Caustic, secondary acid-etching processes are commonly used to determine the presence of harmful grinding burn, which involves changes in both the surface stress and microstructure of ground ferromagnetic workpieces. Now, shops have another option. Germany-based Wenzel (with U.S. headquarters located in Wixom, Michigan) offers a safer, sensor-based technology for use with its gear measuring machines that quickly detects grinding burn and other imperfections on the surface of ground gears and related components.
Developed in conjunction with Stresstech GmbH, a German producer of non-destructive process control equipment, Wenzel’s sensing technology uses magnetic Barkhausen Noise Analysis (BNA) to detect defects on a gear’s ground surfaces. Simply put, BNA examines the microstructure of a material’s surface through inductive measurement of a noise-like signal generated when a magnetic field is applied to a ferrous object. BNA is particularly effective for such inspection applications because grinding modifies both a material’s surface stress and microstructure.
Chris Pomm, technical director for Wenzel, says because gear measuring machines use sophisticated programming software to inspect all geometric features of a gear, it’s logical that a sensor adapted for use on those machines could be used to identify grinding burn and pitting that can occur on the flanks of gear teeth. The company’s new BNA method saves time by enabling users to analyze potential grinding burn on flanks at the same time workpiece measurement occurs. This eliminates the need for an additional inspection process.
The digital BNA system Wenzel offers on its GearTec InovaGear, WGT and LH measuring machines is Stresstech’s Rollscan R300. This system includes the BNA analyzing unit and sensor as well as software that integrates into the host measuring machine’s controller. The BNA sensor is incorporated into a Renishaw SP80 probe that can be conveniently stored in a probe change rack. According to the company, inspection routines with the Rollscan are fast enough to match the production rates of most manufacturing lines, enabling accurate process control in real-time. This offers shops the potential to realize significant quality improvements in addition to reduced material and labor costs.