• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.3
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• pp.218-222
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• 2004

We developed the stamper structured mold with moving core type with nano pattern. Among the factors affecting the quality of injection molding plastic parts, We studied the effects of moving core surface heating method on the transcription of injection molding plastic parts with nano structures. Moving core surface heating has been tested by three different methods. The first was conventional injection molding process without heating moving core surface, the second was halogen lamp radiation heating process and the last was MmSH process using gas flame. As a result of making injection molded parts by using thermoplastic amorphous resins such as COC, PMMA, MmSH method which is the most high temperature of moving core surface showed the best nano pattern transcription of the three methods, but the outcome of conventional injection molding process was not better than others.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.414-419
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• 2016

A study of a precision test according to the control method of an injection molding machine was carried out. The effects of the screw stroke, holding pressure, melt temperature on both the hydraulic and electric injection molding machine were examined. In addition, hypothesis testing was performed to determine the deviation of the data obtained in the experiments. The conclusions obtained in this study were as follows. Significant deviations in the screw stroke, melt temperature and holding pressure occurred in that order. The hydraulic type showed significantly more variation between the products compared to the electric type. In addition, using a mini tab from the statistics program, a hypothesis was proposed and the P value of the injection stroke, holding pressure, melting temperature injection stroke and melting temperature had adopted a null hypothesis ($H_0$). The holding pressure, which showed mutual differences, adopted an alternative hypothesis ($H_1$).

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.171-178
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• 2010

The purpose of this research is to develop a standard model for the compilation of production results in molding business to establish the informatization system for the production facility among informatizadon projects which can generate the performance of medium and short term introduction of the project in implementing the system to small and medium industry. The theory on the development method for the standardization of informatization for production facility in molding business applies PSDM (Production System Development Method) for which a number of researches were already done while developing a standardization model by standardizing two processes of raw material demand/supply management and making sum total for production quantity which are main processes for production management process. On the basis of the result of this research, small and medium companies in molding business and relevant specialized IT companies which desire to establish production facility informatization systems will be able to establish more efficient system by applying standardized model, and the result of research will enable to facilitate the establishment of the system for them while providing reliability of the system. Through the application of the result of this research, it will be possible to accomplish the elimination of unreasonable factors in production process, the enhancement of product quality and the saving of production cost.

• Elastomers and Composites
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• v.35 no.2
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• pp.115-121
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• 2000

In comparison with thermosetting rubber, thermoplastic elastomer (TPE) has various advantages such as simple processing, short cycle time and recycling of scrap. These advantages can lead to development of the high value-added rubber products due to reduction of the waste material, manufacturing cost and the defected product. This article involves a dynamic vulcanization method for EPDM/polypropylene blend, and the manufacturing of a fixed glass weather-strip by glass insert molding method using the blend. In order to investigate mechanical properties of the product, tensile strength, elongation, hardness and specific gravity were measured. Also morphological study was carried out using SEM. Developments of an efficient system of production and automatic process by molding of TPE and glass simultaneously are expected.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.134-136
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• 2005

Homogenization method is adopted to predict the permeability tenor for glass fiber plain woven fabrics. Calculating the permeability tensor numerically is an encouraging task because the permeability tensor is a key parameter in resin transfer molding (RTM). Based on multi-scale approach of the homogenization method, the permeability for the micro-unit cell within fiber tow is computed and compared with that obtained from flow analysis for the same micro-unit cell. It is found that they are in good agreement. In order to calculate the permeability tensor of macro-unit cell for the plain woven fabrics, the Stokes and Brinkman equations which describe inter-tow and intra-tow flow respectively are employed as governing equations. The effective permeabilities homogenized by considering intra-tow flow are compared with those obtained experimentally. Control volume finite element method (CVFEM) is used as a numerical method. It is shown that the asymptotic expansion homogenization method is an attractive method to predict the effective permeability for heterogeneous media.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.153-158
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• 1999

An improved method to predict preferred direction of gas in gas assisted injection molding processes is introduced. Resistance of resin flow is defined and this resistance of resin flow is not directly related to the resistance of gas flow. Pressure drop requirement was believed to be proportional to the resistance to gas flow in our previous work. Instead of using the pressure drop requirement, velocity of resin should be compared to predict the gas flow direction. This method predicts the gas flow direction from the knowledge of process variables such as resin flow length, cross section area of cavity, melt temperature, and short shot. A simulation package was used to confirm the method.

