• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.499-506
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• 2013

Heat-treatment is one of the core technologies to enhance various characteristics such as strength, hardness, toughness, abrasion resistance and fatigue resistance for the mold material. This paper focuses on characteristics of the laser heat-treatment according to the cylindrical bar diameter variation in case of the SM45C. From the results of the experiments, it has been observed that the maximum hardness is 744Hv when the power is 1630W and the travel of laser is 0.5m/min. And then, the hardness width, depth and microstructure were observed for characteristics. Finally, when the cylindrical bar diameter size grow, the hardness width decrease whereas hardness depth increase.

• Korean Journal of Materials Research
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• v.13 no.1
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• pp.6-10
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• 2003

Electroplated Ni and Ni-W micro-molds using LIGA-like process for replication of micro-components such as microfluidic parts and micro optical parts have been investigated. In general, it is hard to produce micro-parts using conventional mechanical processes. Micro-mold formed by LIGA-like process could fabricate micro-parts with high aspect ratio. In this paper, fabrication and properties of electroplated Ni molds with varying applied current types as well as those of Ni-W molds were investigated. Ni molds fabricated under pulse-reverse current showed the highest hardness value of about 160 Hv. Ni-W molds showed the hardness of about 500 Hv which was much harder than that of Ni electroplated molds. The above results suggested that high quality micro-molds could be fabricated by using Ni electroplating of pulse-reverse type for core molds and sequential Ni-W alloys coating.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.266-270
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• 2007

Small injection molded articles such as lens and mobile product's parts are usually molded in multi-cavity mold. The problems occurred in multi-cavity molding are flow imbalance among the cavities. The flow imbalance affects on the dimensions and physical properties of molded articles. First of all, the origin of flow imbalance is geometrical imbalance of delivery system. However, even the geometry of delivery system is balanced well the cavity imbalance is being developed. This comes from the unsuitable operational conditions of injection molding. Among the operational conditions, injection speed is the most significant process variable affecting the filling imbalances in multi-cavity injection molding. In this study, experimental study of flow imbalance has been conducted for various injection speeds and materials. Also, the filling Imbalances were compared with CAE results. The dimensions and physical state of multi-cavity molded parts were examined. The results showed that the filling imbalances vary according to the injection speed and flow property of resins. Subsequently, the imbalanced filling and pressure distribution in the multi-cavity affect on the dimensions and physical states of molded parts.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.170-175
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• 2005

Generally, Aluminum is superior to durability, light, and characteristics of the material are embossed luminant. So, these characteristics of aluminum will be used automobile interior parts by aluminum injection moulding. Especially, The external of Aluminum plate is engraved differing pattern by roller working. This working can use any longer and be seen gracefully. This is the reason why aluminum insert moulding is used. This feature of research can be characterized by simple process to customize aluminum sheet of blanking and forming process with internal parts of configuration if products are injected by aluminum sheet. Besides, to analysis completed Automobile interior parts to be concerned volumetric shrinkage, best gate location, fill time analysis and so on through the mold-flow before the aluminum insert moulding is worked.

• Design & Manufacturing
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• v.15 no.3
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• pp.32-38
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• 2021

Plate-shaped works are one of the materials that can be applied to the entire industry due to their various shapes and sizes. Plate-shaped parts workpieces are thin and wide, and when processing is completed, they are often bent or deformed in various directions, making it difficult to produce normal products. In particular, this study intends to study the processing deformation and distortion of plate-shaped parts fastened to the jig during milling processing. In this study, a method for preventing deformation occurring in plate-shaped parts was derived through jig element change and CAE analysis, and this was applied to actual processing to produce products with stable dimensions. Through a finite element analysis experiment, it was found that installing two supports on the back of the plate-shaped part results in minimal deformation and the optimal distance between the two supports is 150 mm. Through this experiment, when processing a thin plate product, a support was installed in a direction opposite to the cutting force applied to the thin plate to prevent deformation of the product, thereby improving defects.

• Design & Manufacturing
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• v.10 no.1
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• pp.51-54
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• 2016

Metal sheet forming has been commonly used as the core technology in manufacturing parts of automobiles. It guarantees the highest production rate due to the process of mass production employing the press die. For precision of the product, the accuracy of the molds and its mechanic structures are considered as essential factors. One of these is fine blanking, which is utilized for the production of the metal sheet spring, with which clear sheer surfaces can be achieved in one operation from the materials. However, the current designs of press dies perform the forming analysis with the molds of rigid body, so they are focused on weight lightening by a rule of thumb. Therefore, this paper practice structural analysis about developing the semi fine-fine blanking technology. The semi fine-blanking can be run through the combination of the hydraulic cylinders and normal presses, so this paper analyze the amount of deformation according to the oil pressure. In addition, based on the plasticity of 50CrV4, the materials of the mold parts, the structural analysis and life analysis are proceeded, so they are expected to be useful as data for manufacturing the mold.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.41-44
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• 2009

A multi-stage gear mold including gears of 2mm and 1.5mm diameter was designed and machined in this research for developing micro gear mold manufacturing technology with micro endmill. Mechanical shapes having differential micro teeth were analyzed to be formed as designed and processing conditions were optimized by analyzing machined surface chip and cutting force. Based on the results, a prototype of micro multi-stage gear mold was manufactured.

• Design & Manufacturing
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• v.2 no.6
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• pp.38-42
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• 2008

Recently, the demands of digital camera and miniature camera module for mobile-phone is increased significantly. Lenses which is the core component of optical products are made by the injection molding(plastic lens) or GMP(glass lens). Plastic lens is not enough to improve the resolution and performance of optic parts. Therefore, the requirement of glass lens is increased because it is possible to ensure the high performance and resolution. In this paper, the thermal stress analysis of 3 cavity GMP mold for molding glass lens was performed for estimating the thermal stress and amount of deformation. Finally, the modification plan based on the analysis results was deducted.

• The Plant Pathology Journal
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• v.17 no.5
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• pp.305-307
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• 2001

In March 2000, gray mold was found on day lily (Hemerocallis fulva L.) in Korea. Among the symptoms observed was blight or early rot with chlorotic halo of the leaves. All the isolates obtained from the lesions of the diseased plant parts were identified as Botrytis elliptica, based on the morphological characteristics of conidia. Conidia that formed on conidiogenous cells were not in chains, hyaline to pale brown, unicellular, ellipsoidal to obovate with a single hilum at the base, entirely verruculose, and 21-31 x 12-$23\mu\textrm{m}$ in size. Pathogenicity of the fungus was established by artificial inoculation on day lily plants. This is the first record of gray mold on day lily caused by B. elliptica in Korea.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.363-370
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• 2003

Shrinkage of injection molded parts is different form operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It is also various for different resins which have crystalline structure or not. In this study part shrinkage was investigated for various operational condition and resins; PBT for crystalline polymer, and PC and PMMA for amorphous polymer was used in experiment. Crystalline polymer shows higher part shrinkage by about three times than amorphous polymer. Part shrinkage increased as injection temperature and mold temperature increased and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for large gate size. Part shrinkage according to the gate location was that the position in the part with close to the gate showed large shrinkage and this phenomenon might be occurred by residual stress.