• Journal of Convergence for Information Technology
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• v.7 no.1
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• pp.43-48
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• 2017

The design trend is changed with the times. The design trend of recent 21 century is eco-friendly design. The optical illusion design is a new trend of digital convergence era. In this study, optical illusion patterns were designed for furniture with eco-friendly UV-curable resin. The micro-patterns of optical illusion design were fabricated with the micro-mold which was mastered using a semiconductor micro-fabrication process by photolithography technique. The micro-patterns of optical illusion design were manufactured on PET film with a roll-to-roll process using a UV-curable resin. The manufactured PET film of optical illusion micro-pattern exhibits hologram effect, optical illusion effect, and texture of metal with the backside digital printing of metal tone. The furniture of new design concept so-called emotional furniture was manufactured with the various optical illusion design patterns. The optical illusion design patterns by UV mold prospect a new trend of interior design materials.

• Journal of Powder Materials
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• v.19 no.2
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• pp.140-145
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• 2012

This paper describes the manufacturing process of tilting pad gas bearing with a diameter of 5 mm and a length of 0.5-1 mm for power MEMS (Micro Electomechanical Systems) applications. The bearing compacts with nanopowder feedstock were prepared by Ni-metal mold with 2-mold system using LIGA process. The effect of the manufacturing conditions on sintering properties of nanopowder gas bearing was investigated. In this work, Fe-45 wt%Ni nanopowder with an average diameter of 30-50 nm size was used as starting material. After mixing the nanopowder and the wax-based binders, the amount of powder was controlled to obtain the certain mixing ratio. The nanopowder bearing compacts were sintered with 1-2 hr holding time under hydrogen atmospheres and under temperatures of $600^{\circ}C$ to $1,000^{\circ}C$. Finally, the critical batch of mixed powder system was found to be 70% particle fraction in total volume. The maximum density of the sintered bearing specimen was about 94% of theoretical density.

• Journal of Korea Foundry Society
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• v.19 no.6
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• pp.493-500
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• 1999

Squeeze casting was used for fabricating a light metal base composite having high strength and wearresistance. Reactive sintering was used to prepare the preform of Squeeze casting. To utilize Fe-Al intermetallic compounds and SiC particle as a reinforcement, there needs to prepare Fe-Al mixed powder at 50, 60, 70at.%Al, and add SiC powder to the above mixture at 4, 7, 16, 24wt.%. The prepared mixture with SiC was reactive sintered in a tube furnace at $660^{\circ}C$ to get a porous hybrid preform of intermetallic compound and SiC. The preform prepared above was placed in a metal mold, preheated at $660^{\circ}C$ AC4C matrix was injected into the mold with the temperature of the melt at $610^{\circ}C$ After these processes, 66MPa was applied to the mold for 5 minute to finish the whole procedure. The maximum reaction temperature was increased with the increased Al amount, but decreased with the increased SiC amount. The density of the preform was decreased with SiC amount increase in the compacts due to swelling of the preform. An optical microscope was applied to observe the micro structure and the dispersion of the reinforcements. To analyze phases, We utilized XRD, EDS. Hardness test were chosen to get the information of mechanical properties. There were no significant changes in micro structure between the composite and preform. However, it was shown that uniform dispersion of the reinforcers and complete infiltration of the melt into the preform were achieved through the procedure of the squeeze casting. It was observed that the hardness of the composite is decreased with increased SiC amount, resulting from the volumetric expansion of the preform.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.696-701
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• 2016

Multi-stage deep drawing is a widely used industrial manufacturing process, and its applications are gradually expanding to both small products and large metallic products. The USB C-type socket used in smart phones, for example, is manufactured using oval multi-stage deep drawing. The socket is very small and slender and it requires precise manufacturing. The thickness distribution of the final product is guaranteed only if it is uniform throughout the overall process. Therefore, minimizing the height difference between long and short sidewalls after the first operation is important for this goal. An initial blank optimization was performed for an oval-type drawing process based on finite element simulations. The goal was to determine an initial blank geometry that can maintain uniform height and thickness after the first draw operation. The initial blank shape of the sheet metal was optimized, and the results show that it satisfied the conditions of minimal thickness reduction and even thickness distribution. The geometry from the optimized simulation was compared with experimental results, which showed good agreement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.302-307
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• 2016

