New method for real-time surface cleanliness measurement

Abstract

The measurement of the surface cleanliness is a problem of great importance in many industrial and technological processes. Existing methods are based on laboratory procedures, they are not performed in real time, they cannot be automated, and usually they are restricted to a small portion of the sample. In this work we describe a new method for real time measurement of the amount of dirt deposited on a surface. It relies in the ablation of the dirt film by means of a short laser pulse and the subsequent measurement of the sound emitted. The intensity of the sound results proportional with the amount of dirt and provides a direct measurement of the cleanliness of the surface. The method requires a reference for calibration that was developed based in a uniform distribution of points printed on white paper or a transparent film. The point size and density can be easily modified providing a homogeneous, uniform and reproducible standard for the total amount of dirt measurement. Based on this method, we designed patented (P000101241-Argentina and 6.546.784 EEUU) and developed the first industrial instrument (ELMES) for on-line determination of the cleanliness degree of manufactured cold rolled steel plate bobbins.