Factors affecting surface cracking
Factors affecting surface generation are divided into factors in wood construction and factors in manufacturing.
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1 ) Factors in wood structureTree species: Generally, broad-leaved wood is prone to cracking than softwood, and it is prone to cracking than the tree species with a small specific gravity.
Texture: Chopped thin wood is thinner than thin wood, which is easy to produce cracks, staggered tree tumors, and thin wood at the root of the tree is prone to cracks.
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2 ) Manufacturing factors The back crack of the thin wood: When the collage pattern is used, it is often necessary to put the loose surface of the thin wood outward and stick it on the substrate, which causes the surface cracks of each part to be inconsistent. Some people have done experiments, and the result is: the loose side faces outward. The thin wood is more stable than the thin wood facing outwards, and it is not easy to crack. The reason may be that the shrinkage and expansion of the thin wood are concentrated on the original back crack, so no new cracks are generated elsewhere. When the surface is facing outwards, the crack on the back side will develop as a surface crack and the crack will be large. Moisture content of thin wood: When the wet-laid thin wood is not dried, the moisture content of the thin wood is quite high, and the thin wood is attached to the substrate in an expanded state, and the moisture content of the thin sheet should be the equilibrium moisture content in actual use. It is lower than the moisture content of the sticker, so the thin wood often has a tendency to shrink, but is pinned by the substrate, and is often in a state of tensile stress, in which the thin wood is easily cracked. On the contrary, in the case where the moisture content of the thin wood is lower than the equilibrium moisture content in the pasting, the thin wood is subjected to compressive stress and is not easily cracked. The thickness of the veneer is greater than zero . When 4mm , the thin wood should be dried and glued. Water resistance of the rubber layer: In the case where the water resistance of the rubber layer is poor, cracks are easily generated from the different tube grooves in contact with the rubber layer, and the surface is developed. Glue amount: The amount of glue applied is large, and the surface is not easy to crack. But too much is easy to cause penetration. Hot pressing conditions: According to the relevant data, the test of the influence of hot pressing temperature on surface cracking with plywood is introduced. As a result, the higher the hot pressing temperature, the more likely the surface crack is generated. Combination of fiber directions: the fiber direction of the veneer is glued or parallel to the fiber direction of the substrate plywood form plate.Straight adhesive tape has a great influence on the generation of surface cracks.
6 8 compares the yield surface cracks is parallel to the vertical stickers stickersThe situation of the impact, as can be clearly seen from the table, the thickness of the thin wood is
0 . When 3mm , vertical adhesive tape is an effective method to reduce surface cracks, but for 0 . 8mm thick thin wood has little effect. Vertical adhesive tape operation is cumbersome and the bonding strength is low, so the general factory still uses parallel adhesive tape. Buffer layer: already described in the preparation section of the substrate. A paper or cloth material is sandwiched between the veneer and the substrate to reduce surface cracking.We have red, blue, green, pink, black, orange, deep yellow, brown colored tape.
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