• 한국정밀공학회지
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• 제32권5호
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• pp.423-429
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• 2015

Linear motion (LM) ball guides have good accuracy and high efficiency. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, friction force incurs heat between the balls and grooves. Thermal expansion due to the heat deteriorates stiffness and accuracy of the LM ball guides. For accurate estimation of stiffness and accuracy during the linear motion, friction models of LM ball guides are required. To formulate accurate frictional models of LM ball guides according to load and preload conditions, rolling and viscous frictional analyses have been performed in this paper. Contact loads between balls and grooves are derived from Hertzian contact analysis. Contact angle variation is incorporated for the precision modeling. Viscous friction model is formulated from the shear stress of lubricant and the contact area between balls and grooves. Experiments confirm validity of the developed friction model for various external load and feedrate conditions.

• 한국정밀공학회지
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• 제30권7호
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• pp.749-753
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• 2013

Hydraulic systems are used to transform mechanical energy and fluid energy into each other. Its applications are very wide over the whole industries such as automobiles, public works, rockets, machine tools, construction heavy equipments, airplaces and so on. They are hydraulic pumps that transform energy in the systems. In this study, with basic operation principles as a start point, I tried to understand how the rotating radius of a piston affects the lubrication characteristics in more practical conditions, a swash-plate with tilt angle zero capable of rotating motion and other devices was used. In this paper, a slipper was located on 45mm eccentricity from the center of a swash-plate. As a result, through this experiment, it was found that the rotating radius of a piston affects load capacity, leakage flow and lubrication characteristics and it is one of the important parts for improving the pump efficiency.

• 한국정밀공학회지
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• 제30권2호
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• pp.143-147
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• 2013

We present results of the optical design and fabrication of a light-guiding plate (LGP) for a photobioreactor by using sunlight and a linear Fresnel lens. LGP patterns were designed by optical simulations with an illumination design tool, LightTools, and fabricated by using a computerized numerical control machine. Optical characteristics of average deviation of illuminance distribution and light throughput efficiency were measured and compared with simulation results.

• 한국공작기계학회논문집
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• 제14권1호
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• pp.8-14
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• 2005

The purposes of using cutting fluid during cutting have been cooling, lubricating, chip washing, and anti-corroding. However, the present manufacturing industry restricts the use of cutting fluid because cutting fluid contains poisonous substances which are harmful to the human body. Therefore dry cutting becomes an unavoidable assignment and a lot of researches have studied cutting methods without using cutting fluid. Because dry turning is a continuous work, tools life is reduced by continuous heat generation and surface gets rough due to reduced lubrication, so it is important to consider these situations. In this paper, the way of selecting the optimal machining condition by the minimum number of experiments and the effectiveness of using compressed air in high hardness materials through Taguchi method have been found. Dry cutting using compressed air showed better cutting characteristics than normal dry cutting with respect to by cutting force, tool wear, and surface roughness. Also, the optimal machining condition f3r dry cutting using compressed air could be selected through Taguchi method.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.1-9
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• 2001

The development of flexible automation in the manufacturing industry is concerned with production activities performed by unmanned machining system A major topic relevant to metal-cutting operations is monitoring toll wear, which affects process efficiency and product quality, and implementing automatic toll replacements. In this paper, the measurement of the cutting force components has been found to provide a method for an in-process detection of tool wear. The static com-ponents of cutting force have been used to detect flank wear. To eliminate the influence of variations in cutting conditions, tools, and workpiece materials, the force modeling is performed for various cutting conditions. The normalized force dis-parities are defined in this paper, and the relationships between normalized disparity and flank were are established. Final-ly, artificial neural network is used to learn these relationships and detect tool wear. According to proposed method, the static force components could provide the effective means to detect flank wear for varying cutting conditions in turning operation.

• 한국생산제조학회지
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• 제23권4호
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• pp.325-329
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• 2014

This paper proposes a method to predict chatter vibration generated in milling processes and to enhance machining quality and surface finish. Chatter vibration is a common problem in the milling of thin walls and floors. It causes a poor surface finish, or even marks, to appear on the final machined surface. Therefore, an effective method is necessary to predict chatter vibration in machine tools. In this investigation, chatter vibration is measured by an accelerometer, microphone, and Acoustic Emission (AE) sensor in a machining operation. Based on the results of the experiment, a microphone can be applied for the prediction of chatter vibration in milling processes.

• 한국인터넷방송통신학회논문지
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• 제16권5호
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• pp.105-110
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• 2016

현재, 국내 CNC 산업분야는 제조업의 패러다임 변화에 따라 공작기계에 첨단 기술의 적용이 활발하게 추진되고 있다. 즉, 공작기계의 제어를 담당하는 CNC의 IT화는 가장 중요한 부분을 차지하고 있다. 하지만 공작기계 분야에 모션제어 전문기술 부족의 가장 큰 이유는 PC기반의 컨트롤러의 경우 비중을 많이 차지하는 윈도우즈 언어를 사용하기 보다는 G-Code를 직접 좌표에 맞춰 코딩하거나 값비싼 외산 S/W를 통해 변환 하는 경우가 대부분이기 때문이다. 본 논문에서는 다양한 형태의 CAD 데이터를 손쉽게 G-Code 데이터로 변환할 수 있는 G-Code 변환 프로그램 및 CAD&CAM과 응용 소프트웨어를 개발하고 이 변환된 데이터를 바로 로봇을 통해 원하는 동작을 시킬 수 있는 전용 모션 컨트롤러를 구현한다.

• 열처리공학회지
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• 제13권6호
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• pp.412-419
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• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1214-1221
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• 2009

A high-speed spindle can be very sensitive to rotating mass unbalance which has harmful effect on many machine tools. Therefore, the balancing procedure to reduce vibration in rotating system is certainly needed for all high-speed spindles. So, balancing procedure was performed with a spindle-bearing system for CNC automatic lathe by using numerical procedure. The spindle is supported by the angular contact ball bearings and the motor rotor is fixed at the middle of spindle. The spindle-bearing system has been investigated using combined methodologies of finite elements and transfer matrices. The balancing was performed through influence coefficient method and the comparison was made by whirl responses between before balancing and after balancing. As a result, balancing of simple spindle model reduced whirl orbit magnitude in case of a completely assembled spindle model.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권4호
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• pp.234-239
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• 2006

In the past decade, several tools have been developed to automate the floating-point to fixed-point conversion for DSP systems. In the conversion process, a number of scaling shifts are introduced, and they inevitably alter the original code sequence. Recently, we have observed that a compiler can often be adversely affected by this alteration, and consequently fails to generate efficient machine code for its target processor. In this paper, we present an optimization technique that safely migrates scaling shifts to other places within the code so that the compiler can produce better-quality code. We consider our technique to be safe in that it does not introduce new overflows, yet preserving the original SQNR. The experiments on a commercial fixed-point DSP processor exhibit that our technique is effective enough to achieve tangible improvement on code size and speed for a set of benchmarks.