Research on Influencing Factors of the Thermal Contact Resistance in Thin-Wall Injection Molding

Abstract

Thermal contact resistance, a parameter that describes the thermal transferability of the interface between the melt and the metallic wall, exercises a significant influence on the surface quality of the resulting part, especially in thin wall injection molding. In this study, temperature data of the melt was quantitatively measured with only 2 micro thermocouples, and TCR of specimens with 4 kinds of thickness was calculated after data processing with a new mathematical model. It was demonstrated that TCR was deeply affected by mold temperature. When the mold temperature increased from 90 °C to 130 °C, the rate of TCR decline was 56.72 %. Melt cooling simulation was performed with different values of TCR, which played the dominant role of TCR in calculating the temperature distribution in thin-wall injection molding. It showed that TCR exercises a significant influence on the simulation of the cooling rate, and the influence cannot be ignored, especially in thin-wall injection molding.

Investigation of Interface Thermal Resistance between Polymer and Mold Insert in Micro-Injection Molding by Non-Equilibrium Molecular Dynamics

“…It could be seen that the ITR between the Ni layer and the PP layer decreased gradually with the increase of the temperature. The ITR was about with the IT at 335 K, while it dropped about 39% with the IT at 393.17 K. This change of ITR with the temperature was basically the same as that in Ref [ 32 ], but the values of the ITR were about three orders of magnitude smaller than the experimentally measured values reported by Zhu [ 32 ] ( ). The reason was that the work in the above reference was done in the geometry on the macro-scale, not on the nanoscale as in this work.…”

Meta‐analysis of thermal contact resistance in injection molding: A comprehensive literature review and multivariate modeling

“…Hence, higher mold and melt temperatures would lead to smaller TCR by increasing the heat flux. 5 For similar reasons, polymer and mold thermal conductivities also affect the TCR; however, most studies in the literature have not investigated the effect systematically. The analysis must also consider the impact of polymer temperature on melt viscosity.…”

“…TCR generally reduces for a smaller temperature gradient between the mold and polymer temperature. Hence, higher mold and melt temperatures would lead to smaller TCR by increasing the heat flux 5 . For similar reasons, polymer and mold thermal conductivities also affect the TCR; however, most studies in the literature have not investigated the effect systematically.…”

“…3,4 The absence of ideal contact between the two surfaces creates a discontinuity (i.e., TCR) in the temperature distribution, which can be more or less significant depending on many variables. 5 TCR can result in temperature gradients across the mold surface, leading to uneven cooling and warpage of the molded parts. 4 The surfaces are in contact at the polymer/mold interface, and so TCR has been reported to be influenced by various factors, including the contact pressure, 6 surface roughness, 7,8 and thermal conductivity of the materials involved.…”

“…Moreover, the air pockets at the interface can also reduce heat transfer while increasing TCR 3,4 . The absence of ideal contact between the two surfaces creates a discontinuity (i.e., TCR) in the temperature distribution, which can be more or less significant depending on many variables 5 . TCR can result in temperature gradients across the mold surface, leading to uneven cooling and warpage of the molded parts 4 .…”