Analysis of Lubrication and Wear Model With Grease for the Harmonic Reducer

Abstract In most harmonic reducers, wear failure mainly occurs in the flex-spline and flexible bearing. However, in models like the LHD-I-25, the unique tooth profile shifts the primary wear issue to the flex-spline and circular spline contact. Since harmonic reducers like LHD-I-25 are crucial in robotic joints and prone to wear, understanding their wear mechanisms is essential for mitigating failure. This article takes the LHD-I-25 harmonic reducer as the research object and explores the tooth surface lubrication and wear of its flex-spline and circular spline. Considering the working environment of LHD-I-25 harmonic reducer, we derived the Reynolds equation for line contact grease and established the equation for oil film thickness under elastic deformation. On this basis, we derived the wear model of harmonic reducers under mixed lubrication conditions. At the same time, finite element simulation and full life cycle experiments were conducted to obtain a model applicable to the wear of LHD-I-25 harmonic reducer. This model can describe the wear of LHD-I-25 harmonic reducer over time. Through the model, we found that compared with the less sensitive effect of speed on wear, increasing the load will greatly increase the tooth surface wear, and this effect is exponential. Through experimental verification, the model's error is only 2.47%, confirming its accuracy and practicality for predicting wear and optimizing harmonic reducer durability.