• 한국정밀공학회지
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• 제24권10호
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• pp.37-45
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• 2007

End-milling is intermittent cutting process performed by a tool with a number of teeth. Its cutting forces are commonly measured by the tool dynamometer which has rectangular coordinates. In this case, the pattern of cutting forces is different according to cutting conditions. At a certain cutting condition, the sign of cutting force changes from positive to negative during a revolution of one tooth. The change of force direction excites a cutting tool and severe vibration arises when radial depth of cut increases. In this study, cutting experiments and simulations were carried out in order to explain the cause of the change of the cutting force direction. In addition, the effect of the cutting force change was discussed in terms of chatter vibration in end milling.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.135-142
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• 1998

The performances of cutting process is mostly affected by the characteristics of closed loop system constructed with machine tool structure, work piece and tools. The chucking system is very important component in this system to hold work piece correctly in various static and dynamic load condition. Therefore, chucking force and accuracy must be considered carefully, from these reason, this paper describes the stability of chucking system which preserve high stiffness and accuracy of machine tool system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.1063-1066
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• 2002

The wavelet transform is a popular tool for studying intermittent and localized phenomena in signals. In this study the wavelet transform of cutting force signals was conducted for the detection of a tool failure in turning process. We used the Daubechies wavelet analyzing function to detect a sudden change in cutting signal level. A preliminary stepped workpiece which had intentionally a hard condition was cut by the inserted cermet tool and a tool dynamometer obtained cutting force signals. From the results of the wavelet transform, the obtained signals were divided into approximation terms and detailed terms. At tool failure, the approximation signals were suddenly increased and the detailed signals were extremely oscillated just before tool failure.

• Journal of Mechanical Science and Technology
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• 제14권6호
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• pp.622-632
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• 2000

In a high precision vertical machining center, the estimation of cutting forces is important for many reasons such as prediction of chatter vibration, surface roughness and so on. The cutting forces are difficult to predict because they are very complex and time variant. In order to predict the cutting forces of end-milling processes for various cutting conditions, their mathematical model is important and the model is based on chip load, cutting geometry, and the relationship between cutting forces and chip loads. Specific cutting force coefficients of the model have been obtained as interpolation function types by averaging forces of cutting tests. In this paper the coefficients are obtained by neural network and the results of the conventional method and those of the proposed method are compared. The results show that the neural network method gives more correct values than the function type and that in the learning stage as the omitted number of experimental data increase the average errors increase as well.

• 한국생산제조학회지
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• 제9권4호
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• pp.108-116
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• 2000

Undesired trouble such as chatter vibration and burning on the ground surface appears frequently in the cylindrical plunge grinding process. Establishment of a credible fault diagnostic system for the grinding process is the major purpose of this study. Power signals generated during the grinding operation were sampled and analyzed to determine the relationship between grinding troubles and behavior of signal changes. In addition, a neural network was optimized with a momentum coefficient a learning rate, and a structure of the hidden layer through the iterative learning process. Based on the established system, success rates of the trouble recognition were verified.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.350-354
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• 1995

The Tension Leveller of Cold Rolling Mill In POSCO performs levelling the strip in high speed line. But minor variations in operating condition of driving machines such as motor, gear box, and support bearings, a small gap-variation of supporter and strip slip by poor roll revolutions can cause serious problems in the quality of strip. In this study, firstly, A condition monitoring standard for each sensor is made through with the detail analysis of vibration and strip slip. Secondly, An automatic monitoring and diagnosing system was developed to monitor the condition of Tension Leveller, and diagnose the cause of abnormal condition. Finally, A diagnosing algorithm for abnormal condition and man-machine interface (MMI) for easy operation are developed.

• 대한기계학회논문집
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• 제8권2호
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• pp.162-170
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• 1984

대부분의 동적댐퍼들은 주구조물의 진동진폭을 정해진 주파수 변위내에서 최대로 줄이는 것을 목 표로 한다. 그러나 공작기계의 안정성은 시편과 공구사이의 상대변위와 절삭력에 의해 결정되는 전달함수의 최대크기에 의해서보다는 실수부분의 최소치에 의해 결정된다는 것이 잘 알려져 있 다. 본 논문에서는 이 사실에 착안하여 공작기계에서 발생하는 채터를 흡수하기 위한 최적의 댐 퍼를 설계하는 절차를 제시하고 1 자유도로 대표될 수 있는 구조물의 경우에 대하여 구체적인 방 법을 예시하였다. 종래의 최적 댐퍼의 성질을 구하는 방법에 비해 수학적인 절차가 약간 복잡해 지기는 하나 전산기를 이용하여 큰 어려움이 없이 최적의 설계자료를 얻을 수 있다. 댐퍼 질량이 정해졌을 때 감쇠율과 스프링 계수를 변수로 하는 목표함수가 하나의 식으로 유도될 수 없기 때 문 에 간단한 최적화 방법으로 이변수 황금분할법을 사용하였다. 수치적인 예를 통하여 종래의 다른 방법에 의한 결과와 비교하고 제안된 방법론의 타당성을 입증하였다.

• 한국정밀공학회지
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• 제19권12호
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• pp.78-85
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• 2002

The wavelet transform is a popular tool fer studying intermittent and localized phenomena in signals. In this study the wavelet transform of cutting force signals was conducted for the detection of a tool failure in turning process. We used the Daubechies wavelet analyzing function to detect a sudden change in cutting signal level. A preliminary stepped workpiece which had intentionally a hard condition was cut by the inserted cermet tool and a tool dynamometer obtained cutting force signals. From the results of the wavelet transform, the obtained signals were divided into approximation terms and detailed terms. At tool failure, the approximation signals were suddenly increased and the detailed signals were extremely oscillated just before tool failure.

• International Journal of Precision Engineering and Manufacturing
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• 제3권1호
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• pp.5-12
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• 2002

The grinding process has been mainly used fur finishing metal products as final machining stage. But chatter vibration and bum of a workpiece have a bad effect on the machined surface and should be detected in modern grinding process. This paper deals with a fault detection of the cylindrical plunge grinding process by power parameters. During the grinding process the power signals of an induced motor were sampled and used to determine the relationship between fault and change of power parameters. A neural network was used far detecting the grinding fault and an influence of power parameters to the grinding fault was analyzed.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.321-325
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• 2000

To obtain precise surface and high productivity, high speed end milling has been studied recently. Though high speed end milling is explicitly effective for precision surface generation geometrically, tool deflection, chatter vibration and frequency characteristics of end milling system deteriorate the theoretical surface. In this study, simulation algorithm and programming method are suggested to simulate machined surface using acceleration signal in high speed end milling. This simulation is conducted by considering vibrational effect of spindle system which was not considered by other researchers. Between simulated results and experiment results, good agreements were obtained.