Integrating the bucking operation with production control in sawmilling

Sammanfattning: There is an ongoing shift in production strategy in the sawmill industry in Scandinavia from bulk production of standard grades towards customer- oriented production of well-defined products. The bucking operation places limits on the timber that can be sawn from the logs. Thus, it is important to be able to control the bucking process. Knots are the most numerous type of defect in sawlogs. Realistic models of log geometry and internal knot properties can be used to estimate the yield of different production strategies in sawmilling using simulation techniques. In addition, in the process of converting stems and logs to timber products, a precise knowledge of internal defects in every log is required to obtain maximum value yield. The overall objective of this thesis was to augment the Swedish Stem Bank, a database of realistic log models, with parametric descriptions of young Scots pine trees from stands not previously thinned and to evaluate different bucking strategies based on improved characterisation of the stems. In this thesis, a method for extracting detailed descriptions of stem geometry and knot structure in young Scots pine (Pinus sylvestris L.) is presented. Descriptions of 48 stems were obtained from CT images of the stems. Due to low content of heartwood, the knots showed low contrast to the surrounding clearwood and consequently were difficult to segment using traditional image analysis techniques. Instead, an artificial neural network was used for classification of the images. The descriptions obtained were used to augment the Swedish Stem Bank. This thesis also deals with economics in the wood conversion chain with a view to bucking strategies and with a customer-oriented perspective. A realistic sawmill simulator was used to assess the yields of different bucking strategies applied to the Swedish Stem Bank. It was shown that the bucking operation must be based on productivity, as well as product values of the sawmill utilizing the logs. It was also shown that log price lists are unnecessary and that bucking should preferably be based on timber prices and simulated sawing of accurately measured stems. This would lead to improved production control as well as higher value recovery.