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Al 6061 MQL 선삭가공에서 절삭력과 표면거칠기 예측에 관한 실험적 연구
황영국(Young Kug Hwang),정원지(Won Jee Chung),이춘만(Choon Man Lee) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.6
Cooling lubricants are used in machining operations in order to reduce friction at the tool-chip and tool-workpiece interfaces, cool both chip and tool, and remove chip. Furthermore, they influence a strong effect on the shearing mechanisms and, consequently, on the machined surface quality and tool wear. However, several researchers state that the costs related to cutting fluids is frequently higher than those related to cutting tools. Moreover, the cooling lubricants cause an increase in both worker's health and social problems related to their use and correct disposal. Therefore, many researchers have focused on the environmentally conscious machining technologies. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. In this paper, an experimental model to obtain the optimal cutting conditions in MQL turning was suggested, and the effects of cutting conditions on surface roughness and cutting force were analyzed. For these purposes, FFD (Fractional Factorial Design) and RSM (Response Surface Methods) were used for the experiment. Cutting force and surface roughness with different cutting conditions were measured through the external cylindrical turning of Al 6061 based on the experiment plan. The measured data were analyzed by regression analysis and verification experiments with random conditions were conducted to confirm the suggested experimental model.
황영국(Young-Kug Hwang),은인웅(In-Ung Eun),이춘만(Choon-Man Lee),서용원(Yong-Won Seo) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.4
Linear motors are efficient mechanism that offers high speed and positioning accuracy. By eliminating mechanical transmission mechanisms, much higher speeds and greater acceleration can be achieved without backlash or excessive friction. However, an important disadvantage of linear motor system is its high power loss and heating up of motor and neighboring machine components on operation. Therefore, it is necessary to design moving table with high stiffness, high efficiency and light weight construction. This paper presents the development of moving table using composite material. In order to develop light weight construction of moving table, finite element analysis is performed to find best moving table construction and composite stacking sequence. NASTRAN and MINITAB were used as the optimizer. A prototype for the moving table using composite material was created.
절삭력에 의한 공구와 공작물의 상대적 변형량 예측 [1]
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.9
Any relative deformation between the cutting tool and the workpiece at the machining point, results directly in form and dimensional errors. The source of relative deformations between the cutting tool and the workpiece at the contact point may be due to thermal, weight, and cutting forces. Thermal and weight deformations can be measured at various positions of the machine tool and stored in the compensation registers of the CNC unit and compensated the errors during machining. However, the cutting force induced errors are difficult to compensate because estimation of cutting forces are difficult. To minimize the error induced by cutting forces, it is important to improve the machining accuracy. This paper presents the pre-calculated method of form error induced by cutting forces. In order to estimate cutting forces, Isakov method is used and the method is verified by comparing with the experimental results. In order to this, a cylindrical-outer-diameter turning experiments are carried out according to cutting conditions.
고속 주축에서 클램핑력 및 회전수 변화에 따른 주축 인터페이스 접촉률 변화에 관한 연구 (1)
황영국(Young Kug Hwang),이춘만(Choon Man Lee),정원지(Won Jee Chung) Korean Society for Precision Engineering 2006 한국정밀공학회지 Vol.23 No.3
High speed machining has become the main issue of metal cutting. Due to increase of the rotational speed of the spindle, problems, such as the run-out errors, reduced stiffness, must be overcome to improve the machining accuracy. In order to solve the problems, it is important to determine the appropriate clamping unit and tooling system. This paper presents an investigation into an evolution of contact interval which is the interface between spindle taper hole and tool holder shank of the spindle. Finite element analysis is performed by using a commercial code ANSYS according to variation of clamping forces and rotational speeds. This paper proposed fit tolerance in order to evaluate the effects of clamping force and rotational speed on the contact interval in the spindle interface. From the finite element results, it has been shown that the rotational speed rather than clamping force mostly influence on the variation of the contact interval.
