• Journal of Urban Science
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• v.11 no.2
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• pp.25-30
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• 2022

Resin Transfer Molding FRP (RTM FRP) is a fiber reinforced polymeric plastic which is manufactured by applying pressure to fibers, injecting resin into a mold, and then impregnating it. RTM FRP is a new construction material suitable for producing non-continuum structural elements such as sole plate because it has excellent strength and can produce many members in a short time. In this study, experiments were conducted to estimate the capacity of the bolted connection of RTM FRP. First, a tensile test was conducted to confirm the mechanical properties such as the tensile strength of the RTM FRP to be used for the bolted connection experiments. In addition, experiments were conducted on the bolted connection with the thickness of the RTM FRP and the edge distance of the bolt as variables. In the first experiment, F4.8 bolts were used, and shear failure of the bolt occurred before the RTM FRPs were failed. The F4.8 bolt is a general structural bolts used for the sole plate of a bridge bearing, and it was confirmed that the RTM FRP has a higher bold bearing strength than the shear strength of a F4.8 bolt. In the second experiment, G12.9 bolts were used, and shear failure of the bolt and bearing failure of the RTM FRP occurred simultaneously. In addition, as the thickness of the RTM FRP and the edge length of the bolt increased, the strength of the joint increased. When analogized with the bearing fracture equation of steel plate, the bolted connection of RTM FRP showed a bearing strength coefficient of 0.420 to 0.549 compared to the tensile strength, and it is considered that further research is needed.

• Clean Technology
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• v.18 no.2
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• pp.155-161
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• 2012

The purpose of this study is to remove paraffin wax binder effectively from powder injection molded part using supercritical fluids in powder injection molding process. For a thin powder injection molded part about 1-2 mm thickness, paraffin wax binder can be removed rapidly without any defect by traditional supercritical extraction process which has fixed high temperature and pressure condition. But, for a thick powder injection molded part, there are limitations in removing paraffin wax binder by the fixed high process condition because crack occurs at the beginning step. Therefore, here we studied variable condition debinding process that starts with mild process condition at the beginning step and then increase the process conditions simultaneously at each step. To find out the initial process condition that has the highest extraction yield without any defect for each sample thickness, we investigated various supercritical debinding conditions using 1-4 mm thickness ceramic injection molded sample. By using the variable condition debinding process that starts with the initial process condition at the first step and then increasing process conditions simultaneously at each step (temperature from 333.15 to 343.15 K, pressure from 12 to 27 MPa, and $CO_2$ flow rate from 1.5 to 10 L/min), over 95% of paraffin wax binder was removed from the 4 mm thick (10 mm diameter) ceramic injection molded disk samples within 5 hours.

• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.48-53
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• 2007

LCD-BLU(Liquid Crystal Display - Back Light Unit) consists of several optical sheets: LGP(Light Guiding Plate), light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50{\mu}m$ in diameter on the surface. But the surface roughness of LGP with etched dots is very high, so there is much loss of light. In order to overcome the limit of current etched dot patterned LGP, optical pattern design with microlens of $50{\mu}m$ diameter was applied in the present study. The microlens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP and optical simulation was carried out to know tendency of microlens patterned LGP simultaneously. The attention was paid to the effects of different aspect ratio(i.e. $0.2\sim0.5$) of optical pattern conditions to the brightness distribution of BLU with microlens patterned LGP. Finally, high aspect ratio microlens patterned LGP showed superior results to the one made by low aspect ratio in average luminance.

• Design & Manufacturing
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• v.13 no.4
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• pp.1-9
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• 2019

In-mold Coating is a method that can simultaneously perform injection molding and surface coating in injection mold. The material used for coating is two-component polyurethane which is composed of polyol and isocyanate. L-type mixing head can be used to mix polyol and isocyanate uniformly, and inject them inside the mold cavity. The surface quality of the injection molded products by using in-mold coating depends on the mixing uniformity between main agent and hardener. In this study, flow analysis was performed to design a mixing head for uniform mixing of two-component polyurethane. Especially the effects of design parameters of mixing head on mixing uniformity and nozzle pressure were investigated. The parameters of mixing head were mixing chamber diameter, cleaning cylinder diameter, nozzle alignment angle in the horizontal and vertical direction, and cleaning piston position. It was found that optimal design values were mixing chamber diameter of 3.5 mm, cleaning cylinder diameter of 5.0 mm, nozzle horizontal/vertical alignment angles of 140°/160°, and cleaning piston position of 1.8 mm. The optimal values would be used to develop a two-component mixing head achieving an uniform mixing for in-mold coating.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.7-12
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• 2014

A transparent poly methyl methacrylate (PMMA) optical micro-pyramid array-pattern is designed and fabricated using an injection modeling technique. The device's optical characteristics are tested and analyzed theoretically. In the optical pattern generated using the fabricated PMMA pattern, the components, due to not only refraction but also diffraction, are observed simultaneously. Wave optic modeling and analysis reveals that the energy ratio between the diffraction and refraction in the optical pattern are dependent on the critical dimension of the optical pattern such that the refraction and diffraction tend to be directly and inversely proportional to the pattern dimension, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.123-130
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• 2018

