• Journal of Korea Foundry Society
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• v.20 no.5
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• pp.330-335
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• 2000

Functional metal prototypes are often required in numerous industrial applications. These components are typically needed in the early stage of a project to determine form, fit and function. Recent R/P(Rapid Prototyping) part are made of soft materials such as plastics, wax, paper, these master models cannot be employed durable test in real harsh working environment. Parts by direct metal rapid tooling method, such as laser sintering, by now are hard to get net shape, pores of the green parts of powder casting method must be infiltrated to get proper strength as tool, and new type of 3D direct tooling system combining fabrication welding arc and cutting process is reported. But a system which can build directly 3D parts of high performance functional material as metal park would get long period of system development, massive investment and other serious obstacles, such as patent. In this paper, through the rapid tooling process as silicon rubber molding using R/P master model, and fabricate wax pattern in that silicon rubber mold using vacuum casting method, then we translated the wax patterns to numerous metal tool prototypes by new investment casting process combined conventional investment casting with rapid prototyping & rapid tooling process. With this wax-injection-mold-free investment casting, we developed new investment casting process of fabricating numerous functional metal prototypes from one master model, combined 3-D CAD, R/P and conventional investment casting and tried to expect net shape measuring total dimension shrinkage from R/P pare to metal part.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.199-202
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• 2005

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of parts created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool setting errors and surface roughness end tilted mills were used to cut aluminum samples. The results indicate that tool setting errors have significant effects on surface roughness and cutting forces.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.7-13
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• 2005

In the case of fabricating micro pole structures such as column, square-pole and gear shaft by the micro end-milling process, it can be useful in the fields of industry, for example, micro parts, electrode for electrical discharge machining and micro mold for injection molding. In this study, machining factors and the process were analyzed. Machining experiments of various micro pole configurations were performed. Analysis of the change and effect of the cutting force according to the machining conditions was carried out. An analytical study of the deformation of the micro pole caused cutting conditions and cutting force through the finite element method and ANSYS program was carried out. As a result, this research presented a method of fabricating the column pole of below $100{\mu}m$ diameter with high aspect ratio by using micro end-milling process, and based on that, a method of fabricating a variety of applicable structures. Also the minimum size of the pole capable of fabricating through theory and experiment were demonstrated.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.700-707
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• 2009

This paper described finite element analysis (FEA) for fabrication processes of PZT perform using ceramic injection molding (CIM). The viscosity and the PVT characteristics of the manufactured PZT feedstock were measured. The filling patterns, pressure and temperature distributions of the preform were analyzed with TIMON 3D packages during CIM process. The geometrical variables such as gate type, location, and base thickness of the preform were considered. Also the fabrication conditions of the preform were optimized during the entire CIM process. Based on the simulated results, the various good perform was easily fabricated with the CIM process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.627-628
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• 2006

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of pans created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool alignment errors and surface roughness the scallop generating mechanism in the ball-end milling with tool alignement errors has been studied and simulated. The results indicate that tool alignment errors have no significant effects ell the dimension of scallops in for flat planes.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.796-805
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• 2009

In this paper, a fabrication process for PZT preform of 1-3 type piezo-composite were studied using powder injection molding (PIM). The viscosity and the Pressure-Volume-Temperature (PVT) characteristics of the fabricated PZT feedstock were analyzed. The filling patterns, pressure, temperature distributions, and forming defects of the preform were analyzed with 3D TIMON commercial packages during PIM process. Also the fabrication conditions and the delivery system of the preform were optimized during the entire PIM process. Based on the simulated results, the preform having uniform distributions of the PZT rod was fabricated with the PIM process.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.174-178
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• 2006

Pyramid shape of micro pattern is applied to the light guide panel (LGP) to enhance the uniformity of the brightness of the LCD. The micro pyramids are molded in intaglio on the surface of the LGP. The size of each pyramid is 5$\mu$m $\times$ 5$\mu$m on bottom and the height is about 3.5$\mu$m. The pyramids are distributed on the LGP surface randomly to be sparser where the light comes in and denser at the opposite side as a result of a simulation using lightools$^{TM}$ Based on this design, a silicon pattern master and a nickel stamper are fabricated by MEMS process and electro plating process. Intaglio micro pyramids are fabricated on the 6' of silicon wafer from the anisotropic etching using KOH and the process time, temperature of the KOH solution, etc are optimized to obtain precise shape of the pattern. A Wi stamper is fabricated from this pattern master by electro plating process and the embossed pyramid patterns turns out to be well defined on the stamper. Adopting this stamper to the mold base with two cavities, 1.8' and 3.6' LGPs are injection molded.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.130-136
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• 2009

Semi-solid casting(SSC) of magnesium alloys is increasingly being used to produce high quality components. This process is similar to the injection molding of plastics and is called thixomolding. Using this process, higher strength, thinner wall sections and tighter tolerances without porosity are obtained. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. They are widely used for the IT, auto and consumer electronics industries. However, warpage of the thin-walled sections degrade quality of the parts produced in the SCC process. To produce thin-walled magnesium alloy parts, the geometry of gating system on the quality of the finished products should be clearly studied. In this paper, to minimize warpage of the thin-walled sections, Taguchi method is applied to the optimal design of the gate geometry in the thixomolding process. Width, height, length and angle of the gating system are selected for the robust design parameters. Effectiveness of the robust design is verified through the CAE software.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.697-701
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• 2009

A simple method for the fabrication of porous nano-master for the anti-reflection effect on the transparent substrates is presented. In the conventional fabrication methods for antireflective surface, coating method using materials with low refractive index has usually been used. However, it is required to have a high cost and long processing time for mass production. In this paper, we developed a porous nano-master with anti-reflective surface for the molding stamper of the injection mold, hot embossing and UV imprinting by using the aluminum anodizing process. Through two-step anodizing and etching processes, a porous nano-master with anti-reflective surface was fabricated at the large area. Pattern size Pore diameter and inter-pore distance are about 130nm and 200nm, respectively. In order to replicate anti-reflective structure, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.283-289
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• 2014

A Fresnel lens is an optical component which can be used as a cost-effective, lightweight alternative to conventional continuous surface optics. Fresnel lens solar concentrators continue to fulfill a market requirement as a system component in high volume cost effective Concentrating Photovoltaic (CPV) electricity generation. The basic principles of the fresnel lens are reviewed and some practical examples are described. To investigate the performance space of the Fresnel lens, a fast simulation method which is a hybrid between raytracing and analytical computation is employed to generate a cache of simulation data. Injection molders are warming up to the idea of cycling their tool surface temperature during the molding cycle rather than keeping it constant. Heat and cool process are now also finding that raising the mold wall temperature above the resin's glass-transition or crystalline melting temperature during the filling stage and product performance in applications from automotive to packaging to optics. This paper deals with the suitability of Fresnel lenses of imaging and non-imaging designs for solar energy concentration. The concentration fresnel lens confirmed machinability and optical transmittance and roughness measure through manufactured the prototype.