Wear analysis of material measures and stylus probes in repetitive tactile calibration

Tactile industrial measuring instruments are frequently calibrated with material measures defined in ISO 5436-1 to ensure their function, determine their measurement uncertainty and assess the capability of measuring processes. Since these process needs to be repeated on a regular basis, the long-term stability of both material measures and the stylus is essential to enable a repeatable and reliable measurement. Since the tactile sampling of a material measure involves a mechanical interaction, there is the potential for wear when repetitive measurements are performed. We present a comprehensive experimental study on the effects of wear for different stylus instruments - including a reference plane scanning system and multiple skidded scanning systems. Multiple measurement methods are used to determine the state of the stylus and the surface of the material measure, both before and after their mechanical interaction. The impact of the wear on the accuracy of the results can be described, as can the connection between the wear and the hardness of the skidded probe. The study found that significant wear effects on surfaces with even >500 HV become qualitatively visible much earlier than they can be quantitatively detected, with extreme load cases of >1000 repetitive measurements at the same position being necessary to produce major wear influences. Thus, regular visual inspections in case of extensive repetitive measurements can be recommended, just as well as a low measuring force and a reduction of the number of measurements for measurement capability analysis to 12 measurements.