Plywood is a flat panel built up of sheets of veneer called plies, put together under high pressure with glue to create a panel with an strong bond between the plies. Building the panel the plies are glued together in alternating directions, depending on the required thickens the panel usually consists of 3, 5, 7 or 9 layers. The inner plies are called centers or cores, the plies with the grain perpendicular or a right angle to that of the core or faces are called crossbands. Crossbands gives the panel strength and keep the grain of the panels from running all in the same direction. The outside plies are are called faces and back plies. The faces of the panel are usually of higher grade veneer, while the core and back consists of lower grade plies. this makes a plywood panel affordable but also interesting to use because of the beautiful veneer layer on top. Due to the perpendicular buildup of the panel it becomes super strong and very resistant to expansion and shrinkage. therefor plywood panels are popular for construction and industrial purposes, but also often used in the cabinet and furniture industries.
Plywood may be made from hardwoods, softwoods, or a combination of the two. Some common hardwoods include ash, maple, mahogany, oak, and teak. The most common softwood used to make plywood is Douglas fir and several varieties of pine, cedar, spruce and redwood.
Softwood ply tends to be used in the construction industry for walls, roofs and floors.
Hardwood ply tends to be used quality laminate flooring, kitchen units and furniture.
|A||Face and back veneers practically free from all defects.|
|A/B(B)||Face veneers practically free from all defects. Back veneers with only a few small knots or discolorations.|
|B||Both side veneers with only a few small knots or discolorations.|
|B/BB||Face veneers with only a few small knots or discolorations. Back side permitting jointed veneers, large knots, plugs, etc.|
|BB||Both sides permitting jointed veneers, large knots, plugs, etc.|
|C & D||Knots and minimum splits permitted unless exceeding a certain limit|
|WG||well glued only. All broken knots plugged permitted.|
|X||Knots, knotholes, cracks, and all other defects permitted.|
The trees used to make plywood are usually smaller in diameter than those used to make lumber. In most cases, they have been sustainably planted and grown in areas owned by the plywood company. These areas are carefully managed to maximize tree growth and minimize damage from insects or fire. once the tree has grown enough the process is a following.
- Cutting and felling the trees
After the trees are cut and the branches removed they are ready for debarking
With the help of Machines the bark will be removed from the logs
The logs are cut in the appropriate length usually around 2.5meters
- Soaking the logs
Depending on the process and wood specie the logs are soaked or steamed for 12 to 20 hours
- Peeling the logs
With the use of a lathe the complete log will be transformed into a thin sheet of veneer
- Cutting and Grading the veneer
The veneer is then cut into the appropriate size for glueing and sorted on its Grade
- Drying the veneer
The sheets of veneer will then be Kiln dried
The core, crossbands and face layers are then glued and assembled ready for pressing
- Hydraulic hot press
The assembled panels are then pressed in a hydraulic hot press (7.6-13.8 bar|109.9-157.2° C) for 2 to 7 minutes
The panels are then trimmed to the factory size. Most common Plywood dimension is 1,220 × 2,440 millimetres
The panels are sanded and inspected for inconsistencies, then stored for distribution