1、 Twisiting or Warpping caused by water content difference in some internal areas.
In the production of plywood, for example, the chips of particle board and the fibers of medium density fiberboard are not evenly dried in some areas, or are not evenly distributed in the whole process of glue application. The veneer coating is not symmetrical in plywood production. There are differences in water content, curing of adhesive and evaporation of water content, and the stress is uneven, resulting in Twisiting or Warpping.
2、 Twisiting or Warpping caused by improper hot pressing process or the influence of the press itself.
During the whole process of pressing, the plywood is deformed due to the conditions of the press itself, such as Twisiting or Warpping of the pressing plate, insufficient temperature of individual hot pressing plates, or uneven pressure, or the hot pressing process is not properly mastered, the temperature is too high or too low, and the pressure is too large.
3、 Twisiting or Warpping caused by structural asymmetry.
Structural asymmetry is a key factor that causes the internal stress of plates. For example, the particles on the surface and back layers of MDF and chipboard are different in size, and the upper and lower sides of the neutral layer of plywood are different from each other in tree species, fiber arrangement direction, thickness, moisture content, number of layers, and production methods, or the veneer has twist lines, which is also the key reason for warpage.
