In corrugated box production, moisture control is crucial for ensuring the physical properties of the cartons. Excessively high or low moisture levels can lead to reduced strength, deformation, or cracking, further impacting their compressive strength, folding resistance, and stacking stability. Therefore, coordinated control is required across four key areas: base paper management, production environment control, process parameter optimization, and equipment maintenance.
Base paper, the foundation material of corrugated boxes, has a moisture content that directly impacts the quality of the finished product. Upon arrival, base paper undergoes rigorous moisture testing and is typically kept within a reasonable range. If it exceeds the standard, it must be dried or air-dried to return it to an acceptable range. During storage, base paper must be stored in a constant temperature and humidity warehouse, maintained at room temperature and a relative humidity no higher than 40% to prevent moisture absorption or dehydration due to humidity fluctuations. Base paper should be stacked upright, with the stacking height not exceeding the specified value, and the floor must be moisture-proofed to prevent moisture from reaching the bottom of the base paper. Furthermore, base paper should not be stored for extended periods of time, and the "first-in, first-out" principle must be adhered to to minimize moisture changes caused by prolonged storage.
The temperature and humidity of the production environment are key factors affecting moisture content. The workshop temperature must be maintained within a stable range, and the humidity must be controlled within a certain range to avoid high temperatures and high humidity, which accelerate moisture absorption by the base paper, or low temperatures and dry environments, which cause excessive evaporation. For example, during the summer rainy season, workshop ventilation should be enhanced and dehumidification equipment should be used; during the dry winter months, humidifiers should be used to maintain a balanced humidity level. Furthermore, the production area should be isolated from the raw material storage area to prevent cross-contamination. For example, if the humidity in the raw material warehouse exceeds the standard, even if the workshop environment meets the standard, the base paper may still absorb moisture during handling, leading to uncontrolled moisture levels in subsequent production.
Precise control of process parameters is key to moisture control. During the corrugated cardboard forming process, the temperature of the preheating roller must be dynamically adjusted based on the moisture content of the base paper. If the moisture content of the base paper is too high, the preheating temperature should be increased to accelerate evaporation; if the moisture content is too low, the preheating intensity should be reduced and a spray device should be used to replenish moisture. At the same time, the amount of glue applied must be precisely matched to the characteristics of the base paper. Excessive glue application can easily lead to excessive moisture content in the paperboard, resulting in weak bonding or deformation; insufficient glue application can make the paperboard brittle and reduce folding resistance. Furthermore, the dryer's temperature and speed must be controlled in tandem. Excessive speed can result in incomplete drying of the paperboard, while excessive speed can damage the paperboard structure due to overheating.
Stable equipment operation is crucial for moisture control. Key components such as the preheating drum, dryer, and steam traps must be regularly inspected to ensure a stable steam supply and timely discharge of condensate. For example, if the steam trap is clogged, condensate can accumulate in the preheating drum, causing localized low temperatures and uneven evaporation of moisture from the base paper, leading to bowing or bonding defects. Furthermore, the gap between the glue applicator and the gluing roller must be regularly calibrated. Excessive gaps can easily lead to excessive glue application, while insufficient gaps can scratch the base paper surface and affect physical properties.
The combined application of these measures can effectively control moisture content in corrugated box production. For example, a carton factory introduced a digital management system that monitors moisture levels in base paper and board in real time. Combined with automatic process parameter adjustments, this system significantly reduced product moisture content fluctuations and significantly improved the compressive strength and folding resistance of cartons. This case demonstrates that scientific moisture management not only improves product quality but also reduces costs associated with rework and scrap, creating long-term economic benefits for the carton factory.
