At present, there are many kinds of large gear measuring instruments have been applied, but in fact, there is no corresponding gear template for large gear measurement, and there is no high-precision instrument to detect large-scale gear template. So far, there is no large-scale gear value transfer system at home and abroad, and large gear traceability has been a problem.
Due to the urgent need of wind power gear measurement, in 2009 the National Metrology Institute of Germany launched the development of large-scale gear model. The research institute has developed a 50 ° fan-shaped tooth template, with a diameter of 1000 mm, a weight of 450 kg, a normal modulus of 20 mm, a pressure angle of 20 ° and a tooth width of 400 mm. It contains three different types of teeth, i.e. left-handed 20 °, right-handed 10 ° and straight teeth, which can be used for the traceability of involute and helix. The model was designed by the German National Institute of metrology, and several top German enterprises, including hofler, participated in the trial production. The sample manufacturing process is complex and integrates the process technology of many German enterprises.
The National Institute of metrology of Germany uses a high-precision CMM to calibrate the sample. Before calibration, the sample needs to be placed in a constant temperature laboratory for several weeks, and several sensors are used to monitor the internal temperature of the sample. The measurement results and uncertainty of tooth profile deviation and helix deviation are shown in Figure 12 (FH α is the tooth profile inclination deviation; FF α is the tooth profile shape deviation; F α is the total tooth profile deviation; FH β is the helix inclination deviation; FF β is the helix shape deviation; F β is the total helix deviation). The measurement uncertainty of the total involute deviation and helix deviation is 3.4 μ M.