and were found to be working satisfactorily.