Strength grading based on high resolution laser scanning : performance of a procedure newly approved for the European market

Strength grading of timber is necessary to ensure sufficient structural performance of the material, and machines based on different types of non-destructive measurements are available on the market. The purpose of this paper is to present results on an investigation of a new method and procedure for machine strength grading that is based on laser scanning and utilization of the tracheid effect, in combination with dynamic excitation and weighing. The investigated sample comprised more than 900 pieces of timber of Norway spruce (Picea abies) from Sweden, Norway and Finland. The coefficient of determination between the indicating property (IP) to bending strength and the measured bending strength was as high as R2 = 0.69, while the coefficient of determination between dynamic MOE and measured bending strength was R2 = 0.53. A comparison of the performance with what have been presented for machines that are based on X-ray in combination with dynamic excitation indicates that the new method/procedure will surpass such machines.