1. LVL AS A CONSTRUCTION MATERIAL 1.6.4 Layup and hot pressing Glue is mixed on site from resin, hardener and water. In the manufacture of LVL, phenol formaldehyde resins are mainly used at approximately 30 kg dry weight per cubic metre of LVL. Veneer of the required length and proper bonding are achieved by scarfing a bevel at both ends of the veneer. The scarfed veneers are fed to the layup line, glued on one side, and then laid in a staggered configuration (see Fig. 1.40) to form a continuous billet of LVL. The veneers are normally fed parallel to the grain direction, although some veneers are laid crosswise in certain products. LVL is typically assembled from an odd number of plies. Special structures can also be produced to meet specific end use requirements. Layup starts at the layup table where the veneers are laid with a staggered edge spacing of approximately 120 mm (see Fig.19). The resulting staggered jointing maximizes the strength properties of the LVL. Figure1.37. Scarfed veneer end. Figure 1.38. Layup line principle. Figure1.39. Liquid extruder gluing (LEG): glue is applied to the top of the veneer as it passes on the belt conveyor. Figure1.40. Staggered layup ahead of the pre-press. LVL Handbook Europe 31
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