• Journal of the Korean Society for Precision Engineering
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• v.13 no.9
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• pp.130-137
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• 1996

In the present paper the effect of various process conditions on the final weight of injection molded rectangular plates has been investigated in detail. The main parameters involved in the simulations were melt temperature, mold temperature, injection speed and packing pressure. The dimensions of the plate used were 100mm long, 2mm of width and polystyrene was used as a molding material. The shear viscosity of the polymeric material was treated as a function of shear rate, temperature and pressure through the whole processes including packing and cooling stages. By increasing a packing pressure the final weight of sample increased linearly. Furthermore, as the melt temperature, the mold temperature and the injection speed increased, the final weight of the injection molded plate decreased within the molding window.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.214-219
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• 2005

Pressure distribution in the cavity during injection molding affects part quality. In this study pressure distributions in the runner, near gate in the cavity, and end of ail in the cavity have been measured using direct pressure sensors for various molding conditions. Molding conditions were injection speed, injection pressure, packing time from filing stage, and packing pressure. Through experiments it was realized that the packing time from filling stage and packing pressure are the dominant factors on the part quality such as part shrinkage. Experimental results have been compared with computer simulations.

• Korean Journal of Agricultural Science
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• v.31 no.2
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• pp.149-160
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• 2004

This study had carried out an analysis of leaf tobacco production cost by cost items, growing stages, and farm sizes per 10a to provide the basic data for determination of the purchasing price of leaf tobacco by KT&G. Considering the survey results of 12 tobacco farm households, the composition rates of production cost by items revealed as 7-10% for land service, 5-22% for depreciation, 13-25% for material costs, 50-65% for labour cost respectively. The production cost of leaf tobacco by growing stages were shown as 15.3% in nursery bed period, 32.3% in main growing period in field, 30.8% in harvesting period and 21.6% in packing period. The magnitude of wage expenditure was appeared as harvesting stage, packing stage, growing stage on main field and nursery bed stage in order. The amount of material costs were revealed as the growing stage in main field, harvesting stage, nursery bed stage and packing stage respectively. The production costs of leaf tobacco per 10a by farm sizes were shown as 1,615,879won for small farm, 1,446,896won for medium farm and 1,454,408won for large farm respectively. The production cost of leaf tobacco had shown decreasing tendency according to increasing farm sizes. To promote the international market competitiveness of leaf tobacco producing farms, labour saving production technologies and cost effective farm size to decrease tobacco production cost should be developed.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.110-116
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• 1994

In this research, the tensile strength of molded parts and pressure distribution were analyzed to study the cavity filling stage and packing stage in injection molding. The measurement of cavity pressure was obtained by a data acquisition system with the installation of transducers in the cavity. Molded parts were tested by a universal testing machine to obtain the tensile strength. For the experimental work, the tensile strength of molded parts increased with longer packing time and exact freezing time of the gate was obtained by a cavity pressure curve. In addition, the effect of packing did not occur and tensile strength was almost constant after early 1.5 sec of the freezing time of gate. Density tended to be higher about 0.2% due to a larger degree of mold temperature and melt temperature. Also, changing pressure in the cavity was effectively sensed. Thereafter, the possibility of the development of pattern recognition expert system was confirmed on the basis of the experimental results.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2355-2363
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• 2002

The accompanying paper, Part 1, has presented the physical modeling and basic numerical analysis results of both the flow-induced and thermally-induced residual stress and birefringence in injection molded center gated disks. The present paper, Part II, has attempted to investigate the effects of various processing conditions of injection/compression molding process on the residual stress and birefringence. The birefringence is significantly affected by injection melt temperature, packing pressure and packing time. Birefringence in the shell layer increases as melt temperature gets lower. The inner peak of birefringence increases with packing time and packing pressure. On the other hand, packing pressure, packing time and mold wall temperature affect the thermally-induced residual stress rather significantly in the shell layer, but insignificantly in the core region. Injection/compression molding has been found to reduce the birefringence in comparison with the conventional injection molding process. In particular, mold closing velocity and initial opening thickness in the compression stage of injection/compression molding process have significant effect on the flow-induced birefringence, but not on tile thermal residual stress and the thermally induced birefringence.

