In December, 2012, Kevin Groves from FPInnovations visited a Canadian OSB mill to demonstrate an FPInnovations prototype vision scanning system for simultaneously monitoring fines, strand width and alignment on the forming line.
Prior to the mill trial, the width and fines measurements were calibrated based on known quantities of fines and strand width sizes. During laboratory calibration, there was a linear relationship between scanner versus actual width values with an R² correlation of 0.98. The measurement prediction accuracy was estimated with a root mean square error (RMSE) of 0.1 inches. With fines, there was a linear relationship between scanner measurement versus actual values with an R² of 0.99. The measurement prediction accuracy was estimated with a RMSE of 2 % (fines percentage).
The alignment angle of each strand was measured from -90° to 90° with 0° set as the principal forming line direction. The scanner’s measurement of alignment is described by percent alignment (PA) as proposed by Geimer (1976). PA gives an alignment of 100% for perfectly aligned strands and 0% alignment for random strand distribution.
At the mill the camera was set up 36 inches above the top face mat on the forming line. Strand width, alignment and fines measurements were collected continuously from approximately 5:00 pm December 19 to 9:25 am December 20. On December 19 the mill ran overnight with 7/16” panel production at a former height of 5 inches. During this time scanner measurements showed that average alignment remained relatively constant at approximately 70% while average strand width gradually decreased from approximately 0.75 to 0.7 inches, and fines increased from approximately 8% to 18%.
The next morning (December 20) beginning at 7:50 am, the former height was changed in stages from 5 to 8 inches with corresponding scanner measurements showing a decrease in alignment from 70% to 45%. The scanner was effective in tracking these height changes with results showing an inverse linear relationship between former height and alignment. Saved images were later analyzed to determine actual alignment for comparison to the onsite scanner measurements. Results showed a good correlation with an R² of 0.98 between measured versus actual alignment. The accuracy of strand alignment measurement was estimated with a RMSE of 3 PA.
Although this was a short trial, the scanner effectively demonstrated simultaneous, real time measurements of fines, strand width and alignment.