Special measures when injection molding white or transparent products
Injection molding white or transparent products places extremely high demands on production processes and environments. Any tiny impurity or process defect can cause problems such as black spots, yellowing, or turbidity, affecting the product’s appearance and performance. Therefore, when producing these products, a series of special measures must be implemented, strictly controlling every aspect, from raw material control, equipment cleaning, process parameter setting, to production environment management, to ensure that the product meets the expected quality standards.
Strict control of raw materials is fundamental to producing white or transparent products. First, select raw materials of high purity and minimal impurities. Avoid recycled materials or those adulterated with other colors, as these may contain dust, metal particles, and other colored impurities, which can directly affect the product’s whiteness or transparency. During storage and transportation, raw materials must be protected from moisture and dust to prevent contamination. For example, transparent plastics such as PMMA and PC are highly hygroscopic and must be thoroughly dried before use. Otherwise, moisture in the raw materials can create bubbles during the high-temperature melting process, leading to material degradation and defects such as turbidity and silver streaks. During the drying process, clean drying equipment should be used, and the drying temperature and time should be strictly controlled to ensure that the raw materials meet the required moisture content.
Thorough cleaning of equipment is crucial to preventing contamination. Because white and transparent products are extremely sensitive to impurities, the injection molding machine’s hopper, screw, barrel, nozzle, and other components that come into contact with the raw materials must be thoroughly cleaned before production to remove any residual color or impurities. During cleaning, the appropriate cleaning agent should be selected based on the type of raw material previously processed. For materials with difficult-to-remove residuals, specialized cleaning fluids or high-temperature melt cleaning methods can be used. After cleaning, use compressed air to blow out any residual material inside the equipment. A trial run should be conducted to observe the product for impurity contamination. Full production can only begin after confirming that the cleaning process has passed. During production, the equipment should also be regularly inspected and cleaned to prevent metal debris from wear and tear from mixing with the raw materials.
Optimizing process parameters is crucial to ensuring the quality of white or transparent products. Regarding temperature control, the temperature of each barrel section and the nozzle temperature should be appropriately set based on the characteristics of the raw materials. Excessively high temperatures can cause the raw materials to decompose, resulting in yellowing of white products and turbidity in transparent products. Excessively low temperatures can lead to poor plasticization of the raw materials, affecting the product’s transparency and surface gloss. Regarding injection speed and pressure, an appropriate injection speed should be used to avoid excessive shear forces caused by excessive speed, which can lead to raw material decomposition. At the same time, sufficient holding pressure and time must be ensured to reduce internal stress in the product and prevent cracking or deformation that could affect transparency. Furthermore, mold temperature control should not be neglected. Properly increasing the mold temperature can reduce the cooling rate of the melt, facilitate gas discharge and uniform crystallization, and improve product transparency.
Maintaining a clean production environment is also crucial for the production of white or transparent products. The production workshop should be clean, dry, and dust-free. Ideally, it should be an enclosed facility equipped with an air purification system to control the amount of dust particles within the workshop. Operators should wear clean work clothes, a hat, and gloves before entering the workshop to prevent contamination of raw materials and products by impurities such as hair, dander, and dust. Raw material addition should be carried out in a clean environment, and an automated feeding system can be used to reduce contamination from manual operations. Furthermore, the workshop floor and equipment surfaces should be regularly cleaned and disinfected to maintain a hygienic production environment. Only by strictly controlling contamination at every stage can we ensure that the white or transparent products produced have the desired appearance, quality, and performance that meet customer expectations.
