1. In order to improve the anisotropy of natural wood as much as possible, so that the characteristics of plywood are uniform and the shape is stable, the principle of symmetry must be followed when producing multi-layer boards. The principle of symmetry is to require that the veneer on both sides of the symmetrical center plane of the plywood should be symmetrical with each other regardless of the nature of the wood, the thickness of the veneer, the number of layers, the direction of the fiber, the moisture content, etc.
2. When producing multi-layer boards, the principle that the fibers of adjacent layers of veneer should be perpendicular to each other. That is, in the same plywood, veneer of a single species and thickness can be used, or veneer of different species and thickness can be used, but any two layers of veneer species and thickness that are symmetrical to each other on both sides of the symmetrical center plane should be the same, and the fibers of the adjacent layers of veneer are perpendicular to each other.
