• 한국재료학회지
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• 제8권7호
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• pp.641-647
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• 1998

원심 분무법으로 제조된 P/M 2011 AI 합금 압출재의 절삭성을 조사하였다. 압출재 내에 분포된 Pb-Bi 입자들은 매우 균일하고 미세하게 분포된다. 절삭속도가 증가할수록 미세한 칩이 생성되며 이송량이 0.1mm/rev 이하에서부터는 연속칩이 생성된다. 표면의 상태는 이송량에 크게 의존하며 절삭깊이와 절삭속도에는 크게 의존하지 않는다. 불연속칩은 분산된 $AI_2O_3$입자와 공정 Pb-Bi 개재물의 존재로 인해서 생성된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.854-857
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• 2000

This paper presents the experimental results of relationship between the machinability and environmental consciousness due to cutting fluid atomization in machining process. Even though cutting fluid improves the machined part quality through the cooling and lubracating effects, its environmental impact is also increased according to the cutting fluid usage. Cutting tool wear is one of criterion for deciding the machinability. A few turning operations were performed to know the qualitative effectiveness of cutting fluid to tool wear improvement. This research can be used as a basis for environmental impact analysis on the shop floor. It can be also facilitate the optimization of cutting fluid usage in achieving a balanced consideration of productivity and environmental consciousness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.907-910
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• 1997

With increasing the needs for micro and precision parts, micro machining technology has been studied to fabricate a small part with high density such as electronics, optics, communications, and medicine industry more than before. But there are many problems to be solved requiring a high-level technology. So this research presents the new method to fabricate a small part through applying chemical mechanical micro machining (C3M) for the Al wafer. Al(thickness I ,u m) was sputtered on the Si substrate. Al is widely used as a lightweight material. However form defect such as burr has a bad effect on products. To improve machinability of ductile material, oxide layer was formed on the surface of AI wafcr before grooving by chemical reaction with HN03(10wt%). And then workpieces were machined to compare conventional micro-machining process with newly suggested method at different machining condition such as load and feed rate. To evaluate whether or not the machinability was improved by the effect of chemical condition, such as the size, the width of grooves 'and burr generation were measured. Finally, it is confirmed that C3M is one of the feasible tools for micro machining with the aid of effect of the chemical reaction.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1853-1856
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• 2003

Multi-layer printed circuit board(PCB) is being used widely for the product with relatively complex circuits such as TV, VTR and FAX. With the rapid enlargement of electronic and IT industry, the hole machining technology on multi-layer PCB is increasingly required to improve. Thus, the micro drilling with ultrasonic vibration can be a good method for hole machining. Unlike conventional drilling, ultrasonic vibration applied drilling introduces less wear and fracture of not only tool but also internal surface of workpiece due to little cutting resistance, thus, machinability can be improved. The experiment is conducted through the comparison between the results of conventional drilling and ultrasonic micro drilling as well as among each results by the variation according to not only feed rate of drill but also amplitude and frequency of ultrasonic vibration. The multi-layer PCB consists of 6 layers and ${\Phi}$0.3 diameter drill was used. As a result, it was found that the state of internal surfaces of holes on multiple layer PCBs is improved by the application of ultrasonic vibration.

• 열처리공학회지
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• 제13권5호
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• pp.303-308
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• 2000

The ring gears of automobile parts are manufactured generally process chart of which is as follows : forging ${\rightarrow}$ annealing or normalizing ${\rightarrow}$ rough machining ${\rightarrow}$ hardening(Quenching-Tempering or carburizing process) ${\rightarrow}$ finish machining. Isothermal annealing process after forging is most effective in the side of improvment of machinability. On this study we selected two kinds of steel;SCM415, SCM435 of most universal and investigated microstructures to find out most suitable condition of heat treatment in proportion continuous cooling and isothermal annealing. As the cooling rate is $5^{\circ}C$ per minute in continuous cooling process, martensite and bainite are coexisted with ferrite and pearlite in SCM435 steel. If the cooling rate is slower than $5^{\circ}C$ per minute, microstructure were only ferrite and pearlite but formation of band structure can't be avoid. On the other hand, microstructure is only ferrite and pearlite regardless of cooling rate because carbon content of SCM415 steel is low. Moreover formation of band structure isn't exposed by faster cooling rate. Most optimal temperature of the isothermal annealing is from $650^{\circ}C$ to $680^{\circ}C$ in SCM435 steel. When holding time is 60 minute with $650^{\circ}C$, the identical ferrite and pearlite microstructures can be obtained.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.735-738
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• 2000

