Injection molded parts are one of the most widely used plastic products in modern manufacturing. The core of their production lies in the injection molding process, where the plastic material is melted at high temperature and injected into a mold, where it cools and solidifies to form a precise structure. The following describes the process flow, key parameters, and common problems.
The process consists of five steps: First, plastic pellets (such as PP, ABS, etc.) are dried to prevent moisture from affecting their fluidity. Next, the pellets are placed into the injection molding machine barrel and heated at 180-300°C (depending on the material) until they reach a viscous flow state. The screw rotates and pressurizes the melt into the closed mold cavity, maintaining pressure and compensating for shrinkage to prevent shrinkage defects. A cooling system (usually a circulating water channel) ensures the product is set within 30-90 seconds. Finally, the mold is opened and ejected, completing a single cycle.
Controlling key parameters directly impacts quality: ① Temperature must match material properties; excessively high temperatures can lead to decomposition, while excessively low temperatures can result in insufficient mold filling. ② Injection pressure (80-150 MPa) determines filling speed and density. ③ Cooling time accounts for over 60% of the cycle, balancing efficiency with the risk of deformation. ④ Mold design is crucial, requiring precise calculation of gate location, vent depth, and draft angle (typically ≥3°).
Common defects include flash (from loose mold closure), sink marks (from insufficient holding pressure), and warpage (from uneven cooling). These defects can be addressed by adjusting parameters or optimizing mold structure. Efficient production also requires attention to mold maintenance (regular polishing and replacement of consumable parts) and raw material pretreatment (e.g., ensuring uniform mixing of masterbatches).
Mastering these methods and details can significantly improve the yield of injection molded parts and meet the stringent precision and strength requirements of industries such as automotive and electronics.
