Sawing simulation of Pinus pinaster Ait

The paper deals with the sawing simulation of Maritime pine (Pinus pinaster Ait.) and is a report from a project aiming to increase the knowledge in how different raw material characteristics and sawing factors are affecting on the sawing yield of Maritime pine. The conversion was executed by an integrated optimising software system, WooDCIM® developed at VTT Technical Research Centre of Finland, and was used to predict the value yield in the sawing process. The study was based on a sample of 35 maritime pine stems randomly sampled from 4 different sites in Portugal. Based on scanning of boards and mathematical reconstruction algorithms, 3D and 2D representations were obtained for logs and stems allowing the determination and visualisation of external shape as well as of the internal knot architecture. This provides input data set for sawing simulation software for converting logs into end products. Input data concerning final products and process variables was obtained directly from the wood based industry. The effect of some parameters on the volume and value yield of maritime pine stems was studied. Parameters include log dimensions and position within the stem, dimensions and grades of sawn timber products and saw kerf. Results were obtained through a set of simulations using different input variable combinations. The WoodCIM® sawing simulation software has shown potential to optimise the operating instructions in the sawing process of Maritime pine and to clarify the influence of the different raw material characteristics and production parameters on the recovery of sawn timber. Virtual sawing results were close to those realised in practice when similar situations were compared. INTRODUCTION For an efficient raw material utilization with the best possible economical results, the wood conversion chain has to be closely integrated and optimised in its different parts. In the sawing process, yield may be investigated using three alternatives : company's statistics, trial sawing and simulations. In the practice there is always possible to carry out only limited test sawing and empirical work, which is also expensive. It is also very difficult to establish two or more exactly identical log sets and correspondingly it is difficult to keep exactly two identical processing parameter values by sawing different sets of logs. Statistics provide possibility only to analyse what has happened in the past. These are the reasons why a simulation approach is useful : information for management, decision-making and process control is provided based on mathematical models and software tools to simulate production situations. Progress in scanning technology, defect detection and algorithms for virtual reconstruction of logs allowing the study of internal tree structure i.e. knot, heartwood and resin pockets (Oja, 1997 ; Björklund, 1999 ; Pinto et al., 2003) have provided support to improve optimisation and simulation procedures. Sawing simulation software always require extensive input data concerning products, sawing process as well as wood raw material. In some cases, data are derived from the measurement of actual logs (Tsolakides, 1969 ; McAdoo, 1969 ; Cummins and Culbertson, 1972) and simulation of virtual logs is done using computer graphics (Richards, 1973 ; Pnevmaticos et al., 1974 ; Todoroki, 1988, 1990). In other cases, a growth modelling approach is used and tree models representing external and internal stem features are the input data (Leban and Duchanois, 1990 ; Meredieu et al., 1999 ; Lönner and Björlund, 1999). Several research teams have developed computer programs, using input data based on scanning of logs or boards and reconstruction algorithms producing a 3D description of log/stem concerning its internal defects and shape, either derived from computer tomography (Occena and Schmoldt, 1996 ; Schmoldt and Araman, 1996 ; Chiorescu and Grönlund, 2000) and scanning of boards (Åstrand and Rönnqvist, 1994 ; Usenius and Song, 1997 ; Usenius, 1999, 2000). Reprinted with permission from the publisher. APPENDIX III In: Fourth Workshop of IUFRO WP S5.01.04 “Connection between forest resources and wood quality: modelling approaches and simulation software". British Columbia, Canada, 8–15 September, 2002. Ed. G. Nepveu, INRA, Nancy. Pp. 429–438.