Analyzing and sorting of wood veneers

摘要

The invention relates to a method for increasing strength and/or reducing strength variations in multi-layer wood, plywood, and the like sandwich material. The method comprises measuring wood veneers (10) for dry substance density ( rho ) with high-frequency electromagnetic resonance (TEM) and additionally analyzing the homogeneity and/or grain structure of wood veneers from a wood veneer surface in the way of its darkness (R). If the wood veneer comprises a number of local first regions, which are darker than a predominant darkness of the veneer surface, the wood veneer in question has its calculated dry substance density ( rho C) established to be lower than its initially measured value ( rho M ). On the other hand, if the wood veneer has a substantially uniform darkness, the wood veneer in question has the longitudinal and lateral distribution of its dry substance density evaluated and, if those are substantially uniform, the calculated dry substance density ( rho C) of the wood veneer in question is established for a sorting process to be higher than its initially measured value ( rho M). Wood veneers are sorted on the basis of said calculated dry densities for at least two different density categories. In a first density category (A), the dry substance density is higher than in a second density category (B). Wood veneers are laid on top of each other for multi-layer wood, plywood, or some other sandwich material (20), the veneers included in the first density category serving as surface veneers (13) and the veneers included in the second density category serving as middle veneers (14).