• 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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• 1995.10a
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• pp.889-893
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• 1995

This paper verified error of STL file and presented a new application of reformed division method for reducing to appeared error by using Delaunay triangulation method that used to modify error of verified data. First, it is analyzed each vertices in hole error and classified follow case that is 1. case of plan or slope, 2. case of edge, 3. case of apex and 4. case of rapid curve, and reduced volume tolerance between original model and converted model after convert STL file.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.3
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• pp.157-166
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• 2018

Purpose: This study was aimed to compare the consistency between the custom abutment design and the output in two CAD software programs. Materials and Methods: Customized abutments were designed by using 3Shape Dental System CAD software and Delta9 CAD software on a plaster model with implants (CRM STL file). After milling of the designed abutments, the abutments were scanned with a contact method scanner (Test STL file). We overlaid the Test STL file with each CRM STL file by using inspection software, and then compared the milling reproducibility by measuring the output error of the specimens from each CAD software program. Results: The Delta9 showed better milling reproducibility than 3Shape when comparing the milling errors obtained with a full scan of all specimens (P < .05) and also when comparing the axial wall region specifically according to the axial angle. With 0.9 mm marginal radius, the Delta9 showed better consistency between the design and the output than 3Shape (P < .05). While, anti-rotation form had no significant difference in error between the two systems. When cumulative errors were compared, the Delta9 showed better milling reproducibility in almost cases (P < .05). Conclusion: Delta9 showed a significantly smaller error for most of the abutment design options. This means that it is possible to facilitate generation of printouts with reliable reproducibility and high precision with respect to the planned design.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.154-159
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• 2004

This study is aimed to diminish the errors which created during transforming from 3D shape created with CAD program to STL file formation. The length strain which created on X-Y axises at STL file transforming is diminished by using the relation between common shape error and shrinkage rate. As the result of study, we have confirmed the length strain in accordance with facetres value. Also, the shape error is compensated with shrinkage rate by error of length strain. so, we could diminish to shape error by several tens micrometer.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.18-25
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• 1996

In this study, we have developed the stereolithography system that supports the development of a products. This paper presents the development of the stereolithography system. The system is composed of hardware, software and control part. The software converts a STL file to NC data and displays the monitoring figure in control part. The hardware part deals with structure of machine. The most important theme in this paper is LG-SLCAM software. This software can generate NC data and scanning condition data from a STL file semiautimatically. On the basis of three diensional shapes, it makes data for support structure from STL file. The effectiveness of using out stereolithography system is confirmed by processes of good development.

• 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.

• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.78-86
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• 2018

The 3D mesh model is used in various fields, such as virtual reality, shape-based searching, 3D simulation, reverse engineering, 3D printing, and laser scanning. There are various formats for the 3D mesh model, but STL and OBJ are the most typical. Since application systems support different 3D mesh formats, developing technology for converting 3D mesh models from one format into another is necessary to ensure data interoperability among systems. In this paper, we propose a method to convert a 3D mesh model in STL format into the OBJ format. We performed the basic design of the conversion system and developed a prototype, then verified the proposed method by experimentally converting an STL file into an OBJ file for test cases using this prototype.

• 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 Precision Engineering
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• v.23 no.2 s.179
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• pp.191-198
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• 2006

Dieless CNC forming is an innovative technology which can form various materials with complex shape by numerically controlled incremental forming process. In this paper, a method of NC tool path generation based on an STL file for dieless CNC forming is proposed. Tool trajectory adopts the principle of layered manufacturing in rapid prototyping technology, but it is necessary to consider STL offset because of the ball shaped tool with a radius. Vertex offset method which enables to compute offset STL directly is engaged for STL offset. The offseted STL is sliced by cutting planes to generate contouring tool path. Algorithm is implemented on a computer and experimented on a dieless CNC forming machine to show its validity.