Development Of On-line Automatic Measurement Svstem With High Precision For Motor Cover Inner Diameter

Motor cover is one kind of cover parts, and it is also a typical part seen commonly in manufacturing. It mainly plays a supportive role, with the characteristics of many varieties and size and high precision, which has been produced on a large scale recently. The on-line measurement environment of motor cover inner diameter is poor and the factors effecting measurement precision are various. Because of the restriction of working environment and measurement space, it is hard to install highly precise sensor into the inner diameter for automatic measurement, so manual measurement is widely used at present. With the development of numerical control technique, traditional manual measurement can’t meet the requirements of high speed and precision of automatic production lines. Therefore, how to realize the motor cover measurement with high precision and efficiency is a problem need to solve urgently.In this paper, relying on the national science and technology support plan funded project "numerical control new generation mechanical product innovation application demonstration project", a scheme of automatic processing and detection is proposed, based on the original processing and detection methods. Combining with the advanced manufacturing and measurement technology, the automatic production line with the function of on-line measurement is developed, which adapts the manufacturing requirements of motor cover better. It can complete workpiece measurement and feedback the measurement data to PC of the production line in time. Then to compensate or stop processing according to the need. Thus improving the processing quality, avoiding quantities of waste, shortening the auxiliary time and improving the production efficiency.First, the processing of motor cover is analyzed fully to find out the key size through the directed graph theory. Then, the existing measurement methods of inner diameter are analyzed and combining the characteristics that the motor cover automatic production line has requirements of high precision and large quantities and that the measurement space is restricted, a reasonable method is proposed.Then, the measurement conversion mechanism, the core component of measurement system, is developed based on the good stability and high sensitivity of mechanical structure and combining with higly precise inductance displacement sensor. Moreover, a segmentation modeling method of flexibility-rigid-flexibility is proposed. Using the method, the mechanical model of the measurement conversion mechanism is established, which reveals the main factors effecting the transfer accuracy in theory, and the finite element simulation technology is used to validate and analyze the precision of cantilever beam segmentation modeling method. Based on the theory, the prototype of transformation mechanism is designed.Finally, the reliability model of system is established based on the reliability analysis indicators of measurement system and combining with its working environment. So the reliability level can be computed. Also the error source of the measurement system is analyzed and a set of measurement system error compensation method is proposed through the analysis results. The transfer error can be compensated by artificial software, thus providing reliable data source for the subsequent quality statistical analysis and the establishment of quality assurance system.