• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
• /
• pp.422-428
• /
• 2001

The term High Speed Machining has been used for many years to describe end milling with small diameter tools at high rotational speeds, typically 10,000 - 100,000 rpm. The process was applied in the aerospace industry for the machining of light alloys, notably aluminium. In recent year, however, the mold and die industry has begun to use the technology for the production of components, including those manufactured from hardened tool steels. With increasing cutting speed used in modern machining operation, the thermal aspects of cutting become more and more important. It not only directly influences in rate of tool wear, but also will affect machining precision recognized as thermal expansion and the roughness of the surface finish. Hence, one needs to accurately evaluate the rate of cutting heat generation and temperature distributions on the machining surface. To overcome the heat generation, we used to cutting fluid. Cutting fluid play a roles in metal cutting process. Mechanically coupled effectiveness of cutting fluids affect to friction coefficient at tool-work-piece interface and cutting temperature and chip control, surface finish, tool wear and form accuracy. Through this study, we examined the behavior of heat generation in high-speed machining and the cooling performance of various cooling methods.

• 펄프종이기술
• /
• 제46권4호
• /
• pp.1-10
• /
• 2014

In papermaking industry, inorganic fillers are widely used for the purpose of improving opacity, brightness, printability, uniformity and dimensional stability. They are also useful for production costs and energy savings. In the past, inorganic fillers in papermaking industry only focused on micro-scale but recently, new trials on nano-powdered technology are applying. Even nano-powdered fillers are rapidly utilized for improving the optical and surface properties in coating and surface sizing, there still have some problems in wet-end process due to poor dispersibility and retention. In this study, nano-particled calcium carbonate was produced by milling the PCC and its applicability between micro sized and nano sized calcium carbonated was compared in wet-end process, and finally the sheet properties were evaluated. Nano-PCC was not retained in sheet structure without applying retention system, but with retention system nano-powdered PCC was absorbed on fiber surface with expanding the fiber networks. The application of PAM-bentonite system has resulted in high ash retention and bulky structure for copier paper, and good optical properties in brightness and opacity. However, it required to solve the weakness of low tensile property due to interruption of hydrogen bonding by nano fillers.

• 한국정밀공학회지
• /
• 제18권7호
• /
• pp.143-148
• /
• 2001

In this study, a mechanistic model of cutting force components in up and down end milling process is presented. Using this cutting force model of 4-tooth endmills with various helix angles, cutting force variation of inconel 718 has been predicted. Predicted values of cutting force components are coincide well with the measured ones. As helix angle increases, overlapping effects of the active cutting edges increase. In up endmilling the magnitudes of radial and feed cutting force componts FX and FY are lowest when the helix angle is $40\{\circ}$, but in down endmilling the magnitudes of these values increase slightly as helix angle becomes large.

• 산업공학
• /
• 제19권1호
• /
• pp.43-52
• /
• 2006

In order to make best use of NC machine tools with minimal labor costs, they need to be in operation 24 hours a day without being attended by human operators except for setup and tool changes. Thus, unattended machining is becoming a dream of every modern machine shop. However, without a proper mechanism for real-time monitoring of the machining processes, unattended machine could lead to a disaster. Investigated in this paper are ways to using PC camera as a real-time monitoring system for unattended NC milling operations. This study defined five machining states READY, NORMAL MACHINING, ABNORMAL MACHINING, COLLISION and END-OF-MACHINING and modeled them with DEVS (discrete event system) formalism. An image change detection algorithm has been developed to detect the table movements and a flame and smoke detection algorithm to detect unstable cutting process. Spindle on/off and cutting status could be successfully detected from the sound signals. Initial experimentation shows that the PC camera could be used as a reliable monitoring system for unattended NC machining.

