How to control and prevent wood cracking when using Wood Chip Dryer

Surface cracking refers to the longitudinal cracks that occur along the wooden ray on the surface of the sawn timber (usually the outer cutting surface of the chord board).Wood Chip Dryer It is caused by excessive tensile stress at the early stage. When the external tensile stress is gradually increased from the maximum value,Wood Chip Dryer the external cracks begin to gradually decrease. If the crack is not too serious, it can be completely closed in the boring middle and late stages,Wood Chip Dryer and it is not easy to be seen by the naked eye. Mild surface cracking has little effect on quality. However,Wood Chip Dryer when the paint is processed into waste,Wood Chip Dryer the crack will penetrate into the paint and leave traces,Wood Chip Dryer affecting the appearance. Regarding components that receive shear forces, the shear strength along the grain may be reduced. Premature cracking during kiln drying will affect the correct application of the kiln drying process and may develop into obvious dry defects.Wood Chip Dryer Therefore, it is necessary to prevent the occurrence of epidermal cracking as much as possible in the early period of dullness,Wood Chip Dryer and insist on the integrity of the wood. The way to avoid surface cracking is that the previous benchmark should not be too hard,Wood Chip Dryer and pay attention to controlling the development of dry stress.Wood Chip Dryer The intermediate humidity control treatment should be stopped when the initial moisture content is reduced by about 1/3,Wood Chip Dryer because the external tensile stress may reach the maximum value at this time. For thick plates or hard broad-leaved timber,Wood Chip Dryer the intermediate treatment should be stopped several times. It can be treated every time the moisture content is reduced by about 10% or every 2 to 3 days to relieve the surface tensile stress.

The internal crack of the wood occurs inside the wood and cracks along the wooden beam,Wood Chip Dryer such as a honeycomb, also called a honeycomb crack. There are no cracks on the surface,Wood Chip Dryer and only need to be sawed to find it. But usually accompanied by uneven surface or obvious shrinkage, or carbonization,Wood Chip Dryer or light weight. This is an obvious feature of dullness. Internal cracks usually occur in the later period of dryness,Wood Chip Dryer because the external hardening is more serious, and the later dry conditions are more violent,Wood Chip Dryer which causes excessive internal tensile stress. Sawn timber with a relatively large thickness, especially hard-broad-leaved tree species with high basic density, coarse wood rays,Wood Chip Dryer or hard wood, such as oak,Wood Chip Dryer ash, ash, castanopsis, sweetgum, and Liuan, Both are more prone to internal fissure. Internal cracking is a serious dry defect,Wood Chip Dryer which has an extremely adverse effect on the strength, material,Wood Chip Dryer processing and production quality of wood. It is generally not allowed to occur. The method to avoid is to stop the intermediate disposal in the middle and late period of kiln drying in order to relieve the surface hardening. For thick lumber,Wood Chip Dryer especially hard broad-leaved wood,Wood Chip Dryer the later dry temperature should not be too high