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양동열(Dong-Yol Yang),이상호(Sang-Ho Lee),안동규(Dong-Gyu Ahn),김효찬(Hyo-Chan Kim),박승교(Seung-Kyo Park) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
An effective thick-layered RP process, Transfer type Variable Lamination Manufacturing using expandable polystyrene foam (VLM-ST) has been developed to reduce building time, to decrease the stair-stepped effect of parts, to minimize post-processing with thick layers and sloping surfaces. VLM-ST employs a 4-axis synchronized automatic hotwire cutter with the parallelogram mechanism and expandable polystyrene foam sheet with the high packing density. In the VLM-ST process, a material in the form of a plate is cut into a Unit Shape Layer (USL) with thick layers and sloping surfaces by a 4-axis automatic synchronized hotwire cutter according to the cutting path data generated from a CAD model. Each USL is then bonded and built up to fabricate a 3D part. In order to examine the efficiency and applicability of the developed process, various three-dimensional shapes are fabricated on the VLM-ST apparatus.
완전자동화된 단속적 재료 공급식 가변적층 쾌속조형공정 및 장치 개발에 관한 연구
양동열(Dong-Yol Yang),안동규(Dong-Gyu Ahn),이상호(Sang-Ho Lee),김효찬(Hyo-Chan Kim),박승교(Seung-Kyo Park) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.4
Rapid prototyping (RP) technologies have been widely used to reduce the lead-time and development cost of new products. VLM-<SUB>ST</SUB> process has been developed to overcome the currently developed RP technologies such as a large building time, a high building cost, an additional post-processing and a large apparatus cost. VLM-<SUB>ST</SUB> process requires an additional human interaction due to the manual stacking and bonding. Hence, building time, building cost and the part quality are dependent on the skill of labor. A novel RP process, fully automated VLM-<SUB>ST</SUB>process (VLM-(VLM-<SUB>STA</SUB>), has been developed to improve building efficiency of the process and the human dependency of the part. The objective of this work is to propose a VLM-(VLM-<SUB>STA</SUB> process and to develop an apparatus for implementation of the process. VLM-(VLM-<SUB>STA</SUB> process and its apparatus have various technical novelties such as two step cutting using a rotating table, an automatic stacking method using two pilot holes and two reference shapes, a concept of automatic unit shape layer (AUSL), and an automatic bonding using the bonding roller and building magazine. In order to examine the efficiency and the applicability of the proposed process, various three-dimensional shapes, such as a piston, a human head shape and a human bust shape, were fabricated on the apparatus.
김효찬(Hyo Chan Kim),이상호(Sang Ho Lee),양동열(Dong Yol Yang),박승교(Seong Kyo Park) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.6
Recently, life cycle and lead-time of products have been shortened with the demand of customers. Therefore, it is important to reduce time and cost at the stage of manufacturing trial molds. In order to realize a three-dimensional shape on CAD, the machining process has been widely used because it offers practical advantages such as precision and versatility. However, the traditional machining process needs a large amount of time in cutting a product and the remained material causes trouble such as inconvenience for clarity. In this work, a new rapid manufacturing process using the hot tool, Rapid Heat Ablation process, has been developed to overcome such limitations. While the hot tool moves the predetermined path, the heat of the tool decomposes the remained material. The radius of heat affect ed zone related to process parameters was investigated through experiments to improve the quality of ablated parts. In order to examine the applicability of the proposed process, three-dimensional shapes such as hemisphere and standard test part, were ablated utilizing the apparatus.
레이저 빔 단면확대를 이용한 나노 복화(複畵)공정의 패턴 정밀도 향상에 관한 연구
박상후(Sang Hu Park),임태우(Tae Woo Lim),양동열(Dong-Yol Yan),이신욱(Shin Wook Yi),공홍진(Hong Jin Kong) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.1
A laser beam expanding technique is employed to fabricate precise nano-patterns in a nano-replication printing (nRP) process. In the nRP process, some patterns can be fabricated in the range of several microns inside on a polymerizable resin by using a volume-pixel (voxel) matrix that is transformed from a two-tone bitmap figure file. The liquid monomers are polymerized by means of a two-photon-absorption (TPA) phenomenon that is induced by a femtosecond (fs)-pulse laser. The voxels are generated consecutively to merge into adjoining voxels in the process of fabricating a pattern. The resolution of a fabricated pattern can be obtained under the diffraction limit of a laser beam by the two-photon absorbed polymerization (TPP). In this work, a beam-expanding technique has been applied to enlarge a working area and to fabricate precise patterns. Through this work, a working area is expanded by the technique as much as 2.5 times compared with a case of without a beam expanding technique, and precision of outside patterns is improved.
이상호(Sang-Ho Lee),김효찬(Hyo-Chan Kim),양동열(Dong-Yol Yang),박승교(Seung-Kyo Park),김찬국(Chan-Kuk Kim) Korean Society for Precision Engineering 2005 한국정밀공학회지 Vol.22 No.4
The objective of this paper is to develop a multi-functional hotwire cutting system (MHC) using EPS-foam block or plate as the working material. Because the MHC apparatus employs a four-axis synchronized hotwire cutter with the structure of two XY movable heads and a turntable, it allows the easy fabrication of various 3D shapes, such as (1) an axisymmetric shape or a sweeping cross-sectioned pillar shape using the hot-strip in the form of sweeping surface and EPS foam block on the turntable, (2) a polyhedral complex shape using the hotwire and EPS foam block on the turntable, and (3) a ruled surface approximated freeform shape using the hotwire and EPS foam plate. In order to examine the applicability of the developed MHC apparatus, an axisymmetric shape, a polyhedral shape and a large-sized freeform shape were fabricated on the apparatus.
나노 복화(複畵)공정의 역방향 적층법을 이용한 직접적 나노패턴 생성에 관한 연구
박상후(Sang Hu Park),임태우(Tae Woo Lim),양동열(Dong-Yol Yang),공홍진(Hong Jin Kong) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.6
In this study, a new process to pattern directly on a thin metal layer using improved nano replication printing (nRP) process is suggested to evaluate the possibilities of fabricating a stamp for nano-imprinting. In the nRP process, any figure can be replicated from a bitmap figure file in the range of several micrometers with nano-scaled details. In the process, liquid-state resins are polymerized by two-photon absorption which is induced by femto-second laser. A thin gold layer was sputtered on a glass plate and then, designed patterns or figures were developed on the gold layer by newly developed top-down building approach. Generally, stamps for nano-imprinting have been fabricated by using the costly electron-beam lithography process combined with a reactive ion-etching process. Through this study, the effectiveness of the improved nRP process is evaluated to make a stamp with the resolution of around 200㎚ with reduced cost.