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3 차원 나노 스테레오리소그래피의 정밀화를 위한 펨토초 레이저 출력-조사시간 제어방법
박상후(S. H. Park),임태우(T. W. Lim),양동열(D. Y. Yang) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
A scheme to control the laser power and the exposure time was studied to fabricate precise microstructures using the nanostereolithography (nSL) process. Some recent works have shown that a three-dimensional (3D) microstructure can be fabricated by the photopolymerizing process which is induced by two-photon absorption (TPA) with a femtosecond pulse laser. TPA provides the ability to confine photochemical and physical reactions within the order of laser wavelength, so neardiffraction limit features can be produced. In the nSL process, voxels are continuously generated to form a layer and then another layer is stacked in the normal direction of a plane to construct a 3D structure. Thus, fabrication of a voxel with low aspect ratio and small diameter is one of the most important parameters for fabricating precise 3D microstructures. In this work, the mechanism of a voxel formation is studied and a scheme on the control of laser power and exposure for minimizing aspect ratio of a voxel is proposed.
이상적 변형이론을 이용한 박판 초기형상 설계에 관한 연구
박상후(S.H.Park),이동우(D.W.Lee),양동열(D.Y.Yang),김용환(Y.H.Kim),이장희(J.H.Lee) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_1
A new blank design method is introduced to predict the blank shape and the strain distribution in the sheet metal forming process. This method deals with only one step from the final shape to the initial blank using the ideal forming theory. Based on this theory. a three-dimensional membrane finite element code has been developed for ideal sheet forming. In this paper. the designs of initial blanks for forming a cylindrical cup. a rectangular Clip. and a front fender are presented as examples. Also. it compares the two shapes. the final shape with the shape which is deformed from the initial blank using the FEM analysis code.<br/> The results illustrate the information that this. direct design code is useful in the preliminary design state.<br/>
극미세 3 차원 형상제작의 효율성 향상을 위한 영역분할 단면법에 관한 연구
박상후(S.H. Park),임태우(T.W. Lim),양동열(D.Y. Yang),이신욱(S.Y. Yi),공홍진(H.J. Kong),이광섭(K.S. Lee) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월
A subregional slicing method (SSM) is proposed to increase the nanofabrication efficiency of a nano-stereolithography (NSL) process based on two-photon polymerization (TPP). The NSL process can be used to fabricate 3D microstructures via the accumulation of layers of uniform thickness; hence, the precision of the final 3D microstructure depends on the layer thickness. The use of a uniform layer thickness means that, to fabricate a precise microstructure, a large number of thin slices is inevitably required, leading to long processing times. In the SSM proposed here, however, the 3D microstructure is divided into several subregions on the basis of the geometric slope, and then each of these subregions is uniformly sliced with a layer thickness determined by the geometric slope characteristics of each subregion. Subregions with gentle slopes are sliced with thin layer thicknesses, whereas subregions with steep slopes are sliced with thick layer thicknesses. Here, we describe the procedure of the SSM based on TPP, and discuss the fabrication efficiency of the method through the fabrication of a 3D microstructure.