How to control and prevent end splitting (splitting or longitudinal splitting) in wood
The end of the wood is dried first due to the rapid evaporation of water. When the moisture of the end is lower than the fiber saturation point, the end cells begin to shrink. When the dry shrinkage stress reaches the strength limit of the wood, end cracking occurs.That is, longitudinal cracks occur at the pith core or at the thick wood ray or along the outer panel surface. End-cracks along the pith are almost unavoidable in the pith-containing plank because the pith is the place where the ray parenchyma cells are most concentrated and the transverse tensile strength is extremely low. Hard hardwood planks with thick wood rays are also more prone to end cracking. For burr boards with a length of several meters, end cracks within 10cm to 15cm are allowed, because part of the ends must be cut off during processing. However, end cracks are generally not allowed for full-edge boards or floor blanks.
The following measures can be taken to prevent end cracks: ① If permitted, it is best to change the thick plate into thin plates or small squares for drying, which can effectively prevent end cracks and other drying defects. ② Cut off the end cracks that have occurred before kiln drying, because the original end cracks are easy to continue to extend. ③ Apply paraffin oil or thick paint to the end of the board without end cracking to prevent the water from evaporating from the end. ④ When stacking, the spacer at the end of the pile should be pressed as close to the end as possible and aligned up and down. ⑤When installing the kiln, the ends of the piles and piles should be as close as possible to prevent the short circuit of the air flow from the gap between the piles, so as to prevent the ends from drying too fast. ⑥ For hard broad-leaved wood or thick plate that is prone to end cracks, try to use a soft drying process, and pay attention to timely humidity adjustment.
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