Insufficient Filling

The material does not fill the mold cavity. When filling is insufficient, the part shows obvious material shortage at the end of the cavity or at the thinnest wall thickness, with smooth or irregular shortage edges. Similar to short shot in '2079851475616104452, but in compression and transfer molding, insufficient filling may also be directly related to the charging position and charging method — if the material is unevenly distributed in the mold, local material shortage will occur even if the total amount is sufficient. Parts with insufficient filling cannot be used, and their local unfilling of the mold will cause the flow pattern of the next molding to change.

1. Mold design factors: insufficient injection volume, material gels too fast, poor mold venting producing air resistance, gate cross-sectional area too small. 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: increase injection volume, adjust gel time, improve mold venting, enlarge gate cross-sectional area. 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 insufficient filling 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.