• Korea-Australia Rheology Journal
• /
• 제14권3호
• /
• pp.107-114
• /
• 2002

Residual stress distribution in injection molded short fiber composites is determined by using the layer-removal method. Polystyrene is mixed with carbon fibers of 3% volume fraction (4.5% weight fraction) in an extruder and the tensile specimen is injection-molded. The layer-removal process, in which removing successive thin uniform layers of the material from the surface of the specimen by a milling machine, is employed and the resulting curvature is acquired by means of an image processing. The isotropic elastic analysis proposed by Treuting and Read which assumes a constant Yaung’s modulus in the thickness direction is one of the most frequently used methods to determine residual stresses. However, injection molded short fiber composites experience complex fiber orientation during molding and variation of Yaung’s modulus distribution occurs in the specimen. In this study, variation of Yaung’s modulus with respect to the thickness direction is considered for calculation of the residual stresses as proposed by White and the result is compared with that by assuming constant modulus. Residual stress distribution obtained from this study shows a typical stress profile of injection-molded products as reported in many literatures. Young’s modulus distribution is predicted by using numerical methods instead of experimental results. For the numerical analysis of injection molding process, a hybrid FEM/FDM method is used in order to predict velocity, temperature field, fiber orientation, and resulting mechanical properties of the specimen at the end of molding.

• 한국해양공학회지
• /
• 제11권3호
• /
• pp.56-68
• /
• 1997

This work was intended to study the effect of a partial pressure ratio and a total pressure of reactive gases on the properties of TiC$_{x}$N$_{1-x}$ . coated layer. In this regard, various TiC$_{x}$N$_{1-x}$ coatings were synthesized with C2112 and N2 Mixture gas of different compositions by Arc Ion Plating process which has been highlighted for an industrial purpose. It was revealed from colors and X-ray diffraction patterns that the concentration of carbon of a TiC$_{x}$N$_{1-x}$ coating increases with a partial pressure ratio (PC$_{2}$H$_{2}$/PN$_{2}$) as well as a total pressure Of $C_{2}$H$_{2}$ and N$_{2}$ mixture gas. Accordingly, the hardness of TiC$_{x}$N$_{1-x}$ coated layer increased but the adhesion to the substrate of SKH 51 was degraded. On the other hand, the deposition rate was independent of a partial pressure ratio and a total pressure of mixture gas. It was found that a uniform gas distribution is critical for an industrial application since the composition of a coating depends strongly on the location of a substrate inside of the furnace. As a result of milling tests with different TiC$_{x}$N$_{1-x}$ coated end mills, the one which has a low carbon concentration was better than others studied in this work.d in this work.

• 한국세라믹학회지
• /
• 제40권9호
• /
• pp.874-880
• /
• 2003

AIN-BN계 머시너블 세라믹의 미세조직, 기계적 성질 및 기계 가공성에 미치는 h-BN 첨가의 영향을 조사하였다. 소결체의 상대밀도는 h-BN 첨가량의 증가와 더불어 감소하였다. 또한, 4점 굽힘 강도도 AIN 단미의 238 MPa에서 30 vo1% BN 첨가에 의해 182 MPa까지 감소하였다. 낮은 탄성계수와 AIN 매트릭스와 h-BN 입자와의 열팽창계수의 차이에 의해 발생한 잔류인장응력에 의해 AIN-BN 복합재료의 강도가 감소되었다고 생각된다. 판상형태의 h-BN 입자에 의해 균열편향과 pull-out은 증가하였으나, 파괴인성은 BN 첨가량과 더불어 감소하였다. AIN 분말표면에 존재하는 알루미나와 소결조제인 $Y_2$O$_3$와의 반응에 의해 2차상인 YAG상과 ${\gamma}$-Al$_2$O$_3$상이 생성되었다. AIN에 10～30 vo1%의 BN을 첨가한 복합재료에 대하여 수행한 절삭시험에서 절삭력과 배분력은 h-BN 첨가량에 따라 감소하였으며, 우수한 기계 가공성을 입증하였다. 또한, 모든 시편에서 짧은 시간 내에 0.5 $\mu$m (Ra) 이하의 비교적 양호한 표면 거칠기에 도달할 수 있었다.