• International Journal of CAD/CAM
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• 제7권1호
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• pp.81-89
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• 2007

As the modular production is an important issue in globalized manufacturing industries, sub modules or parts of the final product are provided by many suppliers. Some part suppliers design their own products for themselves. In some cases, part supplier may provide the same type product to multiple 1-tier companies. Because all suppliers and 1-tier companies can not use the same CAD system in general case, the engineering change in the CAD model of one company could not propagate to related CAD models of other companies directly. Although they use the same CAD system, it is hard to share their CAD model with each other because of company security policy. In this paper, the neutral reference model, which consists of the neutral skeleton model and the external reference model, is proposed to apply a global top-down modeling approach to collaborating companies.

• 한국CDE학회논문집
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• 제10권4호
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• pp.262-273
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• 2005

For CAD data users, few things are as frustrating as receiving CAD data that is unusable due to poor data quality. Users waste time trying to get better data, fixing the data, or even rebuilding the data from scratch from paper drawings or other sources. Most related works and commercial tools handle the boundary representation (B-Rep) shape of CAD models. However, we propose a design history?based approach for healing CAD model errors. Because the design history, which covers the features, the history tree, the parameterization data and constraints, reflects the design intent, CAD model errors can be healed by an interdependency analysis of the feature commands or of the parametric data of each feature command, and by the reconstruction of these feature commands through the rule-based reasoning of an expert system. Unlike other B Rep correction methods, our method automatically heals parametric feature models without translating them to a B-Rep shape, and it also preserves engineering information.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.355.1-355
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• 2002

Topology optimization is widely accepted as a conceptual design tool for the product design. Since the resulted layout of the topology optimization is a kind of digital images represented by the density distribution, the seamless process is required to transform digital images to the CAD model for the practical use. In this paper, the general process to construct a CAD model is developed to apply for topology images based on elements. (omitted)

• The Journal of Advanced Prosthodontics
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• 제10권3호
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• pp.245-251
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• 2018

PURPOSE. To evaluate the accuracy of a model made using the computer-aided design/computer-aided manufacture (CAD/CAM) milling method and 3D printing method and to confirm its applicability as a work model for dental prosthesis production. MATERIALS AND METHODS. First, a natural tooth model (ANA-4, Frasaco, Germany) was scanned using an oral scanner. The obtained scan data were then used as a CAD reference model (CRM), to produce a total of 10 models each, either using the milling method or the 3D printing method. The 20 models were then scanned using a desktop scanner and the CAD test model was formed. The accuracy of the two groups was compared using dedicated software to calculate the root mean square (RMS) value after superimposing CRM and CAD test model (CTM). RESULTS. The RMS value ($152{\pm}52{\mu}m$) of the model manufactured by the milling method was significantly higher than the RMS value ($52{\pm}9{\mu}m$) of the model produced by the 3D printing method. CONCLUSION. The accuracy of the 3D printing method is superior to that of the milling method, but at present, both methods are limited in their application as a work model for prosthesis manufacture.

• 대한조선학회논문집
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• 제35권4호
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• pp.98-108
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• 1998

중앙 단면도 등의 선박의 초기 구조설계는 여러 가지 이유로 2차원으로 설계되어 다른 설계부서에 도면으로 전달되고 있다. 본 연구에서는 기능이 서로 다른 여러 가지 컴퓨터 시스템사이의 데이터 교환을 위한 예제로, AutoCAD로 작성된 2차원의 초기 구조 설계 데이터를 구조해석(FEM) 시스템이나 상세설계 시스템(AutoDef)등의 다른 시스템에서 사용할 수 있는 데이터를 생성해 보았다. 이를 위해 STEP 제품모델의 방법에 따라 데이터가 정의 되었으며 2D 형상이나 3D 와이어프레임, 솔리드 모델등 다양한 형상을 다룰 수 있는 복합다양체 모델링 형상 도구인 ACIS가 사용되었다.

• International Journal of CAD/CAM
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• 제7권1호
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• pp.1-10
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• 2007

The compression of CAD models is a key technology for realizing Internet-based collaborative product development because big model sizes often prohibit us to achieve a rapid product information transmission. Although there exist some algorithms for compressing discrete CAD models, original precise CAD models are focused on in this paper. Here, the characteristics of hierarchical structures in CAD models and the distribution of their redundant data are exploited for developing a novel data encoding method. In the method, different encoding rules are applied to different types of data. Geometric data is a major concern for reducing model sizes. For geometric data, the control points of B-spline curves and surfaces are compressed with the second-order predictions in a local coordinate system. Based on analysis to the distortion induced by quantization, an efficient method for computation of the distortion is provided. The results indicate that the data size of CAD models can be decreased efficiently after compressed with the proposed method.

