共查询到20条相似文献,搜索用时 635 毫秒
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Professor Sheng H. Chuang W. S. Lin 《The International Journal of Advanced Manufacturing Technology》1997,13(2):109-115
The objective of this paper is to generate tool paths for pockets with freeform curves, i.e. Bezier curves or B-spline curves. Time efficiency and overcut avoidance are two of the most important factors in NC machining. A method, based on the convex hull property of Bezier curves, is thus developed so that the portion of the boundary defined by a Bezier curve is replaced by parts of its convex hull on the cavity side. Therefore, the new pocket boundary, redefined by only segments of straight lines, can be solved efficiently based on current algorithms without overcuts. Cutting tool paths can be generated for pockets with islands avoiding computation of higher degree curve/curve intersections. Furthermore, recursive subdivisions on Bezier curves are used to improve the accuracy of the cut with an allowance criterion based on sizes of convex hulls.The portion of the boundary defined by a B-Spline curve is transformed into piecewise Bezier curves. The tool-path generation for pockets with B-spline curves can thus be solved by reducing the problem to one of pockets with Bezier curves. 相似文献
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J.-L. Shih S.-H. Frank Chuang 《The International Journal of Advanced Manufacturing Technology》2006,29(7-8):714-721
A robust method is proposed to generate tool paths for NURBS-based machining of arbitrarily shaped freeform pockets with islands.
Although the input and output are all of higher-degree NURBS curves, only one simple category of geometric entities, i.e.,
line segments, is required for initial offsetting and for detecting and removing self-intersecting loops. Furthermore, using
those linear non-self-intersecting offsets as the legs of NURBS control polygons, NURBS-format tool paths can be smoothly
reconstructed with G1-continuity, no overcutting, no cusps, and global error control. Since all operations involved in computing tool path curves
are linear geometric calculations, the method is robust and simple. Examples with integrated rough and finish cutting tool
paths of pockets demonstrate the usefulness and effectiveness of this method. 相似文献
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Hong-Tzong Yau Chien-Yu Hsu 《The International Journal of Advanced Manufacturing Technology》2009,41(9-10):897-907
This paper presents a new approach for the generation of NC tool paths from random scanned data. Instead of using smooth or triangulated surfaces reconstructed from raw data, which is usually a time-consuming reverse engineering approach, the point-based surfel models computed by a GPU (graphics processing unit) are used to generate NC tool paths. The tool-path generation is highly efficient and still maintains the advantage of having accurate and smooth machining result. The word “surfel” itself is the combination of the two words “surface” and “element”. It is originally applied to the rendering of scanned data. In this paper, the point-based model is created using an elliptical Gaussian re-sampling filter that is based on a signal re-sampling algorithm. Since the input scanned data is of discrete and random nature, the warping process is utilized to transform the input data into a continuous surface and then re-sample the continuous surface by using GPU. Because the re-sampled data can accurately represent the original surface, tool paths can be generated based on the point data set. For cutting tools with various sizes, adaptive re-sampling schemes are employed to generate sufficient sampled points for the generation of accurate and smooth tool-paths. 相似文献
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A Reverse Engineering Approach to Generating Interference-Free Tool Paths in Three-Axis Machining from Scanned Data of Physical Models 总被引:3,自引:4,他引:3
C.-M. Chuang C.-Y. Chen H.-T. Yau 《The International Journal of Advanced Manufacturing Technology》2002,19(1):23-31
An NC tool path is usually generated by sweeping parametric surfaces of a CAD model. In modern design, freeform or sculptured
surfaces are increasingly popular for representing complex geometry for aesthetic or functional purposes. Traditionally, a
prototype is realised by machining the workpiece using the NC codes generated from a CAD model. The machined part can then
be compared with the CAD model by measurement using a coordinate measuring machine. In this paper, a reverse engineering approach
to generating interference-free tool paths in three-axis machining from the scanned data from physical models is presented.
