Injection molding defect-welding line
In injection molding, when molten plastic flows in the mold cavity and encounters areas of inconsistent flow speed or filling interruption, a welding line will form on the product. Welding lines not only affect the appearance of the product but also affect its structure and functional performance.
What are the causes and solutions of welding lines?
1. Molding process
①. Injection pressure and speed are too low, and barrel temperature and mold temperature are too low, causing the molten plastic entering the mold to cool too early.
②. When the injection pressure and speed are too high, jetting occurs, resulting in welding lines.
③. The speed should be improved and back pressure should be increased to reduce the viscosity of the plastic.
④. The lock force should be reduced to facilitate venting.
2. Mold
①. If there are too many gates in the same cavity, the number of gates should be reduced or symmetrically arranged.
②. Gates should be set to prevent the melt from moving around the insert holes.
③. If the wall thickness varies too much, the wall thickness of the part should be made uniform.
3. Plastic
①. Plastic with poor fluidity or poor heat sensitivity should be appropriately added with lubricants and stabilizers.
②. The plastic contains a lot of impurities. If necessary, use high-quality plastic material as the raw material.
