• Title, Summary, Keyword: NURBS

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Intelligent NURBS Surface Interpolator with Online Tool-Path Planning (온라인 방식의 지능형 NURBS 곡면 보간기)

  • 구태훈;지성철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.471-474
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    • 2004
  • In this paper, a NURBS surface interpolator is proposed which can deal with shapes defined from CAD/CAM programs on a surface basis and can improve contour accuracy. The proposed interpolator is based on newly defined G-codes and includes online tool-path planning suitable for NURBS surface machining. The real-time interpolation algorithm, considering an effective machining method for each machining process and minimum machining time, is executed in an online manner. The proposed interpolator is implemented on a PC-based 3-axis CNC milling system and evaluated through actual machining in terms of machining time and regulation of feedrate and cutting force in comparison with the existing method.

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A STUDY ON THE NURBS GRID GENERATION AND GRID CONTROL (NURBS를 이용한 격자생성 및 제어기법)

  • Yoon, Yong-Hyun
    • Journal of computational fluids engineering
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    • v.12 no.3
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    • pp.20-28
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    • 2007
  • A fast and robust method of grid generation to multiple functions has been developed for flow analysis in three dimensional space. It is based on the Non-Uniform Rational B-Spline(NURBS) of an approximation method. Many of NURBS intrinsic properties are introduced and much more easily understood. The grid generation method, details of numerical implementation. examples of application, and potential extensions of the current method are illustrated in this paper. The object of this study is to develop the surface grid generation and the grid cluster techniques capable of resolving complex flows with shock waves, expansion waves, shear layers. The knot insert method of Non-Uniform Rational B-Spline seems well worked. In addition, NURBS has been widely utilized to generate grids in the computational fluid dynamics community. Computational examples associated with practical configurations have shown the utilization of the algorithm.

High speed machining using a NURBS interpolator (NURBS 보간을 이용한 고속 가공)

  • 이동윤;김현철;양민양;최인휴
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.323-328
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    • 2004
  • Finish machining of a curved surface is often carried out by an NC system with curved interpolation in a high speed machining strategies. This study aims to develop the NURBS interpolator for the PC-NC based machine tools. In the case of a finish cut using a ball-end mill in high speed machining, low machinability at the bottom of a tool produces a harmful effect on surface roughness. The developed interpolator considers the relation between inclined angle, surface roughness, and feed rate, and adjusts real-time feed rate in order to generate surfaces which have isotropic surface roughness. The proposed interpolator is fully implemented and an experimental results are shown.

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Research on Machineability in NURBS Interpolator Considering Constant Material Removal Rate (소재제거율을 일정하게 한 NURBS 보간기에서 절삭성 고찰)

  • Ko Tae Jo;Kim Hee Sul
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.12
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    • pp.60-66
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    • 2004
  • Increasing demands on precision machining of 3D free-form surface have necessitated the tool to move smoothly with varying feedrate. To this regard, parametric interpolators such as NURBS (Non-Uniform Rational B-Spline) interpolator have been introduced in CNC machining system. Such interpolators reduce the data burden in NC code, increase data transfer rate into NC controller, and finally give smooth motion while machining. In this research, a new concept to control cutting load in NURBS Interpolator was tried based on the curvature of curve. This is to protect cutting tool, and to have good machinability. For proof of the system, cutting force and surface topography were evaluated. From the experimental results. the interpolator is good enough for machining a free-form surface.

NURBS Curve Interpolator for Controlling the Surface Roughness (표면거칠기를 고려한 NURBS 곡선보간기)

  • Choi In hugh;Jung Tae sung;Yang Min Yang;Lee Dong yoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.5
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    • pp.698-706
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    • 2005
  • Finish machining of a curved surface is often carried out by an NC system with curve interpolation in the field. This NURBS interpolation adopts a feedrate optimizing strategy based on both the geometrical information and dynamic properties. In case of a finish cut using a ball-end mill, the curve interpolator needs to take the machining process into account for more improved surface, while reducing the polishing time. In this study, the effect of low machinability at the bottom of a tool on surface roughness is also considered. A particular curve interpolation algorithm is proposed fur generating feedrate commands which are able to control the roughness of a curved surface. The simulation of the machined surface by the proposed algorithm was carried out, and experimental results are presented.

