• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.137-143
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• 2018

DICOM images of patellofemoral bones were converted into a stereolithography file, and a Unigraphics CAD program was used to create a CAD modeling in which there exists point, line and facet information. The modeling extraction of joint facets was performed by linking two adjacent points into lines in the stereolithography file by using the Unigraphics rapid spacing function and then linking the lines into facets to complete the entire modeling. This modeling extraction was performed based on the anatomical knowledge of joint facet directions. As a result, a personalized space modeling and solid modeling were produced for the joint facets of patellofemoral bones. This was followed by a CAM control computing operation of solid modeling on graphite materials and 5-axis machining of patellofemoral bones. That is the description of a method for a personalized implant modeling by using DICOM images of patellofemoral bones.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.15-23
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• 2002

With the development of a laser scanner of high precision and increased speed, reverse engineering becomes a key approach to reduce the time for the development of new products. But the modeling process is not so automated enough until now. Modeling in real workshops is usually performed by the experienced operators and it requires a skillful technique to get the resultant surface of high quality and precision. In this paper, a systematic solution is proposed to automate the free-form surface generation from the measured point data. Compatibility is imposed to the measured point data during input curve generation. And the compatibility of cross-sectional curve is also considered for the loft surface generation. The data in each step is produced in IGES file format to make an easy interface to other CAD/CAM software without any further data manipulation.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.51-58
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• 2006

In rapid prototyping, the optimal part orientation during fabrication is critical as it can improve part accuracy, minimize the requirement for supports and reduce the production time. Through investigating the geometric issues of STL model and process planning of RPM, This paper establishes optimizing model based on the considerations of staircase effect, support area and production time. The general satisfactory degree function is constructed employing the multi-objective optimization theory based on the general satisfactory degree principle. The best part-building orientation is obtained by solving the function employing generic algorithm. Experiment shows that the methods can effective resolve the part-building orientation in RP.

• IE interfaces
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• v.13 no.4
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• pp.717-724
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• 2000

In this paper, an integrated system of optimal design, performance evaluation, and die design and manufacturing of axial fans for cooling tower is presented. The design and performance evaluation are developed based on three dimensional flow analysis so as to ensure low noise and high efficiency. The methodologies are implemented on computer as a GUI system including 3-D surface modeling and 2-D drawing file output modules. The CAD/CAM system is engaged to design the die and generate NC tool path, but the processes are also automated and integrated into the system by means of a part program coded from the design data. It is shown that the newly developed fans have superior performance and shortened lead-time compared to the existing dead-copied fans.

• International Journal of CAD/CAM
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• v.4 no.1
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• pp.33-45
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• 2004

In this work, a rational procedure has been formulated for the selection of points approximating slice contours cut in LOM (Laminated Object manufacturing) with first order approximation. It is suggested that the number of points representing a slice contour can be 'minimised' or 'optmised' by equating the horizontal chordal deviation (HCD) to the user-defined surface form tolerance. It has been shown that such optimization leads to substantial reduction in slice height calculations and NC codes file size for cutting out the slices. Due to optimization, the number of contour points varies from layer to layer, so that points on successive layer contours have to be matched by four sided ruled surface patches and triangular patches. The technological problems associated with the cutting out of triangular patches have been addressed. A robust algorithm has been developed for the determination of slice height for optimum and arbitrary numbers of contour points with different strategies for error calculations. It has been shown that optimisation may even lead to detection and appropriate representation of elusive surface features. An index of optimisation has been defined and calculations of the same have been tabulated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1295-1298
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• 2004

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It is used to fabricate desirable part to sinter powder and stack the fabricated layer. To develop this SLS machine, it needs effective scanning path and the development of scanning device. This paper shows how to make fast scanning path with respect to scan spacing, laser beam size and scanning direction from 2-dimensional sliced file generated in commercial CAD/CAM software. Also, we develop the scanning device and its control algorithm to precisely follow the generated scanning path. Scanning path affects precision and total machining time of the final fabricated part. Sintering occurs using infrared laser which has high thermal energy. As a result, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, fast scanning path generation is needed to eliminate the factors of quality deterioration. It highly affects machining efficiency and prevents shrinkage and curling by relatively lessening the thermal distribution of the surface of sintering layer. To generate this fast scanning path, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction must be enabled. This paper addresses path generation method to focus on fast scanning, and development of scanning system and control algorithm to precisely follow generated path.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.239-243
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• 2017

PURPOSE. The purpose of this study is to compare single and three-unit metal frameworks that are produced by micro-stereolithography. MATERIALS AND METHODS. Silicone impressions of a selected molar and a premolar were used to make master abutments that were scanned into a stereolithography file. The file was processed with computer aided design software to create single and three-unit designs from which resin frameworks were created using micro-stereolithography. These resin frameworks were subjected to investment, burnout, and casting to fabricate single and three-unit metal ones that were measured under a digital microscope by using the silicone replica technique. The measurements were verified by means of the Mann-Whitney U test (${\alpha}=.05$). RESULTS. The marginal gap was $101.9{\pm}53.4{\mu}m$ for SM group and $104.3{\pm}62.9{\mu}m$ for TUM group. The measurement of non-pontics in a single metal framework was $93.6{\pm}43.9{\mu}m$, and that of non-pontics in a three-unit metal framework was $64.9{\pm}46.5{\mu}m$. The dimension of pontics in a single metal framework was $110.2{\pm}61.4{\mu}m$, and that of pontics in a three-unit metal framework was $143.7{\pm}51.8{\mu}m$. CONCLUSION. The marginal gap was smaller for the single metal framework than for the three-unit one, which requires further improvement before it can be used for clinical purposes.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.31-38
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• 2023

