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Processes Used to Form Wood Materials Chapter 16 Bonding Processes • Use heat and pressure to compact particles or chips into sheet stock • Creates Composition board • Board made of wood that has been broken down into particles or fibers Three major types of Composition Boards • Hardboard • Continuous mat of pulp that is pressed into a sheet • Used for floor underlayment, cabinet making, etc. • MDF, MDO • Insulation board • • • • Made from pulp wood and bagasse (from sugar cane) Low density High heat resistance Good acoustical barrier • Not common • Particle board • Many varieties • Wood chips mixed with resin are pressed into board shape • Not common Waferboard • Made using high quality wood flakes • About .028” thick, 1.5” wide and between 3” and 6” long • Bonded together under heat and pressure with phenolic resin • Construction and furniture making industries • Not used anymore, replaced by osb type products Oriented Strand Board (OSB) • Made from wood fibers bonded together with resins and glue • Large and irregularly shaped • Layers of fibers are oriented perpendicular to the last layer Lamination Process • Sandwiching sheets or pieces of wood together • Plywood • Gluing layers together • Grain of layers is perpendicular • Odd number of layers so outside layers have parallel grain • Reconstituted wood • Made from plywood cut into strips smaller than .030” • Strips are glued together • Looks like real wood Advantages of Lamination • Less wasteful than cutting • Shapes like large beams or arches • Stronger than solid stock • Grain of layers oriented to add strength • Cost • High quality materials used for faces, lower quality materials used for inside layers Bending Processes • Can be bent across or with grain • With is easier • Done dry or wet • Wet is easier with some woods • Prevents fracture • Some hardwoods suited to bend • • • • • • • White oak Elm Hickory Ash Birch Maple Walnut • Softwoods are difficult to bend Wet or Hot Bending Steaming or soaking • Best method • Stock is subjected to steam or soaked in boiling water • Reaches about 20% moisture content • Then formed into desired shape Laminating in a two-piece mold • Using a forming jig and adhesive Cold or Dry Bending • Hydraulic cold presses used to form plywood • Use of pressure to form into a mold
