How to prevent wood cracking during drying process？
2020-08-05 10:04:08 Hebei Shuowei Metal Manufactuering Co.,Ltd
In the process of wood drying, the end of wood is dried first because of the rapid evaporation of moisture. When the moisture content of the end is lower than the fiber saturation point, the end cells begin to contract. When the drying shrinkage stress reaches the strength limit of the wood, the end crack occurs, that is, the longitudinal crack occurs at the pulp center or at the rough wood ray or along the outer board surface.
It is almost inevitable that there will be end cracks along the core of the wood, because the core is the place where the ray parenchyma cells are concentrated, and the transverse tensile strength is very low. The thick hardwood plates with coarse wood rays are also prone to end cracking. For a few meters long rough edge plate, the end crack is allowed within 10 cm-15 cm, because part of the end must be cut off during processing. But for the whole side plate or floor blank, the end crack is generally not allowed.
The following measures can be taken to prevent end cracking
1. Before the kiln is dried up, the existing end cracks will be cut off, because the original end cracks are easy to continue to extend.
2. Apply paraffin oil or thick paint on the end of the board without end crack to prevent water evaporation from the end.
3. During stacking, the spacer bar at the end of the pile shall be pressed close to the end and aligned up and down.
4. When loading the kiln, the end of the material pile and the material pile shall be close to each other as far as possible, so as to prevent the short circuit of air flow from the gap between the material stacks, so as to prevent the end from drying too fast.
5. For hard broad-leaved wood or thick plate which is prone to end crack, the drying process of soft part should be adopted as far as possible, and the humidity control treatment should be paid attention to in time.
Drying is not simply to control the moisture content of wood, but to eliminate the tensile stress of wood under the premise of ensuring that the wood fiber is not damaged, so as to make it more stable and ensure the product quality. High frequency vacuum wood dryer machine is getting more and more popular all over the world, it is also a good way to slove the end carcking problem. if you are interested in it welcome to talk with Carlos
<< Previous page
Next page >>
if you are interested in the high frequency vacuum kiln, welcome send inquriy to us