Development of an adaptive sawmill- flow simulator template for predicting results of changes at small- log sawmills.

Abstract

Managing or designing sawmills can be an extremely difficult and sawmill managers and designers face a multitude of decisions each day with regard to management of sawmill operations and productivity. Sawmill managers therefore must be skilled enough at balancing the variables that determine sawmill production including: raw materials, personnel, equipment, product mix, product quality, orders and money in order to make profits. Changing any of these variables in one part of the mill can have unforeseen and sometimes detrimental impact upon other parts of the mill. Extreme heterogeneity in raw materials adds significantly to the complexity of sawmill systems. Simulation is one of the most common methods for constructing models that include random behaviour of a large number and a wide variety of components in sawmilling such as reduced availability of large-diameter logs with increased wood demands which may result into smaller-diameter logs entering sawmills. The design and operation of a modern small-log sawmill requires skills different from those needed in a large-log sawmill. Because the log size is small and lumber production per log is low, production must be high. Profitable sawing of small diameter logs requires high speed processing, use of curve sawing, and careful loggeometry and orientation considerations before sawing. Although numerous simulation studies
have investigated sawing process of largediameter logs, only a limited number of
simulators have addressed processing of smalldiameter logs. Further, these latter simulators
concentrated on improving either the lumber volume yield or the lumber grade/value from
logs. The modeling of entire sawmill operations has been far less extensive. The sawmill-flow simulator template (SFST) and a simulation template end–user interface designed on Excel spreadsheets in this study is a unique modeling package that can be used to predict results of changes in production at a small-log sawmills. The SFST encompasses log–sawing and sawmill-flow logics designed to facilitate flexibility in modeling different sawmill
configurations and production scenarios. These may include predicting the impact on sawmill
performance measures due to changes in mill layout, raw material and product pecifications,
sawing solutions, and queue sizes which can greatly help the saw miller to make ellinformed
decisions.

Keywords: Sawmill flow simulator – modular approach – discrete event simulation

Tanzania Journal of Forestry and Nature Conservation Vol. 77 2008: pp. 73-90