There are two steps in this procedure. First, a physical model is scanned by a 3D digitiser, and multiple data sets of the
complex model are obtained. A surface registration algorithm is proposed to align and integrate those data to construct a
complete 3D data set. A shortest-distance method is used to determine the connecting sequence of the neighbouring points between
two adjacent scan lines, such that the scanned data are converted into triangular polygons. Tool paths are then generated
from the tessellated surfaces. Using the Z-map method, interference-free cutter-location data are calculated, relative to
the vertex, edges, and planes of the triangles. The algorithms for tool-path generation are usually different for cutters
of different geometries. Some algorithms found in the literature require complex numerical calculations and are time consuming.
In this paper, an efficient algorithm is developed to calculate interference-free cutter-location data by easy geometric reasoning
without complex computation. This robust method is suitable for generally used cutters such as ball, flat, and filleted end
mills, and the time taken to obtain full tool paths of compound surfaces is short. Some real applications are presented to
validate the proposed approach. 相似文献
8.
C.K. Au 《The International Journal of Advanced Manufacturing Technology》2001,17(8):558-561
The features of a sculptured object are represented by a set of section curves. A fast algorithm is presented to calculate
cutting depths based on the scallop height using these curves. The calculated cutting depth can be used for tool-path generation.
This tool-path generation approach is particularly useful for constant z level contouring and high-speed machining. 相似文献
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Jung-Jae Lee Dr Suk-Hwan Suh 《The International Journal of Advanced Manufacturing Technology》1998,14(11):795-805
Flank milling is the key feature that the five-axis NC machine offers. Compared with bottom-edge based machining (e.g. flat/fillet endmilling), the machinability can be greatly enhanced by flank milling where the side cutting edge is mainly used. As far as tool-path planning is concerned, the conventional method of the cutter-axis parallel to the ruling lines of the generator curves imposes interference problems including overcut/undercut. In this paper, a new interference-free tool-path planning method fortwisted ruled surfaces is presented. Our strategy is to change the tool orientation and offset distance such that the undercut volume is minimised without global tool interference. The validity and effectiveness of the algorithm is demonstrated via several illustrative examples. 相似文献
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An Effective Global Gouge Detection in Tool-Path Planning for Freeform Surface Machining 总被引:1,自引:0,他引:1
L. Zhou Y.-J. Lin 《The International Journal of Advanced Manufacturing Technology》2001,18(7):461-473
This paper examines a usually neglected gouge phenomenon in tool-path planning for machining parts having freeform surfaces with 3-axis ball-end mills. That is, when a freeform surface is being milled with a ball-end cutter, a gouge may exist anywhere around the cutter circumference, in addition to the tool driving plane. A global gouge detection concept is developed to solve this problem. An effective method is proposed to identify the potential gouge areas on the sculptured surface during machining, before generating tool paths. Thus, it greatly simplifies the tool-path planning procedure and improves the accuracy and reliability of machining. It also facilitates geometric design processes of products and cutter radius selection which are crucial to machining efficiency. The designed part surfaces tested by the proposed methodology are constructed based on bicubic B2-splines and are assumed to be at least C 2 and may possess C 1 or C 0 continuity for generality. The tested examples demonstrate the effectiveness of the developed global gouge detection approach.
