Views:8 Author:Site Editor Publish Time: 2020-05-20 Origin:Site
The quality of veneer production determines the quality of plywood. Therefore, the production of veneer is often important in the production of plywood. In addition to the veneer rotary cutting, the veneer drying of the veneer is also a very critical link. Let ’s take a look at the problems that arise during drying.
Wood is a non-homogeneous material. After drying, the shrinkage of each part is inconsistent. The surface of the veneer has the difference between early wood and late wood, so the density of each place on the board surface is also different. When the veneer peeling(rotary cutting machine) and cuts the veneer, the veneer will be divided into front and back. There are cracks on the back and the structure is loose. The front is free of cracks and the structure is relatively tight. Wood itself is a non-homogeneous material, often with defects such as torsion, vortex and knots. These defects will lead to uneven structure of the veneer. After drying, the shrinkage rate of each part will be different, causing deformation and cracking.
When the veneer is dried in the veneer dryer, the edge part of the veneer will evaporate faster than the middle part, and the shrinkage rate of the edge part is affected by the middle part. Therefore, wavy lines are easily generated in the edge portion, and even cracks may occur.
In order to reduce the deformation and cracking of the veneer, the following methods can be used when drying the veneer in the form of a sheet: if the veneer is dried one by one, the front and back edges of the veneer can be overlapped by 1-2 cm to increase the veneer The thickness of the edge of the board. After the thickness of the board is doubled, the evaporation rate of water at the edge of the board is slowed, which can eliminate the deformation and cracking of the board.
When the strip-shaped veneer is dried, water can be used on the 6 mm width of both sides of the veneer to increase the moisture content of the edge of the veneer to achieve the purpose of delaying the evaporation of water from the edge to reduce the wave deformation and cracking . Or, when the veneer is cut, the edge of the wet veneer is affixed with reinforcing tape to increase the tensile strength of the veneer's horizontal grain and prevent the veneer from cracking laterally.