Precision improvement of laser tracking measurement for super large gear

In industry, the gear with diameter over 3000mm is called super large gear, which is the most widely used transmission part in key equipment such as mine, shield and ship. With the continuous improvement of China’s high-end manufacturing level, there are higher standards for the measurement and evaluation of motion accuracy, working stability and contact accuracy of super large gears in key equipment. However, due to the characteristics of large size, large weight, large number of teeth and small tooth angle, large measurement error will be introduced in both in-situ and out of position measurement. Therefore, how to improve the measurement accuracy of super large gear has become a difficult problem to be solved in the whole industry.

With the continuous development of precision measurement technology, laser tracker, as a high-precision and large-scale measuring instrument, is introduced into the measurement technology of super large gear. Shi Zhaoyao of Beijing University of technology proposed a laser tracking in-situ measurement method for super large gear. This method combines the characteristics of laser tracker that can measure large size with in-situ measurement method to complete the in-situ measurement of super large gear. Zhang Bai and Lin Jiachun proposed a pitch measurement method based on laser tracker, which can meet the requirements of single pitch deviation measurement for super large gear with diameter over 6000mm and accuracy grade 8. Chen Hongfang and Yan Hao used the laser tracker multi station measurement method to improve the gear positioning accuracy of the large gear in-situ measurement system.

Although the laser tracking measurement method of super large gear effectively solves the problem that the measurement datum is not unified with the design and manufacturing datum caused by the traditional measurement method, its global measurement accuracy is low due to the large angle measurement error of the laser tracker. Therefore, this paper adopts the measurement method of combining laser tracker with flexible joint coordinate measuring arm, introduces the multilateral measurement method, takes the laser tracker interference ranging value as the constraint condition, completely abandons the angle measurement module of laser tracker, establishes the combined measurement network based on laser tracking multi side measurement method, and effectively improves the measurement accuracy of super large gear.

The combined measurement method is used to improve the measurement accuracy of the extra large gear. The combined measurement network of the extra large gear is established by using the flexible joint coordinate measuring arm point measurement and laser tracker interference ranging technology. The experimental results show that the average measurement error of the combined measurement network is 0.007mm, and the standard deviation is 0.004 mm. Compared with the direct measurement method of laser tracker, the combined measurement network has a strong ability to improve the accuracy. The combined measurement network is also suitable for the reverse engineering measurement modeling of other large parts, which has strong generality.

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