• 한국생산제조학회지
• /
• 제23권3호
• /
• pp.284-290
• /
• 2014

Aluminum alloy is a core material for structural parts of aircraft and automobiles to reduce the weight and maintain high specific strength. This study evaluates the machinability and investigates the optimal cutting conditions considering the surface integrity and productivity for Al7050-T7451 milling. The machining variables considered are the feed per tooth, spindle speed, axial depth of the cut, and radial depth of the cut. The machinability evaluation of Al7050-T7451 is conducted by analyzing the cutting force signals, acceleration signals, AE signals, and machined surface conditions. The optimal cutting conditions are determined by analyzing the experimental results using response surface methodology for stable machining considering the productivity and surface integrity.

• Design & Manufacturing
• /
• 제2권6호
• /
• pp.11-16
• /
• 2008

In order to satisfy the customer's variant needs for a product quality in recent years, a demand for developing higher precision machining technologies in a lot of application areas such as automobile, cellular phone and semiconductor has been increased more and more. Micro-magnetic induced polishing(${\mu}-MIP$) process is one of these precision technologies. In this study, to verify the parameters' effect of the ${\mu}-MIP$ process on the surface roughness improvement of the inclined workpiece, well planned experiment which was called the design of experiments was carried out. Considered parameters were spindle speed, inductor current, abrasive configuration and working gap between the workpiece and the solid tool. As a result, it was seen that the inductor current and the working gap greatly affected the surface roughness improvement. And to predict the surface roughness of the inclined workpiece, S/N ratio and first-order response surface model was developed.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.922-925
• /
• 2002

Klystron which is micro wave amplifier tube are mainly used in fields of science such as accelerator, nuclear fusion, broadcasting, communication fields, and defense industry fields, tract. The quality of Klystron anode and cavity are determined by form accuracy and roughness of the worked surface. Therefore anode and cavity are restricted the from accuracy strictly and the surface roughness be under Rmax 0.03S. As a work material of anode and cavity, the oxygen-free copper, that is used for optical pares of aerospace and laser mirror is selected. An outside diameter of material is $\Phi$100 mm and an inside diameter is $\Phi$30~33 mm. In this study, to find the optimum ultra precision cuffing condition of oxygen-free copper with diamond turning machine, the surface roughness is examined for various diamond toot nose radius, main spindle speed, fred rate and depth of cut. As a result of experiment, we could machined the anode and cavity with a surface roughness within Ra 3.2 nm, a form accuracy within 0.01 $\mu\textrm{m}$.

• 한국분무공학회지
• /
• 제16권1호
• /
• pp.1-6
• /
• 2011

In recent years, the need for more fuel-efficient and lower-emission vehicles has driven the technical development of alternative fuels such as LPG (Liquefied Petroleum Gas) which is able to meet the limits of better emission levels without many modifications to current engine design. LPG has a high vapor pressure and lower viscosity and surface tension than diesel and gasoline fuels. These different fuel characteristics make it difficult to directly apply the conventional gasoline or diesel fuel pump. Self acting lubricated groove design or coating can be used in high-speed and high precision spindle system like a roller-vane type fuel pump, because of its advantages such as low frictional loss, low heat generation, averaging effect leading better running accuracy and simplicity in manufacturing. Those design method can also affect the atomization of fuel from the injector and the formation of fuel film on the intake manifold. In this study, experiments are carried out to get performance characteristics of initial and steady state operation, The characteristics of vane type fuel pump were investigated to access the applicability on LPLi engine.

• 대한기계학회논문집A
• /
• 제25권8호
• /
• pp.1173-1182
• /
• 2001

Recent noticeable advances of CNC machine tools have considerably improved productivity and precision in manufacturing processes. However, in the respect of productivity some defects still remain because selection of machining conditions entirely depends on the experiences of programmers. Usually, machining conditions such as feed rate and spindle speed have been selected conservatively by considering the worst cases, and it has brought the loss of machining efficiency. Thus, the improvement of cutting force controller has been done to regulate cutting force constantly and to maximize feedrate simultaneously in case that machining conditions change variously. In this study, sliding mode control with boundary layer is applied to milling process for cutting force regulation and in a commercial CNC machining center data transfer between PC and PMC (programmable machine controller) of CNC machine is done using a standard interface method. And in the cutting force measurement, an indirect cutting force measuring system using current signal of AC servo is adopted in order not to use high-priced equipment like tool dynamometer. The purpose of this study is to maximize the productivity in milling process, thus its results can be applied to cases such as rough cutting process.

