Plywood standards and production process of plywood

Plywood standards and production process of plywood

1. The technological process of plywood production from log processing: log cutting, log sawing, wood cooking, wood stripping, veneer rotary cutting, veneer drying, veneer finishing, pre-pressing, hot pressing, cutting edge, cutting, inspection and grading, etc. Packing and storage.

2. The technological process of veneer processing and manufacturing plywood: veneer finishing glue coating group blank preloading hot pressing cutting sanding inspection grade packaging and storage.

1. Processing loss: In the whole production process of plywood, log sawing, veneer rotary cutting, veneer drying, veneer finishing, hot pressing, edge cutting and cutting have an impact on wood loss, which is divided into tangible loss (with processing residues) and intangible loss (drying shrinkage and compression). Wood wastage is related to raw wood species, log specifications, equipment status, process technology and finished board specifications.

2. Log sawing: imported logs generally exceed 6 meters in length. They should be sawed according to the length and quality required by the process. The length of the cut wood should be the dimension of the finished plywood and the processing allowance. For example, a finished plywood with a width of 1220 mm X2440 mm is usually 2 600 mm or 1 300 mm in length. The length of logs and the curvature and defect of logs directly affect the yield of plywood. The waste materials are small segments, cutting heads and sawdust. The sawing loss rate of logs is generally 3-10%.

3. Veneer rotary cutting: The veneer produced by rotary cutting method is the most widely used in plywood production. The thickness of veneer back is generally about 0.6 mm, and the thickness of core plate and long and medium plate is generally about 1.8 mm. This process has the greatest loss, first, due to the non-roundness of the wood segment, a considerable part of the broken veneer can not be used; second, the end loss caused by the clamping of the lathe clamp on both ends of the wood segment; third, the core loss. The scrap produced by veneer rotary cutting is broken veneer and wood core. It can be seen that the loss of veneer rotary cutting is related to the material, diameter and equipment performance of the veneer. The loss rate of this part is 15%-25%.

4. Veneer drying: The veneer after rotary cutting has a high moisture content, so the veneer must be dried to meet the requirements of gluing process. After drying, the size of wood becomes smaller, which is called shrinkage. The length, width and thickness of veneer will shrink due to the decrease of moisture content. Dry shrinkage loss is related to the species of veneer, moisture content of veneer and veneer thickness. Dry shrinkage loss rate is generally 4%-10%.

5. Veneer finishing: Veneer finishing includes shearing, splicing and repairing. After drying, strip veneer and zero veneer are cut into specification veneer and spliceable veneer. Narrow veneer is spliced into whole veneer. The defective veneer can meet the quality requirements of the process by repairing. The waste veneer produced by this process is related to the raw wood quality, the quality of rotary-cut veneer, the quality of dry veneer and the familiarity of operators with veneer standards. The loss rate is generally 4%-16%. The process loss rate of plywood processed from imported veneer is generally 2%-11%.

6. Hot pressing: The glue-coated slabs are firmly bonded through a certain temperature and pressure. With the change of slab temperature and moisture content during hot pressing, wood is gradually compressed and slab thickness is gradually reduced. The loss is compression loss, which is related to the hot-pressing temperature, unit pressure, hot-pressing time, tree species and moisture content of plywood. The loss rate is generally 3%-8%.

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

Plywood standards and process flow of plywood

8. Sanding: Sanding the plywood surface to make it smooth and beautiful. The waste produced by this process is sanding powder. When the veneer quality is good, the sanding quantity is small, and the sanding loss rate is generally 2%-6%.

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