Modeling of manufacturing errors in external gear machines and experimental validation

Abstract

Manufacturing errors are always unavoidable in actual machines. In external gear machines (EGMs), some of the manufacturing errors are typically on the same scale as the nominal clearances between the internal parts. These clearances are responsible for leakage flows that reduce the volumetric efficiency of EGMs and impact their overall performance. Current approaches of modeling the operation of EGMs neglect the manufacturing errors which limits their accuracy.This paper proposes a technique to study the operation of EGMs accounting for two common gear manufacturing errors: conicity and concentricity. Furthermore, an alternate technique to model these errors is proposed by defining an “effective gap height”. This latter technique can be used in any existing lumped parameter model as well as for quick estimations. To validate the approach, experiments are performed with gearsets exhibiting varying amounts of conicity and concentricity errors.The results from both the simulations and the experiments show that the volumetric efficiency decreases with an increase of the conicity error. Instead, by increasing the concentricity error, an increase in the volumetric efficiency is found, at least until the conditions of contact between the gears and the casing's internal surface are avoided.