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1. Causes and control measures for indentation on thin plate surfaces
Causes:
Surface indentations manifest as pits on the surface of the board after sanding. This is mainly due to residual wood shavings or other debris adhering to the conveyor belt, pre-pressing mesh belt, or press steel belt of the particleboard production line, which are not detected and removed in time. When these debris comes into contact with the surface of the board, they squeeze the surface wood shavings, forming pits. After hot pressing, these pits cannot be filled, leaving surface indentations. In addition, foreign objects trapped under the press steel belt, causing unevenness in the steel belt, can also cause surface indentations.
Control measures:
Regularly clean and maintain the continuous press steel belt cleaning brush, and use an appropriate amount of steel belt release agent to keep the steel belt surface clean and lubricated. During production, strengthen the inspection of the laying conveyor belt, pre-compression mesh belt, and press steel belt, and promptly remove any foreign objects found on the surface. When foreign objects are trapped under the steel belt, causing local unevenness, use professional maintenance tools to roll the steel belt to restore it to a flat state.
2. Causes and control measures for surface streaks on thin plates
Causes:
Glue spots are mainly caused by clumps of surface wood shavings or glue blocks mixed into the slab during hot pressing. Uneven application of glue to the surface wood shavings, or glue blocks remaining in the shavings conveyor and paving machine falling into the slab, can all cause glue spots.
Dust spots are mainly caused by surface wood shavings or bark fiber clumps adhering to the inner wall of the paving machine and vibrating screen, etc., which solidify in advance and fall off to the surface of the slab, forming dust spots after hot pressing.
The black spots are mainly caused by excessive bark content in the raw materials, which leads to color differences and black spots on the board surface after hot pressing.
Control measures:
The amount of bark incorporated into the raw materials used for thin boards should be minimized. Manufacturers can reduce the impact of bark on the quality of thin boards by using wood peeling equipment and bark sorting equipment. Furthermore, during production, the cooling system of the glue mixer should be kept in good working order, and equipment such as the glue mixer, glue application shavings conveyor, and vibrating screen of the paving machine should be cleaned regularly to reduce surface quality defects such as glue spots, dust spots, and black spots.
3. Causes and control measures for thin-plate hourglass formation
Causes:
When sanding particleboard to a fixed thickness, the basic sanding amount is determined based on the target thickness of the finished product and the thickness of most of the rough boards. When the sanding allowance of the rough boards is too small, in order to ensure that the finished product meets the thickness deviation standard requirements, the sanding amount of the rough boards can only be reduced, which can easily lead to sand leakage on the board surface. When the thickness deviation of the rough boards is too large, the thicker areas are prone to large particleboard particles due to excessive sanding amount, while the thinner areas are prone to sand leakage due to insufficient sanding amount. The main reasons for sand leakage in thin boards include uneven board laying, unstable particleboard moisture content leading to large fluctuations in board weight, fast production speed and untimely adjustment of hot pressing process, and inadequate adjustment of sanding amount.
Control measures:
Stable control of the wood shavings drying moisture content and ensuring the uniformity of slab laying meets production process requirements are maintained. When slab weight fluctuates, the laying equipment and hot pressing process parameters are adjusted promptly to ensure that the slab thickness range and deviation meet product quality requirements. Before sanding, the slab thickness is sampled and measured to determine the sanding process parameters. The feed speed is adjusted according to the sander current fluctuations, and the thickness is appropriately adjusted within the standard deviation range to ensure sanding quality.