What are the common quality defects of plywood?
The reason of the core plate lamination and off seam is that the reserved gap is too large or too small when using the zero slice core, the dislocation or overlap of the core plate when the plate is loaded, and the edge of the blank is not uniform.
Corner glue the cause of this defect is caused by the lack of pressure plate corner wear, edge slab in each interval angle are not aligned, loaded plate slab and put it under pressure are not skew, lack of squeeze veneer rotary cutting edge, edge glue relay is weak, lack of glue, glue early dry plate, local the local temperature is low.
The warpage of plywood is due to the internal stress of plywood. The reason is that the moisture content of the back surface of the sheet is inconsistent, the single board collocation of different tree species is not reasonable, the single plate has twisted grain, the temperature of the individual hot pressing plate is not enough, and the stacking of the plates is unequal.
Bubble and local plastic is the reason for dropping too fast, less adhesive pressure time, veneer moisture content is too high, when the glue point blank or single plate is caused by inclusion, dirt, or the use of pine veneer high temperature causes.
The bonding strength is low, mainly due to the bad quality of the adhesive. The hot pressing condition is not controlled, such as low temperature, insufficient pressure and too short glue pressure. The moisture content of the veneer is too high, the amount of coating is insufficient, the quality of the single board is poor, and the aging time is too long or too short, and it will also reduce the bonding strength.
