Development of an On-Machine Ultrasonic Thickness Measurement System for Thin-Walled Component with Curved Surfaces

Abstract Complex thin-walled structural components are widely used in the aerospace industry, the thickness measurement of which is critical for evaluating their machining accuracy. The ultrasonic method provides a feasible means for on-machine thickness measurement, improving the accuracy and efficiency of thickness measurement. However, this method still has the issues of much noise and difficult signal processing. To address these issues, an on-machine ultrasonic thickness measurement system (OMUTM) that automatically supplies couplant and high-pressure air is developed in this paper. The measuring device of the system is clamped on the tool holder and swings with the spindle, ensuring that the integrated ultrasonic probe remains perpendicular to the measured surface. The system integrated control of the solenoid valves and the peristaltic pump, achieving a fully automated measurement cycle from couplant spraying to measurement and high-pressure air purging. An ideal ultrasound echo signal is generated to evaluate the signal processing methods, and a hybrid methodology for ultrasonic thickness calculation is proposed. Finally, the accuracy evaluation of the proposed filtering method and the robustness evaluation of the developed system are given. The experiments show that an average error of 0.0219 mm and the root mean square error of 5.5 × 10 − ⁴ mm can be obtained, and the average measurement time of a single point reaches 18 s. The proposed OMUTM can realize real-time processing and recording of thickness signals, and improve the accuracy and efficiency of thickness measurement for curved thin-walled components, demonstrating its great potential in thickness measurement.