• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.91-97
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• 2010

Micro-abrasive Jet Machining is one of the new technology which enables micro-scale machining on the surface of high brittle materials. In this technology it is very important to fabricate a mask that prevents excessive abrasives not to machine un-intend surface. Our previous work introduced the micro-stereolithography technology for the mask fabrication. And is good to not only planar material but also for non-planar materials. But the technology requires a 3 dimensional mask CAD model which is perfectly matched with the surface topology of parent material as an input. Therefore there is strong need to develop an automated modeling technology which produce adequate 3D mask CAD model in fast and simple way. This paper introduces a fast and simple mask modeling algorithm which represents geometry of models in voxel. Input of the modeling system is 2D pattern image, 3D CAD model of parent material and machining parameters for Micro-abrasive Jet Machining. And the output is CAD model of 3D mask which reflects machining parameters and geometry of the parent material. Finally the suggested algorithm is implemented as software and verified by some test cases.

• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.373-380
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• 2007

Recently, various 4D CAD systems for visualizing construction schedule data are being developed. Specially, in case of railway project, the numerical information of progress data should be changed with visualized data by long construction section because the railway project consists of long length in construction site. This study suggests a case study of development of 4D CAD system for visualizing schedule information and the major functions of developed system are verified by railway project. The detailed application procedure of 4D CAD system including input data for a railway project is described in the study. The practical application of 4D CAD system can be improved in railway project by these demonstration researches.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.435-438
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• 2001

Reverse engineering technology refers to the process that creates a CAD model of an existing part using measuring devices. Recently, non-contact scanning devices have become more accurate and the speed of data acquisition has increased drastically. However, they generate thousands of points per second and various types of point data. Therefore, it becomes a major issue to handle the huge amount and various types of point data. To generate a CAD model from scanned point data efficiently, these point data should be well arranged through point data handling processes such as data reduction and segmentation. This paper proposes a new point data handling method using 3D grids. The geometric information of a part is extracted from point cloud data by estimating normal values of the points. The non-uniform 3D grids for data reduction and segmentation are generated based on the geometric information. Through these data reduction and segmentation processes, it is possible to create CAD models autmatically and efficiently. The proposed method is applied to two quardric medels and the results are discussed.

• Journal of Computational Design and Engineering
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• v.2 no.4
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• pp.253-260
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• 2015

Feature-based NC machining, which requires high quality of 3D CAD model, is widely used in machining aircraft structural part. However, there has been little research on how to automatically detect the CAD model errors. As a result, the user has to manually check the errors with great effort before NC programming. This paper proposes an automatic CAD model errors detection approach for aircraft structural part. First, the base faces are identified based on the reference directions corresponding to machining coordinate systems. Then, the CAD models are partitioned into multiple local regions based on the base faces. Finally, the CAD model error types are evaluated based on the heuristic rules. A prototype system based on CATIA has been developed to verify the effectiveness of the proposed approach.

• Korean Journal of Computational Design and Engineering
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• v.9 no.3
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• pp.226-237
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• 2004

If the topology changes in the re-generation step of the history-based and feature-based CAD systems, it is difficult to identify an entity in the old model and find the same entity in the new model. This problem is known as 'persistent naming problem'. To exchange parametric CAD models, the persistent naming problem and the naming mapping problem must be solved among different CAD system, which use different naming scheme. For CAD model exchange the persistent naming has its own characteristics compare to that for CAD system development. This paper analyses previous researches and proposes a solution to the persistent naming problem for CAD model exchanges and to the naming mapping problem among different naming schemes.

• Korean Journal of Computational Design and Engineering
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• v.9 no.4
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• pp.373-381
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• 2004

Using standard components of a press die is recognized as a way for a cost reduction and a short lead time. It also provides a way for a quick maintenance of a die under repair. It is expected to contribute to integration of CAD/CAM system for manufacturing dies in the future. This paper presents a 3D CAD library which is constructed using the standard components and is used for designing a press die. This 3D CAD library is generated by a database system made of Microsoft Access for standard components and by CATIA V5 R10 API for geometric features. The library is implemented using Visual Basic 6.0 utility of CATIA API function in the Windows NT environment. It creates a 3D model of the standard components of press die easily when a die designer inputs numerical values of geometric features and the BOM of the completely assembled parts. It also generates automatically the assembly drawing of die set by using variables for standard values of die parts. Therefore users can save the cost of time to design the press die components, and even a beginner can use this program with ease. The test results of the 3D CAD library for designing shearing and bending dies verify its usefulness and feasibility.

• Journal of the Korea Institute of Building Construction
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• v.7 no.3
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• pp.91-98
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• 2007

Recently a construction industry introduces information that brings about many advantages in the early planning phase, design phase and construction phase. Especially it replaces 2D, 3D systems(usually using explanation of drawing information) ai 4D CAD(offering a sort of 4D-having relation of construction schedule and 3D drawing information). Nevertheless a 4D has these benefits, it has limits which are not only usually using 3D modeling but also limit of making full use of practical affairs because of a lack of connecting varietals of progress of work. To solve these uppermost limits, this research is presenting unified systems to use in risk management which are efficient management of space and non-space information, space analysis, making full use of data base, introducing GIS system of easy interaction.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.265-270
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• 2017

PURPOSE. This study is to evaluate the internal fit of the crown manufactured by CAD/CAM milling method and 3D printing method. MATERIALS AND METHODS. The master model was fabricated with stainless steel by using CNC machine and the work model was created from the vinyl-polysiloxane impression. After scanning the working model, the design software is used to design the crown. The saved STL file is used on the CAD/CAM milling method and two types of 3D printing method to produce 10 interim crowns per group. Internal discrepancy measurement uses the silicon replica method and the measured data are analyzed with One-way ANOVA to verify the statistic significance. RESULTS. The discrepancy means (standard deviation) of the 3 groups are $171.6\;(97.4){\mu}m$ for the crown manufactured by the milling system and 149.1 (65.9) and $91.1\;(36.4){\mu}m$, respectively, for the crowns manufactured with the two types of 3D printing system. There was a statistically significant difference and the 3D printing system group showed more outstanding value than the milling system group. CONCLUSION. The marginal and internal fit of the interim restoration has more outstanding 3D printing method than the CAD/CAM milling method. Therefore, the 3D printing method is considered as applicable for not only the interim restoration production, but also in the dental prosthesis production with a higher level of completion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.639-640
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• 2009

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.775-780
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• 2007

Rapid Prototyping (RP) is a technology that produces prototype parts from 3D computer aided design model data without intermediate processing technology rapidly. CAD model data are created from 3D object digitizing systems but presented just as 2D data when they are printed as a hard copy or displayed on a monitor. However, Rapid Prototyping Technology fabricates 3D objects the same that CAD data because it transforms designed 3D CAD data into 2D cross sectional data, and manufactures layer by layer deposition sequentially. But most of all the small and medium scale companies which produce a toothbrush, a toy and such like provisions are in difficult situations to buy RP system because it is very expensive. In this paper, we propose a 3D control system adopting open source programs for implementing Rapid Prototyping Technology in order that RP system can be purchase at a moderate price.