A Brief Analysis Of The Structural Design Of Rotomolding Molds
1. Material selection and processing
Material quality: Make sure to use high-quality rotomolding grade polyethylene (PE) or other suitable plastic materials, and avoid using materials containing impurities or degradation.
Drying treatment: If the material is hygroscopic (such as nylon or some engineering plastics), it must be fully dried before processing to avoid moisture vaporization at high temperature to form bubbles or perforations.
Material fluidity: Select materials with moderate fluidity to ensure that the material can evenly cover the mold surface and avoid local thinness or voids.
2. Optimize process parameters
Heating temperature: Ensure that the heating temperature is uniform and appropriate. Too high a temperature may cause material degradation, while too low a temperature may cause insufficient material fluidity and fail to completely fill the mold.
Cooling rate: Control the cooling rate to avoid excessive cooling that causes uneven shrinkage of the material, resulting in stress concentration or perforation.
Rotation speed: Adjust the rotation speed of the mold to ensure that the material can be evenly distributed on the inner surface of the mold. Too fast or too slow a rotation speed may cause uneven material distribution.
Molding time: Ensure sufficient molding time to allow the material to fully melt and flow, and avoid partial non-filling due to insufficient time.
3. Mold design and maintenance
Mold surface treatment: Ensure that the mold surface is smooth, free of pollution or rust, and avoid poor material adhesion or obstructed flow.
Exhaust design: Check whether the exhaust holes of the mold are unobstructed to avoid air being trapped in the mold to form bubbles or perforations.
Mold temperature uniformity: Ensure that the temperature of each part of the mold is uniform to avoid local overheating or overcooling that causes uneven material distribution.
Mold cleaning: Clean the mold regularly to avoid residual materials or contaminants affecting product quality.
4. Operation and equipment maintenance
Equipment inspection: Regularly check the heating system, cooling system and rotation system of the rotational molding machine to ensure that the equipment operates normally.
Operation specifications: Train operators to ensure that they are familiar with equipment operation and process requirements to avoid problems caused by improper operation.
Material input: Ensure that the material input is sufficient to avoid local unfilled or perforated areas due to insufficient materials.
5. Product design and wall thickness control
Wall thickness uniformity: Avoid excessive wall thickness differences when designing products to ensure that the material can be evenly distributed.
Rib design: Add ribs or fillets to areas prone to perforation (such as sharp corners or edges) to reduce stress concentration.
Avoid sharp structures: Try to avoid designing overly sharp structures, as these areas are prone to perforation due to insufficient material flow.
6. Inspection and quality control
Online inspection: Use tools such as infrared thermometers to monitor mold temperature during production to ensure uniform heating and cooling.
Finished product inspection: Perform air tightness tests or ultrasonic inspections on finished products to promptly detect and solve perforation problems.
Process records: Record the process parameters of each production to facilitate analysis of the cause of the problem and optimize the process.
7. Troubleshooting of common problems
Bubble problem: If the perforation is caused by bubbles, check whether the material is dry and whether the mold exhaust is unobstructed.
Material degradation: If the material degrades due to overheating, reduce the heating temperature or shorten the heating time.
Mold contamination: If there are contaminants on the mold surface, clean the mold thoroughly and check whether the material is pure.
The above methods can effectively reduce or solve the perforation problem of rotomolded products. The key lies in comprehensive analysis and optimization from multiple aspects such as materials, processes, molds and operations to ensure the stability of the production process and consistency of product quality.