Numerical and experimental investigation of plastic injection molding of micro‐engineered surfaces

Abstract

We carried out experimental and numerical investigations into the effects of injection‐molding parameters on the transcription quality and uniformity of micro‐pillar arrays. For the experiment, we used a precise metallic mold insert, which was shaped like an inverted micro‐pillar array. This was fabricated using UV‐photolithography and a nickel electroforming process. With the mold insert, the effects of the distance from gate and uniformity on the transcription quality could be investigated experimentally by varying the main processing parameters, such as flow rate, polymer melt temperature, and mold wall temperature. The results of the injection molding experiment indicated that increasing the three processing parameters improved the transcription quality of micro‐pillar arrays. In numerical investigation, we used the interpolated domain decomposition method. This was based on 2.5D and 3D simulations, and was used to effectively solve the filling behavior of the polymer melt inside the mold which contains multi‐scale cavities. Numerical results revealed that the transcription quality was significantly affected by the mold wall temperature. Based on the experimental and numerical investigations, the local mold heating (LMH) technique for the high mold wall temperature was employed to enhance the replicability of the micro‐pillar array. The result of injection molding with LMH showed that the transcription quality and uniformity were considerably improved. These numerical and experimental results provide insights into the foundations of the field of injection molding of plastic micro‐engineered surfaces. POLYM. ENG. SCI., 58:E73–E81, 2018. © 2017 Society of Plastics Engineers