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