• The Korean Journal of Rheology
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• v.3 no.2
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• pp.124-134
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• 1991

세라믹 재료들을 성공적으로 사출성형하기 위한 적절한 사출조건을 얻기 위하여 그 동안 많은 실험을 하여 왔으나 게이트 크기가 미치는 영향에 대한 연구는 미진하였다. 본 연구에선 압출기를 사용하여 미세한 질화규소분말과 결합제시스템을 혼합하였으며 이러한 세라믹혼합물을 이용하여 사출압력, 보압시간, 보압, 배럴온도, 게이트의 형태와 크기 등을 변화시키면서 사출성형 실험을 수행하였다. 55%의 세라믹혼합물을 사출실험한 결과 적절한 게이트의 크기와 형태를 선택하고 105 MPa의 사출압력과 10초의 보압시간, 24$0^{\circ}C$의 배럴온 도와 같은 사출조건하에서 성형한다면 불완전 충전 체적수축과 젯팅현상을 최소화시킬수 있 어 성공적으로 인장시편과 굽힘시편을 성형할 수 있음을 알수있었다. 상용프로그램인 C-MOLD를 이용하여 사출조건과 게이트의 크기를 변화시키면서 혼합물의 유동특성을 해석 하였다. 유동해석 결과. 세라믹혼합물은 순수고분자보다 열전도도가 크고 비열이 작아서 고 화가 빨리 되므로 게이트의 크기는 사출압력, 배럴온도와 같은 사출조건과 더불어 중요한 사풀변수임을 예측할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.54-71
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• 1990

The fabrication of ceramic machine components by injection molding(CIM : Ceramic Injection Molding) is critically dependent on the shaping and binder extraction techniques. Injection molding is of keen interest to ceramic industries because CIM is suitable for making an intricate shape and manufacturing cost is lower than other process when production scale is large. The success of the molding process is dependent on the correct formulation of the organic vehicle and the achievement of optimum filler loading. Fine alumina powders and polyethylene binder systems were employed to prepare moldable blend then produce a simple specimen by compression molding. Flow characteristics of the mixture was evaluated by viscosity measurement. Optimum binder system and ceramic volume loading for injection molding were determind. A good debinding technique was utilized to improve the quality of debinded parts and save the debinding time. The simple ceramic part was successfully sintered after debinding and its microstructure examined with SEM revealed good consolidation.

• Clean Technology
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• v.18 no.2
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• pp.155-161
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• 2012

The purpose of this study is to remove paraffin wax binder effectively from powder injection molded part using supercritical fluids in powder injection molding process. For a thin powder injection molded part about 1-2 mm thickness, paraffin wax binder can be removed rapidly without any defect by traditional supercritical extraction process which has fixed high temperature and pressure condition. But, for a thick powder injection molded part, there are limitations in removing paraffin wax binder by the fixed high process condition because crack occurs at the beginning step. Therefore, here we studied variable condition debinding process that starts with mild process condition at the beginning step and then increase the process conditions simultaneously at each step. To find out the initial process condition that has the highest extraction yield without any defect for each sample thickness, we investigated various supercritical debinding conditions using 1-4 mm thickness ceramic injection molded sample. By using the variable condition debinding process that starts with the initial process condition at the first step and then increasing process conditions simultaneously at each step (temperature from 333.15 to 343.15 K, pressure from 12 to 27 MPa, and $CO_2$ flow rate from 1.5 to 10 L/min), over 95% of paraffin wax binder was removed from the 4 mm thick (10 mm diameter) ceramic injection molded disk samples within 5 hours.

• The Korean Journal of Rheology
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• v.2 no.1
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• pp.67-78
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• 1990

세라믹 분말의 사출성형성을 평가하기 위하여 다양한 혼합체 시스템에 대한 혼합도 와 유변학적 성질을 질화규소 미세분말의 부피비를 변화시키면서 조사하였다. 열가소성 결 합체 시스템은 폴리에틸린 폴리에틸렌 왁스 그리고 미소량의 첨가제를 혼합하여 사용하였 다. 혼합성능을 평가하기 위하여 비분산혼합에서는 총접촉면적비를 그리고 분산혼합에서는 총파괴표면적비를 혼합척도로서 사용하여 정성적으로 모형화하였다. 사용된 혼합기내의 유 동장을 해석하기 위하여 뉴우톤유체를 가정하여 유동해석을 수행하였다. 혼합물의 혼합도는 각각 5분 30분 동안 혼합된 시편을 주사전자현미경 사진에 의해 관찰하여 평가하였다. 또한 혼합물의 사출성형성 그리고 혼합질 점도 토우크 곡선 사이의 관계를 규명하기 위하여 전단 변형를 속도를 따른 점도를 모세관 점도계를 사용하여 측정하였으며 질화규소의 부피비가 60%일 때까지는 만족할 만한 성형성과 혼합질을 가짐을 알 수 있었다.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.298-299
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• 2001

