• Transactions of Materials Processing
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• v.21 no.1
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• pp.36-41
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• 2012

Gas Assisted Injection Molding is a relatively new low-pressure injection molding technique that provides benefits such as reduced part warpage, excellent surface quality without shrink marks, greater design flexibility, etc. In the gas assisted injection molding process, the injected pressurized nitrogen gas flows through designed gas channels and forms hollow sections within the part. However, due to the characteristics of the gas, the design of the gas channels which are the paths for the injected gas is important in order to avoid defects such as gas blowout, fingering, etc. Therefore, in this study, the gas channel design for gas assisted injection molding of exterior display panels was conducted by examining the results of three CAE analyses. The designed gas channel was verified by conducting tryouts using a 450 ton injection molding machine with 3-stage pressure controlled gas kit. In addition, the hollow shapes which were formed by the gas with the installed gas channels were examined by examining the cross sections of the prototypes that were produced. As a result, it was found that exterior display panels can be produced without any defect by applying the gas assisted injection molding technique.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.228-231
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• 2005

In this paper, we present reusable quartz master fabricated by electron-beam lithography and dry etching process of quartz, and results of injection molding based on the reusable quartz master for the manufacturing of nano-scale information media. Since patterned structures of photoresist can be easily damaged by separation (demolding) process of nickel stamper and master, a master with photoresist cannot be reused in stamper fabrication process. In this work, we have made it possible of the repeated use of master by directly patterning on quart in nickel stamper fabrication process. We have designed and fabricated four different specimens including 100nm, 140nm 200nm and 400nm pit patterns. In addition, both intaglio and embossed carving patterns are fabricated for each specimen. In the preliminary test of injection molding, we have fabricated polycarbonate patterns with varying mold temperature. We have experimentally verified the fabrication process of the reusable quart master and possibility of quartz master as direct stamper.

• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.368-374
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• 2005

In the present study we used a diagrammatic analysis of 6 sigma quality control and Taguchi method for injection molding of monitor back-cover, evaluated the influence on the cycle time with part design, mold design, molding process and standardization activity involving design and molding, adopted analysis of sensitivity and effective factors of the part design and molding process conditions for productivity, identified main design molding factors. The contributing factors for the final cycle time could be enumerated as follows; the thickness of hot spot, main nominal part thickness, coolant inlet temperature, melt temperature and cooling line layout, etc.. As a first step, all the critical factors of design process applied to the current monitor housing were investigated through 6 sigma process. Thereafter, the optimal and better critical factors found in the first step were applied to new product design to prove that our process was correct. The Moldflow was used for injection molding simulation, and Minitab software for the statistical analysis, respectively. Finally, the productivity of new design was increased about 33 percents for our specific case.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.269-272
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• 2004

The present study used a diagrammatic analysis of 6 sigma quality control and Taguchi method for injection molding process of monitor back-cover, evaluated the influence on the cycle time with part design, mold design, molding process and standardization activity involving design & molding, adopted analysis of sensitivity and effective factors of the part design and molding process conditions for productivity, identified main design molding factors, as critical ones influencing on the quality and productivity, of which is summarized as design guidance. The main contribution factors for cycle time can be sequentially enumerated as follows; hot spot, part thickness, coolant inlet temperature, melt temperature cooling line layout, etc.. As a first step critical factors of the design process of current monitor housing were investigated. And the optimal and better critical factors found in the first step were applied to a new product proving our process was correct. Moldflow software was used for injection molding simulation, and Minitab software for the statistical analysis. Finally, the productivity was increased by about 33 percents for our specific case.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.8
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• pp.687-694
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• 2008

