Defects of plywood

Defects of plywood

1. Low bonding strength: mainly due to the poor quality of the glue. If the hot pressing conditions are not well controlled, such as low temperature, insufficient pressure and too short rubber pressing time, such defects will also occur. Excessive moisture content, insufficient glue content, poor veneer quality and too long or too short aging time will also reduce the bonding strength.

2. Bubbling and local opening: The reasons are too fast pressure-reducing speed, insufficient gluing time, too high moisture content of veneer, blank spots or inclusions on veneer, sticky dirt, or too high temperature of pine veneer when gluing.

3. Plywood warpage: It is caused by the larger internal stress of the plywood. The reason is that the moisture content of the surface and back plates is inconsistent, the matching of veneers of different tree species is unreasonable, the veneers have twisted lines, the temperature of individual hot-pressed boards is not enough, and the stacking of boards is unequal.

4. Glue opening at the edge corner: The reason for this defect is that the pressure is insufficient due to the wear of the edge corner of the pressing plate. The edge corner of the blank in each interval is not aligned. When loading the sheet, the slab is put askew and uneven under pressure. When the edge of the veneer is rotated, the pressing degree is insufficient, the bonding force is weak, the edge corner is lack of glue, the glue is dried too early, and the local temperature of the pressing plate is

5. Permeability: The reason is that the glue is too thin, the glue content is too large, the cracks on the back of veneer are too deep, the moisture content of veneer is too high, the aging time and pressure are too large.

6. Core plate lamination and seam separation: The reason is that the reserved seam is too large or too small when manual zero-piece core row is used, the core plate is dislocated or overlapped when loading, and the edges of the zero-piece are uneven, etc.

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