Processes Used to Form Wood Materials

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

Processes Used to Form Wood Materials