• Design & Manufacturing
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• v.6 no.1
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• pp.5-11
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• 2012

The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the boss wall thickness. The volumetric shrinkage is caused by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase the flow rate to a boss part and causes the depth of sink mark to increase. As the molding thickness and the boss wall thickness in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink mark that was generated in the boss wall thickness of injection molded products. The sink mark could also be caused by thickness ratio of boss part. For a given thickness ratio of boss, several molding process parameters such as packing pressure, packing time and melt temperature, affecting to generation of the sink mark were discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.812-815
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• 2000

Injection molding process was taken to manufacture DC motor case that surrounds DC motor used as automobile parts. Up to now, DC motor case has been made by the deep drawing process or bending process of metal materials. Simulations of filling, packing and cooling processes were done by CAE tool like Moldflow software. Optimal delivery system was decided from the analysis of flow balance, and packing and cooling analyses were performed by using the design of experiment to minimize the volumetric shrinkage of molded part and the temperature difference between mold and part.

• Journal of Power System Engineering
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• v.6 no.2
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• pp.68-72
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• 2002

Design of experiment was applied to analyze the shrinkage characteristics of the bobbin molded by injection molding. Among lots of design and processing conditions, the thickness of a bobbin and cooling conditions of a mold were considered. The temperature difference between top and bottom parts of the bobbin was considered as the objective to minimize the shrinkage of a bobbin. Optimal thickness of a bobbin was 2.0mm at the part of body and 1.5mm at the part of wing, respectively. Optimal cooling conditions such as cooling time and coolant inlet temperature were 12 second and $12^{\circ}C$, respectively.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.103-109
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• 2008

The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the boss wall thickness. The volumetric shrinkage is caused by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase the flow rate to a boss part and causes the depth of sink mark to increase. As the molding thickness and the boss wall thickness in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink mark that was generated in the boss wall thickness of injection molded products. The sink mark could also be caused by thickness ratio of boss part. For a given thickness ratio of boss, several molding process parameters such as packing pressure, packing time and melt temperature, affecting to generation of the sink mark were discussed

• Journal of Powder Materials
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• v.9 no.4
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• pp.218-226
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• 2002

The purpose of the present study is to investigate the influence of thermal debinding and sintering conditions on the sintering behavior and mechanical properties of PIMed 316L stainless steel. The water atomized powders were mixed with multi-component wax-base binder system, injection molded into flat tensile specimens. Binder was removed by solvent immersion method followed by thermal debinding, which was carried out in air and hydrogen atmospheres. Sintering was done in hydrogen for 1 hour at temperatures ranging from 1000℃ to 1350℃ The weight loss, residual carbon and oxygen contents were monitored at each stage of debinding and sintering processes. Tensile properties of the sintered specimen varied depending on the densification and the characteristics of the grain boundaries, which includes the pore morphology and residual oxides at the boundaries. The sinter density, tensile strength (UTS), and elongation to fracture of the optimized specimen were 95%, 540 MPa, and 53%, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.1
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• pp.53-61
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• 2008

In this research, the layout and geometry of U-type ribs in the part, including significant process conditions, are automatically optimized to reduce part warpage with robustness in consideration. The optimization procedure are based on an iterative redesign methodology integrated with computer aided injection molding simulation, Taguchi's Design of Experiment(DOE), and a direct search-based optimization method. The robustness of a design alternative is efficiently measured by introducing composite noise factor and Taguchi's signal-to-noise ratio. As a solution search methodology, the modified design space reduction method based on orthogonal arrays is employed to exploit an optimal robust design alternative. To illustrate the proposed methodology, a case study is performed on simulation results, where an optimal robust design alternative is obtained with a moderate number of iterations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.125-131
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• 2002

Surface defects in injection molded parts are due to the unsteady flow of polymer melt which are related to the geometries of cavity and gate, the operational conditions of injection and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for three kinds of PCs which have different molecular weight and structure, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes that are tensile, flexural and impact test specimens with various gate and cavity thicknesses. Through this study we have observed that the formation of surface defect associated with jetting during filling stage in injection molding is strongly related to die swell. This means that the jetting is strongly affected by the elastic property rather than the viscous property in viscoelastic characteristics of molten polymer. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mold design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting and associated surface defects regardless of magnitude of elastic property. It also enlarges process window that can produce steady flow of polymer melt in injection molding.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.322-329
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• 1995

Series of experimental work was performed to mold tensile specimens by using the injection molding machine Mold temperature, melt temperature and packing time were chosen as processing parameters for studying the effects of those conditions on the linear shrinkage of final product. Here, each processing variable was decided from the numerical simulation and resin manufacturer's suggested value. The effects of molding conditions on the linear shrinkage in flow direction of the resin were analyzed by measuring the parts 2, 10, 30 and 60 days after molding. As a result, the linear shrinkage increased with the higher mold and melt temperature, and the change of mold temperature has shown more influence. The linear shrinkage of polypropylene has been found to progress up to 30 day with the lapse of the time, and the amount of the linear shrinkage has shown to be between 2.14% and 2.75%. In addition, the effects of packing pressure on the weight has shown to be extremely significant up to freezing time, and proper packing time of the tensile specimen has been found to be 2.0 seconds.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.426-432
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• 2021

Injection molding is used in many industrial fields such as home appliances, vehicle parts, and electronic device parts because various resins can be molded, leading to mass production of complex shapes. Generally, the empirical prediction method is used to set the initial processing conditions of injection molding. However, this approach requires a lot of cost and its presented solution is not accurate. In this paper, injection molding was simulated through the Moldflow^TM in order to manufacture the spacer for gas insulated switch. Through the simulation, the flow of the resin with respect to the diameter of the inlet was analyzed. It was found that the process was possible at a higher resin temperature as the diameter of the inlet increased. In addition, through thermal analysis during injection of the resin, it was confirmed that a stagnation phenomenon occurred at the insert portion during injection molding, and the temperature of the resin was higher than that of the mold. As in this paper, if the spacer is manufactured by optimizing the injection hole and the temperature of the injection process based on simulation, it is expected that the spacer can be manufactured with high productivity.

• Design & Manufacturing
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• v.17 no.3
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.