• 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 Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.2047-2053
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• 2008

Auto-ID industries and their services have been improved since decades ago, and radio frequency identification (RFID) has been contributing in many applications. Product management can be the foremost example. In our industrial experiences, RFID in ultra high frequency (UHF) band provides much longer interrogation ranges than that of 13.56MHz; many more applications exist thereby. There should be several interesting and useful ideas on UHF RFID; however, those ideas can be limited due to the inevitable environmental circumstances that restrict the interrogation range in shorten value. This paper discusses the propagation interference among different types of readers (e.g, mobile RFID readers in stationary reader zone) in dense-reader environment. In most cases, UHF RFIDs in Korea will be dependent on the UHF mobile RFIDs. In this sense, the UHF mobile users accidently move into the stationary reader's interrogation zone. This is serious problem. In this paper, we analyze propagation loss and propose the effective channel allocation scheme that can contribute developing less-invasive UHF RFID networks. The simulation and practical measurement process using the commercial CAD tools and measurement equipments are presented.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.904-914
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• 2004

The fiber reinforced composite material is widely used in the multi-industrial field because of their high specific modulus and specific strength. It has two main merits which are to cut down energy by reducing weight and to prevent explosive damage proceeding to the sudden bursting which is generated by the pressure leakage condition. Therefore, Pressure vessels using this composite material can be applied in the field such as defence industry and aerospace industry. In this paper, for nonlinear finite element analysis of E-glass/epoxy filament winding of composite vessel subjected to internal pressure, the standard interpretation model is developed by using the ANSYS with AutoLISP and ANSYS APDL languages, general commercial software, which is verified as useful characteristic of the solution. Among the modules of the system, both the process planning module for carrying out the process planning of filament wound composite pressure vessel and the autofrettage process module for obtaining higher residual stress will minimize trial and error and reduce the period for developing new products. The system can serve as a valuable system for experts and as a dependable training aid for beginners.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.61-70
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• 2001

This paper introduces a new digitization method with sensor fusion for shape measurement in reverse engineering. Digitization can be classified into contact and non-contact type according to the measurement devices. Important thing in digitization is speed and accuracy. The former is excellent in speed and the latter is good for accuracy. Sensor fusion in digitization intends to incorporate the merits of both types so that the system can be automatized. Firstly, non-contact sensor with vision system acquires coarse 3D point data rapidly. This process is needed to identify and loco]ice the object located at unknown position on the table. Secondly, accurate 3D point data can be automatically obtained using scanning probe based on the previously measured coarse 3D point data. In the research, a great number of measuring points of equi-distance were instructed along the line acquired by the vision system. Finally, the digitized 3D point data are approximated to the rational B-spline surface equation, and the free-formed surface information can be transferred to a commercial CAD/CAM system via IGES translation in order to machine the modeled geometric shape.

• Journal of Technologic Dentistry
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• v.42 no.2
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• pp.121-128
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• 2020

Purpose: This study aimed to investigate the effects of the sintering conditions of zirconia core on the adaptability. Methods: Ten specimens of each of commercial brand of zirconia(Razor 1100, U&C international, Seoul, Korea) were made and sintered under three different conditions. Specimens were divided into three subgroup(n=10) and sintered with various total time(1hr, 3hr, 9hr) at the maximum temperature(1500℃). The digitized data was superimposed with 3D inspection software to quantitatively obtain the adaptation of a zirconia core, and visual differences were confirmed with a color map. The root mean square(RMS) values of group were statistically analyzed with one-way ANOVA(α=0.05). Results: The overall adaptation of the zirconia cores were as follows; ss-1hr: 36.18±5.2㎛, ss-3hr: 39.55±3.9㎛, cs-9hr: 46.62±4.3㎛. They were statistically significant differences between groups for adaptation(p<0.05). Conclusion: Based on the results of this study, it could be considered that sintering condition of 1500℃ and 1~3 hour is recommended for the better marginal and internal fit. Speed sintering can be widely utilized to fabricate zirconia prothesis as the properties of those almost are to dentistry uses.

