Rust inside the mold

Rust spots appear on the cavity surface, causing poor product surface. When this defect occurs in products of Process No. 1, it is usually related to a specific process parameter range or equipment status. If it persists, it will directly affect the product qualification rate and production cycle, increasing material loss and rework costs. Timely diagnosis and elimination is a basic requirement to ensure stable production.

1. Mold design factor: Mold cooling water leakage, high environmental humidity during long-term storage, corrosive gas (HCl produced by PVC decomposition), and insufficient corrosion resistance of the mold material. 2. Temperature factor: The settings of barrel temperature and mold temperature directly affect melt flowability, cooling rate, and crystallization behavior; relatively low temperature is a common cause of filling and molding quality problems, and precise control is required according to the material's recommended processing window.

1. Process parameter optimization and adjustment: Repair cooling water leakage, apply anti-rust oil when storing the mold, strengthen ventilation to discharge corrosive gas, and use corrosion-resistant mold steel. 2. Systematic troubleshooting method: Troubleshoot item by item in the order of "parameters -> materials -> mold -> equipment". First adjust the parameters that are easiest to change, such as injection pressure and temperature, and observe the effect; if there is no improvement, check the drying and flowability of the raw material; further check the mold venting and gate design; finally check the mechanical state of the equipment (non-return ring, screw). Change only one variable at a time to determine the root cause. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) assessments. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points.

This problem is a typical manifestation of rust inside the mold in '2079851475616104452, and the core of the solution lies in eliminating the root cause of the defect through systematic optimization of process parameters (temperature, pressure, speed) and rationality checks of mold design. It is recommended to start with process parameter adjustment and gradually go deeper to the equipment and mold levels.