Plywood is a material made of three or more thin layers or plies of veneer which are peeled from debarked wood that are joined together with help of adhesive under pressure. Each layer of veneer is normally adjusted with its grain running at right angles to the adjacent layer to create cross- graining pattern in order to improve strength of final piece and reduce the possibility of shrinkage. Plywood outer layers are known as face and back. Plywood is mainly known for its strength, durability, righty and lightness.
Today plywood is used in every field according to its grade and structure. Mainly plywood is used in flooring, walls, kitchen cabinets, furniture, doors and in other industrial areas. Production of plywood is increasing every year. In 2018 2.4 million cubic meter plywood is produced and it is estimated that up to 2022 it will reach at 3.2 million cubic meters. Plywood is produced in every part of world. Big mills are installed to manufacture the plywood where plywood is produced and then transported direct to customers or they have their own stores to sell and all these industries have different name and tags.
Plywood Manufacturing Process
The manufacturing process consist of many steps such as log storage, log debarking and bucking, log heating, veneer cutting, veneer drying, veneer layup and glue spreading, plywood pressing, plywood cutting, plywood finishing such as sanding and trimming. After completing all these steps final product is ready to pack and deliver to customer.
Figure no 2.
The first step is storage of log which are transported to mill. Long yard is used to store logs. Logs are stored to maintain moisture in them, mill use different types of method to maintain moisture in logs. Mill choose many sprinkler systems or Logs are drowned into water so they can easily cut log into pieces and help in peel easier. After that logs are taken at debarking machine where bark of the tree log is removed by sharp- toothed grinding wheels. These logs then move to another machine where it cuts them into pieces according to required size of final product. The next step is to make wood soft by heating and soaking. Once logs are heated then they are peeled using a rotary lathe. A sharp blade peels the log into continuous sheets of veneer. Now sheets of veneers can be stored in multiple-level tray or by wound it into roll or can start next process immediately.
Figure no 3.
Cutting the veneers in usable width is next step in this process where most of companies use scanner system to search for unacceptable defects and if they found any defect, they cut of it. Veneers then shuffled according to grades. Which is done manually or by using optical scanners. The arranged sections are then dried to remove moisture and protect it from fungal decay and allow veneers to shrink before they are glued together. Industrials dryers are used to dry the veneers in which piece move continuously through heating chamber. The process of laying up and gluing pieces work together. Veneers are passed through gluing machine which applies glue on face and back of the veneers but glue is not applied to all pieces of veneers. Then veneers are joined together in pattern glued veneers, unglued veneers, glued and so on. Now pressing process is beginning sheets are placed in hot press that can handle 20-40 sheets at one time. The press compresses all sheets together and heats them to around 110-157 degree Celsius. The pressing takes time 2-7 minutes. Then these sheets are cooled down before further processing. The sheets are passed through a set of saws which trim them into final width and length and remove unwanted material. Then boards face and back are sanded to clean up rough areas. After completing all these processes final product is ready. The final step is stamping the board according to its grade and other factors.
Plywood manufacturing process follows the linear process each activity following the previous one from raw material to finial product. The finish product of one activity become raw product for next.
The fishbone diagram of the 5Ms: –
Machine: – De-barking machine, peeling machine, Dryer, Core composing machine, Glue spreading machine, Presser, Calibrating machine, Sanding machine.
Measurement: – The general size is (8*4, 7*4, 6*4 sq. feet). Thickness (1/4, 1, ? and many more).
Material: – softwood (pine, cedar, redwood), Hardwood (ash, maple, oak and teak).
Method: – linear method
Man: – People have physical capabilities, large number of people are required because most of work in these factories is done manually.