As one of the most widely used plastic molding processes in industrial manufacturing, injection molding production experience directly impacts product quality and cost control. After years of practice, we have summarized several key operational points.
Mold design is fundamental. Gate location and size directly influence mold filling balance. Side gates are suitable for thin-walled parts, while latent gates are more suitable for products with high aesthetic requirements. The vent depth is typically controlled between 0.02-0.05mm. Too shallow can trap air and cause burning, while too deep increases the risk of flash. Regarding mold temperature control, PC/ABS materials are recommended to maintain a temperature of 60-80°C, while PP materials can be lowered to 40-60°C to improve flowability.
Parameter adjustment requires dynamic optimization. Too fast an injection speed can easily produce jetting marks, while too slow an injection speed can result in undershot. The holding pressure is generally set at 60%-80% of the injection pressure; prolonged holding times can lead to internal stress concentration. The melt temperature needs to be adjusted based on the material's properties. For example, PA66 is recommended at 270-290°C, while PVC should be strictly controlled at 180-200°C to prevent decomposition. It's also important to note that in winter, when ambient temperatures are low, the drying time needs to be extended (for example, PET requires more than 4 hours at 120°C).
Defect handling techniques are available. Sink marks can be addressed by increasing wall thickness uniformity or adjusting the holding pressure curve. Silver streaks are often caused by moisture or volatiles, so the drying process should be carefully inspected. If weld marks are insufficiently strong, increase the mold temperature or optimize the gate layout. For products requiring high precision, mold flow analysis is recommended to predict filling conditions.
Regular maintenance of the screw and barrel is crucial during production, as carbide accumulation can lead to material degradation. Establishing a comprehensive SPC quality control system and monitoring CPK of critical dimensions can effectively reduce batch defects. These experiences need to be flexibly applied in conjunction with specific material properties and product structure. Continuous improvement is the key to improving injection molding quality.
