Need to Raise Pass Rate of Eggtray Making Machine?
Pulp molded egg trays, produced by eggtray making machines, is a staple of environmentally friendly packaging for the poultry egg industries, its’ quality can directly impacts product transportation safety, brand reputation, and ultimately manufacturers’ costs and profits. However, many egg tray manufacturers often struggle with uneven egg tray wall thickness, breakage, and low yield rates. The root of these problems often lies in the details. In this article, AGICO will analyze the 4 key factors affecting pulp molded egg tray machine and product quality and provide practical advices to help you easily improve your product’s competitiveness!
Quality Control in Pulp Making Process
Paper pulp is the “skeleton” of the egg tray. If the pulp material is selected incorrectly or handled improperly, no matter how sophisticated the subsequent process is, it will be difficult to save the egg tray.
- Fiber Selection: Long fibers (such as wood pulp, 2-3mm in length) have strong interweaving properties, making the egg trays more resistant to bending and impact. When using waste paper pulp, be careful to filter out impurities (plastic, sand, and gravel) exceeding 3% as this will weaken the fiber bond and cause holes and bulges in the egg tray. We recommend a ratio of 80% waste paper pulp to 20% wood pulp for a 30% increase in toughness and reduced cost.
- Pulp Concentration: If the concentration is too high (>6%), the pulp will have poor fluidity, resulting in uneven fiber stacking during molding and a variation in egg tray wall thickness exceeding ±15%. If the concentration is too low (<3%), the fiber content will be insufficient and the wet billet will be easily damaged. Daily monitoring with an online concentration meter is recommended, and a safe range of 4%-5% is recommended.
- Auxiliary materials: The appropriate amount of adhesive (starch, PVA) to be added is 2%-3% – if it is too little, the strength will not be enough, and if it is too much, the egg tray will become brittle; the waterproofing agent (paraffin emulsion) needs to be stirred evenly, otherwise the waterproof performance of the part will be poor and it will easily absorb moisture and become soft in a humid environment.
Egg Tray Making Machine Molding Process: Vacuum + Mold
Pulp Molding Process is the core step of the egg tray’s “shaping”. Eggtray making machine is consists of vacuum adsorption system, pulp mold die and egg tray transfer system. High standard vacuum adsorption technology and good pulp mold die status directly determine the structural integrity.
- Vacuum Pressure Adjustment: If the vacuum pressure is too low (<-0.06MPa), the wet base will be high in moisture and loose in structure, resulting in deformation upon demolding. If the vacuum pressure is too high (>-0.09MPa), the pulp fibers will be over-compacted, shrinking by more than ±2mm after drying and potentially damaging the mold. We recommend adjusting the vacuum to match the egg tray wall thickness of 1-2mm: -0.07MPa for thin walls and -0.08MPa for thick walls. Keeping the adsorption time within 4-6 seconds ensures more uniform fiber deposition.
- Pulp Mold Permeability: Clogged mold filter and unreasonable exhaust slot design will lead to “vacuum dead zone” – local fiber shortage, egg tray will appear. Clean the filter once a week and check the mold edge regularly (wear “dent”. It is recommended to replace it with a highly breathable nano-coated filter (pore size 0.2-0.3mm). Wear will cause “flash” on the egg tray, which can extend the mold life by 30%.
- Wet Eggtray Transfer: Wet blanks with a moisture content of 60%-70% are prone to tearing and edge collapse if the vacuum is not immediately broken during demolding or the conveyor belt is jolted. A positioning baffle can be installed to control the demolding speed to 30-40 mm/s to minimize breakage.
Eggtray Drying Process: Temperature + Time
Eggtray drying is always take place in multi-layer metal dryer. If the eggtray drying is not proper, the pulp egg tray will either have excessive moisture or be “over-dried and cracked”. The drying process of the egg tray can be controlled by the following 2 aspects:
- Drying Temperature Control: 180-220°C is the most suitable drying temperature. Below 160°C, moisture content is difficult to meet standards (moisture content >15%), and the egg tray is prone to moisture absorption. Above 220°C, the fibers carbonize and become brittle, and the flexural strength drops sharply (from ≥5N to <3N). Thick-walled egg trays can be pre-dried at low temperature and then set at high temperature to avoid moisture entrapment.
- Keep The Hot Air Ducts Clear: Oven fan failure or clogged hot air ducts can lead to uneven drying (cracking on one side and softening on the other). It is recommended to clean the ducts weekly and use an infrared thermometer to monitor the temperature difference between different areas of the oven (control it within ±5°C). This will increase the pass rate by 20%.
Other Factors That Influences Egg Tray Production
Eggtray production line and factory environment also has impacts on egg tray quality, the maintenance of egg tray production equipment and the workshop environment are the “invisible guarantee” of stable quality.
- Eggtray Making Machine Maintenance: Aging vacuum pumps can cause vacuum fluctuations (±0.01 MPa), directly exacerbating uneven wall thickness. Cracks in the vacuum chamber seals (rubber rings) can lead to vacuum leakage and make wet billets prone to falling apart. It’s recommended to check the vacuum pump pressure monthly and replace the seals quarterly to minimize downtime losses.
- Ambient temperature and humidity control: When the relative humidity in the eggtray plant exceeds 75%, the pulp absorbs moisture easily, causing large fluctuations in concentration. A temperature difference of more than 10 °C between day and night can lead to unstable pulp viscosity and egg tray dimensional deviations exceeding ±1mm. A dehumidifier (controlled at 50%-60%) and a constant temperature system can be installed to stabilize production conditions.
Raise the Pass Rate of Pulp Molded Egg Tray
The quality of pulp-molded egg trays is never achieved through a single effort—every step, from raw material ratios to vacuum suction, mold maintenance, and drying temperature control, requires precise control. One customer achieved a 15% reduction in costs by increasing their egg tray qualification rate from 85% to 98% through standardized raw material pretreatment, adjusting molding parameters, and controlling drying temperature zones.
If you want to improve the quality of pulp egg tray production , contact our engineering team!