Plywood is an umbrella term for wood composite boards made up of at least three layers of wood with a grain that is offset from one layer to the next adjoining layer (mostly by 90°). This structure prevents ("locks") the directional movements of the material (the expanding and shrinking of the wood) almost entirely.
The structure of plywood is symmetrical and always comprises an uneven number of layers. The layers can be composed of veneer, solid wood panels, solid wooden slats or other types of wood-based materials.
Depending on their type of layers, plywood is grouped into
- Veneer plywood (veneer boards, special type multiplex board with a thickness of at least 12 mm and at least five layers)
- Block plywood ("core board") with a middle layer of sawn wooden strips or 8 mm thick, upright slats made of peeled veneer
- Cross-laminated plywood made of cross-laminated solid wood panels
- Composite plywood with interior layers made of a different wood-based material (e.g. a veneer plywood board as the top layer).
Since there are so many different types of plywood offering a host of different properties, plywood is used across a wide scope of applications ranging from construction, e.g. cladding panels, to cabinetry.
Processing of plywood
Plywood can be machined (sawing, milling, grinding) and coated in the same manner as solid wood. Since the top layers are always made up of solid wood (mostly layers of veneer), plywood is subject to the same principles that need to be observed during the grinding of solid wood. It is necessary to take into account that the glue will be pushed through the pores in the wood of very thin veneer top layers or in wood with coarse pores when the boards are joined together. This glue will clog the abrasive belt more quickly during the subsequent grinding process.
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