In this study, the optimum design of mold feed systems is determined for plug cover housing (PCH), which is a cover-assembly product that protects the wiring of automobile connectors. The design goal is to achieve the filling balance of the resin in the left and right covers while avoiding the occurrence of weld lines in the hinge as much as possible. For the optimization, an orthogonal array experiment and a main effect analysis of the design factors are performed, and the factors that cause the interactions with the two design characteristics are selected as the design variables. We present some design alternatives, i.e., some combinations of the design variables, and analyze the filling-simulation results, expected molding risk, and cost economics to select an optimum design solution among the design alternatives. In the optimal solution, the weld line is generated at a position outside the hinge, and the filling balance is also acceptable, showing that both design goals can be satisfied simultaneously despite conflicting with each other.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.5-14
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• 2023

In this study, LiDAR-reflective black hollow-structured silica/titania(B-HST) materials are successfully synthesized by employing the NaBH₄ reduction and etching method on silica/titania core/shell(STCS) materials, which also effectively enhance near-infrared(NIR) reflectance. Moreover, core-etched supernatant solutions are collected and recycled for the synthesis of extracted silica(e-SiO₂) process, which successfully applies as filler materials for semiconductor epoxy molding compound(EMC). In detail, B-HST materials, fabricated by the sequential experimental steps of sol-gel, reduction, and sonication-mediated etching method, manifest blackness(L^*) of 13.2 similar to black paint and excellent NIR reflectance(31.1%). Consequently, B-HST materials are successfully prepared as LiDAR-reflective black materials. Additionally, core-etched supernatant solution with silanol precursors are employed for synthesis of homogeneous silica filler materials via sol-gel method. As-synthesized silica fillers are incorporated with epoxy resin and carbon black for the preparation of semiconductor EMC. Experimentally synthesized EMC exhibits comparable mechanical-chemical properties to commercial EMC. Conclusively, this study successfully proposes designing procedure and practical experimental method for simultaneously synthesizing the NIR-reflective black materials for self-driving vehicles and EMC materials for semiconductors, which are materials suitable for the industrial 4.0 era, and presented their applicability in future industries.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1487-1492
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• 2010

The objective of this study is to design the conformal cooling channels for the mould of a plastic drawer of a refrigerator by analysis of three-dimensional injection molding. In order to obtain the desired design of the conformal cooling channels, the influence of the diameter and the position of the conformal cooling channels on the moulding characteristics and the product qualities were quantitatively examined. From the results of the examination, an optimal design of the conformal cooling channels, which ensures uniform cooling and minimum potential deformation of the molded drawers, was estimated. By comparing the designed mould and a conventional mould with linear cooling channels from the viewpoints of the product qualities as well as cooling and cycle times, it was shown that the mould with conformal cooling channels can simultaneously improve the productivity of the injection moulding process and the product qualities.

• Journal of the Korean Society of Safety
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• v.5 no.2
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• pp.32-39
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• 1990

The ${\gamma}$-Fe$_2$O$_3$ compounds were oxidized in the furance after gas detecting sensor made molding as the Fe$_3$O$_4$ the synthesized Fe$_3$O$_4$, by ferrous sulfate and sodium hydroxide. Their sensities on carbon monoxide, ethyl alcohol and L. P. G. were measured at various temperatures, respectively. And then their electrical resistivities, thermal properties (D.T.A. ＆ T.G.A.), were examined about their having an effet on the gas-sensing in company with the effect of pure ${\gamma}$-Fe$_2$O$_3$ and the detecting sensor ${\gamma}$-Fe$_2$O$_3$, which reacts with $K_2$CO$_3$ in the hydrothermal coundition, and the electrical conductive mechanism was reflected simultaneously. It was observed that the electrical conductivities and response ratios showed highest value at the endothermic temperature part, 300~35$0^{\circ}C$ of D.T.A.―curve. Consequently, the response ratios and response times of the hydrothermal detecting sensor were higher than that of pure detecting sensor, the specific surface areas were the highest at the endothermic range of D.T.A.-curve. These response ratios of detecting sensor for $K_2$CO$_3$, process at hydrothermal condition on carbon monoxide appeared higher than that on ethyl alcohol and in case of L.P.G. last.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.22-27
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• 2020

In this paper, we study the methodology to improve productivity and transportation efficiency simultaneously in the manufacturing environment of injection plants which has multiple injection machines arranged in parallel. In general, the post-processes such as finishing are continuously arranged in the injection machine located in the lower level of the injection plants, and one or two workers in charge of post-processing are always arranged. Therefore injection plants have low productivity due to post-processing and the front of the injection machine is very crowded due to various logistics flows. In this paper, we propose the designing methodology of conveyor structure for integrating the post-processes arranged at each injection machine and transporting the injection products to the integrated post-process automatically. Specifically, we propose the models for computing the number of conveyor units into the integrated processes, and for finding the optimal combinations to connect each machines and the conveyors. The proposed model is for the total productivity improvement, which are productivity and transportation efficiency. By applying the proposed model to companies that produce injection parts used for the home appliances, we verify the applicability and the effect of improving productivity and transportation efficiency, which more than 40%.