• Radiation Oncology Journal
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• v.11 no.1
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• pp.143-148
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• 1993

From September 1985 through September 1989,56 patients with stage IIIB carcinoma of the cervix were treated with radiation therapy with curative aim. The overall survival at 5 year was $38{\%}$. The survival rate was better for patients treated with combined external radiotherapy and high dose rate intracavitary radiotherapy than with external radiotherapy alone. No significant survival difference was observed between the unilateral and bilateral parametrial extension of the tumor Seventeen patients experienced recurrence within the irradiated field with a loco-regional recurrence rate of $30{\%}$. Ten patients had complications ($18{\%}$). The complications were mild in three, moderate in four, and severe in three patients. A study was made on the relationship between the fraction numbers of intracavitary radiotherapy, vaginal packing and the complication rate, respectively. In this analysis author observed that the significant treatment factor influencing the survival of cervical cancer was the use of intracavitary radiation, and meticulous vaginal packing could decrease the late complication rate of radiotherapy of cervical cancer.

• Journal of the Korean Dietetic Association
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• v.15 no.2
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• pp.152-167
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• 2009

The purpose of this study was to evaluate changes in the microbiological safety of food ingredients supplied to elementary school food services during processing. For this purpose, fifteen food ingredients and twelve factories were chosen in the provinces of Daegu and Gyeongbuk. Total plate counts and coliform counts were reduced in the ingredients after washing, but they increased after packing. After packing, the following levels of total plate counts and coliforms were detected, respectively: peeled bellflower roots ($1.2{\sim}3.6{\times}10^6$, $3.1{\sim}4.6{\times}10^5$ CFU/g), blanched vegetables ($5.6{\times}10^3{\sim}2.0{\times}10^5$, <5~$1.5{\times}10^4$ CFU/g), soybean curd (<5~$5.4{\times}10^3$, <5~$2.2{\times}10^3$ CFU/g), buckwheat starch jelly (<5, <5 CFU/g), soybean sprouts ($1.2{\times}10^6{\sim}1.8{\times}10^7$, $2.4{\times}10^5{\sim}4.3{\times}10^6$ CFU/g), mackerel ($2.2{\times}10^2$, $1.3{\times}10^2$ CFU/g), chicken ($3.8{\times}10^4$, $6.7{\times}10^2$ CFU/g), pork ($6.7{\times}10^2$, <5 CFU/g), and beef ($9.4{\times}10^2{\sim}5.2{\times}10^4$, <5~$2.1{\times}10^3$ CFU/g). Generally, the microbiological safety of the food ingredients was better during the processing stage than during the other stages, with the exception of packing. Staphylococcus aureus, E. coli, and Bacillus cereus were detected in small amounts on the peeled bellflower roots, chicken, and pork, respectively. These results indicate that peeled bellflower roots, chicken, and pork need to be sanitized at the washing stage and cross contamination must be prevented at the packing stage.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.224-229
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• 2016

Recently, polymeric micro-fluidic biochips with numerous micro patterns on the surface were fabricated by injection molding for realizing low-cost mass production of devices. To evaluate the effects of process parameters on large-scale micro-structure replication, a $50{\times}50mm^2$ tool insert with surface structures having a patterns of trapezoidal shapes (height: $30{\mu}m$) was employed. During injection molding, PMMA was used; packing phase parameters and mold temperature were investigated. The replicated surface textures were quantitatively characterized by confocal laser microscopy with 10-nm resolution. The degree of replication at low mold temperatures was found to be higher than that at high mold temperature at the beginning of the packing stage. Thereafter, the degree of replication increased to a greater extent at higher mold temperatures; application of higher mold temperatures improved the degree of replication.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1150-1160
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• 1993

The behavior of polystyrene in the strip cavity during the packing and cooling stages for an injection molding process is examined numerically. The mathematical model is based on the unified post-filling model and finite element/finite difference methods are used to solve simultaneously the continuity, momentum and energy equations coupled to an equation of state. Simulated results show that the density of the molded parts is lower in the core than at the skin, and that the hotter the melt or the higher the packing pressure, the higher the density in the core. The density variation during the packing stage comes up to 50% compared with the total density variation. Also, the density variation after gate sealing and the effect of cooling rate on the equation of state are negligible.