• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.284-287
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• 2002

During resin transfer molding(RTM) process, in case of thick parts, resin flow and void formation should be modeled three dimensionally even though for parts of small thickness, resin flow and void formation can be modeled two dimensionally. In this study, numerical simulations of three dimensional mold filling and void formation during RTM process.

• Design & Manufacturing
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• v.16 no.3
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• pp.58-65
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• 2022

Micro-fluidic chip has been fabricated by lithography process on silicon or glass wafer, casting using PDMS, injection molding of thermoplastics or 3D printing, etc. Among these processes, 3D printing can fabricate micro-fluidic chip directly from the design without master or template for fluidic channel fabricated previously. Due to this direct printing, 3D printing provides very fast and economical method for prototyping micro-fluidic chip comparing to conventional fabrication process such as lithography, PDMS casting or injection molding. Although 3D printing is now used more extensively due to this fast and cheap process done automatically by single printing machine, there are some issues on accuracy or surface characteristics, etc. The accuracy of the shape and size of the micro-channel is limited by the resolution of the printing and printing direction or layering direction in case of SLM type of 3D printing using UV curable resin. In this study, the printing direction and thickness of each printing layer are investigated to see the effect on the size, shape and surface of the micro-channel. A set of micro-channels with different size was designed and arrayed orthogonal. Micro-fluidic chips are 3D printed in different directions to the micro-channel, orthogonal, parallel, or skewed. The shape of the cross-section of the micro-channel and the surface of the micro-channel are photographed using optical microscopy. From a series of experiments, an optimal printing direction and process conditions are investigated for 3D printing of micro-fluidic chip.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1020-1027
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• 2003

A traditional mold design has been conducted by an experience-based trial and error, whereby the mold designer would decide the gate locations and processing conditions based on the caring characteristics and its functional requirements. The paper suggests an optimal gate location and processing conditions in the injection molding using a global search method referred to as micro genetic algorithm( ${\mu}$ GA). ${\mu}$ GA yields the optimal solution with a small size of population without respect to design variables for saving time that is needed to calculate the fitness of many individuals. Due to the reason, the paper uses a commercial analysis package of injection molding(CAPA) to analysis a state of flux. In addition to that, axiomatic approach .is applied in the beginning of design. It is a useful method to draw a well-organized and reasonable idea to handle a problem.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.1-6
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• 2020

Micro-structure components applied to various disciplines are steadily demanded with lighter weight and better quality. This is because that ultra thin-wall injection molding has been paid attention with a lot of benefits such as cost reduction, shorter process period, and so forth. However, this technology is complicate and difficult to obtain high quality of products compared with conventional injection molding due to warpage caused by uneven shrinkage and molecular orientation. Since warpage of products directly affects product quality and overall performance of devices, it is essential to predict deformation behavior to achieve high precision of molded products. Therefore, this study aims to find out adequate thin-wall mold design for FPC connector housing by employing Moldflow simulation before application. In addition, experimental research is performed by using a fabricated mold structure based on simulated results to prove accuracy and reliability of the suggested simulation for warpage analysis.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.40-46
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• 2018

The light-weight of the research and development materials is actively carried out by overseas automobile companies and technology development continues in Korea. For the sake of fuel efficiency, the development of lightweight technology by improving the manufacturing method has been very effective. Recently, to maximize the effects of light weight, automotive interior parts have been applied by the micro-cellular injection molding using supercritical fluids and we call the Mucell manufacturing. This technique causes a problem in the quality of the surface of the products, because the shooting cells are revealed as the surface layer of the products by forming micro cells at the center of the products during injection molding. To overcome these phenomenon, we increased the temperature of injection molding using joule heating until critical value. In this study, we have predicted the problem of Mucell injection molding through the finite element analysis as changed the temperature by joule heating. From the result of finite element analysis, we have determined the optimized process and made the injection mold included electric current heating system with Mucell manufacturing analyzed the surface characteristics of the injection product according to changing mold temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.176-179
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• 2009

Injection molding is one of the most general manufacturing processes of polymers. The deformation of final molded parts occurs because of the change of temperature and pressure during injection molding process. The deformation of injection molded parts depends on many operational conditions, such as, melt temperature, injection speed, mold temperature, packing pressure, and the structure of mold. In the present paper, injection molding experiments were performed to find the process conditions to affect the average shrinkage in thickness direction and the replication ratio of fine patterns on the surface for the final injection-molded LGP samples. As a results, in the cases of PC(Polycarbonate), when the melt temperature was under $285^{\circ}C$, both average shrinkage and replication ratios were mainly influenced by packing pressure. However, the replication ratio was more influenced by melt temperature than packing pressure for the cases of higher melt temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.158-166
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• 2003

The paper describes the development and application of advanced evolutionary computing techniques referred to as micro genetic algorithms ($\mu$GA) in the context of engineering design optimization. The basic concept behind $\mu$GA draws from the use of small size of population irrespective of the bit string length in the representation of design variable. Such strategies also demonstrate the faster convergence capability and more savings in computational resource requirements than simple genetic algorithms (SGA). The paper first explores ten-bar truss design problems to see the optimization performance between $\mu$GA and SGA. Subsequently, $\mu$GA is applied to a realistic engineering design problem in the injection molding process optimization.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.940-944
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• 2003

With the increasing demand for plastic micro components, micro-/nano-molding using the mother stamper has received much attention. If the replication temperature is too high, the adhesion between the stamper and the polymer melt may deteriorate the surface quality of the replicated part, excessively wearing down the stamper. In this paper, an experimental method analyzes the temperature dependency of the anti-adhesion property between the actual stamper with patterns of sub-micrometer and the polymer melt. As a practical example, a correlation between the contact angle of the stamper and the surface quality of the molded substrates as a function of the replication temperature, respectively, was obtained quantitatively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1209-1216
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• 2009

Nano-micro hierarchical structures that nanoprotrusions were formed on the network-type microstructures were fabricated using an ultrasonic vibration forming technology. A commercial ultrasonic welding system was used to apply ultrasonic vibration energy. To evaluate the formability of ultrasonic vibration forming, nickel nano-micro hierarchical mold was fabricated and polyethylene (PE) was used as the replication material. The optimal molding time was 3.5 sec for PE nano-micro hierarchical structures. The molding process was conducted at atmospheric pressure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.40-44
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Accordingly, the usage of sandwich structure is very widely applied to the aircraft, the automobile and marine industry, etc., because of these advantages. In this paper, we have investigated the buckling protection of an inner structure plate and the useful corrugated configuration for contact, and the fabrication method of the inner structure plate for large area using the continuous molding process. Also, we have guaranteed the accuracy of the molding process through the micro corrugated mold fabrication and secured the accuracy and analyzed aspect properties of the inner structure plate fabricated for a large area using the partial mold process.