Effect of Surface Roughness-Based Thermal Contact Resistance on Heat Loss in Hot Runner Systems

초록

This study investigates the quantitative impact of surface roughness-derived Thermal Contact Resistance (TCR) onthe thermal stability of hot runner systems. The primary objective was to evaluate how different machiningprocesses—general lathe (Case 1, Ra: 2.101㎛), CNC lathe (Case 2, Ra: 0.703㎛), and cylindrical grinding (Case 3,Ra: 0.201㎛)—affect heat loss and gate temperature (Tgate). Numerical analysis, incorporating Mikic’s TCR modelunder a 50 MPa contact pressure, revealed that Case 1, with the highest roughness, exhibited the maximumTCR, resulting in the lowest heat flux. Specifically, Case 1 maintained a Tgate of 71.03℃, which is approximately1.59℃ higher than that of the precision-ground Case 3. These results demonstrate that increasing surfaceroughness within a functional range provides a beneficial thermal insulation effect at the sprue-mold interface. This study concludes that optimizing machining specifications to enhance TCR is a cost-effective strategy forstabilizing Tgate and preventing resin solidification defects in injection molding.

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