• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.588-593
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• 2012

Compatibility of unsaturated polyester (UP) and low profile agent (LPA) of polystyrene (PS) have been investigated under various mixing conditions such as the ratio of UP and LPA, mixing time, mixing temperature, and input amount of 2nd UP. It was possible to obtain mixture with small particle size and low phase separation in condition of 35 g of LPA, 25 g of 1st UP input, 5 min of mixing time, 1700 rpm of mixing speed, and 45 g of 2nd UP input. It was found that compatibility of UP and LPA was very sensitive to mixing conditions. In addition, molded sample using sheet molding compound prepared by stable mixing condition appeared good properties such as low water adsorption, low shrinkage, and high gloss.

• Journal of Powder Materials
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• v.4 no.3
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• pp.170-178
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• 1997

An investigation was performed to apply the M3/2 grade high speed steel for metal injection molding using both prealloyed and elementally blended powders. The injected samples were subjected to a debinding step in $H_2/N_2$ gas atmosphere at a ratio that affected the carbon content of the material. The carbon content ranged from 1.4wt.% to 1.43wt%. with increasing $H_2$ content up to 80% $H_2$ in $H_2/N_2$ atmosphere for the prealloyed powders. The carbon contents of the elementally blended powders exhibited 1.44wt.% and 1.62wt.% at 10% $H_2/N_2$ and 20% $H_2/N_2$ gas, respectively. This level decreased to 0.17wt.% upon increasing the $H_2$ content. The sintered density of both powders increased rapidly as the temperature reached the liquid phase forming temperature. After forming the liquid phase, the density rapidly increased to the optimum sintering temperature for the prealloyed powders, whereas the density of mixed elemental powders goes up slowly to the optimum sintering temperature. The optimum sintering temperature and density are 126$0^{\circ}C$ and 97.3% for the prealloyed powders and 128$0^{\circ}C$ and 96.9% for the elementally blended powders, respectively. The microstructure of the specimen at the optimum sintering temperature consisted of fine grains with primary carbides of MC and $M_6C$ type for the prealloyed powders. The elementally blended powders exhibited coarse grains with eutectic carbides of MC, $M_2C$ and $M_6C$ type.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.553-556
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• 2003

End-milling have been used in the industrial world because it is very effective to the manufacture of mechanical parts with various shape. Recently the end-milling processing is needed the high-precise technique with good surface roughness and rapid time in aircraft, automobile part and molding industry. Therefore this study carried to decide the optimum cutting condition for surface roughness and rapid manufacturing time using design of experiment and ANOVA. From the results of experimentation, surface roughness have an effect on cutting direction, spindle speed and depth of cut. And then the optimum condition used Taguchi design is upward cutting in cutting direction, 600rpm in spindle speed, 240mm/min feed rate, 2mm in axial depth of cut and 0.25mm radial depth of cut. By using design of experiment, it is effectively represented shape characteristics of working surface in end-milling.

• Polymer(Korea)
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• v.33 no.6
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• pp.561-568
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• 2009

Small injection molded articles are generally molded by multi-cavity injection molding. The most important thing in multi-cavity molding is flow imbalance among the cavities because it affects the physical property and the quality of products. The cavity filling balance can be achieved by flow balance in the runner through the thermal balance. In this study, novel screw type runner or helical type runner has been developed for the flow balance in the runner and performed experiment and computer simulation. Flow balance has been observed using various screw type runners for several resins such as amorphous and crystalline polymers including low and high viscosities grades. Flow balance experiments have been performed for various injection speeds since the flow balance can be affected by injection speed among the injection conditions. Experimental results have been compared with computational results and they showed good agreement. The cavity filling balance can be achieved by the screw runner where the temperature distribution is uniform through the circulation flow along the screw channel in the screw runner. It has been verified that the novel screw runner is very effective device in flow balance in the multi-cavity injection molding. cavity filling imbalance, multi-cavity injection molding, runner design, screw runner, thermal balance.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.402-407
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• 2002

Laminate tooling process is a fast and simple method to make metal tools directly for various molding processes such as injection molding in rapid prototyping field. Metal sheets are usually cut, stacked, aligned and joined with brazing or soldering. Through the joining process, all of the metal sheet layers should be rigidly joined. When joining process parameters are not appropriate, there would be defects in the layers. Among various types of defects, non-bonded gaps of the tool surface are of great importance, because they directly affect the surface quality and dimensional accuracy of the final products. If a laminate tool with defects has to be abandoned, it could lead to great loss of time and cost. Therefore a repair method for non-bonded gaps of the surface is essential and has important meaning for rapid prototyping. In this study, a rapid laminate tooling system composed of a CO2 laser, a furnace, and a milling machine was developed. Metal sheets were joined by furnace brazing, dip soldering and adhesive bonding. Joined laminate tools were machined by a high-speed milling machine to improve surface quality. Also, repair brazing and soldering methods of the laminates using the $CO_2$ laser system have been investigated. ill laser repair process, the beam duration, beam power and beam profile were of great importance, and their effects were simulated by [mite element methods. The simulation results were compared with the experimental ones, and optimal parameters for laser repair process were investigated.

