Basic principles of plywood

In order to improve the anisotropic properties of natural wood as much as possible, and to make plywood characteristics uniform and stable in shape, generally plywood should follow two basic principles in structure: one is symmetry; the other is that the adjacent veneer fibers are perpendicular to each other. The principle of symmetry is that the veneers on both sides of the center plane of symmetry of the plywood should be symmetrical to each other regardless of the nature of the wood, the thickness of the veneer, the number of layers, the fiber direction, and the moisture content. In the same plywood, veneers of a single species and thickness can be used, or veneers of different species and thickness can be used; however, any two veneer species and thicknesses that are symmetrical to each other on both sides of the symmetry center plane should be the same. The front and back panels are not allowed to be the same tree species.

To make the structure of plywood meet the above two basic principles at the same time, its number of layers should be odd. Therefore, plywood is usually made into three layers, five layers, seven layers and other odd layers. The name of each layer of plywood is: the surface veneer is called the surface plate, the inner veneer is called the core plate; the front surface plate is called the face plate, the back surface plate is called the back plate; in the core plate, the fiber direction is parallel to the surface plate Is called long core board or middle board. When forming the cavity board slab, the face plate and the back plate must face tightly outward.