Efficacy comparison of two methods for determining the position of the rebate edge (formed after MDF machining) during automatic monitoring of workpiece delamination

Abstract

Delamination is one of the most common defects in the processing of wood-based materials. It has a massive impact on the quality of the final product. In order to determine the delamination indicators simply and reliably, the automatic image processing method can be used (Śmietańska et al., 2020). Bator and Śmietańska (2019) proposed a special algorithm to estimate the straight line representing a milling edge. However, this algorithm is quite complicated. The aim of this article is to check whether the aforementioned (complicated) algorithmic way can be replaced by a much simpler idea – the precise manual positioning of the scanned sample on a scanner (using a very simple device installed on the scanner). Special experimental research was carried out to compare the effectiveness of the two different methods. The straight line representing the rebate edge identified by the Bator and Śmietańska (2019) algorithm was usually accurate to 1 pixel (0.02 mm). Based on the assumption that the scanned samples were perfectly positioned on the scanner, the analogue line only sometimes fit just as well. At worst, the distance between these lines is 0.2 mm. Usually, the distance did not exceed 0.16 mm but it was significant and quite random. There was no statistically significant correlation between this parameter (Dmax) and tool condition (VB). It means that the samples were not perfectly positioned. They were placed, more or less, in the same position because of the imperfect stiffness of the frame installed on the scanner and human errors.