In pulp molding production, one of the most common technical problems that affects product quality and production efficiency is mold clogging. When vacuum holes or water spray holes in the forming molds become blocked by pulp fibers, water flow and suction are restricted — resulting in incomplete forming, poor surface texture, or even product rejection.
This article explains the main causes of mold clogging, the effective cleaning and prevention methods, and how to maintain your pulp molding machines for optimal performance.
1. Understanding Mold Clogging
In a pulp molding machine, the forming mold and transfer mold work together to shape wet pulp into the desired product through vacuum suction and air pressure.
Each mold contains hundreds or even thousands of micro-holes that allow water to pass through while holding the pulp fibers on the surface.
When these holes become blocked by:
- Excessive pulp fibers,
- Dried fiber residues, or
- Impurities from recycled paper,
the suction effect weakens, leading to uneven product thickness and poor demolding.
2. Common Symptoms of Mold Clogging
You can identify mold clogging problems through several production signs:
- Uneven product surface or density
- Thin or incomplete forming at specific mold areas
- Slow vacuum suction and increased forming time
- Difficulty during demolding
- Higher rejection rate due to shape defects
If you observe any of these issues, mold clogging should be checked immediately.
3. Major Causes of Mold Clogging
Poor Pulp Filtration
If the pulp slurry contains large impurities or paper scraps, they can easily block the fine holes of the forming mold.
Improper Pulp Concentration
Overly thick pulp (high consistency) increases the risk of fiber accumulation inside suction holes.
Inadequate Water Circulation
Stagnant or unfiltered circulating water causes fiber build-up over time.
Insufficient Mold Cleaning
Failure to clean molds regularly results in hardened fiber residues inside vacuum channels.
Low-Quality Mold Material or Design
Some molds have tiny, deep holes or poor air-flow paths that make cleaning difficult.
4. Effective Solutions for Mold Clogging
(1) Routine High-Pressure Water Cleaning
Use high-pressure water guns to flush the forming and transfer molds daily after production.
Focus on all suction holes and drain channels.
Use warm water if necessary to soften dried pulp residues.
(2) Ultrasonic Cleaning
For serious blockages, ultrasonic cleaning tanks can effectively remove fibers and mineral deposits from tiny holes without damaging the mold surface.
(3) Vacuum Back-Blowing (Air Reverse Cleaning)
Apply compressed air from the vacuum side to blow out any fibers or residues trapped in suction holes.
This method is often used between production shifts for maintenance.
(4) Chemical Cleaning
When physical cleaning is insufficient, mild alkaline cleaning agents or enzymatic cleaners can dissolve stubborn fiber residues.
⚠️ Be sure to follow manufacturer guidelines to avoid mold surface corrosion.
(5) Improve Pulp Filtration System
Install multi-stage filtration in the pulp preparation line (e.g., pressure screen, vibrating sieve, or fine mesh filter).
This ensures that large impurities are removed before the pulp reaches the forming section.
(6) Optimize Pulp Concentration
Maintain the pulp consistency at the recommended level — typically 0.8%–1.2% for egg tray machines and 0.5%–1.0% for fine packaging lines.
Thicker pulp leads to clogging; too thin pulp affects forming strength.
(7) Maintain Circulating Water Quality
Regularly clean sedimentation tanks, replace filter screens, and keep the water system in continuous motion to prevent fiber settling.
5. Preventive Maintenance Tips
Schedule daily mold inspections and weekly deep cleaning.
Always dry molds completely before restarting production.
Keep the vacuum pump filters and pipelines clean.
Use anti-rust oil or mold protection spray if the molds will remain idle for long periods.
Train operators to identify early signs of clogging and take immediate action.
6. Recommended Equipment Enhancements
Modern pulp molding machines — especially those from professional manufacturers like HGHY — now feature:
- Automatic mold cleaning systems (integrated water and air flushing)
- Improved vacuum and water circulation design
- Easily detachable molds for quick maintenance
- Optimized hole diameter and distribution for efficient airflow
Upgrading to a machine with these intelligent features can significantly reduce downtime and maintenance costs.
HGHY: A Leading Manufacturer of Pulp Molding Machines
HGHY is a renowned name in the field of pulp molding machinery. With a reputation for innovation and quality, HGHY offers a range of machines suitable for various applications, including egg box production. Their machines are characterized by:
– Advanced Technology: HGHY machines incorporate cutting-edge technology, ensuring efficiency and precision in production.
– Customization Options: HGHY provides tailored solutions to meet specific production requirements, from small-scale operations to large-scale industrial setups.
– Environmentally Friendly: HGHY’s machines are designed with sustainability in mind, utilizing recycled materials and minimizing waste.
The Molded Pulp Insert Machine is more than equipment—it’s a gateway to joining the supply chain of the world’s leading smartphone brands. With a production capacity of 650–800 kg per day, rapid ROI, and compliance with global eco-packaging regulations, it positions manufacturers at the forefront of a booming, future-proof industry.
As Apple, Samsung, and other high-end electronics brands continue to expand sustainable practices, the companies that invest in molded pulp packaging today will secure not only business growth but also a role in shaping the green industrial ecosystem of tomorrow.
