• 제어로봇시스템학회논문지
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• 제15권9호
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• pp.877-880
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• 2009

A curing process in post-printing section of R2R process is required for an electrical property of the printed pattern when devices such as RFID, Solar cell are printed. PEN as well as heat-stabilized PET which is used as a plastic substrate would be deformed at high temperature due to change of its elastic modulus. And crack in the printed pattern, which is on the plastic substrate is occurred due to the deformation of the substrate. The occurrence of crack causes electrical resistance to increase and the quality of the device to deteriorate. In case of RFID antenna, the range of reading distance is shortened as the electrical resistance of the antenna is increased. Therefore, the deformation of the plastic substrate, which causes the occurrence of crack, should be minimized by setting up low operating tension in R2R process. In low tension, slippage between a moving substrate and a roller would be generated when the operating speed is increased. And scratch would be occurred when slippage is generated due to an air entrainment, which is related to the thickness of the air film. The thickness of the air film is increased when operating speed is increased as shown by simulation based on mathematical model. The occurrence of scratch in conductive pattern printed by roll to roll process is a critical damage because it causes degradation or failure of electrical property of it.

• 한국정밀공학회지
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• 제26권10호
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• pp.65-73
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• 2009

For mass production of printed electronics in roll-to-roll fashion, precision tension control is important to reduce register errors. Register error should be minimized within several to tens of microns for many electronic devices to be manufactured through printing technology. In order to achieve this goal, tension disturbance must be attenuated before printing process within a certain range. In this paper, a certain tension range which allows maintaining register error within 10 micron was defined with specific operating conditions. A LQG controller was proposed instead of the conventional PI controller for precision tension control using a multivariable feedback. A guideline to determine design parameters for calculating LQ gain was proposed. The proposed LQG controller was compared to both PI controller and LQ regulator with white noise by numerical simulations. Results showed that the proposed LQG controller was effective for attenuating tension disturbance with white noise.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.584-589
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• 1994

A time-varying nonlinear mathematical model was derived to consider the effect of change in roll radius on tension varation during winding and unwinding. A variable-gain PID controller was designed for tension control at start and stop in a multi-span continuous process system. The controller gains are updated at every control loop as roll radii continuously change. Computer simulation was carried out by using the mathematical model and the controller developed for a typical operating condition including acceleration and deceleration. When the variable-gain PID controller was used, the tension control performance was improved compared with that of existing control method during start-up and stop.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1159-1162
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• 1995

In the continuous process systems, traction between a moving web and rollers is one of key mechanisms for the study of major issues including the distributed control of tension, guiding, wrinkling, and scratching. Energy is transferred from the driven rollers to the web and from the web to the idle rollers through traction. The characteristics of friction plays a major role in the determination of the traction force between the moving web and the rollers. In this paper, a procedure to determine the frcition coefficient between the moving web and rollers is devoloped. An experimental setup to validate the procedure is devised. Experimental results showed that the value of traction coefficient decreases as the operating web speed increases and increases as the operating web tension and wrap alngle increase.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.103-109
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• 2010

An ink transfer is modeled and experimentally verified using roll-to-roll electric direct gravure printing process. The ink transfer model based on the physical mechanism for the maximum ink transfer rate is proposed, and experimented by the electric printing machine in FDRC for the relations of the maximum ink transfer rates to the printing pressure, the operating speed, the operating tension, the surface roughness of substrates, and the contact angle between substrate and silver ink. The free ink split coefficient and immobilized ink under the maximum ink transfer rate are calculated by the physical parameter in a printing process and contact angle between substrates and ink. Numerical simulations and experimental studies were carried out to verify performances of the proposed ink transfer model. Results showed that the proposed ink transfer model was effective for the prediction of the amount of transferred ink to the substrate in a direct gravure printing systems.

• 한국산학기술학회논문지
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• 제16권12호
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• pp.8812-8819
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• 2015

콘크리트 궤도 건설의 증가로 인한 레일 체결장치의 중요성이 커지고 있는 상황에서 최근 레일 체결장치의 부속품인 텐션클램프가 절손되는 사고가 발생되었다. 이는 현장상태, 운영기관, 열차운행조건 및 빈도 등 다양한 요인에 의한 것으로 텐션클램프의 거동관련 연구가 필요하다. 본 논문에서는 실내실험 및 유한요소해석을 통해 텐션클램프의 역학적 거동을 분석하였다. 실내실험을 수행하여 텐션클램프 체결력에 따른 응력 및 변위를 도출하고 이를 유한요소해석 결과와의 비교를 통해 해석 모델을 검증하였다. 또한 검증된 모델을 적용하여 열차 하중에 따른 텐션클램프의 변형과 응력을 도출하고, 응력 분석을 통해 텐션클램프의 피로에 대한 취약도를 파악하였다.