Purpose: This in vitro study aimed to compare the trueness of 3-unit fixed dental provisional prostheses (FDPs) fabricated by three different additive manufacturing and subtractive manufacturing procedures. Methods: A reference model with a maxillary left second premolar and the second molar prepped and the first molar missing was scanned for the fabrication of 3-unit FDPs. An anatomically shaped 3-unit FDP was designed on computer-aided design software. 10 FDPs were fabricated by subtractive (MI group) and additive manufacturing (stereolithography: SL group, digital light processing: DL group, liquid crystal displays: LC group) methods, respectively (N=40). All FDPs were scanned and exported to the standard triangulated language file. A three-dimensional analysis program measured the discrepancy of the internal, margin, and pontic base area. As for the comparison among manufacturing procedures, the Kruskal-Wallis test and the Mann-Whitney test with Bonferroni correction were evaluated statistically. Results: Regarding the internal area, the root mean square (RMS) value of the 3-unit FDPs was the lowest in the MI group (31.79±6.39 ㎛) and the highest in the SL group (69.34±29.88 ㎛; p=0.001). In the marginal area, those of the 3-unit FDPs were the lowest in the LC group (25.39±4.36 ㎛) and the highest in the SL group (48.94±18.98 ㎛; p=0.001). In the pontic base area, those of the 3-unit FDPs were the lowest in the LC group (8.72±2.74 ㎛) and the highest in the DL group (20.75±2.03 ㎛; p=0.001). Conclusion: A statistically significant difference was observed in the RMS mean values of all the groups. However, in comparison to the subtractive manufacturing method, all measurement areas of 3-unit FDPs fabricated by three different additive manufacturing methods are within a clinically acceptable range.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.524-531
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• 1992

S/W의 구성은 기능을 실제로 수행하는 계산처리부와 사용자와 정보를 주고받는 User Interface부로 크게 나누어 볼 수 있다. 대부분의 S/W는 그 기능의 충실도와 아울러 편리한 사용법이 잘 어울려야 제역할을 할 수 있다. 따라서 편리한 User Interface를 만드는 일은 훌륭한 기능을 제공하는 것과 마찬가지로 S/W 개발자들이 지향해야 할 목표중 하나라 하겠다. 그러나 편리한 User Interface를 만드는 일은 전체 시스템개발 기간중 상당한 부분을 차지한다. 특히 CAD/CAM관련 S/W와 같이 사용자와 정보를 Graphic으로 주고받는 경우에는 User Interface의 구성이 더욱 더 어려워지며, 개발기간중 User Interace가 차지하는 비중은 더욱 커지게 된다. GUI는 최근들어 상당히 각광을 받고 있는 분야이며, 상당수의 GUI가 개발되어 있고, 이중 Unix용의 X-Window MS-DOS용의 MS-WINDOWS 3.0이 널리 사용되고 있다. 그러나 이러한 Window System들은 매우 다양한 기능을 제공하고 있음에도 불구하고, GUI자체의 덩치가 매우크고, S/W개발자가 익혀야하는 내용이 너무 복잡하여, 중/소형의 S/W개발에 사용하기에는 적합하지 않다. 본 연구에서는 GUI(Graphic User Interface)부분을 계산처리부와 완전분리하여, 범용성있는 개발용 Tool Kit을 구성함으로써 S/W개발자는 계산처리부만을 만들면되는 방안을 제시하고 있다. GS-GUI는 Menu처리부, Mouse/Keyboard입력처리부, Text/Graphic출력처리부로 나뉘어진다. Menu처리부는 Menu File로 주어지는 Menu Tree를 Pop-Up형태로 보여주며 User가 Menu를 선택할 수 있도록하며 선택된 Menu Item에 대한 Action Code를 계산처리부로 넘겨준다. 입력처리부에서는 Mouse와 Keyboard 어느것으로나 입력이 가능하도록 해준다. 출력처리부에서는 Action Code에 따라 계산처리부에서 계산된 결과를 화면에 보여주기 위한 각종 2D/3D Graphic Routine들이 포함되어있어 계산처리부에서 불러쓰도록 되어있다.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.1
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• pp.1-8
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• 2017

Purpose: The purpose of this study is to compare the accuracy of the CT guided implant template that was produced by using an intraoral scanner according to the edentulous distance. Materials and methods: Five maxillary casts were fabricated using radiopaque acrylic resin with the second premolars, first molars, and second molars missing. Then a virtual cast was acquired by scanning each resin cast. Implant treatment was planned on the missing sites by superimposing the presurgical CT DICOM file and the virtual cast. Then the implants were placed using a surgical template followed by postsurgical CT scan. The distance and angle of the platform and apex between the presurgical implant and postsurgical implant were measured using the X, Y, and Z axis of the superimposed presurgical CT and postsurgical CT via software followed by statistical analysis using Kruskall-Wallis test and Mann-Whitney test. Results: The implant placement angle error increased towards the second molars but there was no statistically significant difference. The implant placement distance error at the platform and apex also increased towards the second molars and there was a statistically significant error at the second molars. Conclusion: Although the placement angle had no statistically significant difference between the presurgical implant and postsurgical implant, the placement distance at the platform and apex showed a larger error and a statistically significant difference at the second molar implant.