Melamine veneer will crack in daily use, mainly due to the unevenness of the various parts of the wood. The parts of the industry that are based on cracks are generally called cracking, cracking, internal cracking, and wheel cracking; the size and number of cracks will vary depending on the dry conditions, tree species, and wood section size.
1. End face crack.
End splitting is limited to the section of the wood and may extend to one or both sides of the end, which is often referred to as a fracture.
The primary reason is that the wood along the grain direction of the water conductivity is far greater than the horizontal grain direction, when the wood is dry, water from the end of the transpiration is much faster than from the side of the transpiration. The moisture content at the end is lower than the middle part, and the shortening of the end part is restricted by the wood in the middle part. Therefore, when the tensile force exceeds the tensile strength of the transverse grain of the wood, the end face will crack.
2. External crack.
Surface crack refers to the original wood itself or the appearance of the crack, crack is usually limited to the chord surface, and along the direction of the development. Shallow surface cracks can be removed with planing, but deep surface cracks are not only ugly, and will reduce the strength of the wood, especially shear strength. Exterior crack also affects the paint quality of lumber, the melamine that has a surface crack after paint, can attack crack to open and close because of the change of climate condition, cause paint film to burst.