Finite Element Analysis of Metal and Nonmetal Strain Wave Gear

Abstract This paper studies the feasibility of using polymer for strain wave gear based on finite element analysis (FEA). The FEA model includes strain wave gear’s three major components: flexspline, circular spline, and wave generator. It uses high quality quadrilateral elements for the three-dimensional tooth surfaces, which have conjugated tooth profile and its modifications. The simulation has been verified by a prototype strain wave gear’s contact pattern testing. A theoretical model to analyze the strain wave gear’s stress has been established to guide the selection of high-performance polymers for the strain wave gear. A sample design has been studied to comparing the polymer and metal strain wave gear. The simulation results show that polymer can reduce the strain wave gear’s circumferential stress by up to 98%, and torque induced stress by up to 70% at rated torque. The factor of safety against static load reduces by 21%, however the fatigue factory of safety increases by 16% according to Soderberg criteria. The polymer strain wave gear’s torsional stiffness is lower than metal, and the transmission error at different torque is characterized by the FEA simulation. Due to strain wave gear’s operating theory, polymer has unique advantages when used for strain wave gears than used for solid gears. Polymer’s flexibility will directly reduce the stress induced by flexspline’s designed deformation, and reduce the stress induced by torque load because of the contact ratio’s increase. Together with properties such as light weight, high specific strength, self-lubrication, and low material and manufacturing cost, high performance polymer is an ideal material candidate for strain wave gears.