• Proceedings of the Membrane Society of Korea Conference
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• 1994.10a
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• pp.20-20
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• 1994

오일폐액처리에 있어서 한외여과막을 이용하는 기술은 이미 산업분야에서 성공적으로 적용되고 있다. 그러나 오일폐액처리에 있어서 농도분극 및 겔층 (Gal layer) 형성에 의한 플럭스 감소와 막의 수명 단축은 해결해야할 중요한 숙제로 남아있다. 이와같은 문제제기로부터 본 연구에서는 한외여과막에 의한 오일처리에서 공기를 유입함으로써 플럭스를 향상시켰고, 긍극적으로 막에 의한 수용성 오일 처리 기술의 경제적 효율을 높이는 방법을 연구하였다. 수용성 오일의 막 분리는 일반적으로 농도에 따른 플럭스의 변화가 Gel Polarization Model을 따르는 것으로 보고 있다. 즉 오일의 농도가 농축됨에 따라 플럭스가 급격히 감소하여 어느 농도이상 농축시키기 위해서는 비경제적인 운영을 해야만 한다. 본 연구에서는 플럭스를 향상시키기 위해 오일 용액내로 공기를 유입시켰다. 절삭유 용액속에는 에멀젼을 안정화 시키기 위한 계면활성제가 포함되어 있어 공기를 유입할 경우 용액의 상이 액체에서 거품과 액체와의 혼합상으로 변하게 된다. 이러한 상의 변화로 인해 농도에 따른 플럭스가 Gel Polarization Model을 따르지 않고 농도에 따른 감소가 현저히 둔화됨을 관찰하였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.130-136
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• 2001

The purpose of this study is an evaluation of flat end mills to develop appropriate tools for the high speed machining. First of all, several flat end mills which are produced by different makers are selected to analyze the performances of the tools. Experimental works are also executed to measure cutting farce, tool wear and surface roughness for different cutting conditions. And then the results are compared and analyzed for developing optimal cutting tool in the high speed condition.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.18-19
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• 2002

Si 웨이퍼제조 시 나오는 페슬러지에서 SiC 연마재와 절삭유를 분리해내면 Si 분말을 얻을 수 있다. 본 연구에서의 SiC는 폐슬러지 Si 분말에 C 분말을 혼합하여 제조할 수 있다. Si-C-O 3성분계는 Si, $SiO_2$, SiC, C 4개의 응축상과 CO, SiO, $CO_2$, $O_2$ 4개의 기체상이 가능하고 생성물들 간의 평형관계를 깁스 자유에너지에 의해 평형 반응식이 계산되어질 수 있다. 계산된 평형 반응식은 2개의 SiO, CO 분압이 각각 X, Y 좌표평면에 나타나는 상안정도를 그려볼 수 있다. 상안정도에서 자유도가 2인 경우는, $SiO_2$가 불안정하므로 SiC와 C가 공존하는 영역에서 온도를 독립 변수로 놓으면 나머지 독립 변수는 SiO 나 CO 기체 분압 둘 중 하나가 되어 하나의 직선으로 나타낼 수 있다. 직선을 경계로 각 응축상들의 안정영역을 하나의 좌표평면에 나타낸 후 온도에 따른 SiC의 안정영역을 알아본다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.41-41
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• 2001

포항가속기의 초고진공 세정기술은 초고진공 영역에서의 기체방출을 최소화하기 위한 것으로 발생한 오염원을 추적하여 큰 오염원 부터 시작하여 단계적으로 진행해 미세한 오염원 을 제거해 나가는 방법을 적용하고 있다. 이러한 극청정한 진공표면을 얻기 위해서는 표면과 오염물질 사이의 결합에너지를 극복해야 한다. 오염물 제거 방법으로는 물리.전기.화학적인 방법을 모두 적용하며 그리스 및 절삭유를 비롯해 흡착된 탄화수소와 불순물 성분 또는 산소나 황과 같은 반응성 원소와의 화합물 등을 효과적으로 제거한다. 또한, 세정 과정 에서 생성될 수 있는 수소, 불규칙한 산화물, 질화물, 염화물, 그리고 탄수화물을 최소화하여 초고진공 영역에 도달할 수 있는 방법을 제공한다. 본 논문에서는 포항가속기 연구소의 초고진공 환경을 확보하기 위한 화학세정 설비 및 응용기술, 주요 진공 구성재료의 표면 분석 결과를 소개하고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.69-76
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• 2004

This paper presents a prediction model for the aerosol generation of cutting fluid in turning process. Experimental studies have been carried out in order to identify the characteristics of aerosol generation in non-cutting and cutting cases. The indices of aerosol generation was mass concentration comparable to number generation, which is generally used fur environment criterion. Based on the experimental data, empirical model for predicting aerosol mass concentration of cutting fluid could be obtained by a statistical analysis. This relation shows good agreement with experimental data.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.49-55
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• 2011