• Design & Manufacturing
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• v.2 no.1
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• pp.45-50
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• 2008

Micro channel is to fabricate desired pattern on the polymer substrate by pressing the patterned mold against the substrate which is heated above the glass transition temperature, and it is a high throughput fabrication method for bio chip, optical microstructure, etc. due to the simultaneous large area patterning. However, the bad pattern fidelity in large area patterning is one of the obstacles to applying the hot embossing technology for mass production. In the present study, stamper of cross channel with width $100{\mu}m$ and height $50{\mu}m$ was manufactured using UV-LiGA process. Micro channel was manufactured using stamper manufactured in this study. Also replicability appliance was evaluated for micro channel and factors affected replicability were investigated using Taguchi method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.50-55
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• 2007

The purpose of this research is to enhance the luminance of the LED and to improve the implementation of color by mounting an array lens on the LED without special technology in process. The workmanship of key components considering the economical efficiency and the injection molding technology for high quality of the product are essential to achieve it. In this paper, the mold was computer-aided was designed and manufactured by CAM software (NX4) and high speed machining center. the applied final machining conditions were 3,000-5,000mm/min feed speed, 15,000-25,000rpm and ${\Phi}0.3mm$ ball end-mill. And the Flow analysis was performed using the mold flow software(MPI) in order to get uniformity of resin. Injection conditions acquired by the flow analysis and the injection experiment are as follows. The cylinder temperature is $220-260^{\circ}C$, the mold temperature is $70-80^{\circ}C$, the injection time is about 1.2sec, the injection pressure and velocity is each 7.8-14.7Mpa, and the injection velocity is 0.8-1.2m/sec.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.1
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• pp.92-99
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• 2014

An aspherical lens, which resolves several problems with a spherical lens,typically serves asa key part of an optical system. Generally, an aspherical lens is fabricated using a diamond turning machine or by mean of injection molding. However, residual stress and/or tool marks can arise when using a commercial fabricating method such as DTM or injection molding. A polishing process, thus, is commonly used to obtain a high-precision aspherical lens. In this study, a polishing method using MR fluid was applied to minimize several problems, in this case residual stress and the creation of tool marks, during the cutting process. The MR polishing system was developed to polish aspherical lenses. A series of experiments were performed to obtain a very fine surface roughness. PMMA (the lens material for molding) was used as a workpiece, and the gap size, magnetic field intensity, wheel speed and feed rate were selected as the parameters in this study. Finally, a very fine surface roughness of Ra=2.12nm was obtained after MR polishing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.418-423
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• 2018

Recently, research and development of high-value leisure vessels has been carried out in Korea to revitalize the marine leisure industry and tap into the global maritime leisure market. FRP composite materials, which have excellent physical properties and are available for the manufacture of light hulls, are used widely. One of the most important design technologies is to secure structural safety of leisure vessels made from FRP composite materials. In this study, the structural strength was assessed for the design of an 8-meter high-speed planing leisure boat made from FRP composite materials. The design loads to verify the structural safety were calculated according to the rules for the classification of high speed light craft (KR, 2015), and structural analysis was conducted using a finite element model composed of an isotropic shell element, which has equivalent bending rigidity with the FRP sandwich panel. The analysis results were compared with the results of the strength test for fabricated specimens, and all internal structural components are sufficiently satisfied with the structural strength.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.38-43
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• 2007

This paper describes ultrasonically assisted grinding used to obtain a glossy surface quickly and precisely. High-quality surfaces are required for plastic injection molding dies used in the production of plastic parts such as dials for cellular phones. Traditionally, in order to finish the dies, manual polishing by a skilled worker has been required after the machining processes, such as electro discharge machining (EDM), which leaves an affected layer, and milling, which leaves tooling marks. However, manual polishing causes detrimental geometrical deviations of the die and consumes several days to finish a die surface. Therefore, a machining process for finishing dies without manual polishing to improve the surface roughness and form accuracy would be extremely valuable. In this study, a 3D positioning machine equipped with an ultrasonic spindle was used to conduct grinding experiments. An electroplated diamond tool was used for these experiments. Generally, diamond tools cannot grind steel because of excessive wear as a result of carbon atoms diffusing into bulk steel and chips. However, ultrasonically assisted grinding can achieve a fine surface (roughness Rz of $0.4{\mu}m$) on die steel without severe tool wear. The final aim of this study is to realize mirror surface grinding for injection molding dies without manual polishing. To do this, it is necessary to fabricate an electroplated diamond tool with high form accuracy and low run-out. This paper describes a tool-making method for high precision grinding and the grinding performance of a self-electroplated tool. The ground surface textures, tool performance and tool life were investigated A ground surface roughness Rz of 0.14 um was achieved Our results show that the spindle speed, feed rate and cross feed affected the surface texture. One tool could finish $5000mm^2$ of die steel surface without any deterioration of the ground surface roughness.