Oriented strand board (OSB) is manufactured in wide mats from cross-oriented layers of thin, rectangular wooden strips compressed and bonded together with wax and synthetic resin adhesives (95% wood, 5% wax and resin. The moisture gauge alerts if moisture is too high which can lead to a board blow. Similarly, the moisture gauge alerts if moisture is too low which can result in fires. The layers are created by shredding the wood into strips, which are sifted and then oriented on a belt or wire cauls. The mat is made in a forming line. Wood strips on the external layers are aligned to the panel’s strength axis, while internal layers are perpendicular.
The number of layers placed is determined partly by the thickness of the panel but is limited by the equipment installed at the manufacturing site. Individual layers can also vary in thickness to give different finished panel thicknesses (typically, a 15 cm layer will produce a 15 mm panel thickness). The mat is placed in a thermal press to compress the flakes and bond them by heat activation and curing of the resin that has been coated on the flakes. Individual panels are then cut from the mats into finished sizes. The largest production facilities can make over a million square feet of OSB per day. A moisture gauge is used in virtually every unit operation of production.