1. LVL AS A CONSTRUCTION MATERIAL 1.7 FURTHER PROCESSING LVL manufacturers offer further processing of their products according to customer specifications as value-added services. This is done either directly at the mill or by subcontractors equipped with special machinery for LVL processing. The value-added services save time and minimize waste for the customer and on the building site. 1.7.1 Sanded surfaces: optical or calibration sanding Standard LVL is delivered unsanded. It can, however, be sanded with two alternative specifications. The visual appearance of LVL can be improved by optical sanding, which cleans and smoothens the surface by removing dark glue stains and equalizing local colour differences of the veneers. Optical sanding can be carried out on one or both sides and reduces the thickness of the product by approximately 2 mm (1 mm per surface). In visible applications it must be noted that on the front face of the LVL member the scarf-joints of the surface veneers are glued with colourless glue, but on the bottom side the scarfjoint glue line is dark brown, similar to the glue lines between veneers 11. Another sanding treatment that can be performed is calibration sanding for thickness calibration, which is carried out on both sides of the LVL. Calibration sanding reduces the thickness of the product by approximately 3 mm (1.5 mm per surface) and the thickness tolerance after calibration is ± 0.5 mm. Unless a non-transparent coating is used on the surfaces, calibration sanding is not recommended for visible applications because it can sand through the surface veneers revealing the dark glue line, especially in thicker products. The nominal sanded dimensions of the product must be used in structural design calculations. Figure 1.47. Principle of diagonal sawing of LVL panel to produce single-tapered column and rafter members of portal frames. 1.7.3 CNC Machining CNC machining enables drillings, holes, notches and end sloping of beams. The machining requires a geometry file of the members from the customer, e.g. a DWG drawing at 1:1 scale drawn with closed lines for each different type of member to be machined. Figure 1.48. Holes in LVL panels. 1.7.2 Special cutting LVL panels or beams can be sawn to special shapes or sawn diagonally to produce tapered beams or columns. Manufacturers may also have special cutting tolerances for tailored products, e.g. of industrial customers. Metsä Wood 1 2 3 Figure 1.46. Appearance of LVL veneer surface 1. Unsanded face side. 2. Optical sanded face side. 3. Calibration sanding revealing the dark glue line. 34 LVL Handbook Europe
RkJQdWJsaXNoZXIy MjU0MzgwNw==