Mixing head self-cleaning plunger stuck

The plunger cannot move, causing production interruption. 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. Material factor: Material solidifies in the plunger clearance, plunger surface wear produces burrs, drive cylinder failure, and plunger bending deformation. 2. Mixing quality factor: In the RIM process, the mixing uniformity of the two components is the foundation of all quality; the Reynolds number of the mixing head, the impingement mixing energy, and the residence time distribution are the key engineering parameters that determine the mixing quality. 3. 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: Strengthen the cleaning program, replace worn plungers, overhaul the drive cylinder, and correct the straightness of the plunger. 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).