• 한국CDE학회논문집
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• 제12권4호
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• pp.233-244
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• 2007

Web Services are a distributed component technology based on XML and Web. The Web Services are used to integrate heterogeneous systems under the distributed environment. In this study, the concept of Web Services for CAD (WSC) is introduced, which aims at interoperation with CAD systems using the Web Services. This paper introduces one part of the WSC which enables remote users or applications to retrieve the geometries and the design history of CAD models using the Web Services. This paper proposes an architecture of the WSC, the data model and the interfaces for retrieving CAD model information, and the way to apply the WSC to commercial CAD systems.

• 한국CDE학회논문집
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• 제11권1호
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• pp.27-40
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• 2006

The exchange of parameterized feature-based CAD models is important for product data sharing among different organizations and automation systems. The role of feature-based modeling is to gonerate the shape of product and capture design intends In a CAD system. A feature is generated by referring to topological entities in a solid. Identifying referenced topological entities of a feature is essential for exchanging feature-based CAD models through a neutral format. If the CAD data contains the modification history in addition to the construction history, a matching mechanism is also required to find the same entity in the new model (post-edit model) corresponding to the entity in the old model (preedit model). This problem is known as the persistent naming problem. There are additional problems arising from the exchange of parameterized feature-based CAD models. Authors have analyzed previous studies with regard to persistent naming and characteristics for the exchange of parameterized feature-based CAD models, and propose a solution to the persistent naming problem. This solution is comprised of two parts: (a) naming of topological entities based on the object spore information (OSI) and secondary name (SN); and (b) name matching under the proposed naming.

• 한국건설관리학회논문집
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• 제5권4호
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• pp.107-114
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• 2004

4D 모델은 프로젝트 수행 이전에 다양한 공정대안을 비교 검토해볼 수 있는 기능을 제공하나 아직 그 활용이 미비한 실정이다. 이는 4D 모델의 구현에 수반되는 기술적, 경제적 문제에 기인하는 바 크다. 본 논문에서는 3D모델 정보의 활용을 통해 이러한 문제의 해결방안을 제시하였다. 즉, 기 생성된 3D 모델 정보를 가공하여 동일한 3D 모델에 대해 여러 가지 공정대안을 신속하게 생성해내는 공정 자동생성 기능을 이용함으로써 기존 4D시스템 연구에서 문제점으로 지적되었던 정보 변경에 따른 4D 모델 재구현 문제를 상당부분 개선하였다. 또한, 특정 작업기간에 따른 소요물량을 간편하게 산출해내는 물량정보 검색 기능을 통해 4D 모델의 대안검토 기능을 보완하였다. 특히 공정 자동생성 기능에서는 수평 및 수직적 우선순위의 조정을 통해 부재간, 층간 우선순위를 결정할 수 있도록 함으로써 공정순서를 신속하게 생성해낼 수 있는 환경을 제공하였다. 이것은 3D 모델이 변경되지 않은 상태에서 다양한 공정대안의 신속한 생성을 통한 비교 검토에 효과적으로 활용할 수 있으며, 3D 모델이 변경된 경우에도 4D 모델 생성을 위한 이후의 작업과정을 손쉽게 진행시켜 나갈 수 있는 장점이 있다. 아울러 3D 모델로부터 생성되는 물량정보와 공정계획 결과로부터 생성되는 일정정보를 연계시킴으로써 간편하게 일정별 소요물량 정보를 검색할 수 있게 하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.523-528
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• 2002

Topology optimization is widely accepted as a conceptual design tool for the product design. Since the resulted layout of the topology optimization is a kind of digital images represented by the density distribution, the seamless process is required to transform digital images to the CAD model for the practical use. In this paper, the general process to construct a CAD model is developed to apply for topology images based on elements. The node density and the morphology technique is adopted to extract boundary contour of the shape and remove the noise of images through erosion and dilation operation. The proposed method automatically generates point data sets of the geometric model. The process is integrated with Pro/Engineer, so that the engineer in practice can directly handle with curves or surface form digital images.