Plywood is what we usually say plywood, which is a three-layer or multi-layer plate-like material made of wood segments cut into veneer or thin wood by wood planing, and then glued with adhesive, usually with odd layers of veneer, and the fiber direction of adjacent layers of veneer is vertically glued to each other. Plywood is one of the commonly used materials for furniture, is a kind of wood-based board.
How to produce plywood?
The process flow of log processing and production of plywood: log → log sawing → log debarker → veneer peeling → veneer drying → veneer composer→ gluing speader → pre-pressing → hot pressing → edge trimming → sanding
The length of imported logs is generally more than 6 meters, which should be sawed according to the length and quality of the process requirements, and the cut wood segment should be the size of the finished plywood plus the length of the processing allowance. For example, for finished plywood with a format of 1220mmX2440mm, the length of the wood segment is usually 2600mm or 1300mm. The length of the log and the curvature of the log, defects, etc., directly affect the output rate of the plywood, the generated waste has small wood segments, intercepts and sawdust, etc.
The invention of plywood peeling machine has greatly improved the work efficiency, peeling is not only only peeling. But also removing the irregular protrusion of the wood skin, scraping round, and then convenient storage and processing. So no matter what the wood processing, the first peeling process is essential。
The most widely used in the production of plywood is the veneer produced by the rotary cutting method. The thickness of the back plate is generally about 0.6mm. And the thickness of the core board, long and middle board is generally about 1.8mm. This process is the largest loss, one is due to the wood segment is not round. A considerable part of the broken veneer can not be used. The second is the end loss caused by the clamping head of the rotary cutting machine on both ends of the wood segment. Third, wood core loss. The waste generated by veneer spinning is broken veneer and wood core. So it can be seen that the loss of veneer spinning is related to the material. Diameter and equipment performance of the wood segment.
The water content of the veneer after spinning is very high. And the veneer must be dried to meet the requirements of the gluing process. After drying, the size of the wood becomes smaller, which is called drying shrinkage. The length, width, and thickness of the veneer will shrink due to reduced water content. The shrinkage loss is related to the species of veneer, the moisture content of veneer and the thickness of veneer.
Veneer finishing includes cutting, assembling and repairing. After drying, the strips and pieces are cut into standard boards and splicing boards. And the narrow strips are spliced into whole boards. The defective whole boards can be repaired to meet the quality requirements of the process. The amount of waste veneer produced in this process is related to factors such as log material, quality of rotary cut veneer. Quality of dried veneer and operator’s familiarity with veneer standards.
Cold press machine is the auxiliary in plywood production line, which is used to shorten the cycle time of hot press. And improve the quality of plywood before gluing board. It belongs to the pressing machine. Cold press machine is mainly used to press the gluing veneer. So that make the initial shape, and then into the hot press machine to press. It is important to improve the quality of plywood, and it is an significant part.
The coated slab is firmly glued together by a certain temperature and a certain pressure. With the change of the temperature and moisture content of the slab during hot pressing. The wood is gradually compressed and the thickness of the slab is gradually reduced. This loss is compression loss, and the plywood hot pressing temperature, unit pressure, hot pressing time, tree species and water content and other factors.
Cut the hot-pressed sheet into specification sheet. The amount of cut corner waste is related to the processing allowance and the size of plywood. The larger the size of plywood, the smaller the cutting loss rate
The surface of the plywood is sanded to make the surface smooth and beautiful. The waste produced by this process is sanding powder, when the quality of the veneer is good. The sanding amount is small, and the sanding loss rate is generally 2% to 6%