Skin Layer and Core Layer Separation

The surface layer of the part debonds from the core. When this defect appears in parts of Process No. 2, it is usually related to specific process parameter ranges or equipment conditions. If it persists, it will directly affect the part qualification rate and production cycle, increasing material loss and rework costs. Timely diagnosis and elimination is a basic requirement for ensuring stable production.

1. Reaction process factors: large curing rate difference between skin layer and core layer, insufficient interfacial bonding force, reaction exotherm causing interfacial bubbles. 2. Mixing quality factors: 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 determining mixing quality. 3. Temperature control factors: raw material temperature affects component viscosity and reaction rate, mold temperature affects the curing process and part surface quality, and both need to be precisely controlled within a narrow window.

1. Process parameter optimization and adjustment: adjust the formulation to match the curing rates of the skin layer and core layer, improve interfacial bonding, control reaction exotherm. 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, then check 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) evaluation. For recurring problems, use fishbone diagram or 5Why analysis to trace the root cause, and fix the countermeasures as PFMEA control points.

This problem is a typical manifestation of skin layer and core layer separation in the RIM process; the core of the solution lies in ensuring the precise ratio and full mixing of the two components, while controlling the reaction temperature and curing conditions within the optimal window. It is recommended to start troubleshooting from the mixing system and metering accuracy.