Mixing head liner wear

The inner wall of the mixing head wears, causing the mixing quality to decrease. In the cross-section of products with uneven mixing, obvious layered or marble-like streaks can be seen, with alternating light and dark colors, and the hardness, density, and mechanical properties of local areas are inconsistent with the whole. In extreme cases, insufficiently mixed components form independent enriched areas inside the product, which may become crack initiation points when stressed. The evaluation of mixing quality can be carried out by microscopic observation of the product cross-section or ultrasonic C-scan for non-destructive testing.

1. Equipment factor: Long-term high-speed mixing scouring wear, fillers accelerating wear, insufficient hardness of the mixing head material, and material corrosion. 2. Temperature control factor: The raw material temperature affects the component viscosity and reaction rate, and the mold temperature affects the curing process and product surface quality; both need to be precisely controlled within a narrow window.

1. Process parameter optimization and adjustment: Use wear-resistant and corrosion-resistant material for the mixing head liner, regularly check the inner wall wear, control the filler content, and regularly replace the liner. 2. Systematic troubleshooting method: RIM problem troubleshooting follows the order of "formulation -> mixing -> temperature control -> equipment". First check the two-component ratio and catalyst dosage, then check the mixing head and self-cleaning function, next troubleshoot the raw material and mold temperature control, and finally check the accuracy of the metering pump and hydraulic system. 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.

RIM mixing quality is the first element determining product consistency. The core control points are: the impingement mixing Reynolds number of the mixing head (ensuring turbulent mixing), the matching of the viscosities of the two components (reducing viscosity differences), the accuracy of the metering pump (ensuring constant ratio), and the effectiveness of self-cleaning (preventing residual curing blockage).