Basic principles
In order to improve the anisotropy characteristics of natural wood as far as possible, so that the plywood characteristics uniform, stable shape, generally plywood in the structure should comply with two basic principles: one is symmetry; Second, the adjacent layers of veneer fibers are perpendicular to each other. The principle of symmetry is that the veneer on both sides of the symmetric center plane of plywood should be symmetrical with each other, regardless of the nature of wood, veneer thickness, layer number, fiber direction, water content, etc. In the same piece of plywood, you can use a single tree species and thickness of veneer, or can use different tree species and thickness of veneer; But any two layers of symmetrical veneer on either side of the center of symmetry plane should be the same species and thickness. Not the same tree species are allowed on the back surface.
To make the plywood structure conform to both of these basic principles, it should have an odd number of layers. So plywood is usually made in odd numbers of three, five, seven layers. The name of each layer of plywood is: the surface veneer is called the surface board, the inner veneer is called the core board; The front plate is called the panel, the back plate is called the backplane; In the core board, the fiber direction is parallel to the surface plate called long core board or medium board. When forming a chamber slab, the panel and back must face outward.
Species
In order to make full and reasonable use of forest resources to develop plywood production and make the best use of the material, the newly formulated national standard (draft for approval) divides plywood into finishing plywood (for furniture with transparent coating on the surface, sewing machine table and various electrical casing and other products) and finishing plywood (for construction, furniture, decoration, etc.) according to the use of plywood. Decoration materials for vehicles and ships), generally plywood (suitable for packaging, lining and other uses) and thin wood decorative plywood (used as senior decoration materials for buildings, furniture, vehicles, ships and so on), plywood types are divided into:
(1) Class I (NQF)– weather resistant, boiling water resistant plywood.
This kind of plywood is durable, resistant to boiling or steam treatment and can be used outdoors.
(2) Class II (Ns)– water resistant plywood.
It can withstand cold water or short-term hot water immersion, but does not tolerate boiling.
(3) Class Ⅲ (Nc)– moisture resistant plywood.
Post time: Nov-24-2022