The rapid development and continued worldwide production growth of Oriented Strand Board (OSB) since the early 1980's has led to the realization that the better understanding and improved of the theoretical description of OSB manufacturing processes are important. This knowledge is needed to improve the present day mat forming, quality control technology and effective design and engineering of the next generation of composite wood products. Horizontal density distribution (HDD) is one of the

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... t important factors determining the presence of voids and high density areas inside mat that greatly influences the board properties. However the formation mechanism of HDD and how it influences the panel properties are not fully understood. This project focuses on studying the influence of the spatial organization of wood elements inside a three-layer oriented flake mat on the manufacturing process, HDD, and end-use properties of OSB. Unlike previous studies with limitation of one or two variables at one time which results in difficulties when comparing and applying the results to production practices, this study reveals the combined effect of three important processing parameters — flake slenderness ratio, flake orientation, and panel density on panel properties. Also, with the help of a robot mat formation system and a X-ray machine, the mat simulation model established by Dai and Steiner (1994) is verified. The research program was divided into two parts. A pilot study was conducted first to verify the possibility of using a robot mat formation system to manufacture panels. Four types of structures structures with different face-to-core ratios and core flake arrangements for three-layered OSB were formed using the robot as a tool. The panels were then hot-pressed and tested for horizontal density distribution (HDD), bending modulus of elasticity (MOE), internal bond (IB) and thickness swelling (TS). Linked with the existing panel simulation program and X-ray density data, a suitable panel structu [...]