PA66 is a widely used engineering plastic with high strength, toughness, wear resistance and self-lubrication. It is commonly used in structural parts, gears, connectors, fasteners and automotive components. Due to its strong hygroscopicity, fast crystallization, temperature sensitivity and high shrinkage, strict control during injection molding is required to ensure stable dimensions, good appearance and qualified performance.
Raw Material Drying and StoragePA66 absorbs moisture easily, which will decompose under high temperature and cause defects such as bubbles, silver streaks and brittle cracks. Therefore, sufficient drying is essential. Raw materials must be fully dried with a dehumidifying dryer at 80–100°C for 4–6 hours until the moisture content is below 0.05%. Dried materials should be sealed and used as soon as possible. Continuous heat preservation and drying should be maintained in the hopper during production to prevent moisture reabsorption.
Temperature Setting RequirementsBarrel temperature directly affects plasticizing quality, fluidity and crystallization. Generally, the rear section is set at 250–270°C, the middle section at 270–290°C, and the front section at 260–280°C. Low temperature leads to insufficient plasticizing and high internal stress, while excessive temperature causes degradation, discoloration and performance reduction. Nozzle temperature is slightly lower to prevent drooling.
Mold temperature significantly affects crystallization and dimensional stability. Higher mold temperature improves rigidity and dimensional stability, while lower mold temperature provides better toughness. The typical mold temperature is 60–100°C.
Injection Pressure and SpeedPA66 has good fluidity, but pressure and speed must match the product structure. Moderate injection pressure is used to avoid flash, stress and deformation. High speed is suitable for thin-walled products, while medium-low speed is used for thick products to prevent gas trapping and burning. Holding pressure and time are set reasonably to reduce sink marks and dimensional deviation.
Mold and Venting DesignPoor venting can cause burning, short shots and surface defects. The venting groove depth should be controlled within 0.02 mm to avoid overflow. Runner and gate design should reduce flow resistance. PA66 has a shrinkage rate of about 1%–2%, so shrinkage compensation must be fully considered in mold design to ensure product dimensional accuracy.
Cooling, Demolding and Post TreatmentSufficient cooling time is required to avoid warping caused by incomplete solidification. The ejection system should be balanced with proper ejector pins and sufficient draft angle to prevent sticking or damage. For precision parts, moisture conditioning is recommended to stabilize dimensions and improve toughness. Finished products should be stored away from high temperature, direct sunlight and heavy pressure.