안경렌즈는 유리를 연마하여 제작하거나 단량체를 세라믹 금형에 넣어 캐스팅공법으로 플라스틱 렌즈를 만드는 것이 일반적인 방법이었다. 한편 사출성형에 의한 렌즈 및 안경의 제작은 광학적으로 우수한 재료 및 금형을 개발하지 못하여 국내에서는 시도조차 못하는 형편이다. 구미나 유럽의 일부 국가는 PMMA 및 PC를 이용하여 안경 및 안경렌즈를 개발하고 있으며, 이는 공정을 대폭 줄이기 때문에 대량 생산 및 원가 절감을 이룩할 수 있다. 본 연구에서는 PMMA 및 PC를 이용하여 그동안 성형할 때에 가장 문제가 되었던 오목 렌즈를 제작하기 위한 근본적인 금형 설계의 문제점 해결과 이를 이용한 일체형 안경과 고강도 렌즈의 제작을 고찰하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.37-42
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• 2001

Multi funtional spectacles-cases were designed and manufactured. And folding jointed fishing box-tools were designed and manufactured. Also improments of products by color mathing and ceramic adding were presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.21-26
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• 2014

When iodine container for dental mouth treatment is opened, thread for treatment is cut by the blade in cap of container. Due to the problem of corrosion in a short period time after the reaction of metal blade to iodine solution, it gives impact on patient hygiene. In order to solve the problem, alternative products such as ceramic blade are developed and produced recently. In case of ceramic blade, it is produced by handwork and machine work. In this study, for the quantity production of ceramic blade with powder injection molding, we proposed a delivery system to have uniform charge of 20 cavity. Using Moldflow, simulation on 20 Cavity flow was performed. And then the mold was obtained through mold production and modification.(based on simulation) After injection molding, debinder, sintering process was achieved for ceramic blade, and the cap product was completed via insert injection on ceramic blade. In this study, we verified possibility of quantity production of ceramic blade which showed effective performance for cutting.

• 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 Ceramic Society
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• v.41 no.5
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• pp.395-400
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• 2004

The effects of compositions of binders on the rheological properties of mixtures and the preparation conditions on the formation of defects and the debinding characteristics of compacts for the injection molding of ceramic powders (65 wt% aluminaㆍ35 wt% feldspar) were studied. Ceramic powders were coated with 2 wt% of stearic acid and then mixed with 15, 20, and 25 wt% of Paraffin Wax (PW) and High Density Polyethylene (HDPE) as binders at $160^{\circ}C$ for 2 h. Rheological properties were investigated by using capillary rheometer. Apparent viscosities of mixtures were 80∼300 Paㆍs at 1,000$s^{-1}$ of a shear rate, it was good for the injection molding and depending on the compositions of binders. Short shot was formed at 15H5P5 (the ratio of HDPE : PW=5 : 5 in 15 wt% of binders) compacts without injection pressures and any noticeable defects were not formed at 45 kgf/$cm^{2}$ in 20H5P5 compacts. PW and HDPE were removed by the solvent extraction and thermal debinding method. Thermal debinding of HDPE at $450^{\circ}C$ for 5 h, which followed the extraction of PW was using n-heptane solvent at $70^{\circ}C$ for 5 h. Continuous pores in compacts, which facilitate the removal of HDPE by the thermal debinding, were found to form in the compacts when PW was removed by the solvent extraction. The optimum composition of binder at which binder was removed by thermal debinding without defects while maintaining the compact strength was 20H5P5. Bulk density, porosity and 3-point bending strength of 20H5P5 compact sintered at 1,30$0^{\circ}C$ for 5 h were 2.8, < 3%, and 2,400 kgf/$cm^{2}$, respectively, and can be used as a structural materials.

• Clean Technology
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• v.14 no.1
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• pp.1-6
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• 2008

Removal of paraffin wax from a ceramic injection mold using supercritical $CO_2$ has been studied. The paraffin wax is used as a binder in the ceramic injection molding process. The effects of pressure, temperature and flow rate of supercritical $CO_2$ on the removal of the paraffin wax were investigated. The removal rates were measured with various flow rates of $CO_2$ in the range of 328.15 - 348.15 K and 15 - 30 MPa. The removal rate of paraffin wax increased as the pressure increased. In the effect of temperature, the paraffin wax was effectively removed over 329.15K (melting point of paraffin wax), however, the efffct of temperature was not significant when the temperature was further increased. The increase of $CO_2$ flow rate also affected the removal of paraffin wax. However, the effect of flow rate was not observed when the flow rate reached a certain value. Propane was used as a co solvent in order to remove the paraffin wax effectively. When the propane was added to the $CO_2$, the removal efficiency was improved. The paraffin wax was completely removed from the ceramic injection mold without any change in their shape and the structure.