From Tactile to Optical - Advancements in Shaft Lead Analysis

Tactile measuring instruments were used for a long time to measure surface characteristics of sealing counterfaces and are still state of the art today throughout the industry. The data measured are roughness profiles in the axial direction of the shaft. Rapid developments in computer hardware and software have improved optical measurement technology, advancing its application in the analysis of sealing counterfaces. The measurement data are topographies that represent partial areas of the shaft with high resolution in both the axis and circumferential direction. These characteristics are especially useful for the analysis of shaft lead. Lead describes all types of structural features on the shaft surface that axially pump oil in sealing contact during operation. Their pumping effect influences the sealing mechanism depending on the direction of rotation of the shaft and can result in leakage. Lead structures appear in various forms and sizes – micro and macro lead, which are superimposed on the shaft surface. Optical measurements enable the detection of the superimposed structures with a single measurement run. Specially developed segmentation algorithms can be used to sperate micro and macro lead and then identify flow channel-like structures as individual elements in surface topographies. The statistical analysis of the segmentation results offers an objective characterization of the sealing counterface. This article presents the benefits of utilizing optical measurement techniques in conjunction with innovative structure-based analysis approaches for lead on shaft counterfaces. The outcome can improve the reliability of sealing systems and associated products.