주축회전수 및 절삭력 변화에 따른 주축 인터페이스부 정강성 변화에 관한 연구
황영국(Young-Kug Hwang),정원지(Won-Jee Chung),조영덕(Young-Dug Cho),이춘만(Choon-Man Lee) 한국생산제조학회 2005 한국생산제조시스템학회 학술발표대회 논문집 Vol.2005 No.10
High speed machining has become the main issue of metal cutting. Due to increase of the rotational speed of the spindle, problems, such as the run-out errors, reduced stiffness, must be overcome to improve the machining accuracy. In order to solve the problems, it is important to determine the appropriate clamping unit and tooling system. This paper presents an investigation into an evolution of static stiffness in the main spindle interface. Finite element analysis is performed by using a commercial code ANSYS according to variation of cutting force, clamping force and rotational speeds. From the finite element results, it has been shown that the rotational speed and clamping force mostly influence on the variation of the static stiffness in the main spindle interface.
MQL 선삭가공에서 절삭력과 표면거칠기 향상에 관한 연구
황영국(Young-Kug Hwang),정원지(Won-Jee Chung),정종윤(Jong-Yun Jung),이춘만(Choon-Man Lee) 한국생산제조학회 2006 한국생산제조학회지 Vol.15 No.4
At present, industry and researchers are looking for ways to reduce the use of lubricants because of ecological and economical reasons. Therefore, metal cutting is to move toward dry cutting or semi-dry cutting. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. This research presents an investigation into MQL machining with the objective of deriving the optimum cutting conditions for the turning process of SM45C. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed rate, oil quantity and so on, with MQL and flood coolant. The surface roughness and cutting force results of tests were measured and the effects of cutting conditions were analyzed by the method of Analysis of Variance(ANOVA). From the experimental results and ANOVA, this research proposed optimal cutting conditions to improve the machinability in MQL turning process.
실험계획법을 이용한 MQL 선삭가공의 가공성 향상에 관한 연구
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee),정종윤(Jong-Yun Jung) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
At present, industry and researchers are looking for ways to reduce the use of lubricants because of ecological and economical reasons. Therefore, metal cutting is to move toward dry cutting or semi-dry cutting. One of the technologies is known as MQL(Minimum Quantity Lubrication) machining. This research presents an investigation into MQL machining with the objective of deriving the optimum cutting conditions for the turning process of SM45C. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed rate, oil quantity and so on, with MQL. The surface roughness and cutting force results of tests were measured and the effects of cutting conditions were analyzed by the method of regression analysis. From the experimental results, this research proposed optimal cutting conditions to improve the machinability in MQL turning process.
꼭지점 계획을 이용한 주축 사이즈와 베어링간 길이 결정
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee) 한국생산제조학회 2008 한국생산제조시스템학회 학술발표대회 논문집 Vol.2008 No.10
The spindle is the main component in machine tools. The static and dynamic stiffness of the spindle directly affect the machining productivity and surface integrity of the workpiece. The static and dynamic stiffness of the spindle depend on the shaft size, bearing arrangement, bearing span length, and so on. Therefore, the selection of shaft size and bearing span length are important to improve the spindle stiffness. This paper presents an determination of shaft size and bearing span length in spindle design step. In order to select the optimal bearing and built-in motor locations with constraint conditions, the extreme vertices design was applied. The results show that extreme vertices design is usable for spindle design with design constraints.
공작기계용 고속ㆍ고능률 주축을 위한 가변예압량 결정에 관한 기초연구
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee) 한국생산제조학회 2009 한국생산제조시스템학회 학술발표대회 논문집 Vol.2009 No.10
Modern machine tool spindles simultaneously require high stiffness and fast rotation characteristics for high speed, highly efficient processing, as well as for a wide range of use rotation. In order to this, a variable preload technology is needed so that the bearing that can apply a greater preload to raise the stiffness of the spindle at the low speed range and a smaller preload at the high speed range to reduce heat generation, as opposed to greater stiffness, and to allow high speed rotation. This paper propose the algorithm for determining the variable preload. For determination of a variable preload, the bearing life, rigidity, and the gyroscopic slip were considered as the constraint conditions. The bearing life was calculated by simultaneously considering the spindle rotational speed and external load.