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Commercial plywood is one of the commonly used materials for furniture, and it is a kind of man-made wood board. The number of layers or multi-layer board-like materials, layer-by-layer veneer, usually with odd layers of single fiber direction vertical and vertical plywood.
One of the commonly used materials for furniture is a kind of man-made board. A group of veneers is usually formed by gluing the adjacent layers of wood grains perpendicularly to each other. The surface board and the inner board are usually symmetrically arranged on both sides of the central layer or the core. A slab made of glued veneer in a crisscross pattern in the direction of the wood grain is pressed under heating or non-heating conditions. The number of layers is generally odd, and a few have even numbers. The physical and mechanical properties of the vertical and horizontal directions are relatively small. Commonly used are three plywood, five plywood and so on. Plywood can improve the utilization rate of wood and is a main way to save wood. It can also be used as materials for airplanes, ships, trains, automobiles, buildings and packing boxes etc.
The usual length and width specifications are: 1220×2440mm, and the thickness specifications are generally: 3, 5, 9, 12, 15, 18mm, etc. The main tree species are: miscellaneous wood, birch, poplar, eucalyptus, etc.
in order to make full and reasonable use of forest resources to develop plywood production and make the best use of materials, my country’s newly formulated national standard (draft for approval) divides plywood into plywood for finishing (the surface needs to be painted with transparent coatings) based on the current use of plywood. Furniture, sewing machine tabletops and various electrical appliances shells), decoration plywood (used as decoration materials for buildings, furniture, vehicles and ships), general rubber tableboards (suitable for packaging, cushioning and other purposes) And veneer decorative plywood (used as a high-level decorative material for buildings, furniture, vehicles, ships, etc.),the types of plywood are divided into:
(1) Type I (NQF)-weather resistant, boiling water resistant plywood. This kind Plywood is durable, resistant to boiling or steam treatment, and can be used outdoors.
(2) Type Ⅱ (Ns)-water-resistant plastic platen. It can withstand cold water or short-term hot water immersion, but it is not resistant to boiling.
(3) Class III (Nc)-moisture-resistant plywood.It has a certain degree of moisture resistance and is suitable for indoor use.
(4) Type IV (BNc)-non-moisture-resistant plywood.
3.The basic principle.
In order to improve the anisotropy of natural wood as much as possible, and make the plywood have uniform characteristics and stable shape, the structure of plywood generally must comply with two basic principles: one is symmetry; the other is that the fibers of adjacent layers of veneer are perpendicular to each other. The principle of symmetry requires 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 direction of the fiber, and the moisture content. In the same plywood, you can use veneers of a single species and thickness, or you can use veneers of different species and thicknesses; however, any two layers of symmetrical veneer species and thickness on both sides of the center plane of symmetry 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 names of the layers of plywood are: the surface veneer is called the surface board, and the inner veneer is called the core board; the front surface board is called the front board, and the back surface board is called the back board; in the core board, the fiber direction is parallel to the surface board. It is called long core board or middle board. When forming the cavity table slab, the face plate and the back plate must face outwards tightly.
1 Wood grain Grain wood The texture formed by the arrangement direction of the Chinese fibers.
2. Straight grain The wood grain is straight and parallel or nearly parallel to one of the two main directions (long direction or width direction) of the veneer
3. The angle grain of diagonal grain is not perpendicular to the edge of the veneer.
4. Irregular grain The wood grain is straight down due to the abnormal structure of the wood.