Date of Award

5-2010

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Stephen M. Shaler

Second Committee Member

Robert W. Rice

Third Committee Member

William A. Halteman

Abstract

This research examined the effects of strand length and starting position on the dynamics of strand movement from the forming bunker through the orienting deck in an industrial oriented strand composite (OSC) facility. The trend toward the use of longer strands in composites such as oriented strand lumber and laminated strand lumber has not been accompanied by any significant changes in the OSC industry's forming technology. Simply using a scaled-up version of the shorter stranded oriented strand board forming line may not be the most efficient use of resources to produce these higher performing products. Quantifying the effects of strand length and starting position on the movement through the forming line enables improvements in forming practices that enhance final product performance while maintaining or reducing raw material usage. Since these were original experiments, a large portion of time was dedicated to develop experimental protocols and measurement techniques. These methods included tracking the movement and orientation of strands through several stages of the OSC forming process using human-eye identification and optical measurements of strands from images. The methods developed here can be used by industry to determine flow characteristics on their respective forming line setups. Results showed that all of the strands' lateral movement and mixing occurred in the strand chute prior to entering the orienting deck; likely because of strand-disc interactions and freefall characteristics. In addition, shorter strands were shown to spread further across the strand chute compared to longer strands. Significant pre-alignment of nine-inch strands occurred before the orienting deck presumably due to the dynamic interactions of the strands and the rotating tines. In addition, strand length affected the strand orientation and distance travelled (projection) along the orienting deck. As expected, longer strands aligned significantly better and projected significantly farther along the orienting deck compared to shorter strands. The experiments, as conducted, also raised concerns with the orienting deck length being insufficient to allow all nine-inch strands to orient and pass through before the end of the deck. Fines analysis of the collected strands showed a decrease in strand geometry and that 70% of the geometric damage was done by the rotating tines in the strand chute. A reduction in geometry will result in shorter travel distance along the length of the orienting deck as well as a reduction in orientation quality. Statistical modeling of a 50-50 mixture of four and nine-inch strands predicted a 50% reduction in mat orientation quality as the percent of four-inch strands increased. Quantifying and understanding the dynamic interactions responsible for strand flow and their effects on OSC manufacturing is an integral part of achieving the ultimate goal of developing a comprehensive computer model of the OSC manufacturing process. Industry would be able to use this model to predict how process variables (i.e. strand geometry, orienter disc spacing or rotational speed, feed speed, etc.) would affect the final product. Over the past two years, a tandem project has been developing a physics-based computer model to describe the behavior observed in this research.

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