• Transactions of Materials Processing
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• v.18 no.2
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• pp.128-134
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• 2009

The present study covers an integrated simulation method to evaluate optical performance of an aspheric plastic lens by connecting an injection molding analysis with a ray tracing simulation. Traditional ray tracing methods have based on the assumption that the optical properties of a lens are homogeneous throughout the entire volume. This assumption is to a certain extent unrealistic for injection-molded plastic lenses because material properties vary at every point due to the injection molding effects. To take into account the effects of the inhomogeneous optical properties of the molded lens, a numerical scheme is developed to calculate the distribution of refractive index induced from the injection molding process. This index distribution is then reflected onto CODE $V^{(R)}$ simulation and used to calculate ray paths in inhomogeneous media. The proposed tracing scheme is implemented on the tracing of an aspheric lens for a mobile phone camera module.

• Design & Manufacturing
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• v.2 no.6
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• pp.7-10
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• 2008

Injection-stretch blowing system for preform has been developed in this study. The preforms for injection blow molding and injection stretch blow molding are being manufactured by injection molding. However it contains gate mark that affects the bottom crack in the PET bottle. The compression molded preform does not contain gate mark, thus the appearance quality of bottle has been increased and the residual stress near gate(bottom of the bottle) has been reduced. The thickness distributions, haze, and transmittance are well accepted for the preform. Also, flow characteristics of the resin between a core and cavity could be analyzed through computer simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.375-378
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• 2003

In the present study, a new approach to predict the strength of sintered materials has been carried out and a new framework combining neck growth model and ideal pore model has been established based on the results of tensile tests on powder injection molded specimens with the various porosity. Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. PIM delivers structural materials in a shaping technology previously restricted to polymers. 17-4 PH stainless steel powders with average diameters of 10 $\mu\textrm{m}$ were injection-molded into flat tensile specimens sintered at the various temperatures ranging from 900 to 1350$^{\circ}C$ for 1h. The relationships between strength and porosity were applied to the experimental results and verified.

• Transactions of Materials Processing
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• v.16 no.7
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• pp.549-554
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• 2007

The objective of this paper is to investigate into the fabrication technology of cores for the injection mould with three-dimensional conformal cooling channels to reduce the cooling time. The location of the conformal cooling channels has been determined through the injection molding analysis. The mould has been manufactured from a hybrid rapid tooling technology, which is combined a direct metal rapid tooling with a machining process. Several injection molding experiments have been performed to examine the productivity and the validity of the designed mould. From the results of the experiments, it has been shown that the proposed mould can mold a final product within a cooling time of 3 seconds and a cycle time of 21 seconds, respectively.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.173-178
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• 2011

Environmental Stress Cracking(ESC) is one of the most common causes of unexpected brittle failure of thermoplastic polymers. The exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. In this study, ESC of acrylonitirile butadiene styrene(ABS) was investigated as a function of the molding conditions such as injection velocity, packing pressure, and melt temperature. A constant strain was applied to the injection molded specimens through a 1.26% strain jig and a mixture of toluene and isopropyl alcohol was used as the liquid chemical. In order to examine the effects of the molding conditions on ESC, an experimental design method was adopted and it was found that the injection velocity was the dominant factor. In addition, predictions from numerical analyses were compared with the experimental results. It was found that the residual stress in the injection molded part was associated with the environmental stress cracking resistance (ESCR).

• Transactions of Materials Processing
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• v.22 no.1
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• pp.48-53
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• 2013

As the adoption of injection molding technology increases, injected-molded optical products require higher dimensional accuracy and optical stability than ever before. In the present study, four kinds of molding methods, i.e., conventional injection molding (CIM), injection/compression molding (ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding (RICM) were selected in order to investigate the optical anisotropy of a 7 inch Light Guide Plate(LGP) by examining the gap-wise distribution of birefringence and the extinction angle. The results indicate that the compression process can decrease flow-induced birefringence over the whole region and that rapid heating can decrease the birefringence level better than conventional molding. In addition, for the combination of compression and rapid heating a reversal flow was detected from the distribution of the extinction angle near the gate.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.54-59
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• 2011

Optical properties in injection molded plastic lenses for mobile phone camera have been simulated using commercial program, 3D TIMON. Four plastic lenses are being used in mobile phone camera. The quality of photographs taken by mobile phone camera is strongly depends upon optical characteristics of lenses. The variety of optical properties has been investigated according to the injection conditions through the computer simulation. Consequently optimal injection conditions for four lenses have been determined and simulation results of birefringence have been compared with experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.7
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• pp.823-832
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• 2007

This paper presents the static characteristics of EGR-WI combined system. The water injection system was statically characterized by recording the engine exhaust outlet $NO_x$ emissions for comparison with baseline $NO_x$ emissions. Effects of the water injection system on CO and HC emissions and fuel consumption were examined. The research engine used for these experiments was a 103 kW turbocharged, intercooled, 2.5 L VM Motori CIDI engine equipped with a cooled EGR system. Water injection in the intake system demonstrated the potential for significant reductions in engine outlet $NO_x$ emissions. The system has reduced engine outlet $NO_x$ emissions by 40-50%, but caused significant increases in CO and HC emissions, particularly at low loads. Fuel consumption effects were minimal.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.50-56
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• 2011

Injection molding process is one of the popular manufacturing methods to produce plastic parts with high efficiency and low cost. Ball seat for automobile suspension is made by an injection molding process as a part to support pivot function of ball joint consisted of ball stud and housing. It is necessary for a ball seat to have a dimensional stability in the three dimensional inner area to be contacted with ball stud. In this paper, the dimensional stability of inner surface is indirectly analyzed by checking the difference of inner diameter around the circumferential direction and the thickness variation at the top part of ball seat. Measurement was performed by using the coordinate measuring machine and the fixture to hold ball seat. Optimization of injection molding processes such as injection time, cooling time and temperatures of cylinder barrel was derived to reduce the difference of inner diameter and the thickness variation at the top part of ball seat based on the Taguchi method.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.4
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• pp.285-289
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• 2007

This study presents the preform injection molding of the injection stretch-blow molding process for PET bottles. The numerical analysis of the injection molding of a preform is considered in this paper using CAE with a view to minimize the warpage. In order to determine the design parameters and processing conditions in injection molding, it is very important to establish the numerical model with physical phenomenon. In this study, a three dimensional model has been introduced for the purpose and flow simulations of filling, post-filling and cooling process are carried out. The simulations resulted in the warpage in good agreement with the measurements. Also, from the result of numerical analysis, we appropriate -ly predicted the warpage, deformation and thickness distribution along the preform wall.