A Study of Human Body Section Curve Modeling by Using Least Square NURBS Approximation Method (최소자승 NURBS 근사법을 이용한 인체 단면곡선 생성)

  • Han Sung Soo;Bae Han Jo;Park Jung Whan;Kwon Oh Hyun
    • Textile Science and Engineering
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    • v.42 no.5
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    • pp.323-328
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    • 2005
  • The paper proposes a method of constructing the three-dimensional CAD model from digitized cloud-of­points data of the human body, thereby automatically extracting several featured dimensions. The main steps are; segmentation, sectioning, fairing and surface approximation. In segmentation process the input three-dimensional set of points are grouped into each functional part of the human body by searching the boundary points when being viewed from a certain direction. The next step slices the grouped points to obtain section curves which will be faired (smoothed) by the difference-fairing method. Each faired section curve (a set of points) is approximated to the NURBS form by use of well known method, from which we can construct a NURBS surface. The parametric surfaces for functional parts of a human body are interrogated to extract several featured dimensions of a human body.

Volumetric NURBS Representation of Multidimensional and Heterogeneous Objects: Concepts and Formation (VNURBS기반의 다차원 불균질 볼륨 객체의 표현: 개념 및 형성)

  • Park S. K.
    • Korean Journal of Computational Design and Engineering
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    • v.10 no.5
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    • pp.303-313
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    • 2005
  • This paper proposes a generalized NURBS model, called Volumetric NURBS or VNURBS for representing volumetric objects with multiple attributes embedded in multidimensional space. This model provides a mathematical framework for modeling complex structure of heterogeneous objects and analyzing inside of objects to discover features that are directly inaccessible, for deeper understanding of complex field configurations. The defining procedure of VNURBS, which explains two directional extensions of NURBS, shows VNURBS is a generalized volume function not depending on the domain and its range dimensionality. And the recursive a1gorithm for VNURBS derivatives is described as a computational basis for efficient and robust volume modeling. In addition, the specialized versions of VNURBS demonstrate that VNURBS is applicable to various applications such as geometric modeling, volume rendering, and physical field modeling.

Study on the Preheating Method of NURBS Shaped Workpiece by Laser Assisted Machining (레이저보조가공에서 NURBS 곡면 형상의 예열방법에 대한 연구)

  • Kim, Eun-Jung;Lee, Choon-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.2
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    • pp.101-107
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    • 2016
  • Laser-Assisted machining (LAM) is a new method for processing hard-to-cut materials. However, curved shapes are difficult to predict the preheating effect of by LAM because heat sources are changed by moving laser module. So, it is necessary to study the preheating effect of the laser heat source irradiated on a 3-dimensionally shaped workpiece, such as a NURBS shaped workpiece. In this study, thermal analysis and preheating experiment of the LAM for the NURBS shaped workpiece are performed. Also, two machining methods are proposed to avoid interference of laser module and cutting tool. The results of the analysis can be applied to various shaped workpieces by LAM.

Design of Jerk Bounded Feed Rate with Look Ahead using Adaptive NURBS Interpolator (NURBS 적응보간기를 이용한 Jerk 제한 이송속도 생성)

  • Kweon S.H.;Mohan S.;Yang S.H.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.457-458
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    • 2006
  • A method for obtaining smooth, jerk bounded feed rate profile in high speed machining has been developed. This study proposes a NURBS interpolator based on adaptive feed rate control with a well developed look ahead algorithm which takes into account the machining dynamics as well. Limitation of jerk and proportional torque rate result in smoothened loads on the machine which effectively reduces excitation of the resonant frequencies of the machine. It is found that the values of the feed rate of the down stream sharp corner have profound effect on the feed rate of the upstream sharp corners. By using a windowing scheme the feed rate profile obtained after look ahead method is re-interpolated to reduce the jerk related problems. This is compared with the adaptive NURBS interpolator to show the effectiveness of the proposed method. Simulation results indicate that the consideration of 'ripple effect' is important in avoiding jerk and thereby increasing the machining accuracy.

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Trimmed NURBS surface tessellation with sharp shape constraint (Sharp Shape를 유지하는 trimmed NURBS 곡면의 삼각화 방법)

  • Cho, Doo-Yeoun;Kim, In-Ill;Lee, Kyu-Yeul;Kim, Tae-Wan
    • Journal of Korea Game Society
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    • v.2 no.1
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    • pp.62-68
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    • 2002
  • This paper presents a method for tessellating trimmed NURBS surface with preserving sharp shape Although several existing approaches need a large number of triangular meshes to represent sharp shape of surface, resulting triangular meshes may not reflect sharp edges properly. In this study, we flit detect the sharp shape of NURBS surface automatically using C1 continuous condition and then use constraint Delaunay triangulation method to present exact sharp shape with the minimum triangular meshes. And we also use approximated developed surface domain as triangulation domain of rimmed NURBS surface. In this way, the shape of triangular elements on the triangular domains is approximately preserved and can avoid distortion when mapped into three-dimensional space. finally, we show examples that demonstrate the effectiveness of the proposed scheme in terms of reducing the number of triangular meshes and preserving sharp shape of surface more exactly.

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