A new non-contact approach for the measurement and uniformity evaluation of coating thickness for sheet metal

To realize the automatic measurement and uniformity evaluation of the coating thickness for sheet metal, a new non-contact detection method for coating thickness was proposed based on a double laser probe and mechanical servo system. Non-contact measurement of coating thickness can be achieved by differential measurement principle of double laser probe, and the influences of sheet metal's Z position changes and platform's vibration on the measurement results can be removed by this method. A new coating thickness evaluation algorithm by integrating the least squares principle and cubic spline interpolation was given, which can fit the discrete thickness data into visual and accurate 3D graphics; and the measurement accuracy was evaluated based on grey theory, solving the problem of low accuracy by using limited measurement data to evaluate the thickness uniformity of an entire sheet metal. The stability and reliability of the system are verified by experiments, and the measurement results of the specimen show that the measurement uncertainty is 0.016 mu m and the maximum range of the uniformity evaluation result is 1.4 mu m. Published by AIP Publishing.