Magnetization System for Spindle Axial Thermal Elongation Measurements

Due to friction between components, significant amount of wasted energy is inevitably generated inside a rotary machine during operation. Such wasted energy is commonly in the form of thermal energy that is transferred to machine components through heat conduction, causing the components to expand in geometry. The amount of change also directly affects the machine’s processing accuracy. The study presented in this article aims to use a magnetic encoder and a magnetoresistive (MR) sensor to build a measurement system that can be directly embedded into a high-speed motor to monitor thermal elongation of the motor’s rotating shaft in axial direction. CoMnP is used as magnetic coating on which novel magnetic polarity patterns are magnetized incrementally along the shaft’s axis by utilizing permanent magnet. The proposed system discussed herein this article is designed to determine proper installation specifications and to examine the assembly tolerance, including the pitch, yaw, row, and flying height errors of the MR in a rotating machine. The results demonstrate that the measurement system senses with a 2 kHz sampling rate can real-time monitor the shaft’s thermal elongation while it rotates with high speed from 1000 to 24 000 r/min. Moreover, compared with a commercial product, the measurement system is found to be feasible to provide accurate the shaft’s thermal elongation values with satisfactory accuracy error.