Particle Board QC Inspection Checklist : Part 1 Problems and product quality defects in hot pressing of particleboard or fiberboard
In the production process, due to various reasons such as raw material quality, operation level and equipment operation status, many potential adverse factors will be exposed in the hot pressing process, resulting in various defects of products. The more common ones are: bubbles,
In the production process, due to various reasons such as raw material quality, operation level and equipment operation status, many potential adverse factors will be exposed in the hot pressing process, resulting in various defects of products. The common ones are: bubbling, delamination, warpage, uneven thickness, local softness and surface indentation, etc.
Bubble refers to the rapid vaporization of hot water in the Particle Board during the pressure reduction process of the hot press, and the sudden release of a large amount of steam, which destroys the bonding force between particles or fibers. Bubbles are loud, mostly in the middle of the Particle Board, and there is a protrusion on the Particle Board surface. Bubbles can occur in one place or in many places, and in severe cases can fill many parts of the board with bubbles.
The main reasons for bubble defects are: too high moisture content of slab, too fast pressure reduction speed, etc.
Particle Board delamination means that a large area of degumming occurs in the board, forming a certain separation boundary. Layering occurs mostly at the edges and corners of the board, and sometimes in the middle of the board.
The main reasons for delamination are: too high moisture content of particles or fibers, too low hot pressing temperature, too short pressing time, poor curing of core adhesive, insufficient unit pressure, poor quality of adhesives, too little sizing or uneven sizing. In addition, too low moisture content of particles or fibers and too fast pressure-reducing speed will also make the board stratified.
3 Warpage Deformation
Warpage deformation means that the edge and center of the Particle Board are not on the same horizontal plane. That is, the edge is warped and the middle is concave. Warpage deformation is expressed by warpage degree. The method to measure warpage is to place the concave Particle Board face up on the horizontal platform, and place the Particle Board ruler 1 m long in the diagonal direction of the Particle Board surface. The maximum chord height is measured with 150 mm steel ruler along the two diagonal directions, respectively.
The main reasons for warpage deformation are asymmetry of the paved slab, which makes the particle or fiber specifications of the symmetrical layer inside the slab inconsistent; or symmetrical of the paved slab, but too bumpy vibration in the transport process, which makes the fine particles or fibers deposited on the bottom of the slab and become asymmetrical structure, so that the slab will be warped when pressed into the slab. The pavement slab is not uniform, the density of the slab is different, the internal stress of the product is large, and the warping deformation is easy to occur. In addition, the asymmetry of hot pressing process can easily cause warpage deformation of products. For example, the temperature difference between upper and lower pressing Particle Boards is large, and the temperature distribution of the same pressing Particle Board is extremely uneven. It is easy to make the stress in the Particle Board uneven, thus making the product warpage deformation. The moisture content of the whole slab is not uniform, and even the storage of the flat slab is unreasonable, warpage deformation may occur to varying degrees.
- uneven thickness
The uneven thickness of the Particle Board can be expressed as a whole or a part. The main reasons are: uneven thickness of cushion, deflection of hot press, debris sticking on thickness gauge or wear of thickness gauge itself, insufficient stiffness of hot press Particle Board and deformation during pressure.
The products with uneven thickness bring more trouble to decoration and use, increase sanding allowance, waste of raw materials, and invisibly increase product cost.
- Local softness
Non-uniform slab pavement or local collapse during slab transportation results in local flake or insufficient fibre or weak bonding in slab. In severe cases, particles or fibers may fall off.
6 Surface indentation
Due to the improper control in the production process or the problems of the equipment itself, the surface of the processed Particle Board may be partly uneven, which is called surface indentation.
There are many reasons, such as falling large pieces of wood or other debris during paving, uneven or damaged cushion, hard debris sticking on cushion or hot pressing board, etc.
Keywords : China Particle Board inspection ,Chinese Particle Board QC, Particle Board grading rules , Particle Board manufacturing defects , Particle Board quality control ,
Examples of particleboard surfaces: (top-left) quality surface, (top-right) hollow near the border, (bot- tom-left) pool of oil, (bottom-right) blot.
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