Here are the slides from my bit of the BM TRADA webinar on strength grading of timber, Thursday 18 April 2024. This covers machine grading (plus a few general things, and quick update on EN1912 for visual grading).
And here is a small version of one of the grading animations. The property being graded (the grade determining property) is on the x-axis and the property being used for grading (the indicating property) is on the y-axis. We would like to be able to grade on the basis of the grade determining property – make a vertical cut – but we can’t. Instead we have to use the indicating property – make a horizontal cut. The idea is to put that horizontal cut so that we get no more than 5% of the graded population below our critical “characteristic” value. A better correlation between indicating and grade determining property can make the grading more efficient, although the benefit is less when the ungraded timber is already close to the grade target. Due to randomness there will be some variation in the grading performance.
