• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.126-131
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• 2005

In the present study, warpage characteristics of mobile phone cover through injection molding process were investigated by using design of experiments. Warpage in plastic injection molding process has a significant effect on quality of product. Effects of injection time, packing pressure, packing time, mold temperature ana melt temperature on warpage of mobile phone cover were considered by CAE analysis and experiment with Taguchi method. The degree of warpage for the injection molded product was measured by using three dimensional CMM. It was shown that temperature parameter has more significant effect on the warpage of mobile phone cover than pressure parameter.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.77-84
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• 2006

An effective technique of sludge separation is required for excess sludge of sewage or wastewater plant. The separation of bulking sludge of paper manufacturing plant was studied using DAF(Dissolved Air Flotation) system. The effects of parameters such as nozzle type, A/S(air/solid) ratio. pressure, injection time of pressured water and saturation time were examined. The results showed that the best nozzle type was flat which had small orifice hole, The optimum A/S ratio and pressure were $7.070\times10^{-3}$(recycle ratio of pressured water $20\%$) and 5atm, respectively. Injection times of pressurized water around 20-25 sesc and flotation time of 30 min appeared to be optimal for the DAF operation. The order of performance of packing was 18 mm > 22 mm > 32 mm.

• Tribology and Lubricants
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• v.25 no.5
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• pp.298-304
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• 2009

An angled labyrinth seal is used for the diaphragm-packing-ring seal design of steam turbine due to its leakage reduction characteristic. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted angle which yields the best leakage reduction. Results show that the optimum value of slanted angle is $-30^{\circ}$ independent of number of labyrinth teeth, inlet pressure, and tooth height to pitch ratio. 3D CFD analysis has been performed for predicting leakage of the angled labyrinth seal. Comparing with the result of 2D CFD analysis, 3D CFD analysis shows 1.4% smaller.

• Clean Technology
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• v.9 no.1
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• pp.43-48
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• 2003

As a result of study on factor affecting absorption efficiency using the structured packing, Mellapak N. 250Y for the chemical absorption of $CO_2$ that cause global warming due to development of industry, it is shown that Mellapak N. 250Y has lower pressure drop and superior efficiency of mass transfer than 25mm Pall ring. Also, in the absorption process, it produces high efficiency in the increase of load and concentration of absorption liquid and produces low efficiency in the increase of temperature. In the effect of overall mass transfer coefficient for 15% MEA on the temperature variation of absorbent, when absorbent temperature for 15% MEA varied as 25, 50, $80^{\circ}C$, overall mass transfer coefficients were shown as 0.83, 1.00, $0.90kmol/m^3-h-kPa$.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.2
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• pp.47-53
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• 2004

In this experiment the effects of the packing structure of pigment on the surface characteristics (smoothness and gloss) of coated paper are studied. Four different kinds of inorganic pigments(clay), ground calcium carbonate(GCC), two of precipitated calcium carbonates(PCC), and two organic pigments(solid bead and hollow type) were used. The method of measuring the relative sediment volume(RSV) was used to analyze the packing structure of coating layer. The relative sediment volume was measured, using the pressure dewatering dry-cake method(PDDM) and centrifuge method. Also, the particle size distribution of coating pigment was determined. The results showed that small amount of organic pigment, added to inorganic pigment, improved smoothness and its effect was greater when GCC was used as inorganic pigment. The efficiency of organic pigment depended upon the inorganic pigment since the organic pigment is packed in the pores formed by the inorganic pigment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.316-319
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• 2002

Injection mold is a manufacturing process used to produce parts of complicated shape at a low cost. Many factors affect the quality of injection molded part during injection molding process. A study on the optimization of injection mold is progressed by using a simulation software like Moldflow. Filling, packing and cooling phases of injection molding processes are analyzed according to the mold design considering the shrinkage of molded part, the degree of filling rate and the wearing of a mold. Taguchi method is applied to analyze the significance of processing parameters and the dynamic characteristics according to the variation of processing parameters. From the results, the mold temperature and packing pressure influenced strongly the shrinkage of injection molded part.

• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.59-63
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• 2008

A theoretical model was developed to describe the flow behavior of a filled polymer in the packing stage of reaction injection molding and predict the residual stress distribution of thin injection-molded parts. The model predictions were compared with experiments performed for phenol-formaldehyde resin filled with wood dust and cured by urotropine. The packing stage of reaction injection molding process presents a typical example of complex non-isothermal flow combined with chemical reaction. It is shown that the time evolution of pressure distribution along the mold cavity that determines the residual stress in the final product can be described by a single 1D partial differential equation (PDE) if the rheological behavior of reacting liquid is simplistically described by the power-law approach with some approximations made for describing cure reaction and non-isothermality. In the formulation, the dimensionless time variable is defined in such a way that it includes all necessary information on the cure reaction history. Employing the routine separation of variables made possible to obtain the analytical solution for the nonlinear PDE under specific initial condition. It is shown that direct numerical solution of the PDE exactly coincides with the analytical solution. With the use of the power-law approximation that describes highly shear thinning behavior, the theoretical calculations significantly deviate from the experimental data. Bearing in mind that in the packing stage the flow is extremely slow, we employed in our theory the Newtonian law for flow of reacting liquid and described well enough the experimental data on evolution of pressure.

• Composites Research
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• v.29 no.1
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• pp.7-15
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• 2016

The quality of polymeric automotive parts depends highly on an injection molding process, which causes various defects, such as warpage, sink marks, weld lines, shrinkage, residual stress, etc. This study is to determine the optimum processing parameters, such as packing pressure, mold temperature, melting temperature, and packing time for the manufacture of polycarbonate buttons in cars on the basis of FEM, the Taguchi method, and analysis of variance (ANOVA). As a result, the optimum processing parameters of buttons made of polycarbonate material were obtained as follows: 140 MPa of packing pressure, $105^{\circ}C$ of mold temperature, $292.5^{\circ}C$ of melting temperature and 1 second of packing time. A gain of S/N (signal to noise) ratio, 10.2, was obtained with the optimum values. Moreover, the melting temperature was found to be the most significant factor followed by the mold temperature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.111-114
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• 2005

Experimental and numerical studies were carried out in order to investigate the processability and the transcriptability of the injection molding of micro structures. For this purpose, we designed a mold insert having micro rib patterns on a relatively thick base part. Mold insert has a base of 2mm thickness, and has nine micro ribs on that base plate. Width and height of the rib are $300{\mu}m\;and\;1200{\mu}m$, respectively. We found a phenomenon similar to 'race tracking', due to 'hesitation' in the micro ribs. As the melt flows, it starts to cool down and melt front located in the ribs near the gate cannot penetrate further because the flow resistance is large in that almost frozen portion. When the base is totally filled, the melt front away from the gate is not frozen yet. Therefore, it flows back to the gate direction through the ribs. Consequently, transcriptability of the rib far from the gate is better. We also verified this phenomenon via numerical simulation. We further investigated the effects of processing conditions, such as flow rate, packing time, packing pressure, wall temperature and melt temperature, on the transcriptability. The most dominant factor that affects the flow pattern and the transcriptability of the micro rib is flow rate. High flow rate and high melt temperature enhance the transcriptability of micro rib structure. High packing time and high packing pressure result in insignificant dimensional variations of the rib. Numerical simulation also confirms that low flow rate causes a short shot of micro ribs and high wall temperature helps the filling of the micro ribs.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.5
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• pp.316-322
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• 2002

A newly isolated heterotrophic marine bacterium, Vibrio alginolyticus, was used to remove a high load of ammonia gas under non-sterile condition. The cells were inoculated onto an inorganic packing material in a fixed-bed reactor (biofilter), and a high load of ammonia, in the range of ammonia gas concentration of 170 ppm to 880 ppm, was introduced continuously. Sucrose solution and 3% NaCl was supplied intermittently to supplement the carbon source and water to the biofilter. The average percentage of gas removed exceeded 85% for 107-day operation. The maximum removal capacity and the complete removal capacity were$19\;g-N\;kg^{-1}$ dry packing material $day^{-1}$ and $16\;g-N\;kg^{-1}$ dry packing material $day^{-1}$, respectively, which were about three times greater than those obtained in nitrifying sludge inoculated onto the same packing material. On day 82, the enhanced pressure drop was restored to the normal one by NaOH treatment, and efficient removal characteristics were later observed. During this operation, the non-sterile condition had no significantly adverse effect on the removability of ammonia by V. alginolyticus.