Papers by Keyword: Microinjection Molding

Abstract: Laser surface texturing (LST) is increasingly adopted to functionalize the surface in injection molding, enabling the control of interfacial and tribological phenomena without altering bulk material properties. While most studies have focused on mold cavities, the functionalization of ejection system components remains largely unexplored, despite its critical role in part release and process stability. This work presents a preliminary investigation of laser surface texturing for cylindrical ejector pins to promote lubricant retention at the pin–mold interface. A parametric study was first carried out on a flat to define a process window compliant with the maximum allowable groove depth constraint (20 µm). Based on this campaign, a stable ablation regime was identified and transferred to cylindrical ejector pins, where textures were fabricated along axial length. Different micro-texture geometries and spatial distributions were designed to generate controlled micro-reservoirs for lubricant retention. The textured surfaces were characterized in terms of groove depth, morphology and uniformity, confirming the feasibility of producing shallow and well-defined features within industrial constraints. The preliminary results demonstrate the technical feasibility of laser texturing on cylindrical ejector pins and its potential to modify the pin–mold interface. However, the comparative effectiveness of the different texture geometries in promoting lubricant retention will be further evaluated under extended service conditions. The study, therefore, establishes the basis for the functional optimization of textured ejection systems in injection molding applications.

Abstract: Based on our previous work, the present work intends to reveal the origin of the process-parameter effects in fabricating polymer micromixers using microinjection molding. First of all, the effects of the process variables including the melt temperature, injection velocity, packing pressure and packing time, on replication quality of the micromixers were numerically investigated using Moldex3D software. The simulation results were found to agree well with the reported experimental ones, that’s, among the investigated variables, the melt temperature was the only significant factor influencing the replication quality of the micromixers. Moreover, the rheology behavior and the cooling behavior of the PMMA melt were analyzed and identified as the origins of the process-parameter effects.

Abstract: The ability for polymer melt to flow into the microstructure is a crucial factor for successful molding in the microinjection molding of plastic parts. In this study, a simplified analytical model with a direct hot runner nozzle and was constructed to estimate the filling percentage of mold’s cavity. The filling behavior of polymer melt was observed by 3D simulation software Moldflow. The effects of the mold temperature, melt temperature, injection pressure, injection rate, and packing pressure on the filling behavior of polymer melt were investigated. Results revealed that the filling percentage increased with respect to the increase of mold temperature and melt temperature which didn’t exceed its degradation temperature. The injection pressure and packing pressure dramatically influence the filling percentage, and it made no sense to lift the injection speed to fill the cavity when the injection speed reached the relatively high values, and only processing parameter combined available could guarantee the perfect flow and filling for the microstructure.

Abstract: Microinjection molding has been drawing more and more attention due to its great advantages such as cost effectiveness and mass production capability. In this work, an experimental study was carried out in order to investigate the effect of the mold surface roughness on the achieved filled length of the molded microfeatures. For this purpose, an aluminum mold insert with microchannels having different surface roughness values was designed and fabricated using ultraprecision diamond machining and micromilling method. The experimental results revealed that increasing surface roughness of the microchannel wall led to a decrease in the filled length of the molded microfeatures. It was also found that with increased melt temperature or injection velocity, the effect of surface roughness was weakened by high-pressure trapped air inside the microchannels during injection process. Finally, the influence mechanism of the mold surface roughness was discussed.

Abstract: In recent years, microinjection molding has been widely used for fabricating polymer components due to its cost effectiveness and mass-production capability. In this work, the fabrication process of a polymer micromixer was presented. The micromixer was designed in such a way that the fabrication process could benefit from the process capabilities of ultraprecision micromachining and microinjection molding. An amorphous polymer material polymethylmethacrylate was used to make the micromixers. Moreover, in order to investigate the effects of processing parameters on replication quality of the micromixer, four important factors in microinjection molding, namely the melt temperature, injection velocity, packing pressure and packing time were selected as variables. The experimental results showed that the melt temperature was the most important factor influencing the replication, followed by the injection velocity. However, the packing pressure and packing time had no obvious influence on the replication of the micromixer.

Abstract: This study investigates the flow characteristics of microinjection-molded lightguiding plates. This study also analyzes the position of melt fronts on lightguiding plates. Viscous heating, temperature and velocity distribution are utilized to analyze delay or advancement of the melt front experimentally and using three-dimensional (3D) numerical simulation. A slow injection speed reduces viscous heating. As viscous heating decreases, the temperature distribution decreases and plastic viscosity increases. A high plastic viscosity increases flow resistance and melt plastic velocity decreases. The advancing melt front of a lightguiding plate is delayed in this situation. The key of this research is that the plastic melt front can arrive the end position at the same time on filling stage of lightguiding plate for microinjection molding. In this research, the authors find increasing the injection speed can help the previous situation. Experimental results demonstrate that filling in the experiment is very close to that in 3D numerical simulation.