• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.205-210
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• 2005

This paper addresses the correlation between the change of file size and the scanning path build time by the slicing height of STL file. Though the study about STL file has been achieved quite actively scanning path build time using STL file is not investigated so much to be satisfied. The file size depends on the number of polygon created by the slicing height specified. And this number of polygons increases in a regular rate. The correlation between the number of polygons and the scanning path build time is examined and verified.

• Journal of Korea Multimedia Society
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• v.5 no.5
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• pp.552-561
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• 2002

In this paper, a new watermarking algorithm for STL files which contains 3D geometric information as triangular facets is proposed. STL files are widely used in rapid prototyping industry as a standard interchange format. The proposed algorithm inserts multi-bit watermark information into the surface normal vector and vertex description area of STL file without distorting the original 3D geometric information. According to the watermark bits, the position of normal vector and the direction of vertex sequence are modulated. The proposed algorithm is robust to the attack of changing the order of the triangular meshes. In addition, the invisibility requirement is also satisfied. Experiment results show that the proposed algorithm can encode and decode watermark bits into the various STL files without any distortion of 3D shape.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.105-108
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• 1997

To reduce design period, demands for rapid prototyping system is increasing. Among the rapid prototyping system, as a concept modeler, 3D Printer appears before the footlights. In spite of short production time and convenience, 3D Printer causes post processing problem. And that is too slow to adapt to the demand of workshop. In this research, we developed a system for reducing build time and roughness using splitting operation. Also, propose BFS(B-rep For STL) data structure to maintain model data, split STL model and implement Euler Operation for input and output.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.997-999
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• 2015

SketchUP은 최근 인기를 얻고 있는 3D 모델링 도구지만, 3D 프린터용 표준 파일 포맷인 STL을 지원하지 않는 단점이 있다. 본 논문에서는 SketchUp에서 만든 3D 모델(FBX)을 불러 와서 사용하고, STL로 변환할 수 있는 프로그램을 구현하는 방법을 논한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.53-56
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• 2001

Reverse engineering has been widely used for the shape reconstruction of an object without CAD data and it includes some steps such as scanning of a clay or wood model, and generating some manufacturing data in an STL file. A new approach to remove point data with Delaunay triangulation is introduced to deal with the size problems of STL file and the difficulties in the operation of RP process. This approach can be used to reduce a number of measuring data from laser scanner within a specified tolerance, thus it can avoid the time for handing point data during modeling process and the time for verifying and slicing STL model during RP process. Developed software enables the user to specify the criteria for the selection of group of triangles either by the angle between triangles or the percentage of triangles reduced, and thus RP models with accuracy will be helpful to automated process.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.465-470
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• 2008

Sound transmission characteristics are investigated on the honeycomb panels used for railway vehicles. Equivalent orthotropic plate model and equivalent mass law are applied to predict the sound transmission loss (STL) of the honeycomb panels. The predicted values of the STL are compared with the measured values. The reliability and the limitation of the prediction models are investigated. Coincidence effect and local resonance effect on STL are considered. The result of the study shows that the equivalent orthotropic plate model can be used as a good prediction model, if the local resonance frequency is properly applied. finally, ways to improve the severe STL drop by local resonance are proposed and the effect on the sound insulation performance is analysed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.739-746
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• 2007

Recently, models in STL files are widely used in reverse engineering processes, CAD systems and analysis systems. However the models have poor geometric quality and include only triangles, so the models are not suitable for the finite element analysis. This paper presents a general method that generates finite element mesh from STL file models. Given triangular meshes, the method estimates triangles and makes clusters which consist of triangles. The clusters are merged by some geometric indices. After merging clusters, the method applies plane meshing algorithm, based on domain decomposition method, to each cluster and then the result plane mesh is projected into the original triangular set. Because the algorithm uses general methods to generate plane mesh, we can obtain both tri and quad meshes unlike previous researches. Some mechanical part models are used to show the validity of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.587-591
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• 1996

Usually triangular patches are used to transfer geometric shape in Rpaid Prototyping CAM system. STL, a list of triangles, is de facto in RP industry. Because STL has no topology data, it can cause errornous results. So, STL should be verified before using. After adding support structures to anchor the part to the platform and to prevent sagging or distortion, slicing and layer by layer manufacturing process are done. But triangular patch is surface model and cannot provide dufficient information on geometry in the above processes. So, geometric modeling is necessary in verifying STL, adding support structures, and slicing. It is natural that triangle based modeling is the best when traingular patches are used as input. Considering support structures, solid and faces coexist in RP process. Therefore non-manifold modeler is required. In this study, triangle based non-manifold geometric modeling is proposed for RP system consitent with STL input.

• Korean Journal of Computational Design and Engineering
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• v.6 no.1
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• pp.48-58
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• 2001

One of the biggest problems of rapid prototyping(RP) technologies lies in their standard file format for CAD data exchange. Current methods using the de facto industry standard 'STL'have at times resulted in problems such as accuracy, redundancy, and integrity. In this paper we propose a STEP based data exchange framework for rapid prototyping systems. In this paradigm of data exchange, STEP models can be imported and converted into faceted B-rep. solid models for visualization and 2-D layer data for RP. Also an STL model, on the other hand, can be converted into a faceted B-rep. STEP model and exported as a new data exchange model with RP information.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.1
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• pp.68-74
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• 2000

The STL file format is an approximation of 3-D model with triangular facets. STL is a standard input file format of Rapid Prototyping(RP) equipment In computer graphics a circle has been approximated with an inscribed polygon which causes an error between the real and approximated circles. In this study an intersecting polygon has been used to approximate the circle and applied to produce more accurate RP part. The newly proposed method shows it's excellence in part accuracy.