Simple and highly accurate measuring method for evaluating the cleanliness levels of laser-cleaned surfaces according to the ISO standard

Abstract

Surface cleaning is highly demanded in the construction, mechanical, and automotive industries. Laser surface cleaning is increasingly being used due to its advantages such as high selectivity, fast cleaning, and efficient response to many different materials. However, if pulsed lasers with a high peak power are used for surface cleaning, they can damage the surface material if the technological parameters are not controlled appropriately. Therefore, it is necessary to develop accurate and high-speed measurement methods to evaluate the surface quality after cleaning. In this paper, a steel cleaning system using a nano-pulsed laser with a wavelength of 1064 nm was proposed. To evaluate the cleanliness of samples, a simple and rapid measurement system based on image processing was developed. The ISO 8501 standard was chosen as the standard cleanliness level. The surface after cleaning was captured using a scientific camera. The percentage of dark pixels in the captured image was determined using the histogram method. The surface quality after cleaning was determined by comparing it with the cleanliness level of the ISO 8501 standard. Thus, this proposed method is used to evaluate the influence of the average power of the laser source on the cleanliness of the steel surface. This method was observed to be compact, cost-effective, and highly accurate; it also proved to be easy to integrate into cleaning systems.