Effective measures to improve injection molding quality
Improving injection molding quality is a core goal of injection molding production, directly impacting product performance, appearance, and service life, while also impacting a company’s market competitiveness. Injection molding quality is influenced by multiple factors, including raw materials, equipment, molds, and process. Problems in any of these steps can lead to defects in the molded part, such as dimensional deviations, surface scratches, and internal bubbles. Given the current market’s increasing demands for product quality, taking effective measures to improve injection molding quality has become crucial for companies to reduce production costs and increase efficiency. For example, by optimizing process parameters, the yield rate of molded parts can be increased from 85% to 98%, significantly reducing scrap rates and minimizing raw material waste.
Strict control of raw material quality is fundamental to improving injection molding quality. Plastic raw material performance indicators such as melt index, density, and moisture content have a direct impact on the injection molding process and part quality. When sourcing raw materials, select suppliers with consistent quality and require detailed material certification and test reports. Each batch of raw materials should be sampled and tested to ensure that their performance meets production requirements. Hygroscopic plastics such as PA and PET must be thoroughly dried before use, and dried raw materials should be used immediately to prevent reabsorption of moisture. During the raw material mixing process, the type and proportion of additives, such as toughening agents and flame retardants, must be strictly controlled to ensure a uniform mix and prevent uneven part performance due to excessive localized additives. Furthermore, the use of raw materials with excessive recycled content should be avoided. The amount of recycled material added should generally not exceed 30%, and it must be screened, cleaned, and dried.
Optimizing injection molding equipment performance is key to ensuring injection molding quality. The performance of the injection molding machine’s injection system, clamping system, and hydraulic system directly impacts the stability of the molding process. When selecting equipment, choose an appropriate specification based on the part’s size, weight, and material properties, ensuring that parameters such as injection volume and clamping force meet production requirements. Regularly maintain the equipment, inspect the injection screw and barrel for wear, and replace any wear promptly to avoid uneven melt flow caused by excessive clearance. Regularly inspect the hydraulic system to ensure stable pressure and flow, preventing dimensional deviations in the molded parts caused by pressure fluctuations. Furthermore, advanced control systems, such as closed-loop control technology, can be used to monitor parameters such as injection pressure, speed, and temperature in real time and automatically adjust based on feedback, improving process parameter stability. For example, an electronic ruler can precisely control the injection stroke with an accuracy of up to 0.01mm, effectively ensuring the dimensional accuracy of the molded parts.
Scientifically designed mold structures play a crucial role in improving injection molding quality. The mold’s cavity accuracy, parting surface design, and gate location all impact part quality. During the mold design phase, the number and arrangement of cavities should be determined based on the part’s structural characteristics to ensure even filling of each cavity with the melt. The machining accuracy of the cavity and core must be controlled within 0.01-0.02mm, and the surface roughness Ra should be less than 0.8μm to avoid surface scratches caused by surface roughness. Gate design should adhere to the principle of “nearest feed, uniform filling.” For large parts, multiple points should be used, while for small parts, single-point gates should be used. Gate size should be determined based on part thickness and material fluidity to ensure smooth melt flow. Furthermore, the mold’s exhaust system should be properly designed, with exhaust slots located at the final point of melt filling to ensure smooth discharge of gases within the cavity and prevent burns or missing parts caused by trapped gases.
Optimizing process parameters and strengthening process control are key to improving injection molding quality. Parameter settings require targeted adjustments based on the type of plastic and part structure. The injection temperature should be kept within the plastic’s melting temperature range. For example, the injection temperature for PP is 180-220°C, and for PC, it’s 260-300°C. Excessively high temperatures can cause plastic decomposition, while excessively low temperatures can affect melt fluidity. Injection pressure and speed should be determined based on the complexity and wall thickness of the part. Complex parts require higher pressures and speeds, while thick-walled parts require lower speeds to reduce internal stress. Holding pressure and time should be determined through mold trials to ensure adequate melt shrinkage and avoid shrinkage or sinking. During production, a comprehensive quality inspection system should be established, with each batch of parts sampled and tested for dimensional accuracy, surface quality, and mechanical properties. Process parameters should be adjusted promptly if any issues are identified to ensure consistent product quality.