• Korean Chemical Engineering Research
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• 제52권4호
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• pp.516-521
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• 2014

고점성이며 낮은 표면장력 매체로 구성된 기포탑에서 축방향 국부 열전달 계수와 총괄 열전달 계수에 대해 고찰하였다. 기체공탑유속(0.02~0.10 m/s), 액체 점도($0.1{\sim}0.3Pa{\cdot}s$) 그리고 액체 표면장력($66.1{\sim}72.9{\times}10^{-3}N/m$)이 국부 및 총괄 열전달 계수에 미치는 영향을 검토하였다. 열전달 영역은 기포탑 내부 열원과 기포탑 간의 열전달계로 구성하였다. 즉, 기포탑의 중앙에 수직 열원을 설치하여 내부 열원으로 하였다. 열전달 계수는 주어진 운전조건에서 열원에 제공되는 열량과 내부 열원과 기포탑 간의 온도차를 연속적으로 측정하여 결정하였다. 국부 열전달 계수는 기체공탑유속이 증가함에 따라 증가하였으나 기체 분산판으로 부터의 축방향 거리가 증가함에 따라, 액체의 표면장력이 증가함에 따라 감소하였다. 총괄 열전달 계수는 기체공탑유속이 증가함에 따라 증가하였으나 액상의 점도와 표면장력이 증가함에 따라서는 감소하였다. 총괄 열전달 계수는 기체공탑유속, 액상의 점도와 표면장력의 함수로 상관계수 0.91의 상관식을 얻을 수 있었으며 넛셀 수, 레이놀즈 수, 플란틀 수 그리고 웨버 수의 함수로 상관계수 0.92의 상관식으로 나타낼 수 있었다. $$h=2502U^{0.236}_{G}{\mu}^{-0.250}_{L}{\sigma}^{-0.028}_L$$ $$Nu=325Re^{0.180}Pr^{-0.067}We^{0.028}$$.

• 한국자동차공학회논문집
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• 제4권6호
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• pp.109-120
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• 1996

Serpentine belt drive system offers the advantages of light weigh, low cost, quientness, and efficiency. Since these belts are typically longer than conventional belts, a tensioner component is added to maintain acceptable belt tension levels and make no slippage between pulleys and belts. This paper addresses the modeling and analysis of the automotive belt drive systems and also addresses the predicton of slippage on rotational modes. Vibration characteristics are determined from the eigenvalue problem governing the free response. Under certain engine operating conditions, the dynamic tension fluctuations may be sufficient to cause the belt to slip on particular accessory pulleys, It is found that this slippage can be reduced by adding the tensioner component from the analysis of belt tension and belt compression.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.873-878
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• 2007

Stability of high-speed roll-to-roll printing machines is one of the most important factors that are required for the printing machines to operate properly and to obtain reasonable printing performance. This paper proposes a new model for the web-tension system of a high-speed gravure printing machine considering span-length variations due to dancer rollers, and analyzes the stability of plant dynamics of the printing machine using the proposed model. Span-length variations due to dancer motions are considered for the modeling of plant dynamics in two ways; one is to include the effect of span-length variations without considering dancer inertias and viscous frictions, and the other is to include the effect of span-length variations with considering dancer inertias and viscous frictions. The stability of the plant model is analyzed for various web-speeds using the eigenvalues of the linearized model about operating points.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.468-475
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• 2002

This paper reports on the friction characteristics of a piston ring pack with consideration of mixed lubrication. The analytical model is presented by using the average flow antral asperity contact model. The effect of operating condition, and design parameters on the MOFT, maximum friction force, and mean frictional power loss are investigated. Piston ring prick shows mixed and hydrodynamic lubrication characteristics. From the predicted results, it was fand that the ring tension and height of surface roughness have great influence on the frictional power losses in a ring pack. Especially, ring tension is a dominant factor for the reduction of friction loss and maintenance of oil film thickness.