Core Deflection in Plastics Injection Molding: Direct Measurement, Flow Visualization and 3D Simulation

During plastics injection mold filling of long thin hollow parts, the melt may race ahead, asymmetrically, along one side of the core, and thus deflect the core. Several literatures have reported analytical or simulation results, but no experimental measurement has been done so far. The present study aimed to measure the developing core deflection during mold filling by flow visualization. A borescope behind a transparent quartz block was mounted upon a specially designed mold cavity to directly observe core deflection. The melt front advancement is also captured by a high-speed camera. The measured deflection closely resembles but falls below the simulated ones. The formation of the frozen layer may be suppressing core deflection, but more investigations are still needed.