AGICO, as a professional provider of pulp molding equipment and process solutions, understands that moisture control during the wet-pressing stage is critical. It directly impacts product quality, production efficiency, and energy consumption. Below are key technical points and considerations for addressing excessive moisture content, based on common production scenarios.
Balancing Vacuum Setting
Vacuum level is a parameter that requires precise adjustment. Many on-site issues are directly related to it. If the vacuum is too low, the pressure difference between the mold cavity and the external suction hood is insufficient. This prevents effective water extraction, leading to excessively high moisture content in the greenware at demolding. This not only increases energy consumption and reduces efficiency in subsequent hot-pressing but also raises the risk of product mold growth.
However, higher vacuum is not always better. Excessively high vacuum creates too large a pressure difference. This can over-compact the fiber layer and reduce moisture content too much. Ironically, this may hinder fiber bonding and heat transfer during hot-pressing, potentially resulting in brittle products with poor strength.
Therefore, AGICO recommends finding an optimal vacuum range through testing. This range should consider pulp characteristics, product grammage, and mold structure. It is also crucial to ensure the vacuum system is well-sealed and maintains stable performance.
The Foundational Impact of Pulping
Sometimes, the root cause traces back to the pulping stage. In some cases, operators might over-beat the pulp in pursuit of high consistency or thorough fiber separation. This can excessively cut the plant fibers, reducing their length and strength. While short fibers may make the slurry appear more uniform, they actually worsen drainage during forming. Over-cut fibers retain more water between them, making it harder to remove moisture effectively during wet-pressing.
when processing waste paper, it is essential to avoid unnecessary mechanical cutting beyond what is needed for proper fiber swelling and separation. Preserving the inherent strength of the fibers provides a better foundation for subsequent forming and dewatering.
The Interplay Between Suction and Blow-back Time
Suction time and blow-back time are two interconnected process parameters that need optimization. Insufficient suction time means water is not fully extracted, naturally leading to high greenware moisture. However, blindly extending suction time has drawbacks. First, after a certain point, extending time has minimal effect on further reducing moisture. It only slows production cycle time and increases unit energy consumption. Second, prolonged suction can place a continuous load on the vacuum system. If the system capacity is limited, this may cause an overall drop in vacuum level.
Blow-back time is another critical parameter. Its main purpose is to clear fine fibers that may clog the mold screen after suction, restoring drainage channels. If blow-back time is too long, the high-pressure water or air can damage the partially formed greenware. It may even cause water to flow back into the mold cavity, leading to product deformation or demolding difficulties. Conversely, if blow-back time is too short, the cleaning effect is poor. Residual pulp can cause uneven fiber distribution during the next forming cycle, increasing defect rates.
Integrated Management and Systematic Thinking
Beyond these specific operational points, controlling moisture in wet-pressed pulp trays is a systematic task. Many factors can influence the final greenware moisture. These include mold design, screen selection and cleanliness, pulp temperature (which affects water viscosity and flow), and even workshop ambient temperature and humidity.
For example,unreasonable drainage channel design in the mold creates high flow resistance, hindering dewatering even with sufficient vacuum. Incorrect screen mesh selection or untimely cleaning can cause severe clogging. When AGICO provides solutions to clients, we emphasize diagnosing and optimizing from a full-process perspective. This covers pulping, forming, wet-pressing, and hot-pressing, rather than adjusting a single variable in isolation. Stable, efficient, and low-consumption production requires systematic process data recording and analysis.
In summary, addressing high moisture content in wet-pressed pulp trays requires avoiding simplistic, symptom-focused adjustments. AGICO advises production teams to adopt a systematic view. Start from fiber preparation and examine pulping, the vacuum system, mold condition, and the setting of various process times. Through refined process management and parameter optimization, the goal is to achieve efficient moisture removal and stable, economical operation. This must be done while ensuring final product quality and strength.