• 한국CDE학회논문집
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• 제3권2호
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• pp.87-102
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• 1998

Given a sequence of cross-sectional curves, the skinning method generates a freeform surface that interpolates the given curves in that sequence. This thesis presents a construction method of a B-spline skinning surface that is fair and satisfies volume constraints. The fairness metric is based on the parametric energy functional of a surface. The degrees of freedom in surface control are closely related lo control points in the skinning direction. The algorithm fur finding a skinning surface consists of two step. In the first step, an initial fair surface is generated without volume constraints and one coordinate of each control point is fixed. In the second step, a final surface that meets all constraints is constucted by rearranging the other coordinates of each control point that defines the initial surface A variational Lagrange optimization method produces a system of nonlinear equations, which can be solved numerically. Moreover, the reparametrization of given sectional curves is important for the construction of a reasonable skinning surface. This thesis also presents an intuitive metric for reparametrization and gives some examples that are optimized with respect to that metric.

• 한국CDE학회논문집
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• 제15권1호
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• pp.33-42
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• 2010

In this study, new medial surface calculation methods using Voronoi diagrams are investigated for the point samples extracted on closed surface models. The medial surface is defined by the closure of all points having more than one closest point on the shape boundary. It is a one of essential geometric information in 3D and can be used in many areas such as 3D shape analysis, dimension reduction, freeform shape deformation, image processing, computer vision, FEM analysis, etc. In industrial parts, the idealized solid parts and shell shapes including sharp edges and vertices are frequently used. Other medial surface extraction methods using Voronoi diagram have inherent separation and branch problems, so that they are not appropriate to the sharp edged objects and have difficulties to be applied to industrial parts. In addition, the branched surfaces on sharp edges in shell shapes should be eliminated to obtain representative medial shapes. In order to avoid separation and branch problems, the new approach by analyzing the shapes and specially sampling on surfaces has been developed.

• 한국광학회지
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• 제28권6호
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• pp.273-280
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• 2017

본 논문에서는 낮은 도로 조명을 위한 freeform reflector를 설계하였다. 높이에 비해 넓은 차선까지 배광을 보내야 하는 낮은 도로 조명의 경우, 기존의 등주식 도로 조명에 비해 균제도를 맞추기 힘들다는 단점이 있다. 조명 등급 M3를 만족시키기 위해 reflector를 part 9개로 나누어 part 별 반사면의 기울기를 변화시켜 원하는 배광을 갖도록 하였고, 각 점을 기준으로 fitted curve를 그려 이에 따른 수식을 도출하였다. LightTools의 street light simulation을 통해 M3 조명 등급에 만족하는 것을 확인하였고 직접 제작하여 실제 도로상에서 조명 등급을 만족시키며 설계 결과에 대한 타당성을 입증하였다.

• 천문학회보
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• 제46권2호
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• pp.75.2-76
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• 2021

MESSIER is a science satellite project to observe the Low Surface Brightness (LSB) sky at UV and optical wavelengths. The wide-field, optical system of MESSIER is optimized minimizing optical aberrations through the use of a Linear Astigmatism Free - Three Mirror System (LAF-TMS) combined with freeform mirrors. One of the key factors in observations of the LSB is the shape and spatial variability of the Point Spread Function (PSF) produced by scatterings and diffraction effects within the optical system and beyond (baffle). To assess the various factors affecting the PSF in this design, we use PhoSim, the Photon simulator, which is a fast photon Monte Carlo code designed to include all these effects, and also atmospheric effects (for ground-based telescopes) and phenomena occurring inside of the sensor. PhoSim provides very realistic simulations results and is suitable for simulations of very weak signals. Before the application to the MESSIER optics system, PhoSim had not been validated for confocal off-axis reflective optics (LAF-TMS). As a verification study for the LAF-TMS design, we apply Phosim sequentially. First, we use a single parabolic mirror system and compare the PSF results of the central field with the results from Zemax, CODE V, and the theoretical Airy pattern. We then test a confocal off-axis Cassegrain system and check PhoSim through cross-validation with CODE V. At the same time, we describe the shapes of the freeform mirrors with XY and Zernike polynomials. Finally, we will analyze the LAF-TMS design for the MESSIER optical system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.716-721
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• 2004

