Holistic Evaluation of Involute Gears

The geometry measurement of involute gears is a key step within modelling, manufacturing, and performance evaluation to assure the delivery of high performance and cost-effective gears and gearboxes. Current challenges in manufacturing metrology can be summarized in five keywords: fast, accurate, reliable, flexible, and holistic. Moreover, modern non-generative production methods such as five-axis milling may need different inspection strategies for reliable quality assurance.

Standardized strategies refer to the most relevant 2D-sections, single helix, and profile line inspection, which has been state of the art for many decades. These methods are still relevant and continue to deliver high performance gears, but other options are becoming available. Modern coordinate metrology systems such as CMMs or GMMs gather holistic information about dimension and surface form of gears with high point density and accuracy in a short time. Currently, however, we do not know how to use this holistic information.

This paper introduces a 3D evaluation strategy for cylindrical involute gears used at Physikalisch-Technische Bundesanstalt. The focus is on describing the holistic evaluation of synthetic and measured data. Considering the complete gear surface in one common model allows us to a) determine deviations along the whole flank, b) obtain more relevant and stable geometrical fitting parameters, c) find correlations between gear fitting parameters and d) properly understand possible manufacturing errors.

The paper also shows how Newcastle University’s Design Unit used holistic evaluated data to investigate gear surface harmonic analysis methods. Harmonic analysis of 2D profile and helix measurement data is routinely used by some industries to control gear noise and characterize machine tool performance, but the evaluation of 3D surface measurement data has not been investigated. A review of some candidate methods using synthetic and measured data is presented and some of the challenges interpreting the results is discussed.

Authors: Anita Przyklenk, Martin Stein, Tom Reavie, Robert Frazer

ISBN: 978-1-64353-111-3