On-machine Measurement System Analysis Of Motor Cover Digital Machining

As the productivity develops, consumers need the products with higher and higher quality level. However, measurement results always differ from the true value more or less because of numerous factors. The reliability of the measurement data has a direct impact on the usage of quality tools, such as Shewhart control chart, process capability and eligibility check, thus influencing the process quality evaluation. So it’s necessary to conduct measurement system analysis for the new measurement systems or the ones that have been used for a long time.The thesis conducts the on-machine measurement system analysis and optimizes the measurement error acceptance criterion based on the motor cover digital machining production line and inner bore on-machine measurement platform, which are supported by the First Generation NC Project in Ministry of Science and Technology—’Mechanical Products Innovation Application of the First Generation NC Project in Zhejiang Province’. The thesis’s research findings reveal the measurement system’s statistical characteristics and reflects the products’manufacturing conditions, which makes it meaningful to improve the quality and yield. The thesis content is as follows:Firstly, the thesis introduces the measurement system analysis by stability, repeatability, reproducibility, bias and linearity based on literature review both at home and abroad. And it also explains the computing method of the repeatability and reproducibility deviation. By analyzing the performance index, measurement error can be confirmed, the error sources can be found,and the measurement system ability can be known.Secondly, the thesis quantificationally analyses the measurement error’s impact on Shewhart control chart average run length, process capability index and misclassification rate on the basis of introduction of the above three aspects, reveals the mechanism of error and gives out the advice for reducing the error’s influence.Thirdly, the thesis introduces the process capability acceptance criterion and measurement system error acceptance criterion, and uses the two criteria synthetically to evaluate the measurement system. Then it dissects the limitation of the traditional measurement error acceptance criterion and puts forward a new one based on process quality optimization and establishes a new measurement system evaluation method.Finally, the thesis applies the optimized error acceptance criterion to the on-machine measurement system analysis of the motor cover inner bore and gives out the adjustment advice. The research result shows that:As to the limitation of the repeatability and reproducibility deviation, it can improve the measurement precision and ability by using the optimized measurement error acceptance criterion. It also makes the system satisfy the manufacturing and measurement needs, and offers a new idea for the relevant researches in the fields. What’s more, the research verifies the measurement error acceptance criterion optimization method.