Causes and control measures for warping and deformation of thin particleboard produced by continuous press

In today's increasingly personalized world, with the diversification of residential layouts, traditional ready-made furniture struggles to meet consumer demands, leading to a growing preference for customized furniture. Reducing particleboard thickness or using thinner particleboard directly for panel furniture components is a primary way for customized furniture companies to decrease particleboard consumption. However, reducing the thickness of customized furniture components places higher demands on the quality of the various particleboard specifications used to ensure the stability and strength of the furniture structure.

This article focuses on analyzing the main quality problems and causes of thin particleboard (hereinafter referred to as thin board) with a thickness of less than 10 mm, and proposes improvement measures in order to provide useful reference for particleboard enterprises to improve product quality.

1. Causes of warping and deformation in thin plates

Particleboard warping refers to the unevenness and deformation of the board surface. Warping is particularly prominent in the production and use of thin boards, and its causes are multifaceted.

1) Asymmetrical slab installation structure. When thin slabs are installed, the slab structure is asymmetrical, resulting in excessive density differences after pressing. The density deviation increases the internal stress of the slab, ultimately causing warping and deformation.

2) Inappropriate hot pressing parameters. Different hot pressing process parameters produce thin plates with different cross-sectional densities. If the hot pressing temperature and pressure in the high-pressure zone of the continuous press are too high, the cross-sectional density gradient in the thickness direction of the thin plate will be too large, and the peak value of the cross-sectional density curve will be too sharp and narrow. It will be difficult to ensure the symmetry of the cross-sectional density in the thickness direction after sanding, resulting in deformation.

3) Inadequate cooling treatment. After the thin plates are hot-pressed, there is non-uniform stress inside. If they are stacked immediately without cooling treatment or if the cooling is insufficient, warping and deformation are likely to occur.

4) Uneven surface sanding amount. The cross-sectional density distribution of conventional particleboard is "saddle-shaped". If the sanding amount of the upper and lower surfaces is inconsistent, the cross-sectional density curve in the thickness direction of the sanded board will be asymmetrical, and the peak value of the upper and lower surfaces will be too large, which will cause the board to warp and deform.

5) Improper stacking and storage. When stacking and storing thin plates, if the number of padding strips under the stack is too small, the distribution is uneven, the spacing is too large, or the padding strips of the upper and lower stacks are not aligned, the thin plates will be deformed in a wavy shape.

2. Measures to control warping deformation of thin plates

1) Control the symmetry of slab laying. To ensure the dimensional stability of thin slabs, the principle of structural symmetry should be followed when laying thin slab blanks. That is, the size, density, and thickness of the wood shavings in the corresponding layers on both sides of the symmetrical center plane of the thin slab should be the same or similar.

2) Use a reasonable hot pressing curve. When producing thin plates with a continuous press, the zone temperature and pressure gradient should be set reasonably. The temperature and pressure settings in the high-pressure zone should not be too high to avoid an excessively large density gradient in the thickness direction of the thin plate.

3) Ensure sufficient cooling of the sheet material. After hot pressing, the thin sheet material needs to undergo cooling treatment to passivate the temperature and moisture content gradients between the surface and core layers, reducing internal stress. Due to the high production speed of thin sheets and the limited number of storage compartments in the cooling and flipping machine, the cooling time for thin sheets is relatively short. To ensure sufficient release of internal stress, finished thin sheets should be naturally stacked and cooled for at least 2-3 days before sanding.

4) Control the consistency of surface sanding amount. In order to ensure that the finished thin plate has uniform thickness and a smooth and clean surface, the thickness tolerance of the raw plate should be controlled during hot pressing, and the sanding amount of the upper and lower surfaces should be controlled to be consistent, so that the density curve of the thickness section of the plate after sanding is symmetrical.

5) Properly stack and store the boards. When stacking and storing thin boards, the number of padding strips under the stack should be increased appropriately, and the spacing between the padding strips should be reduced. The padding strips under each stack should be evenly distributed and aligned vertically. A thick board should be placed at the bottom and top of each stack for protection to prevent deformation during stacking and storage.