A prototype scanning system successfully demonstrated the capability of real-time, log pocket monitoring that can be used to alert operators of improper pocket filling practice.
Several previous FPInnovations studies have shown that the log pocket filling is often poorly controlled resulting in poor log alignment and/or incomplete filling that adversely affects both flake quality and strander productivity. Until now there have been no systems available to automatically measure the alignment of logs being fed into the strander or measurement of the actual filling of the strander pockets. An automated monitoring system is needed to signal operators when the log pocket is improperly loaded. This feedback can allow operators to maintain proper log filling procedure to maximize flaking quality.
In March 2013 a machine vision scanning system comprised of a camera, 2 line lasers and computer with image analysis software, was tested for two days at the Peace Valley OSB mill (PVOSB) in Fort Saint John, BC. The scanner’s camera and lasers were mounted 13 feet above the center of the log pocket base. Images of pocket filling were acquired and analyzed for pass/fail conditions. Two image groups were selected for analysis, one of full pocket, aligned logs (pass) and the other containing misaligned logs and/or insufficient pocket fill (fail). For all pocket scans, scanner measurements were compared to manual visual classification.
Approximately 50 different pockets were scanned with results and images saved for analysis. For fill height and vertical log alignment measurement, the scanner correctly identified >95% of all the pockets examined. However, log alignment measurement in the horizontal x-y plane did not function as intended due to poor image contrast that could not be resolved during the mill trial. This technique has been shown to work well in previous pilot plant tests (Groves, 2012) which confirms that the underlying measurement fundamentals are sound. It is recommended that only minor lighting adjustments are required for the scanning system to work well in a mill setting.
Implementing this technology in OSB mills should help to reduce the occurrence of poor pocket filling that can adversely affect strand quality. It should be noted that even small improvements to strand quality and productivity can yield significant cost benefits. It is estimated that reducing fines by a modest 1% and improving productivity by 1% can return in excess of $1 million/year based on an average size Canadian OSB mill.