• International Journal of CAD/CAM
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• v.3 no.1_2
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• pp.19-29
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• 2003

Disassembly is a fundamental process needed for component reuse and material recycling in all assembled products. Integral attachments, also known as 'snap' fits, are favored fastening means in design for assembly (DFA) methodologies, but not necessarily a favored choice for design for disassembly. In this paper, design methods of a new class of integral attachments are proposed, where the snapped joints can be disengaged by the application of localized heat sources. The design problem of reversible integral attachments is posed as the design of compliant mechanisms actuated with localized thermal expansion of materials. Topology optimization technique is utilized to obtain conceptual layout of snap-fit mechanisms that realizes a desired deformation of snapped features for joint release. Two design approaches are attempted and design results of each approach are presented, where the geometrical configuration extracted from optimal topologies are simplified to enhance the manufacturability for the conventional injection molding technologies. To maximize the magnitude of deformation, a design scheme has been proposed to include boundary conditions as design variables. Final designs are verified using commercial software for finite element analysis.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.613-627
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• 2010

Ships and off-shore plants have very long lifecycles. Design data of ships and off-shore plants are used as master data in the subsequent phases after the design phase. Therefore, it is an important issue how to convert native design data generated from commercial shipbuilding CAD systems into neutral data with the use of international industrial data standards. International standard-based exchange of ship outfitting and off-shore plant data needs the construction of a library for specifications data of equipment and materials and the provision of external referencing mechanism for retrieving data stored in the library. This paper proposes an approach to construct a specifications data library with the use of ISO 15926 process plants. This library is used for providing specifications data through external referencing when translating ship outfitting data from TRIBON system into ISO 10303 STEP AP 227-formed data.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.21-29
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• 2003

This paper describes a research work on the development of computer-aided design system for deep drawing & ironing of a high pressure vessel. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plasticity theories, handbook, experimental results and empirical knowledge of field experts. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM software, DEFORM and ANSYS, to form a useful package. It is composed of five main modules, which are calculation of product thickness, input, production feasibility check, process planning, and autofrettage process modules and two submodules, which are folding check and process variable verification submodules. Programs for the system have been written in AutoLISP on the AutoCAD 2000 using personal computer. The developed system makes it possible to design and manufacture large high pressure vessel requiring D.D.I. process more efficiently.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.42-50
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• 2017

A cerebral aneurysm is a ballooning arising from a weakened area in the wall of a blood vessel in the brain. In this study, the flow analysis of the blood vessel, including the cerebral aneurysm and the stent, was conducted to investigate the effect of the stent shape on reduction of blood flowing into the cerebral aneurysm. We used the Carreau model to describe Non-Newtonian behaviors of blood flow. Two kinds of stents, which had different cross angles were modelled by the commercial CAD program and the geometries of those stents were reflected in the analysis domain of the blood vessel. From the results of the flow analysis, we found that the blood flowing into the cerebral aneurysm was decreased as the cross angle of the stent was decreased.

• Korean Journal of Computational Design and Engineering
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• v.4 no.4
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• pp.381-390
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• 1999

In this study, a pseudo ship structure data model for the :.hip cargo hold structure based on STEP is proposed. The proposed data model is based on Application Reference Model of AP218 Ship Structure which is the model that specifies conceptual structures and constraints used to describe the information requirements of an application. And the proposeddata model refers the Ship Common Model framework for the model architecture which is the basis for ongoing ship AP development within the ISO ship-building group and the ship product definition information model of CSDP research project for analyzing the relationship between ship structure model entities. The proposed data model includes Space, Compartment. Ship Structural System, Structural Part and Structural Feature of cargo hold. To generate this data model schema in EXPRESS format, ‘GX-Converter’was used which enables user to edit a model in EXPRESS format and convert schema file in EXPRESS format. Using this model schema, STEP physical file containing design data for ship cargo hold data structure was generated through SDAI programming. The another STEP physical file was also generated containing geometry data of ship cargo hold which was extracted and calculated by SDAI and external surface/surface intersection program. The geometry information of ship cargo hold can be then transferred to commercial CAD system, for example, Pro/Engineer. Examples of the modification of the design information are also Presented.