Blockboard English: BLOCKBOARD or laminated wood board
The blockboard is commonly known as the large core board, which is made up of two pieces of veneer laminated in the middle. The middle wooden board is made of high-quality natural wood board after heat treatment (ie drying in the drying room), and processed into a certain specification of wood strips, which are formed by splicing machine. The spliced ​​wooden board is covered with two layers of high-quality veneers on both sides, and then pressed by cold and hot press. Compared with particleboard and medium density fiberboard, its natural wood characteristics are more in line with human natural requirements; it has the advantages of light weight, easy processing, good nail holding power and no deformation, and is an ideal material for interior decoration and high-grade Furniture production.
Construction: The outermost board of the blockboard is called the table board, the inner board is called the middle board, the core layer is called the wood core board, and the small wooden strips that make up the wood core board are called the core strips, which stipulate the wood grain direction of the core strip. For the longitudinal direction of the plate.
The main function of the wood core board is to provide a certain thickness and strength for the board. The main function of the middle board is to make the board have sufficient lateral strength, and at the same time buffer the adverse effects caused by the unevenness of the wood core board to the board surface. In addition to making the board look beautiful, it can also increase the longitudinal strength of the board.
Because the blockboard is a special plywood, in order to avoid the warping deformation of the sheet in the production process, as a thick board, the blockboard has the beautiful appearance and similar strength of ordinary thick plywood, but Blockboard is lighter than thick plywood, consumes less glue and saves investment.
Compared with solid wood panels, blockboard is stable in size, not easy to deform, effectively overcomes wood anisotropy, and has high lateral strength. Due to strict adherence to the principle of symmetrical blanking, the warpage of the sheet is effectively avoided. The blockboard is beautiful in appearance, wide in size and easy to use. Blockboard is mainly used in furniture manufacturing, door panels, siding and so on.
The core strip accounts for more than 60% of the size of the blockboard, which has a lot to do with the quality of the blockboard.
The tree species for making the core strip are preferably made of softer materials, uniform wood structure, small deformation, small shrinkage ratio, and small difference in wood string direction and radial shrinkage ratio. The size and shape of the core strip are easy to process. Accurate, the finished board surface is flat, the sheet is not easy to be deformed, and the weight is light, which is beneficial to use.
Generally, the core strip moisture content is 8%--12%, and the northern air drying can be 6%-12%. In the south, the air humidity is large, but it should not exceed 15%.
The production process of the core strip:
Dry sheet ===〉double-sided planing ===〉multi-piece saw ===〉cross-section saw ===〉core strip
(1) Thickness of the core strip: the thickness of the wood core board plus the machining allowance of the flat surface of the wood core board.
(2) Width of the core strip: the width of the core board is generally 1.5 times the thickness, preferably not more than 2 times. Some of the quality of the blockboard strips with high quality requirements cannot be greater than 20mm. The wider the strip, the more the moisture content changes. The deformation of the core strip is larger.
(3) Length of the core strip: The longer the core strip, the higher the longitudinal bending strength of the blockboard, but the longer the core strip, the lower the wood utilization.
(4) Material of the core strip: The resin strip is not allowed to leak resin, it is not allowed to decay, and no crawling is allowed.
(5) Processing of core board: using core strip glue machine
After the wood core board is glued, the board surface is rough and uneven, usually using a planer, and the machine core board with high precision of the core strip processing can be used for sanding instead of planing.
Blockboard characteristics
The blockboard has good screw strength, high strength, good quality, sound absorption, heat insulation, etc., and the water content is not high, between 10% and 13%, the processing is simple and the most widely used.
Blockboard is more stable than solid wood, but it is afraid of moisture. It should be avoided in the kitchen.
The processing technology of blockboard is divided into two types: machine and hand. Hand-made is to manually insert the wooden strip into the splint. The wooden strip is subjected to less pressing force, uneven splicing, large gap, poor nail holding force, and cannot be sawed and processed. It is only suitable for sub-projects of partial decoration. Such as the solid wood floor cushion board and so on. The plate of the machine is subjected to a large pressing force, the gap is extremely small, the splicing is flat, the bearing capacity is uniform, long-term use, compact structure and not easy to deform.
Different materials and different quality. The large core board is divided into “excellent productsâ€, “first-class products†and “qualified products†according to the quality of the materials and the texture of the surface materials. There are also companies that mark the grades of grades A, double A and triple A, but this is only corporate behavior, which is inconsistent with national standards, which is currently not allowed on the market.
There are many kinds of wood core boards, such as poplar, birch, pine, and paulownia. Among them, poplar and birch are the best, the texture is dense, the wood is not soft and hard, the nail holding power is strong, and it is not easy to be deformed, and the paulownia The texture is very light, soft, absorbs large water, has poor nail holding power, and is not easy to dry. During the use of the produced sheet, when the water evaporates, the sheet is easy to dry and deform. The hard wood is hard, not easy to press, the splicing structure is not good, the nail holding power is poor, and the deformation coefficient is large.
Use of blockboard
Furniture, doors and windows and sets, partitions, false walls, heating covers, curtain boxes, etc.
Blockboard selection
The surface of the blockboard should be flat, without warping, deformation, no blistering or dent; the core strips are evenly arranged, the gap is small, the core strip is free from decay, breakage, wormholes, thrift and so on. Some blockboards cut corners, and the gap between the solid wood strips is large. If nails are nailed in the gap, there is basically no nail holding force. Consumers can look at the sun when they choose, and the gap between the solid wood strips will be white. If the glue strength of the blockboard is not good, it will have a "å±å±" opening sound when it is self-financing. If the large core board emits a fragrant wood smell, it means that the formaldehyde emission is less; if the smell is pungent, it means that the formaldehyde is released more.
The quality of blockboard is very different and should be carefully checked when purchasing. First of all, see if the core material is dense, whether there are obvious seams and decaying wood strips, whether there are obvious seams and decaying wood strips, there may be eggs in the decaying wood strips, and insects will occur in the future; The phenomenon of filling the putty, this phenomenon is generally to compensate for the internal cracks or voids; then it is to use the sharp-mouthed instrument to strike the surface of the board, to hear whether the sound is very different, if the sound changes, there is a cavity inside the board. These phenomena will weaken the overall bearing capacity of the board, and the uneven long-term stress will cause the sheet structure to be distorted and deformed, which will affect the appearance and use effect.
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