1. LVL AS A CONSTRUCTION MATERIAL Figure1.35. Composing principle. Figure1.36. Green veneer composing line. The target moisture content is below 5%. Automatic regulation maintains the speed, temperature and humidity inside the dryer at an optimal level. The energy required to dry the veneer can be produced from the mill’s own by-products. A fully automatic machine vision system analyses veneer defects, such as knots, splits, breakages, micro-splits, decay, resin pockets and discolouration, at process speed. The image data is analysed in milliseconds and used to stack the veneers into different bins at the stacker. The dried veneer is measured for moisture content to ensure the target moisture has been achieved. Density measurement and strength grading of the veneer are also carried out based on radio frequency analysis and ultrasonic propagation time. Veneer pieces of different sizes – i.e. ‘randoms’ – can be composed into veneer sheets of required width. Composed veneers are used as core veneers. The aim is to increase veneer yield by maximizing the use of peeled material. Randoms can be collected from peeling line and broken veneers from the drying line. Veneer can be composed green or dry. At the composer, the randoms are glued or taped together to form full-size veneer sheets for LVL production. 30 LVL Handbook Europe
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