• 한국CDE학회논문집
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• 제4권3호
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• pp.259-268
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• 1999

In order to reduce the cost of product and save the processing time, optimal nesting of two-dimensional part is an important application in number of industries like shipbuilding and garment making. There have been many studies on finding the optimal solution of two-dimensional nesting. The problem of two-dimensional nesting has a non-deterministic characteristic and there have been various attempts to solve the problem by reducing the size of problem rather than solving the problem as a whole. Heuristic method and linearlization are often used to find an optimal solution of the problem. In this paper, theoretical and practical nesting algorithm for rectangular, circular and irregular shape of two-dimensional parts is proposed. Both No-Fit-Polygon and Minkowski-Sum are used for solving the overlapping problem of two parts and the dynamic programming technique is used for reducing the number search spae in order to find an optimal solution. Also, nesting designer's expertise is complied into the proposed algorithm to supplement the heuristic method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.66-69
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• 2002

In the ideal forming theory(1), which has been deviously developed as a direct method for optimizing forming process, material elements are required to deform following the minimum plastic work path (or the proportional true strain path). Besides the general theory(2,3), specific ideal forming theories have been developed for membrane sheet forming(4) as well as two-dimensional steady bulk forming(5-7). In this work, the ideal forming theory was successfully applied for non-steady bulk forming under the plane strain condition. Here, the shape change complying with the minimum plastic work path, was effectively described by developing a numerical code based on the characteristic method. Numerical results obtained for a specific industrial part also include the optimum pre-forming shape and its evolving shape change to the final shape as well as the boundary traction history.

• 한국통신학회논문지
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• 제19권4호
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• pp.614-623
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• 1994

얼굴을 마주보며 인간끼리 대화하는 것처럼 인간과 자연스럽게 대화할 수 있는 휴먼인터페이스를 실현하기 위해서는 임성의 합성과 얼굴영상의 합성이 필요하다. 본 논문은 얼굴영상의 합성을 대상으로 한다. 얼굴영상의 합성에서는 표정변화와 입모양의 변화를 3차원적으로 실현하기 위하여 얼굴의 3차원 형상모델을 이용한다. 얼굴의 3차원 모델을 얼굴 근육의 움직임에 따라 변형하므로서 다양한 얼굴표정과 음절에 어울리는 입모양을 합성한다. 우리말에서 자모의 결합으로 조합가능한 음절은 14,364자에 이른다. 이 음절에 대한 입모양의 대부분은 모음에 따라 형성되고, 일부가 자음에 따라 달라진다. 그러므로, 음절에 어울리는 입모양의 변형규칙을 정하기 위해, 이들을 모두 조사하여 모든 음절을 대표할 수 있는 입모양패턴을 모음과 자음에 따란 분류한다. 그 결과, 자음에 영향을 받는 2개의 패턴과 모음에 의한 8개의 패턴, 총 10개의 패턴으로 입모양을 분류할 수 있었다. 나아가서, 분류된 입모양패턴의 합성규칙을 얼굴근육의 움직임을 고려하여 정한다. 이와같이 분류된 10개의 입모양패턴으로 모든 음절에 대한 입모양을 합성할 수 있고, 얼굴근육의 움직임을 이용하므로써 다양한 표정을 지으면서 말하는 자연스런 얼굴영상을 합성할 수 있었다.

• Journal of Welding and Joining
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• 제9권3호
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• pp.52-61
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• 1991

In the recent years the computer-numerical controlled cutting process such as a plasma arc cutting and a laser cutting is widely applied to reduce the time and cost expense for generating NC part program of the parts to be cut. In the present study, a CAD system(C-CAD) was developed to generate automatically the NC part programs with CLDAT(Cutter Location Data)for the CNC plasma arc cutting system. The NC part programs are composed of the 2-dimensional drawing of the parts to be cut and the technological data. The shape data of the parts drawn in the Auto-CAD can be also used in the C-CAD, since the data file generated by the C-CAD is compatible with that by the Auto-CAD. In order to check its applicability, the C-CAD and CAM system were applied to cut the parts, and which showed the satisfactory results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 대한토목학회논문집
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• 제28권4B호
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• pp.429-439
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• 2008

본 연구에서는 잠제의 제원(천단수심, 천단폭, 사면경사, 제장)에 따라 해빈상을 전파하는 풍파의 처오름 높이 변화특성을 논의하기 위하여, 기존의 수리모형 실험치와 계산치를 비교 검토를 통해 타당성과 유효성이 검증된 수치모델로서, 파 투과성구조물 해빈의 상호간섭을 직접 해석할 수 있는 3D-수치모델(LES-WASS-3D; 허와 이, 2007)을 이용하여 잠제 2기의 제원에 따른 수치시뮬레이션을 실시하였다. 그 결과 천단수심, 천단폭, 사면경사, 제장의 변화가 연안에서의 처오름 높이에 미치는 영향에 관하여 검토하였으며, 아울러, 잠제 주변의 파고분포 및 상층흐름특성과의 관계에 대해서도 논의하였다.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2005년도 춘계학술발표대회 논문집
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• pp.3-8
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• 2005

The robot systems are widely used in the welding manufacturing. The essential tasks to operate the welding robot are the acquisition of the position and/or shape of the parent metal. For the seam tracking or the robot automation, many kinds of contact and non-contact of the system which monitors the shape of the welding part is described. This system uses the line-type structured laser diode and the visual sensor. It includes the correction of radial distortion which is often found in the image from the camera with short focal length. Direct Linear Transformation (DLT) is used for the camera calibration. The three dimensional shape of the parent metal is obtained after simple linear transformation. Therefore, the system operates in real time. Some experiments are carried out to evaluate the performance of the developed system.

• 한국CDE학회논문집
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• 제7권3호
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• pp.148-156
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• 2002

Most Rapid Prototyping (RP) processes adopt a solid Computer Aided Design (CAD) model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; and eventually the stacked layers from a physical part of the model. A new RP process, the transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-ST), has been developed to reduce building time and to improve the surface finish of parts with the thick layers and a sloping surface. This paper describes the generation of Unit Shape Layer (USL), the cutting path data of the linen. hotwire cutter for the VLM-ST process. USL is a three-dimensional layer with a thickness of more than 1 mm and a side slope, and it is the basic unit of cutting and building in the VLM-ST process. USL includes data such as layer thickness, positional coordinates, side angles of each layer, hotwire cutting speed, the heat input to the hotwire, and reference shape. The procedure of generating USL is as follows: (1)Generation of the mid-slice from the CAD model, (2)Conversion of the mid-slice into a simply connected domain, (3)Generation to the reference shape for the mid-slice, (4)Calculation of the rotation angle of the hotwire of the cutting system.

• 한국기계연구소 소보
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• 통권19호
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• pp.163-169
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• 1989

Many computer programs are being developed to aid the design of physical models. These efforts highlight the importance of computer model of three dimensional object. In this paper a CAD application program is introduced which can be implemented to modeling some part that composed with 3 types of surface form ; free form surface, fillt surface, surface of revolution, and a geometry description language which can represent a shape efficiently is preseneted.

• 한국정밀공학회지
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• 제21권4호
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• pp.109-119
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• 2004

Rapid prototyping (RP) technologies have been widely used to reduce the lead-time and development cost of new products. $VLM-_{ST}$ 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. $VLM-_{ST}$ 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 $VLM-_{ST}$ process ($VLM-_{ST}$), 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 $VLM-_{ST}$ process and to develop an apparatus for implementation of the process. $VLM-_{ST}$ 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.