Several Solid Freeform Fabrication Systems(SFFS) are commercialized in a few companies for rapid prototyping. However, they have many technical problems including the limitation of applicable materials. A new method of speedy prototyping is required for the recent manufacturing environments of multi-item and small quantity production. The objectives of this paper include the development of a novel method of SFFS, the ${CAFL}^{VM}$(Computer Aided Fabrication of Lamination for Various Material), and the manufacture of the various material samples for the certification of the proposed system and the creation of new application areas. For these objectives, the technologies for a highly accurate robot path control, the optimization of support structure, CAD modeling, adaptive slicing was implemented. In this paper, we design an algorithm that the cutting path of a laser beam which is controlled with constant speed. The laser beam is tangentially controlled in order to solve the inaccuracy of a 3D model surface. The designed algorithm for constant-speed path control and tangent-cutting control is implemented and experimented in the ${CAFL}^{VM}$ system.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.3895-3899
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• 2012

본 연구에서는 시작형 몰드재료인 실리콘 레진(RTV-3040)을 이용하여 엠보패턴을 활용한 몰드금형 개발을 위한 것이며, 상용패키지(Freeform)를 사용하여 필요한 패턴을 선택 한 후 면에 투영 엠보 면을 만들어 부품에 적용 가능을 검토하였다. 소량의 부품 개발 시 부식패턴이 필요로 한 제품들은 알루미늄 금형과 같은 시작형을 제작하여 대응하였으나, 부식패턴을 적용한 실리콘 금형 개발로 시간단축 및 원가절감이 가능한 것으로 나타났다.

• 한국정밀공학회지
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• 제27권12호
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• pp.15-21
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• 2010

Recently, there is a demand for a thermal imaging microscope in the medical field as well as the semi-conductor industry Although the demand of the advanced thermal imaging microscope has been increased, it is very difficult to obtain the technology of developing a thermal camera, because it is used for defense industry. We developed the ${\times}5$ zoom microscope which has $3\;{\mu}m$ spatial resolution to research the design and fabrication of the IR (Infrared) optical system. The optical system of the IR microscope consists of four spherical lenses and four aspheric lenses. We verified individual sensitivity of each optical parameter as the first order approach to the analysis. And we also performed structure and vibration analysis. The optical elements are fabricated using Freeform 700A. The measurement results of surface roughness and form accuracy using NT 2000 and UA3P are Ra 2.36 nm and P-V $0.13\;{\mu}m$. Finally we ascertained resolution power of $3\;{\mu}m$ using USAF (United State Air Force) 1951 IR resolution test chart.

• 한국산학기술학회논문지
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• 제3권2호
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• pp.126-130
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• 2002

본 논문은 쾌속제작법을 이용한 임의형상을 가공하는 새로운 방법의 개념을 소개하고 있다. 본 시스템은 레이저 절단, 이송. 적층, 소결의 단계를 통하여 세라믹재료로 된 임의형상을 가공할 수 있다. 시스템을 구성하는 주요장비로는 레이저 발생장치, X-Y테이블, 이송시스템, 그리고 전기로 등이 있다. 이 시스템을 사용하면 표면의 거칠기가 매끄러운 형상을 상대적으로 짧은 시간에 제작할 수 있는 장점이 있다. 또, 2차 공정을 거치지 않고, 바로 물체를 제작할 수 있어 효율성이 높다고 할 수 있다. 제작된 모형은 바로 조립되어 사용될 수 있기 때문에 응용분야가 다양하다.

• 한국CDE학회논문집
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• 제6권2호
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• pp.111-124
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• 2001

In this paper, we propose rounding operations on shell meshes, which give a constant or variable radius of rounding directly to sharp edges on a shell mesh. The rolling-ball methods for freeform surface rounding are introduced to devise the algorithms for these operations. Our algorithms consists of three steps as follows: detecting sharp edges, generating a rolling-ball surface contacting with two face groups adjacent to the sharp edges, and then replacing the rounding area of the original mesh with the mesh generated on the rolling-ball surface. In addition, this paper shows their application to the area of stamping die design. These operations enable CAE engineers to directly change the meshes of stamping tools without modification of CAD models for dies and regeneration of their meshes.

• 한국정밀공학회지
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• 제17권8호
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• pp.46-52
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• 2000

3D Welding and Milling is a solid freeform fabrication process which is based on the combination of welding as additive and conventional milling as subtractive technique. This hybrid approach enables direct building of metallic parts with high accuracy and surface finish. Although it needs further improvements it shows an application potential in rapid tooling of injection mold inserts as the investigation results show. To optimize the process for higher surface quality and accuracy effectively Taguchi method is applied to the experimental investigation. in this way relationships between process parameters and final product qualities such as tensile strength and surface hardness are found with minimal efforts.