Causes and control measures of surface indentations and streaks on thin particleboard

1. Causes and control measures of indentation on thin plate surface

Cause:

Surface indentations manifest as pits on the board surface after sanding. This is primarily due to debris such as residual shavings stuck to the conveyor belts, pre-pressing mesh belts, or press belts on the particleboard production line. These debris, when not promptly detected and removed, come into contact with the slab surface, squeezing the surface shavings and forming pits. After hot pressing, these pits cannot be filled, leaving surface indentations. Additionally, foreign matter trapped under the press belts, causing localized unevenness of the belts, can also cause surface indentations.

Control measures:

Regularly clean and maintain the continuous press steel belt cleaning brushes, and use an appropriate amount of steel belt release agent to keep the steel belt surface clean and lubricated. During production, strengthen inspections of the conveyor belt, pre-pressing mesh belt, and press steel belt. Remove any foreign matter immediately. If foreign matter is trapped under the steel belt, causing local unevenness, use specialized maintenance tools to roll the steel belt to restore it to a flat state.

2. Causes and control measures of thin plate surface patterns

Cause:

Glue spots are mainly caused by the clumping of surface wood chips or the mixing of glue blocks into the slab during hot pressing. Glue spots can also be caused by uneven glue application on the surface wood chips or residual glue blocks that fall into the slab from places such as the glued wood chip conveyor and the paving machine.

Dust spots are mainly caused by surface shavings or bark fiber clusters adhering to the inner wall of the paving machine and the vibrating screen, which solidify in advance and fall off to the surface of the slab, forming dust spots after hot pressing.

Black spots are mainly caused by excessive bark content in the raw materials, which causes color difference and black spots on the board surface after hot pressing.

Control measures:

The amount of bark used in the raw materials of thin boards should be minimized. Manufacturers can use wood debarking and bark sorting equipment to reduce the impact of bark on thin board quality. Furthermore, the glue mixer's cooling system should be kept in good working order during production, and equipment such as the glue mixer, glue shavings conveyor, and vibrating screen of the paving machine should be cleaned regularly to reduce surface defects such as glue spots, dust spots, and black spots.

3. Causes and control measures of thin plate hourglass

Cause:

When sanding particleboard to a desired thickness, the basic sanding amount is determined based on the target thickness of the finished product and the thickness of most rough boards. If the rough board sanding allowance is too small, the sanding amount must be reduced to ensure the finished product meets the thickness deviation standard, which can easily lead to sand leakage on the board surface. If the rough board's thickness deviation is too large, excessive sanding can cause large particles to form in thicker areas, while insufficient sanding can cause sand leakage in thinner areas. The main causes of sand leakage in thin boards include uneven slab laying, unstable particle moisture content leading to large fluctuations in slab weight, rapid production speeds leading to untimely adjustments to the hot pressing process, and inadequate sanding amount adjustments.

Control measures:

Stably control the drying moisture content of wood chips and ensure that the slab laying uniformity meets production process requirements. When the slab weight fluctuates, promptly adjust the laying equipment and hot pressing process parameters to ensure that the rough board thickness range and deviation meet product quality requirements. Before sanding, sample the rough board thickness to determine the sanding process parameters, and adjust the feed speed according to the sander current fluctuations. The thickness is appropriately adjusted within the standard deviation range to ensure sanding quality.