This revised version with a corrected online cover date was published online in April 2004. 相似文献
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对自由曲面用带角圆柱铣刀3轴NC加工提出了系统的刀具干涉检测方法。加工自由曲面时,刀具干涉可以出现在包括刀具驱动面的刀具周围的任何地方。本文提出先检测自由曲面上可能产生刀具干涉的区域,然后再生成刀具路径,这样不但可极大地简化安排刀具路径的过程,改善加工的精度和可靠性,而且有利于产品的几何设计和影响加工效率的刀具选择。研究表明所提方法和算法是合理有效的。 相似文献
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Dr R. M. Boogert H. J. J. Kals F. J. A. M. van Houten 《The International Journal of Advanced Manufacturing Technology》1996,11(3):186-197
This paper reports on the development of a module to calculate automatically tool paths and cutting conditions for metal cutting operations. Process planning must select correct cutting conditions to minimise disturbances on the shop floor owing to tooling problems. Tool path and cutting condition algorithms to generate reliable NC programs have been designed. The algorithms have been implemented in the framework of a generative computer-aided process planning system, called PART. Geometrical requirements to avoid chipping of cutting teeth are considered in tool-path calculation. The cutting conditions are calculated using metal cutting process models. A method has been developed to calculate cutting forces for milling operations based on experimental data of cutting forces in turning. In the process models, various constraints of the machine tool, cutting tool, and the workpiece are considered. 相似文献
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提出了一种直接从测量的散乱数据点云用球头刀对自由曲面进行三轴数控加工时生成刀具路径的方法。不同于现有散乱点云基于逆向工程的刀具路径生成方法,本法考虑并估计了曲面加工误差和粗糙度。将散乱数据点云向XY平面投影,以获得的投影边界为刀具路径的主方向,然后根据曲面所需的加工误差和残留高度要求划分该投影数据点云,得到一系列刀位网格单元。通过最小化每个刀位网格单元的加工误差以确定每个刀位网格的节点位置,加权平均相关联刀位网格节点来对齐相邻刀位网格单元的边缘。为了缩短加工时间,裁去刀位路径上多余的线段,最终生成高效合理的数控加工刀具路径。已用实测的数据点云验证了本法直接生成刀具路径的有效性。 相似文献
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Many fractal generation methods have been developed and used to create an image of a natural scene. Nonlinear dynamic systems
employ fractal theory for population growth. Fractals have also been used to model chaotic problems. In numerical control
(NC) machining, fractal curves have been used in tool-path generation. Although the visualisation of fractal geometry has
been successfully demonstrated by computer graphics, a manufacturing method for physical fractal objects is not available.
Moreover, contemporary computer-aided design (CAD) systems consider only Euclidean geometry and none of them addresses fractal
geometry. Fractal curves have been used in tool-path planning for Euclidean objects, but there is no report on rapid prototyping
(RP) of objects defined in fractal geometry.
In the paper, a new data structure, called the radial–annular tree (RAT) structure, is proposed and implemented to bridge
the gaps between CAD, RP, and fractal geometry. A typical fractal curve, the Koch snowflake curve, will be examined in detail.
Based on the RAT representation, higher-level fractal curves can be generated more efficiently, and repeated information can
be represented concisely. Traversal algorithms are also devised to generate a maximally connected tool path directly. The
tool path can then be used to generate a physical fractal curve without any additional conversion. 相似文献
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Contour-parallel offset machining for trimmed surfaces based on conformal mapping with free boundary 总被引:1,自引:1,他引:0
Yuwen Sun Fei Ren Xinghua Zhu Dongming Guo 《The International Journal of Advanced Manufacturing Technology》2012,60(1-4):261-271
The parametric surfaces of some manufactured parts are often subjected to the Boolean operation of other objects; generating suitable NC tool paths from such trimmed surface remains a challenge. This paper presents a new planar development-based method to generate contour-parallel offset paths of trimmed surfaces. To avoid direct frequent identifications and removals of interferences of offset curves on 3D-trimmed surface possibly with multiple holes or restricted regions, the original surface is flattened in the plane domain using a two-stage approach which consists of conformal mapping with free boundary and further nonlinear accuracy improvement. Then, sequent offsets of the boundary curves of the planar region are generated, and the global interferences are detected and removed using an efficient and robust divide-and-conquer strategy. Based on a tree data structure, a tool-path linking algorithm is also given with less or no tool retractions, and subsequently, the resulting planar paths are inversely mapped to the physical space. Illustrated examples have been conducted to testify the affectivity and the applicability of the proposed contour-parallel offset machining method. 相似文献
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Jian-Zhong Yang Qi-Fu Wang Zheng-Dong Huang Li-Ping Chen 《The International Journal of Advanced Manufacturing Technology》2007,35(1-2):179-185
Presented in the paper is a novel tool path generation method for 3-axis NC machining of compound surfaces. Tool path generation
procedure consists of two core steps: firstly, the extended cut region (ECR) of every surface is constructed; secondly, CL-curves
are computed on every ECR and the final tool paths are achieved by sorting, trimming and connecting the CL-curves. The developed
ECR method can solve the gouging problems caused by tangent discontinuity, surface overlap or surface gap among surface elements.
The proposed method has been implemented and applied to tool path generation in a general CAM system that has been developed
by authors. Our case study has demonstrated the validity of the proposed algorithms. 相似文献