This paper is focused on the improvement of MOS device reliability related to deuterium process. The injection of deuterium into the gate oxide film was achieved through two kind of method, high-pressure annealing and low-energy implantation at the back-end of line, for the purpose of the passivation of dangling bonds at $SiO_2/Si$ interface. Experimental results are presented for the degradation of 3-nm-thick gate oxide ($SiO_2$) under both negative-bias temperature instability (NBTI) and hot-carrier injection (HCI) stresses using P and NMOSFETs. Annealing process was rather difficult to control the concentration of deuterium. Because when the concentration of deuterium is redundant in gate oxide excess traps are generated and degrades the performance, we found annealing process did not show the improved characteristics in device reliability, compared to conventional process. However, deuterium ion implantation at the back-end process was effective method for the fabrication of the deuterated gate oxide. Device parameter variations under the electrical stresses depend on the deuterium concentration and are improved by low-energy deuterium implantation, compared to conventional process. Our result suggests the novel method to incorporate deuterium in the MOS structure for the reliability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.73-81
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• 2014

In this paper, multiple gate locations and process conditions under concern are automatically optimized by considering robustness to minimize the injection pressure required to mold an automotive dashboard. Computer simulation-based experiments using orthogonal arrays(OA) and a design-range reduction algorithm are consolidated into an iterative search scheme, which is then used as a tool for the optimization process. The robustness of a design is evaluated using an OA-based simulation of process fluctuations due to noise as well as the signal-to-noise ratio. The optimal design solution for the automotive dashboard shows that the robustness of the injection pressure is significantly improved when compared to the initial design. As a result, both the die clamping force and the pressure distribution in the part cavity are also much improved in terms of their robustness.

• Design & Manufacturing
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• v.11 no.3
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• pp.1-7
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• 2017

The fabrication process of micro pattern structure with high precision and high aspect ratio using powder injection molding (PIM) is developed. In the PIM process, the metal powder is mixed with the binder systems and the mixture is injected into the metal mold. The injection molded green parts are debinded and sintered to reach final shape and properties. In this method, the optimization of physical properties such as fluidity and strength of the binder system is essential for perfect filling the high aspect ratio micro-pattern. For this purpose, the correlation between the properties of the binder system and feedstock and ${\mu}-PIM$ process was investigated, and a binder system with low viscosity at low temperature(about $110^{\circ}C$) and high strength after cooling was investigated and applied. Employing this process, high precision parts with line type micro pattern structure which has pattern size $160{\mu}m$ and aspect ratio more than 2 can be manufactured.

• Transactions of Materials Processing
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• v.11 no.4
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• pp.312-322
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• 2002

In this study, an innovative semi-solid die casting technology to replace heavier cast iron compressor parts with lightweight aluminum castings was proposed, and the application possibility for home-appliance component was investigated. The most important factors regarding the semi-solid die casting process are the reheating process of the raw materials to the semi-solid state, specifications of the forming machine, the optimal injection conditions and die design. Materials used in this study were A3S7 and hSn alloys fabricated by the electromagnetic stirring process. The optimal injection conditions for semi-solid die casting process were Presented with the reheating conditions of the semi-solid materials. To investigate the effect of plunger tip shape on the formability and mechanical properties in semi-solid die casting process for complicated shape part, two kinds of plunger tip shape with long and short plunger tip taper are proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.341-345
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• 2001

New technoloty called microcellular foaming process was developed at MIT in 1980's. Although it has many good things, it could not be used it all sides of manufacturing plastics. Because it takes a long time for making foamed goods. So microcellular foaming injection molding process appeared to solve this problem. The first purpose of this research is to measure the impact strength as foaming magnitude of microcellular foamed plastics. There are two methods such as batch process and microcellular foaming injection molding process in making foamed plastics. According to the experimental data, the impact strength of each specimen was measured to find out the influence of foaming magnitude of microcellular foamed plastics.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.61-67
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• 2002

The present work is investigated optimal design for the injection molding process of a hand brake cover. The viscoelastic flow through a hand brake cover shape in the mold were calculated and compared with the experimental data. Numerical analysis reasonably predicted the general performance i.e hold pressure, cooling time and hold pressure time. In order to determine optimal process parameters, Numerical analysis and experiments have been performed for various process conditions. In this study, we obtained to increase in the productivity by $160\%$ by optimal process conditions.