An analysis of strand and horizontal density distributions in oriented strand board (OSB)

Oriented strand board (OSB) is a well-established wood based panel product. The production and consumption has strongly increased during the past deca de. It is well known that mast of the wood based panel properties are stron gly related to the specific gravity of the panel. The EN 300 requires that the specific gravity within a panel or the horizontal density distribution (HDD) is within +/-10%. For identification of different influences of raw m aterial and process parameters, computer simulation programs of HDD were de veloped under laboratory conditions (Dai, Steiner 1994a, b, c). In this stu dy commercial strands and OSB panels are investigated to verify and improve the suitability of the computer simulation models for industrial condition s. First, a wide range of strand dimensions is determined where strand widt h seems to exhibit the greatest coefficient of variation. Second, an analys is of the density within an OSB panel of 8 ft by 24 ft indicates that HDD c learly exceeds the EN 300 limit. Finally, the computer simulation program w as improved by considering the effects of strand types (dimensions and shap e), amount of fines, strand orientation, and compartment of strands due to orienting discs and rollers during mat forming. Results of the improved com puter simulation correspond accurately to the experimental HDD. The model p redicts that the fines and the strand compartment strongly affect the panel density distribution.