• 한국주조공학회지
• /
• 제21권6호
• /
• pp.350-358
• /
• 2001

The machinability of cast iron is closely related to its microstructural property. In this study, the effect of graphite mophology and matrix microstructure on machinability in several commercial cast irons(GC 25, GCD 45, GCD 50, GCD 70, GCD HSMo, GCMP) was investigated. To estimate the machinability, turning test was carried out under conditions of spindle speed 80m/min, depth of cut 0.25mm, feed 0.16mm/rev and cutting distance 1 km. Thrust force in turning test decreases in the order of GCMP, GCD 70, GCD 50, GC 25, GCD 45 and GCD HSMo. i.e. machinability increases in this order. The superior machinability of GC 25 is caused by flake type graphite which acts as chip braker and provides lubrication during machining. Consequently, soft ferritic cast irons exhibit superior machinability compared with pearlitic cast irons.

• 한국인터넷방송통신학회논문지
• /
• 제10권2호
• /
• pp.13-18
• /
• 2010

오늘날의 스팸 메일이 메일 서버와 네트워크 저장장치의 대부분을 차지함으로 인해 네트워크 부하와 같은 부정적인 문제가 발생하고 있으며 사용자 입장에서는 스팸을 삭제하기 위한 시간과 자원 소모 같은 문제를 가지고 있다. 자동 스팸 메일 필터링은 문제 해결위한 필수적인 요소로 부각 되었다. 대표적인 방법은 나이브 베이지안 방법과 달리 PCA를 통하여 많은 차원을 가지는 스팸 테이터 집합을 몇 개의 주축으로 차원을 축소 시켜 연차 처리의 부담을 줄이고 특정 집으로 분류를 위한 로지스틱 회귀 분석 방법을 사용하여 스팸 필터링을 하였다. 이를 통하여 속도와 성능 두가지의 성과를 얻을 수 있었다.

• 한국기계가공학회지
• /
• 제11권5호
• /
• pp.60-67
• /
• 2012

In the study, the effect grinding condition on the workpiece arithmetical average roughness(Ra) to 10 steps leading to cutting each section with the spindle rotational speed 8000rpm and feed rate 150mm/min of grinding in GC(green silicon carbide) grinding processing after heat treatment and non heat treatment of SCM415 material. Also the following conclusions were obtained analysis of stress distribution displacement and finite elements method(FEM) on assemble parts with 3+2 axis simultaneous control through grinding and gave a load 11kg on ATC arm both sides gave a load of 11kg. For the centerline average roughness(Ra) in the heat and non-heat treatment work pieces, which were appeared the most favorable in the fifth section were $0.511{\mu}m$ and $0.514{\mu}m$, that were shown in the near the straight line section was the smallest deformation of curve. In addition, the bad surface roughness appeared on the path is too long by changing angle, the more inclined depth of cut, because the chip discharging is not smoothly.

• 한국기계가공학회지
• /
• 제6권1호
• /
• pp.27-33
• /
• 2007

Hard turning on modern lathes becomes a realistic replacement for many grinding applications. Because CBN tools are expensive, excessive tool wear can eliminate economic advantages of hard turning. This paper describes a study of investigating the cutting force and the characteristics of tool wear in hard turning of hardened steels, AISI 52100. Cutting forces generated using CBN tools have been evaluated. The radial thrust cutting force was the largest among three cutting force components. It increased dramatically as a result of progressive tool wear. On the other hand, the result shows significantly different wear characteristics between high CBN and low CBN. Backpropagation neural network was used for the estimation of tool wear. The networks were achieved the reliability of 96.3% even when the spindle speed and feed rate are changed.

• 대한기계학회논문집A
• /
• 제24권11호
• /
• pp.2680-2687
• /
• 2000

The Reynolds equation, incorporating Elrods cavitation algorithm, is discretized on a rectangular grid in computational space through coordinate mapping in order to accurately analyze a herringbone grooved journal bearing of a spindle motor in a computer hard disk drive. The pressure distribution and cavitation area are determined by using the finite volume method. Predicted results are compared to experimental data of previous researchers. It was found that positive pressure is developed within the converging section of the bearing and that a cavity occurs in the diverging section. Cavitation has been neglected in the previous analysis of the herringbone grooved bearing. Load capacity and bearing torque are increased due to the increased of eccentricity and L/D and the decrease of the grooved width ratio. The maximum load capacity was found to occur at a groove angle of 30 degrees while bearing torque remains constant due to the variation of the groove angle. The cavitation region is significantly decreased with the inclusion of herringbone grooves. However, the region increases with the increase of the eccentricity, L/D, groove angle and the rotational speed and the decrease of the grooved width ratio.