The technology of multistage deep drawing has been widely applied in the metal forming industry, in order to reduce both the manufacturing cost and time. A battery can used for mobile phone production is a well-known example of multistage deep drawing. It is very difficult to manufacture a battery can, however, because of its large thickness to height aspect ratio. Furthermore, the production of the final parts may result in assembly failure due to springback after multistage deep drawing. In industry, empirical methods such as over bending, corner setting and ironing have been used to reduce springback. In this study, a bottoming approach using the finite element method is proposed as a practical and scientific method of reducing springback. Bottoming induces compression stress in the deformed blank at the final stroke of the punch and, thus, has the effect of reducing springback. Different cases of the bottoming process are studied using the finite element program, DYNAFORM, to determine the optimal die design. The results of the springback simulation after bottoming were found to be in good agreement with the experimental results. In conclusion, the proposed bottoming method is expected to be widely used as a practical method of reducing springback in industry.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.56-62
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• 2000

A fast and precise technique to make 3-dimensional object which is called direct metal shaping process is processed. It is very useful technique in design and inspection. Using this developed system, a solid object is made. In experiment, test parts are built by varying three factors, laser power, scan path, scan speed. This process used device, which is different from the widely used in rapid prototyping in that powder feeding device is used. Spraying powder directly at the focused laser beam and then three dimensional object is made by the deposit of melted metal powder. The optimum scanning path is found to be zigzag path, which had little thermal affection on base metal. As a result of these experiments, it was found that optimum scanning speed is 15mm/sec laser power is 50W. This constructed 3-dimensional object could be used in mold manufacturing directly.

• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.369-376
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• 2020

The life of conventional steel plastic injection molds is long but manufacturing cost and time are prohibitive for using these molds for producing prototypes of products in limited numbers. Commonly used 3D printers and rapid prototyping methods are capable of directly converting the digital models of three-dimensional solid objects into solid physical parts. Depending on the 3D printer, the final product can be made from different material, such as polymer or metal. Rapid prototyping of parts with the polymeric material is typically cheaper, faster and convenient. However, the life of a polymer mold can be less than a hundred parts. Failure of a polymeric mold during the injection molding process can result in serious safety issues considering very large forces and temperatures are involved. In this study, the feasibility of the inspection of 3D printed molds with the surface response to excitation (SuRE) method was investigated. The SuRE method was originally developed for structural health monitoring and load monitoring in thin-walled plate-like structures. In this study, first, the SuRE method was used to evaluate if the variation of the strain could be monitored when loads were applied to the center of the 3D printed molds. After the successful results were obtained, the SuRE method was used to monitor the artifact (artificial damage) created at the 3D printed mold. The results showed that the SuRE method is a cost effective and robust approach for monitoring the condition of the 3D printed molds.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.78-84
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• 2012

Mold may experience deterioration of molding quality as the abrasion of mold occurring due to friction between mold and molded product works as allowance in the course of press process. Therefore, to improve the wear-resistance of mold, methods like nitriding, carburizing, flame and induction surface hardening treatment etc have been applied. However, as such methods are accompanied by problems like shape limitation or product deformation etc, laser surface treatment technology is under review as surface treatment method that can solve such problems. Therefore, in this study, mold material cast iron was surface-treated by using high power diode laser. In previous report 1 and report 2, the heat treatment characteristics were compared by the differences of die materials and shapes, then this paper observed microstructure by using optical microscope and scanning electronic microscope to analyze the structural difference of hardened zone, interface area and base metal after heat treatment. And the structural condition was grasped through EDS. As a result of microstructure, hardened zone showed formation of acicular martensite.

• Korean Journal of Materials Research
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• v.8 no.10
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• pp.879-883
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• 1998

In the vacuum casting process for superalloys, molten metal are poured into the heated ceramic mold up to $1000^{\circ}C~1700^{\circ}C$. The mold has to have the high temperature strength during casting and made by hlgh purity alumina. In this sturdy, the mold was made by low purity alumina and changed silica contents intended to have high strength The 7.7wt.% SiOz specimens have 10- 55% higher strength than others in room and high temp. Therefore, the cast mold has been developed in this study for single crystal vacuum cast by controlling the ratio of fused alumina and colloidal silica which are used commercially for conventional casting in industries.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.2
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• pp.87-92
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• 2015

The injection molding process is widely used in the production of most plastic products. In order to make metal-colored plastic products like those found in modern luxury home alliances, metallic pigments are mixed with a basic resin material for injection molding. However, process control for metal-colored plastic products is extremely difficult due to the non-uniform melt flow of the metallic resin pigments. In this study, the effect of process parameters on the quality of a metal-colored plastic product is evaluated. A rapid mold cooling method using a compressed cryogenic fluid is also proposed to decrease the content of undesired compounds within the plastic product.