• Journal of Powder Materials
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• v.7 no.4
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• pp.228-236
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• 2000

An investigation was carried out on the possibility whether the ball-milling process of low energy could successfully improve the packing density and flowability for MIM application in W-20wt%Cu system. In this study, W-20wt%Cu powder mixture was prepared by ball-milling. W powder was not fractured by low mechanical impact energy used in the present work during the critical ball-milling time, but the ductile Cu powder was easily deformed to the 3 dimensional equiaxed shape, having the particle size similar to that of W powder. The ball-milled mixture of W-20wt%Cu powder had the more homogeneous distribution of each component and the higher amount of powder loading for molding than the simple mixture of W-Cu powder with an irregular shape and a different size. Accordingly, the MIM W(1.75)-20wt%Cu powder compacts were able to be sintered to the relative density of 99% by sintering at $1400^{\circ}C$ for one hour.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.765-766
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• 2006

[ $Mo_2FeB_2$ ] boride base cermets produced by a novel sintering technique, called reaction boronizing sintering through a liquid phase, have excellent mechanical properties and wear and corrosion-resistances. Hence, the cermets are applied to the injection molding die-casting machine parts and so on. We investigated that the effect of deoxidization and sintering temperature on mechanical properties and deformation of the MIM processed cermets. As a result, deoxidization temperature of 1323K and sintering temperature of 1518K were suitable. The MIM products of the cermets showed allowable dimensional accuracy and the same mechanical properties as the press-sintered ones.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.219-220
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• 2006

To understand the effect of powder characteristics on the thermal debinding behavior, PIM parts produced with powders with different particle sizes and particle shapes were examined to determine their weight losses during thermal debinding. The results show that the average diameter of the pore channel in the compact increased when the temperature increased and when coarse powders were used. However, the weight loss rates did not increase proportionally with the pore size. This suggests that the different powders that are frequently used in PIM parts do not affect the thermal debinding rate significantly. This is because the pore size is much larger than the mean free path of the decomposed gas molecules. Thus, the diffusion rates of the gases are not rate-controlling in thermal debinding. The controlling mechanism of the thermal debinding rate is the decomposition of the backbone binder in the PIM parts.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.215-216
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• 2006

To lower the cost of MIM products, the gate and runner materials and green parts with defects are usually recycled. It is necessary to understand what causes the recycled products to deteriorate. The results show that the viscosity of the 1R (recycled once) feedstock was slightly lower than that of the fresh material. However, as the number of recyclings increased, the viscosity increased, while the density decreased, and more defects were noticed duri ng solvent debinding. These deteriorations were mainly caused by the increase of the melting point of the backbone binder and the oxidation of the filler or paraffin wax.

• Design & Manufacturing
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• v.11 no.2
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• pp.9-14
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• 2017

The design and manufacturing tehcnology of IC sockets beyond 0.3mm pitch were presented. We compared the developed IC socket with the conventional one especially on the core metal-insulation part. Advanced machining techniques were employed to provide high precision. Our wire electrodischarge machining and high speed machining centers were able to maintain the micro-scale precision. We performed an injection molding analysis using a commercial analysis tool to predict the performance of the developed IC socket. We found that the solidification of the plastic resin and the high level of the clamping force are responsible for the defects such as incomplete filling and short shot. From these results, we modified the IC socket and successfully remove the defects. We were also able to find out that the new design socket needs less maintenance cost.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1761-1765
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• 2005

The plastic injection molding industry is increasing pressure to reduce the cycle time in order to improve the productivity. The time of a cooling die is a large part of the cycle time. The conformal cooling channels can reduce the cooling time effectively as compared with conventional production die. It is hard to make the die with a conformal cooling channel by the conventional method. This paper introduces the method of a conformal cooling channel manufacturing by the DMT (Direct Metal Tooling) that is a new technology.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.94-97
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• 2002

Micromolding methods are most suitable for mass production of plastic microlens and lens array with low cost. Among the procedures related with micromolding of microlens array, fabrication of mold insect which contains micro cavity of lens shape is the most important stage. In this study, nickel mold inserts for 45 $\mu\textrm{m}$ and 95 $\mu\textrm{m}$ diameters lens way were fabricated using electroforming process. The mother for metal mold inset was made using reflow method. A micro compression molding with polymer powders was used to test the qualities of the metal mold insets. Micro lens profile and surface roughness was measured by interferometric technique and AFM, respectively. The final molded lens replicated the mother well, and had good surface quality.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.759-760
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• 2006

Ti-6Al-4V has low specific gravity, high corrosion resistance and superior mechanical properties but it is very difficult to control oxygen content in MIM process. It is necessary to use powders with coarse particle size to decrease oxygen content of powders, so feedstocks with poor fluidity and sintered bodies with lower density are obtained in such cases. Fine titanium hydride-dehydride powders were blended with atomized powders to accomplish higher fluidity and sintered density. Sintered bodies had higher sintered density and mechanical properties equivalent to those of wrought materials by controlling oxygen content less than 0.35mass%.

• Journal of Environmental Health Sciences
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• v.18 no.1
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• pp.1-5
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• 1992

A study was performed to measure the heavy metal concentrations of suspended particles in iron castings during February, 1990. The heavy metal concentrations were analyzed using patricles atomic absorption spectrophotometer. The results were as fellows 1. The concentrations of suspended paticles by casting process were at furnace 4.19mg/m$^{3}$ at pouring 2.93mg/m$^{3}$ at nonferrous furnace 3.90mg/m$^{3}$, at molding 1.17mg/m$^{3}$, jung ja 2.23mg/m$^{3}$, desanding 5.42mg/m$^{3}$, sand treatment 4.82mg/m$^{3}$, finishing 1,20mg/m$^{3}$. 2. Among the total of 8 iron casting workplaces, the concentrations Fe of furnace was 0.36mg/m$^{3}$, Cu of nonferrous furnace 0.02mg/m$^{3}$, Pb of pouring 0.02mg/m$^{3}$, Cr of desanding 0.01mg/m$^{3}$ and Mn of furnace 0.03mg/m$^{3}$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.9-14
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• 2015

The Direct Metal Tooling (DMT) process is a kind of additive manufacturing processes, which is developed using various commercial steel powders, such as P20, P21, SUS420, and other non-ferrous metal powders. The DMT process is a versatile process that can be applied to various fields, such as the molding industry, the medical industry, and the defense industry. Among them, the application of the DMT process to the molding industry is one of its most attractive and practical applications, since the conformal cooling channel cores of injection molds can be fabricated at a slightly expensive cost by using the hybrid fabrication method of DMT technology compared with parts fabricated with machining technology. The main objectives of this study are to provide various characteristics of the parts made using the DMT process compared with the same parts machined from bulk materials and evaluate the performance of the injection mold equipped with a conformal cooling channel core fabricated using the hybrid method of the DMT process.