image: Tooth flank of the profile waviness artifact and analysed spectrum. view more
Credit: PTB
This release is also available in German.
The precise measurement of periodic surface textures on the flanks of toothed gears is becoming increasingly important since it allows conclusions to be drawn with regard to their functional properties (such as wear, efficiency and operating noise) within drive assemblies. Therefore, PTB has developed a method by means of which wavy structures on the flank surfaces of involute cylinder gears can be modelled, represented and, especially, traceably measured for the first time.
The traceable detection of wavy surface textures on involute tooth flanks can be best ensured by means of suitable artifacts. Recent investigations at PTB, however, show that the Fast Fourier Transform (FFT) which is usually used for determining wavy shape deviations on open structures can only be applied in a limited way. For the exact spectral analysis by means of FFT, the ratio measuring length to largest existing wavelength should be comparatively high (> 20) – a requirement which cannot always be metrologically fulfilled. Therefore, a profile waviness artifact as well as a new analytical method have been developed.
For the production of the standard, first the modelling of the surface texture was important. The transition kinematics of meshing cylinder gear pairs had to be taken into account in order to derive the direct relations between the surface texture of the involute flank of a driving gear and the running behaviour of a driven gear. Since several teeth can be meshing at the same time, also the wavy structures of adjacent teeth are modelled to obtain a complete description of a gear. The patented profile waviness artifact is called „Involute Waviness Artifact“ (IWA). As it is quite a handy artifact, it is suitable for the acceptance test of gear measuring instruments with the corresponding analysis.
The newly developed analytical system is based on Bayes‘ statistics. As has been proved metrologically and numerically, it is able to analyse waves on open structures reliably, compared to other methods. Together with the profile waviness artifact, it represents from now on the basis of a reliable and traceable analysis of gear drive properties which are caused by wavy surface textures on toothed gear flanks.