How to make plywood

Mar. 02, 2020

Plywood is a three-layer or multi-layer board formed by wood veneer which is rotary peeled from wood block, and then glued with adhesive. Usually, plywood have an odd number of veneers The fiber directions of adjacent veneers are glued perpendicular to each other. Plywood is one of the commonly used materials for furniture and is a kind of artificial board.

How to make plywood

First, the process of plywood production from log processing: log → log sawing → wood block cooking → wood block debarking → veneer rotary cutting → veneer drying → veneer finishing → rubberized blank → pre-pressing → hot pressing → trimming → Cut out → Check and grade → Packing and storage.

Second, the process of veneer processing to produce plywood: veneer finishing → glue-coated blanks → pre-pressing → hot pressing → cutting → sanding → inspection grade → packaging and storage.

1. Processing process loss: During the entire production process of plywood, sawn logs, veneer rotary cutting, veneer drying, veneer finishing, hot pressing, trimming, and light cutting have an impact on wood loss. It is divided into tangible losses ( With processing residues) and intangible losses (dry shrinkage and compression). Wood loss is related to factors such as log species, log specifications, equipment status, process technology, and finished board specifications.

2. Log sawing: The length of imported logs is generally more than 6 meters. The saw logs should be cut according to the required length and quality of the process. The intercepted wood segment should be the length of the plywood finished product plus the processing margin. For example, the finished plywood with a width of 1220mm × 2440mm is usually 2600mm or 1300mm in length. The length of the log and the curvature and defects of the log directly affect the yield of the plywood. The waste generated includes small wood segments, stubs, and sawdust. The sawing loss rate of the log is generally 3 to 10%.

3. Rotary cutting of veneer: The most widely used in plywood production is the veneer produced by the rotary cutting method. The thickness of the backplane is generally about 0.6mm, and the thickness of the core board and long middle board is generally about 1.8mm. This process has the most losses. First, due to the roundness of the wood segment, a considerable part of the broken veneer cannot be used; second, the end of the wood segment is clamped by the rotary cutter's chuck, and third is the wood core loss. The waste generated by veneer rotary cutting is broken veneer and wood core. It can be seen that the veneer rotary cutting loss is related to the material, diameter and equipment performance of the wood segment, and this part of the loss rate is 15% to 25%.

4. Veneer drying: The moisture content of the veneer after spinning is very high. The veneer must be dried to meet the requirements of the gluing process with veneer dryer. After drying by veneer dryer machine, the wood becomes smaller in size and is called dry shrinkage. Due to the reduced moisture content, the length, width and thickness of the veneer will shrink. Dry shrinkage loss is related to veneer tree species, veneer moisture content, and veneer thickness and other factors. The dry shrinkage loss rate is generally 4% to 10%.

5. Veneer finishing: Veneer finishing includes cutting, jigsaw and repair. The dried strip veneer and piece veneer are cut into standard veneer and splicable veneer. The narrow veneer is spliced into a whole veneer. The defective whole veneer can be repaired to achieve the process. Quality requirements. The amount of waste veneer produced in this process is related to factors such as the log material, the quality of the rotary cut veneer, the quality of the dry veneer, and the familiarity of the operator with the veneer standard. The loss rate is generally 4% to 16%. The process of directly imported veneer processing into plywood generally has a loss rate of 2% to 11%.

6. Hot pressing: The glued slabs are glued together firmly through a certain temperature and a certain pressure. As the temperature and moisture content of the slab change during hot pressing, the wood is gradually compressed and the thickness of the slab gradually decreases. This loss is compression loss, which is related to factors such as the hot pressing temperature, unit pressure, hot pressing time, tree species and moisture content of the plywood. The loss rate is generally 3% to 8%.

7. Trimming: Cut the hot-pressed wool board into standard board. The amount of cut corner waste is related to the processing allowance and the size of the plywood. The larger the plywood width, the smaller the trimming loss rate, which is generally 6% to 9%.

8. Sanding: Sand the surface of plywood to make the surface smooth and beautiful. The waste generated in this process is sanding powder. When the veneer quality is good, the sanding amount is small, and the sanding loss rate is generally 2% to 6%.

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