An image processing algorithm for detection and analysis of slicing checks

Abstract

In this paper, a new method of measuring slicing checks for flat-sliced veneers was evaluated. The method is based on image analysis of veneer cross-sections, having highlighted the slicing checks using surface staining. The segmentation of the checks consists of global thresholding followed by some morphological operations. The outputs of the algorithm are check depth ratio and check frequency. The method was tested on flat-sliced oak (Quercus robur L. and Quercus petraea (Matt). Liebl.) veneers of different thicknesses (1.5, 2.5, 3.5 and 4.5 mm). Two distinct wood qualities and two different cutting directions (lengthwise-sliced and plain-sliced veneers) were evaluated. The algorithm performance resulted in an overall accuracy of 85% enabling an accessible method for relatively fast and accurate measurements of slicing check characteristics in lamella cross-sections. Regression analysis indicated a lack of fixed bias but the presence of proportional bias with the presented method. Check measurements indicate that by varying cutting parameters, it is possible to achieve desired check characteristics independent of slicing thickness. The semi-automated slicing check detection method could benefit further research and optimisation of the slicing process parameters and pave the way towards industrial quality control of slicing checks. The intended area of application is veneer-laminated products for interior use with the focus on veneered wood flooring.

The Impact of Top-Layer Sliced Lamella Thickness and Core Type on Surface-Checking in Engineered Wood Flooring

“…CDR was defined as the check depth relative to the nominal veneer thickness, while CF was defined as the number of checks per inspected material's length. Slicing checks presence was proved independent of SL thickness [23], and CDR was shown to increase with an increase in lamella thickness [22], be somewhat independent of the lamella thickness [23], or decrease with lamellae thickness [24]. CDR and CF are usually positively correlated [7].…”

“…Prior research has quantified veneer quality in relation to slicing check presence using parameters such as check depth ratio (CDR) and check frequency (CF) [9,11,[22][23][24][25]. CDR was defined as the check depth relative to the nominal veneer thickness, while CF was defined as the number of checks per inspected material's length.…”

“…Multi-factorial interactions were found for adhesive, slicing and core type, and slicing check side orientation [26]. Slicing check measurements were typically conducted manually under a magnification lens [11,23] or automatically using image-based detection procedures [22,24,25]. Similarly, SC has commonly been measured using manual detection under a magnification lens and SC counting [12,16].…”

The Influence of Slicing Thickness on the Perpendicular to Grain Tensile Properties of Oak (Quercus robur L. and Quercus petraea L.) Lamellae

“…Sliced lamellae thickness can impact the sustainability aspects of sliced-lamellae-based products, i.e., reduced adhesive consumption with increasing sliced lamellae thickness due to fewer adhesive layers. The check depth ratio was positively correlated with the veneer thickness for rotary-cut beech veneers [9,10], but a negative correlation was found in plain-sliced oak lamellae [18]. Such discrepancies in results may be due to the significant wood fracture mechanisms when cutting in different wood growth directions, i.e., the tangential direction in rotary cutting and a mixture of the tangential and radial direction in plain slicing.…”

“…The slicing quality depends on the wood species, mainly due to macro-anatomical features such as rays [14]. Maple, birch, and beech sliced lamellae and rotary-cut veneers were found to be tight-cut, i.e., with a check depth ratio below 50% [10,12,16,17], while oak species were found to be loose-cut, i.e., with a check depth ratio above 50% [9,16,18].…”