Melamine plate cracking or dry crack refers to the wood in the drying process or after drying of a kind of cracks, mainly because of the wood parts are not uniform drying caused.According to the part where the crack occurs, it is divided into fracture, surface crack, internal crack and wheel crack.The size and number of cracks can be divided into drying conditions, tree species and the size of wood section.
1. End face crack
End splitting is limited to the section of the wood or extends to one or both sides of the end, which is often referred to as a crack.The main reason is that the water conductivity along the grain direction is far greater than the horizontal grain direction. When the wood is dry, the evaporation of water from the end face is much faster than that from the side.The moisture content at the end is lower than that in the middle, and the shrinkage of the end is limited by the wood in the middle, thus producing a stretching effect at the end. When the tensile force exceeds the tensile strength of the transverse grain of the wood, the end face will crack.
2. Surface cracks
Table crack refers to the original wood itself or the surface of the crack.Cracks are usually confined to the chord surface and develop in a direct direction.Shallow table crack can be removed with the method of plane smooth, but deep surface crack not only ugly, and can reduce the strength of wood, especially shear strength.Surface crack also affects the paint quality of wood, with the surface crack of melamine plate paint, can occur because of the change of climate conditions crack open and close, cause paint film rupture.
3. Internal crack
Internal fissures are also often called honeycomb fissures.Internal cracking occurs in late drying period, sometimes during the storage period of dry materials.Usually not easy to find from the outside of the wood, but serious, can be judged according to the surface of the melamine plate sag, internal crack is caused by the pull of the plate inner layer.
In the early stage of drying, the surface of melamine plate will not only produce stretch elastic deformation, but also produce stretch residual deformation under the action of tensile force.Until the late drying period, when the moisture content of the inner melamine plate drops below the fiber saturation point, the inner wood begins to shrink. However, due to the limitation of the stretched outer wood, the internal stress in the material is opposite to that in the early drying period.
4, drying wheel crack
The cracks develop along the growth direction, often extending to adjacent growth rings.Wheel crack happens in dry initial stage commonly, appear the end face of lumber, as dry progress crack deepens, lengthen.zhangzhou xinhuacheng machinery manufacturing co.ltd. 10 years of professional in melamine plate, is a domestic professional.For more information, please call for 24-hours 86-18250660142 or visit directly