• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.137-143
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• 2002

Silica sand, zircon sand, and steel shots were used as mold packing materials in lost foam casting of the aluminum alloy bar. Vibration acceleration in three directions and temperatures in the casting and mold were measured, and packing and cooling characteristics of these materials were investigated. Packing densities increased with increase in vibration magnitude and time, and were $1.41{\sim}1.49g/cm^2$ for silica sand, $2.54{\sim}2.86g/cm^2$ for zircon sand, and $3.92{\sim}4.52g/cm^2$ for steel shots. Sound castings were obtained only without evacuation of the flask during pouring. Solidification time became faster in order of silica sand, zircon sand and steel shot packing because steel shot has the highest cooling capacity of them. Solidification time of steel shot packing was shortened to about 1/2 of silica sand packing. Cooling capacity of sand mold was generally evaluated by heat diffusivity of the mold, however could be simply evaluated with specific heat per unit volume of the packing material in lost foam casting.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4392-4397
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• 2012

In this study, we used the commercial package (Unigraphics) to construct a junction box cable car when laser plastic parts have been processed using urethane resin(TSR-755) as a starting mold material. After construction, we carried out the filing, packing, cooling, and deforming analyzation using Injection Molding Analysis (Simpoe-Mold) to determine the gate positioning and automatic cooling cycle through the examination. The results show that inserting into the injection mold after processing ceramic has reduced the time of thermal conductivity of molding and cooling; and quick selection of gates and cooling lines could possibly cause an improvement of productivity.

• 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.

• Design & Manufacturing
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• v.14 no.1
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• pp.1-7
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• 2020

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.751-756
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• 2017

A molding-type power inductor is an inductor that uses a hybrid material that is prepared by mixing a ferrite metal powder coated with an insulating layer and an epoxy resin, which is injected into a coil-embedded mold and heated and cured. The fabrication of molding-type inductors requires various techniques such as for coil formation and insertion, improving the magnetic properties of soft magnetic metal powder, coating an insulating film on the magnetic powder surface, and increasing the packing density by well dispersing the powder in the epoxy resin. Among these aspects, researches on additives that can disperse the metal soft magnetic powder having the greatest performance in the epoxy resin with high charge have not been reported yet. In this study, we investigated the effect of silanes, KBM-303 and KBM-403, and a commercial dispersant on the dispersion of metal soft magnetic powders in epoxy resin. The sedimentation height and viscosity were measured, and it was confirmed that the silane KBM-303 was suitable for dispersion. For this silane, the packing density was as high as about 72.49%. Moreover, when 1.2 wt% of dispersant BYK-103 was added, the packing density was about 80.5%.

• Design & Manufacturing
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• v.6 no.1
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• pp.67-72
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• 2012

Most of the plastics products have been manufactured by injection molding. Molding trouble in injection-molded parts is caused by changing a molding product and molding process condition, etc. In this study, warpage in the injection molded part have been studied. Specimens are rectangular flat shape with and without ribs. Non-crystalline resins (ABS+GF30%, PC+GF30%) and crystalline resins (PP+GF30%, PA66+GF30%) were used for material. Flat shape ribs showed higher warpage than flat shape without rib by 10 to 41%. the specimens with ribs that are located parallel to flow direction has higher warpage than the specimens with rib that are located perpendicular to flow direction by 11 to 50%. crystalline resins have higher warpage than non-crystalline resins by 22 to 78%. Warpage decreases as packing time increases as injection temperature increases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.46-50
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• 2001

Due to its ability in producing a net-shape product to high precision in a very shot cycle time, injection molding has become one of the most important polymer-processings in the industry today. Recently the CAE applications in the field of injection molding have provided significant contributions to the mold design and process optimization. As a part of such an application the packing process has been studied using C-PARK. The prediction of pressure variations during post-filling stage for amorphous material has been compared with an experimental observation for a simple rectangular geometry of uniform thickness. And the optimal packing processes were calculated using the cavity pressure curve near the gate. As a case study, a warpage simulation was carried out for a DY-HOLDER with the variable number of gates.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.2
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• pp.64-72
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• 2001

Weld line is one of serious troubles which are observed in a plastic part manufactured by a injection molding process. This is caused by many process factors, which are molding pressure, temperature, velocity, location of a injection gate, mold geometry and material properties. investigation on the effects of these process factors to the appearance of a weld line was carried out using a finite element method. Filling and packing analyses were carried out by modifying both the configuration of the injection gates and cavity thickness. Proper locations of the injection gates could be determined by considering molding pressure, temperature, velocity and frozen layer, and whereby the weld line was controled. In order to make a weak appearance of the weld line, flow velocity and flow front in a cavity were also investigated by modifying a cavity thickness. As a result, flow front was extended around the corner in the cavity by changing the flow velocity and hence the appearance of the weld line was much weakened.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.650-654
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• 2020

A combination of Polycarbonate (PC) material and Polymethylmethacrylate (PMMA), fabricated using an injection molding machine, has been investigated to determine its advantages, as studied in Ref. 1). This paper aims to investigate the optimization of PMMA/PC blend for both tensile yield strength and impact strength. Furthermore, interaction effects of process conditions on mechanical properties including tensile yield strength and impact strength of PMMA/PC blend by injection molding process are interpreted in this study. Tensile and impact specimens are designed following ASTM, type V, and are fabricated by injection molding process. The processing conditions such as melt temperature, mold temperature, packing pressure, and cooling time are applied; each factor has three levels. As a result, in comparison with optimization of separated responses, mechanical properties of PMMA/PC are found to decrease when optimizing both tensile and impact strengths simultaneously. The melt temperature is found to be the most significant interaction parameter with the mold temperature and packing pressure. In addition, there is more interaction between the mold temperature and cooling time. This investigation provides a useful understanding of the control of injection molding processing of polymer blends in optical application.