• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.617-628
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• 1995

본 논문에서는 상용화된 이 기종 CAD/CAM 시스템간의 CAD 데이타 교환기능을 가지는 IGES Translator 시스템의 구조를 제안한다. 제품생산의 여러 단계에서 CAD/CAM의 사용이 보편화되어감에 따라 상용 CAD/CAM 시스템들은 응용분야에 맞는 특수한 도구로 사용되는 경향이 생겨났다. 예를 들어, ALIAS는 주로 스타일링 디자인에, I-DEAS와 PRO/ENGINEER는 엔지니어링 디자인에, EUCLID는 금형 디자인에, 그리고 OMEGA와 Z-MASTER는 NC 공구경로생성에 주로 사용되고 있다. CAD 데이타 교환을 위해 제안된 중립파일형식(Neutral File Format)중에서, IGES(Initial Graphics Exchange Specification)는 대부분의 상용 CAD/CAM 시스템에서 지원을 하고 있으며 가장 널리 쓰이는 파일형식이다. 그런데, IGES를 통한 CAD 데이타 교환은 다음과 같은 문제점들을 가지고 있다. 즉, patch의 사라짐, 경계곡선의 왜곡, patch의 overlap 또는 gap, trimming error, 곡면각의 꺾임각도 등이 그것이다. 이 논문의 목적은 이러한 문제점들을 해결할 수 있는 범용 IGES Translator를 개발하는데 있다. 이 논문의 주요한 기여 내용은 다음과 같다. 1) 주요 상용 CAD/CAM 시스템의 IGES Interface 기능의 비교 분석, 2) 주요 상용 IGES Translator의 기능 분석, 3) 사용자의 기능적 요구사항의 분석, 4) 사용자 관점 및 시스템 관점에서의 IGES Translator의 구조 제안, 5) Prototype IGES Translator의 개발 및 테스트 결과 제시.

• The Journal of Advanced Prosthodontics
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• v.10 no.5
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• pp.335-339
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• 2018

PURPOSE. The purpose of the present study was to compare scanning trueness and precision between an abutment impression and a stone model according to dental computer-aided design/computer-aided manufacturing (CAD/CAM) evaluation standards. MATERIALS AND METHODS. To evaluate trueness, the abutment impression and stone model were scanned to obtain the first 3-dimensional (3-D) stereolithography (STL) file. Next, the abutment impression or stone model was removed from the scanner and re-fixed on the table; scanning was then repeated so that 11 files were obtained for each scan type. To evaluate precision, the abutment impression or stone model was scanned to obtain the first 3-D STL file. Without moving it, scanning was performed 10 more times, so that 11 files were obtained for each scan type. By superimposing the first scanned STL file onto the other STL files one by one, 10 color-difference maps and reports were obtained; i.e., 10 experimental scans per type. The independent t-test was used to compare root mean square (RMS) data between the groups (${\alpha}=.05$). RESULTS. The $RMS{\pm}SD$ values of scanning trueness of the abutment impression and stone model were $22.4{\pm}4.4$ and $17.4{\pm}3.5{\mu}m$, respectively (P<.012). The $RMS{\pm}SD$ values of scanning precision of the abutment impression and stone model were $16.4{\pm}2.9$ and $14.6{\pm}1.6{\mu}m$, respectively (P=.108). CONCLUSION. There was a significant difference in scanning trueness between the abutment impression and stone model, as evaluated according to dental CAD/CAM standards. However, all scans showed high trueness and precision.

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.81-86
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• 2019

Purpose: The purpose of the present study was to compare the internal fit of two different temporary restorations fabricated by dental CAD/CAM system and to evaluate clinical effectiveness. Methods: Composite resin tooth of the maxillary first molar was prepared as occlusal reduction(2.0mm), axial reduction(1mm offset), vertical angle(6 degree) and chamfer margin for a temporary crown and duplicated epoxy die was fabricated. The epoxy dies were used to fabricate provisional restorations by CAD/CAM milling technique or 3D-printing technique. The inner data from all crowns were superimposed on the master die file in the 'best-fit alignment' method using 3D analysis software. Statistical analysis was performed using a Wilcoxon's rank sum test for differences between groups. Results: It showed that the internal RMS(Root Mean Square) values of the additive group were significantly larger than those of other group. No significant differences in internal discrepancies were observed in the temporary crowns among the 2 groups with different manufacturing method. Conclusion: All the groups had the internal fit within the clinical acceptable range (< $50{\mu}m$). The continuous research in the future to be applied clinically for the adaptation of additive manufacturing technique are needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.592-596
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• 1996

The CAD/CAM System oriented to StereoLithographic Rapid Prototyping was constructed and developed. The software architecture uses a 586PC running the windows NT operating system. An .STL file brought into the software program can be verified in divers view points and focused for a detail of concern. A variety of Entity was applied to define an array of triangular facets and sliced loops. The system provides Edit, Scale, Orient, Copy and Divide commands to modify .STL model. The NC codes are created according to various laser beam scan pattern and the software show the parts on the platform before they are constructed. This system is written in Visual C and has been proved as a powerful tool for producing solid parts directly from a CAD modelling, using actual applications.

