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Cylindricity is a key parameter to describe the accuracy and quality of the small-size cylindrical parts. Cylindrical parts such as needle roller bearing is widely used as a core part in RV gearboxes, hydraulic pumps and other mechanical components, and the geometric accuracy of the needle roller affects the performance and service life of the mechanical product. The small-size cylindrical part is also used as precision standard part to help measure and position. The cylindricity error can propagate with the manufacture and assemble process. Therefore, the cylindricity is of great significance in the fields of industrial robots, aerospace, medical devices, and so on. It is necessary to evaluate the cylindricity of the small-size cylindrical part and analyze the measurement uncertainty to guarantee the geometric accuracy and improve the device performances.
Non-contact cylindricity measuring of the small-size cylinder is investigated by the chromatic confocal sensor in both relatively fixed and unfixed manners. The uncertainties of the both cylindricity measurement systems need to be analyzed and compared. When applying both measurement systems, the measuring accuracy is negatively affected by angular misalignments of the small cylinder and the measuring light source when the linear scan method is used. When the unfixed scheme is applied, the motion error of the precise translation stage has negative impact on the scanning process. The mounting and distribution error of the light spots effect the scanning coordinate precise when using the fixed scheme. The different sources are discussed respectively. According to the uncertainty result of the coordinates, a measurement uncertainty analysis is carried out through numerical calculations based on a Monte Carlo method. Proven by the experiments, the final result shows the fixed line spot manner has advantages in accuracy due to the better stability of the measurement system.
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