Stylus tip radius and wear estimation using the Rsk or the Rp and Rv parameter of a sine wave (Type C1) standard

Abstract

Determination of the stylus tip radius and its wear or damage is a classical problem in tactile surface topography measurements. The determination of the stylus geometry may be tedious and inconvenient, therefore we looked for an easily applicable method. This study shows that the Rsk parameter and the difference between the Rv and Rp parameter may indicate the stylus tip radius as well as wear when using a sine-wave profile material measure, which is commonly supplied with a roughness tester for calibrating and/or adjusting the vertical amplification coefficient. This effect is derived from theoretical calculations on real and simulated styli and specimens and verified experimentally using two commonly used specimens and stylus tips with radii of nominally 1, 2, 5, and 10 µm. When using a standardized stylus with a nominal 2 µm tip radius and 60° cone angle on a typical C1 reference specimen with nominal parameters Ra = 3 µm and RSm = 100 µm, the Rsk value should be approximately -0.01. Any stylus wear will decrease the measured Rsk value. When the Rsk value decreases to a value of -0.06 or lower it may be time for closer inspection and/or replacement of the stylus.