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고속ㆍ정밀 이송용 리니어모터 개발을 위한 열적 안정성 향상에 관한 연구
황영국(Young Kug Hwang),이춘만(Choon Man Lee),은인웅(In-Ung Eun) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.6
Linear motors are efficient mechanism that offers high speed and positioning accuracy. By eliminating mechanical transmission mechanisms such as ball screw or rack-pinion, much higher speed 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. For the application of the linear motors to precision machine tools an effective cooling method and thermal optimizing measures are required. This paper presents an investigation into the thermal behavior of linear motors with the objective of deriving the optimum cooling conditions. To reach these goals several experiments were carried out, varying operating and cooling conditions. From the experimental results, this research proposed cooling conditions to improve the thermal characteristics of the linear motors.
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.
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee) 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.2
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 the 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.
황영국(Young-Kug Hwang),정원지(Won-Jee Chung),이춘만(Choon-Man Lee) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.1
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 and 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 analysis 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 speed. From the finite element results, it is 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.
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.
주축 런아웃이 절삭흔과 표면거칠기에 미치는 영향에 관한 연구
황영국(Young-Kug Hwang),이춘만(Choon-Man Lee) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.2
The radial error motion of a machine tool cutter/spindle system is critical to the dimensional accuracy of the parts to be machined. This paper presents an investigation into spindle run-out effects on cutting mark and surface roughness. We experimented the effects of spindle run-out on surface roughness in flat-end milling by cutting AL 7075 workpiece in various cutting conditions. In order to analyze the effects of run-out on the surface roughness, the spindle's radial error motions was measured by mounting a sphere target onto the spindle as a reference. From the experimental results, it was found that spindle run-out makes a directive effects on surface roughness in flat-end milling.
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.