The characteristics of wire electrical discharge machining (WEDM) are governed by many factors such as the power supply type, operating condition and electrode material. This work deals with the effect of wire electrode materials on the machining characteristics such as, metal removal rate, surface characteristics and surface roughness during WEDM A wire's thermal physical properties are melting point, electrical conductivity and vapor pressure. One of the desired qualities of wire is a low melting point and high vapor pressure to help expel the contaminants from the gap. They are determined by the mix of alloying elements (in the case of plain brass and coated wire) or the base core material(i.e. molybdenum). Experiments have been conducted regarding the choice of suitable wire electrode materials and influence of the properties of these materials on the machinability and surface characteristics in WEDM, the experimental results are presented and discussed from their metallurgical aspect. And the coating effect of various alloying elements(Au, Ag, Cu, Zn, Cr, Mn, etc.) to the Cu or 65-35 brass core on them was reviewed also. The removal rate of some coated wires are higher than that of 65-35 brass electrode wire because the wire is difficult to break due to the wire cooling effect of Zn evaporation latent heat and the Zn oxide on the surface is effective in preventing short circuit. The removal rate increases with increasing Zn content from 35, 40 and Zn coated wire

• 한국세라믹학회지
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• 제32권10호
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• pp.1194-1202
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• 1995

The influences of TiC additions to the α-SiC on microstructural, mechanical, and electrical properties were investigated. Electrical discharge machinability of SiC-TiC composites was also studied. Samples were prepared by adding 30, 45, 60 wt.% TiC particles as a second phase to a SiC matrix. Sintering of SiC-TiC composites was done by hot pressing under a vacuum atmospehre from 1000 to 2000℃ with a pressure of 32 MPa and held for 90 minutes at 2000℃. Samples obtained by hot pressing were fully dense with the relative densities over 99% except 60wt.% TiC samples. Flexural strength and fracture toughness of the samples were increased with the TiC content. In case of SiC samples containing 45 wt.% TiC, the fracture toughness showed 90% increase compared to that of monolithic SiC sample. The crack propagation and crack deflection were observed with a SEM for etched samples after Vicker's indentation. The electrical resistivities of SiC-TiC composites were measured utilizing the four-point probe. The electrical dischage machining of composites was also conducted to evaluate the machinability.

• 한국정밀공학회지
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• 제25권12호
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• pp.47-54
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• 2008

Hard turning process can be defined as a single-point machining process carried out on "hard" materials. The process is intended to replace or limit traditional grinding operations that are expensive, environmentally unfriendly, and inflexible. The purpose of this study is to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, tool wear shape and chip formation by the outer cutting of a kind of wear resistant tungsten carbide V30. Hard turning experiments were carried out on this alloy using the PCD (Poly Crystalline Diamond), cBN (cubic Boron Nitride) and PcBN (Polycrystalline cubic Boron Nitride) cutting tools. The PcBN and the usual cBN tools were used to be compare with the PCD tool and the dry turning was carried out. The PcBN is attractive as the tool material which replaces the PCD. The tool wear width and cutting force were measured, and the worn tool and chip were observed. The difference of the tool wear mechanism among the three tool materials was investigated.

• 한국정밀공학회지
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• 제18권2호
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• pp.84-89
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• 2001

In recent years, there is increasing demand of esthetic design and complex function in aerospace, automobile and die/mold industry, which brings into limelight high-precision, high-efficient machining of sculptured surface. This paper deals with the establishment of the optimal tool path on free form surface in high speed ball end milling. Ball end milling is widely used for free form surface die and mold. In this machining, the cutting direction was changed with tool path. The cutting characteristics, such as cutting force and surface form are varied according to the variation of cutting directions. In this paper, the optimal tool path with down cutting in free form surface cutting is suggested.

• 청정기술
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• 제2권2호
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• pp.165-175
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• 1996

절삭가공 공정에 있어서 절삭유제는 환경영향이 가장 큰 요인들 중의 하나이다. 현재의 기술수준에서 환경영향을 줄이기 위한 공정개선의 방법으로 유제의 환경부하에 대한 평가 및 저부하 유제로의 사용대체가 있다. 본 논문에서는 기존의 절삭성을 바탕으로한 절삭유제의 선택방법과 환경영향을 고려한 선택방법을 비교하여 절삭유제의 선택기준을 제시하고 환경부하의 평가방법으로 AMP 방법을 소개한다. 중절삭이며 저속가공인 드릴링가공을 통하여 절삭성과 환경영향을 함께 고려한 절삭유제의 선택과정을 예시한다. 절삭가공의 물질수지를 고려하여 다섯가지의 환경영향의 평가요소를 선정하고 한국공업규격의 다섯가지의 절삭유제를 비교한다. 비수용성 절삭유제가 성능 뿐만 아니라 환경적인 면에서도 수용성 유제에 비하여 우수한 결과를 보여주었다.