Recently, various efforts to make more speedy and precision machine tool to improve productivity and also various efforts to solve environmental problem are going on, so that dry cutting in manufacturing industry, which needs environmental conscious design and development of manufacturing technique, is becoming a very important assignment to solve. Because dry cutting does not use cutting fluid, we need other methods that can be used instead of cutting fluid, which does cooling, lubricating, chip washing, and anti-corrosion. Especially, because turning is a continuous work, the consideration of tool life and surface roughness due to continuous heat and poor lubrication is important. The purposes of this paper are the consideration of how well the compressed air can work instead of cutting fluid, and also the development of the method to select the optimum machining condition by the minimum numbers of experiments through the Taguchi method.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.114-120
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• 2001

It is necessary to develop a new metal cutting technology which does not use cutting fluid, since cutting fluid can have undesirable effect on workers's health and working environment. For this to be possible, it is necessary to replace the conventional method of using cutting fluid, whose basic functions are removing chip and heat, and providing lubrication between tool and chip. In this work, cooled air is utilized in order to replace cutting fluid. Experiments were carried out while cutting workpiece with HSS flat endmill under a variety of supply conditions for cooled air. Also the performance characteristics of the air cooling system. which was built for the experiments, were carefully analyzed. For the reliable operation of air cooling system. moisture contained in the cooled air had to be removed before being supplied to the workpiece and tools. It was found that depending on the amount of its flow rate the temperature of cooled air changes at the time of injection from the nozzle. The flow rate of cooled air also plays an important role in removing the accumulated chip on the workpiece. After comparing the flank wear for the three cases of using cooled air, cutting fluid, and pure dry technique, it was demonstrated that the level of flank wear was similar for the cases of cooled air and cutting fluid. The pure dry technique, however, showed higher level of flank wear than cooled air.

• Resources Recycling
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• v.30 no.2
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• pp.61-67
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• 2021

Scraps are a byproduct of the machining process used for transforming titanium ingots into useful mechanical parts. Scraps take two forms, namely, bulky scraps, which are produced by cutting, and chipped scraps, which are produced by milling. Bulky scraps are comparatively easier to recycle because of their small surface area and less oxygen content; as a result, they pose only a small risk of explosion. In contrast, chipped scraps pose a higher risk of explosion, because of which, their recycling is complicated, resulting in most such scraps being discarded. With the aim of avoiding this waste, we proposed a novel process for converting chipped scraps into stable carbide materials. Methods typically applied to reduce particle size and impair the formation of solid solution type phase in the carbide materials were used to improve the mechanical properties of carbides prepared from chipped scraps. Our novel recycling process reduced carbide production costs and improved carbide quality.

• Membrane Journal
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• v.8 no.4
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• pp.203-209
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• 1998

The cutting oil emulsion microfiltration was carried out on dead-end call and crossflow systems equipped with 0.22 $\mu$m GVHP Millipore and 0.2 m stainless steel Mott microfiltration membranes, respectivdy. The oil drop size in the emulsion was varied from 0.07 to 0.22 $\mu$m. Cake filtration(CFM) and standard pore blocking models(SPBM) were applied to predict the permeation flux. The permeation fluxes of 0.01 vol% oil emulsion followed CFM for dead-end system very well under the condition of 400 rpm and below 100 kPa. The SPBM was, however, suitable for the permeation flux at 400 rpm and above 150 kPa. The oil layer on the membrane surface was destroyed and reproduced repeatedly as operating pressure was suddenly changed from 60 to 200 kPa, and then returned to 60 kPa. Also, we estimated the critical entry pressure(CEP) which is changed from CFM to SPBM, and CEP for dead-end system was around 100 kPa. The CEP increased from around 100 to 150 kPa for the crossflow system as the oil concentration increased from 0.01 to 0.03 vol% when Reynolds number was 7080.

• Clean Technology
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• v.16 no.3
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• pp.172-181
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• 2010

Hydrofluoroethers (HFEs) with fluoride molecules in their structure which are evaluated as the third generation replacement alternatives to chlorofluorocarbons (CFCs) are known to be excellent for removal of nanoparticles and fluoride-type soils due to their low surface tension and high wetting index. In addition, HFEs have good physical properties with no flash point and excellent drying characteristics. But, HFEs also have shortcomings in that they are not effective for removal of organic soils due to their poor solubility in soil. In this study, $C_5$ HFE-based cleaning agents were formulated through addition of solvents such as isopropyl alcohol (IPA), ethyleneglycol monoether (EG), propyleneglycol monoethylether (PM) to HFE-7100 [$CF_3CF_2CF_2CF_2OCH_3$] or HFE-mec-f [$CF_3CHF=CF_2OCH_2CF_3$] with its maximum amount, respectively, in order to have no flash point for the safety in the working environment. These solvents are known to be excellent for dissolving organics in soil. Their physical properties and cleaning abilities for fluxes, water-insoluble cutting oils, and fluoride-type oils were evaluated and compared with those of other cleaning agents with single components. The experimental results show that the HFE-based formulated cleaning agents have various good physical properties which are almost similar to those of a single type of HFE cleaner. They show excellent cleaning ability for fluxes, water-insoluble cutting oils, and fluoride-type oils. These results indicate that the HFE-based formulated cleaning agents can be applicable to various industrial cleaning fields because of their good physical properties and cleaning abilities for various soils.