• Archives of Plastic Surgery
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• v.33 no.2
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• pp.263-267
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• 2006

In both cosmetic and functional aspects, loss of digital pulp is a common problem. Compound or composite defects of the hand and fingers with exposed denuded tendon, bone, joint, or neurovascular structures may require flap coverage. Most often these lesions can be repaired by using simple local flap, neurovascular flap, thenar flap, and cross-finger flap. But microvascular reconstruction is sometimes needed for large defects. But Authors do not recommend these procedures in case of severe crushing injuries involving multiple finger pulp losses because they have possibility of damage of the vascular network and infection. So we applied distant flaps such as chest flaps, groin flaps, abdominal flaps and etc. And then we applied surgical rubber gloves for remodeling the flap after cutaneous healing. We have acquired satisfactory results, after the simple molding method for distant flap finger by using surgical rubber gloves treatment.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.210-221
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• 2000

Plastic mold designers and frequently faced with optimizing multi-quality issues in injection molded parts. These issues are usually in conflict with each other and thus tradeoff needs to be made to reach a final compromised solution. in this study an automated injection molding design methodology has been developed to optimize multi-quality characteristics of injection molded parts. The features of the proposed methodology are as follows : first utility theory is applied to transform the original multi-objective problem into single-objective problem. Second is an implementation of a direct search-based injection molding optimization procedure with automated consideration of robustness against process variation. The modified complex method is used as a general optimization tool in this study. The developed methodology was applied to an actual mold design and the results showed that the methodology was useful through the CAE simulation using a commercial injection molding software package. Applied to production this study will be of immense value to companies in reducing the product development time and enhancing the product quality.

• Transactions of Materials Processing
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• v.17 no.5
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• pp.322-327
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• 2008

LGP is a key component of LCD back light unit because it determines brightness and sharpness of the display image. Usually, it has optical patterns fabricated on the bottom surface. These optical patterns convert point or line sources placed in the side of LGP to plane source at the top surface by changing the propagating direction of the incident light. In the present paper the LiGA-reflow method was applied to fabricate the LGP mold. Furthermore, the optical simulation considering the replication ratio of pattern height was applied to the pattern design. The optical simulation through systematic correction scheme was adopted to find the optimum distribution of pattern density. Finally, the stamper fabricated by this method was installed in the mold and LGP was produced by injection molding. As a result of luminance measurement for the final product, the average luminance and luminance uniformity was measured 3,180 nit and 84%, respectively. Consequently, the mold fabrication method using the LiGA-reflow and optical simulation(CAE) can save the expense and time compared with the existing fabrication methods(laser ablation and chemical etching).

• Journal of Powder Materials
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• v.6 no.1
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• pp.88-95
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• 1999

The purpose of this study is to investigate the manufacturing feasibility of WC-Co milling inserts via Powder Injection Molding (PIM) process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were Iimited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom is design. P30 grade WC powder (WC-Co-TiC-TaC system) was mixed with RIST-5B133 binder and injection molded into milling inserts (Taegu Tech. Model WCMX 06T 308). The mean grain size of the powder was about 0.8$\mu$m. Injection molded specimens were debound by solvent extraction and thermal degradation method at various conditions. The specimens were sintered at 140$0^{\circ}C$ for 1 hr in vacuum. Carbon content, weight loss, dimensional change, and macro defects of the specimen were carefully monitored at each stage of the PIM process. PIMed WC-Co milling inserts reached 100% full density after sinteing. Its mechanical properties and micro-structures were comparable with the press and sintered milling insert. Carbon content of the sintered WC-Co insert was mainly determained by the atmosphere of thermal debinding. By controlling powder loading and injection molding condition, dimensional accuracy could be obtained within 0.4%. We confirm that PIM can not only be an alternative manufacturing method for WC-Co parts economically but also provide a design freedom for more effieient cutting tools.