• International Journal of CAD/CAM
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• v.5 no.1
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• pp.69-81
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• 2005

As collaborative design and configuration design gain increasing importance in product development, it becomes essential to exchange parametric CAD models among participants. Parametric CAD models can be represented and exchanged in the form of a macro file or a part file that contains the modeling history of a product. The modeling history of a parametric CAD model contains feature specifications and each feature has selection information that records the name of the referenced topological entities. Translating this selection information requires solving the problems of how to identify the referenced topological entities of a feature (persistent naming problem) and how to convert the selection information into the format of the receiving CAD system (naming mapping problem). The present paper introduces the problem of exchanging parametric CAD models and proposes a solution to naming mapping.

• The Journal of Society for e-Business Studies
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• v.3 no.1
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• pp.1-22
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• 1998

SDAI (Standard Data Access Interface) is an interface specification of accessing various storage systems such as file systems and database management systems for STEP data. Using SDAI, both application program developers and CAD/CAM system developers can be relieved from dealing with STEP physical file or system dependent DBMS operations. In this paper, we present implementations of SDAI on different data models, i.e., relational, extended relational, and object-oriented. In order to implement SDAI, we need to translate the EXPRESS information model into target data models. The schema translation process for three different data models are compared and other implementation issues are discussed.

• International Journal of CAD/CAM
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• v.2 no.1
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• pp.55-67
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• 2002

In many areas of industry, it is desirable to have fast and reliable systems in order to quickly obtain suitable solid models for computer- aided analyses. Nevertheless it is well known that the data exchange process between CAD modelers and CAE packages can require significative efforts. This paper presents an approach for geometrical data exchange through triangulated boundary models. The proposed framework is founded on the use of STL file specification as neutral format file. This work is principally focused on data exchange among CAD modelers and FEA packages via STL. The proposed approach involves the definition of a topological structure suitable for the STL representation and the development of algorithms for topology and geometry data processing in order to get a solid model suitable for finite element analysis or other computer aided engineering purposes. Different algorithms for model processing are considered and their pros and cons are discussed. As a case study, a prototype modeler which supports an exporting filter for a commercial CAE package has been implemented.

• 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.

• International Journal of CAD/CAM
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• v.2 no.1
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• pp.13-21
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• 2002

It is not possible to exchange parametric information of CAD models based on the current version of STEP. The design intent can be lost during the STEP transfer of CAD models. The Parametrics Group of ISO/TC184/SC4 has proposed the SMCH schema, which includes constructs for exchange of parametric information. This paper proposes a macro-parametric approach that is intended to provide capabilities to transfer parametric information including design intents. In this approach, CAD models are exchanged in the form of macro files. The macro file contains the history of user commands, which are used in the modeling phase. To exchange CAD models using the macro-parametric approach, the modeling commands of several commercial CAD systems are analyzed. Those commands are classified and a set of standard modeling commands has been defined. Mapping relations between the standard modeling commands and the native modeling commands of commercial CAD systems are defined. The scope of the current version is limited to parts modeling, not assemblies.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.4
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• pp.478-486
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• 2021

This report demonstrates a method of generating a chair-side and computer-aided template for implant surgery based on the Top-Down and restoration-driven concept. Compared to the traditional CAD-CAM process which requires multiple steps to be taken between dental clinic and laboratory, this alternative procedure, VARO guide system (VARO Guide, CAD, Pre-Guide, VARO-mill, NeoBiotech, Seoul, South Korea) enables accurate and patient-friendly implant surgery as well as immediate provisional restoration in a single visit. First, bite-registration at centric jaw relation and CBCT were taken using the Pre-Guide. The CBCT data was then reorganized directly through the chair-side CAD, and we could determine the most appropriate 3-dimensional position of implant. The STL file was extracted and put into the chair-side CAM (VARO-mill) to fabricate a VARO. This surgical guide allowed the implants to be accurately positioned into the planned sites within an hour.