UBC Theses and Dissertations

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UBC Theses and Dissertations

Computer simulation of overseas product manufacturing potentials of a redesigned multipass headrig mill in coastal British Columbia Orbay, Laszlo


Modification of the sawmill Woodroom #3, MacMillan Bloedel Ltd., at. Harmac became necessary because of its uneconomical operation. The key concept of the modification plan was to gain flexibility in serving seven overseas and U.S.A. markets. Stochastic components of sawmilling and the high cost of reconstruction make investment decisions complex and risky. A new computer simulation model was needed and developed to evaluate behaviour of the redesigned mill. In building the model, two major factors were taken into consideration which affect mill performance, log breakdown and log throughput. Thus, the model is a combination of FLOWSIM, a newly developed dynamic piece flow simulator and SAWSIM, an existing sawing simulation package. A special simulation language GPSS/H, the most effective version of GPSS, was employed to build FLOWSIM. SAWSIM, providing a log breakdown logic for FLOWSIM, simulates sawing patterns more accurately than any other model. Using SAWSIM with FLOWSIM reduced programing effort and improved accuracy of sawmill simulation. Interacting auxiliary programs were written and organized into one system which supported the operation of the two major simulators and the data transmission between them. Six market runs were carried out to test market flexibility of production. Simulation results of log demand, lumber value and volume of production, and machine and transportation equipment utilization provided a basis for the final investment decisions. Model output helped to locate flow problems and was used to recommend further mill design modifications. To estimate the effect of machinery breakdown on productivity, three runs were accomplished. As an example of breakdown sensitivity analyses, an additional run was made to estimate- the lost production in dollars per hour of machine "down" time. All runs simulated mill operation for one shift. Simulation of Woodroom #3 modification plans shows that it is possible to build a flexible sawmill capable of producing for various overseas markets. Although, the simulation model of this thesis was designed to analyze a particular sawmill of MacMillan Bloedel, the model building concepts could be used to help develop a general model for sawmill simulation in other mills and other regions.

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