Predictions of Wear and Transmission Errors of Cylindrical Worm Gears

Abstract

Transmission error (TE) is an important transmission parameter for precision worm gears. Modern cutting methods in conjunction with modern software allow manufacturers to deliver worm gear products of high accuracy to the highly competitive market. However, the initial shape of a bronze wheel tooth changes dramatically due to bedding-in and wear when gears mesh under load, and hence transmission characteristics change. A computer program is being developed to predict wear during bedding-in and constant wear rate stages for involute worm gears. A progressive wear over given number of tooth engagements is estimated using both the available experimental wear data and theoretical considerations. Being subtracted from an “as-cut” geometry, a new shape of worm wheel tooth surface can be predicted. The calculations can be executed iteratively for as many wear steps as necessary. The model takes load sharing and contact stress distribution into account to estimate the lubrication oil film thickness and wear intensity. Contact patterns, TE, load cycles and meshing stiffness are also modeled. A comparison between theoretical wear predictions and experimental wear data is made. Predictions of wear and transmission errors are useful for optimization of existing worm gear design and for development of worm gears of new designs.