Investigation of Sawmill Management and Technology on Yield Optimisation at Selected Sawmills in Moratuwa

Abstract

Sawmilling is a primary industry which provides raw materials to other industries such asconstruction, joinery, furniture and others. The raw material used in sawmills consists of logswhich come from different forests. Logs are classified by diameter, length and quality.Depending on the consumer demand for the products and the nature of the productionprocess, each sawmill has to determine the quantity of different type of logs required tosatisfy the consumer demand. Optimization models are referred as a main branch inOperations Research used to support decisions in the forestry industry. The yield optimisationsystem can significantly improve timber value recovery in sawmills. A hybrid volume valueoptimized solution will allow maximum utilisation of each log while achieving the highestpossible value recovery from logs. The key objective of this study is to construct a yieldoptimization model suggesting best cutting pattern for the logs taking its dimensions intoconsideration.

A sample of twenty one sawmills were selected out of 206 registered private sawmills inMoratuwa based on the sampling percentages determined from an initial survey. The selectedsawmills represent all types of sawmills available in Sri Lanka namely frame saw, circularsaw and band saw mills. Length, mid diameter, diameter at top, diameter at the bottom, taperand eccentricity of two hundred and ten (210) logs were measured and recorded.

A yield optimization model was developed using the data obtained during this study. Thedeveloped model which can be categorised as a non linear integer programming model iscapable of generating optimum cutting patterns in order to minimise the wastage. There aretwo assumptions considered such as the usable area of the log is half cone shaped and thereare no internal defects of the usable area in the log in order to reduce the complexity of theproblem.

In the subsequent stage the model will be solved using a suitable algorithm with the help ofoptimisation computer software.