Multi-gate filling imbalance

Inconsistent filling speeds of multiple gates cause uneven flow fronts. When filling is insufficient, the product shows obvious material shortage at the end of the cavity or at the thinnest wall, with smooth or irregularly shaped shortfall edges. Similar to the short shot of '2079851475616104452, but in compression molding and transfer molding, insufficient filling may also be directly related to the feeding position and feeding method — if the material is unevenly distributed in the mold, local material shortage will occur even if the total amount is sufficient. Underfilled products cannot be used, and the local unfilling of the mold will cause the flow pattern of the next molding to change.

1. Mold design factor: The runner lengths of the gates are different, the gate sizes are inconsistent, the mold temperature distribution is uneven, and the venting is uneven. 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.

1. Process parameter optimization and adjustment: Balance the runner lengths, adjust the gate sizes, make the mold temperature uniform, and improve the venting of each part. 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.

This problem is a typical manifestation of multi-gate filling imbalance in the RIM process, and the core of the solution lies in ensuring the precise ratio and sufficient 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.