New material standards for traceability of roundness measurements of large scale rotors

Large scale rotors in the paper and steel industry are called rolls. Rolls there are periodically reground and roundness measurements are made throughout the machining process. Dimensional measurement systems for large rolls (diameter < 2000 mm) are available on the market. They are typically based on the roundness measurement algorithm from Aoki and Ozono. This method can separate roundness of the rotor from its movement. For reliable measurement results, every measurement should be traceable with an estimation of measurement uncertainty. Therefore, three different material standards in the form of discs (diameter > 500 mm) with different roundness profiles were and will be made during this research. They will be measured at least in the laboratories of two national metrological institutes. Later the discs can be used to calibrate measurement devices. In first tests with one of the discs measurement results of two different measuring devices were compared with measurement results from the coordinate measurement machine of the Finnish national metrology institute. They showed deviation in amplitudes of the harmonics to be 2.3 μm or less. This shows that reliable roundness measurements of rolls are possible. Index Terms – Material standard, roundness, paper machine roll, steel mill roll, measurement uncertainty