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熔融堆积成型技术在成型过程中对环境无污染而得到广泛应用,尤其适合在办公环境下使用.扫描过程是实现区域填充过程,类似于传统加工中的刀具路径规划,因而合理规划扫描路径直接影响成型的效率和制件的精度.在分析现有扫描方式的基础上,提出了基于层面轮廓凸分解的分区自适应扫描法,根据顶点可见性的原理进行轮廓凸分解.实际应用表明,该方法即保证了制件的精度又克服了三角剖分扫描效率低的缺点. 相似文献
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选择性激光烧结新型扫描方式的研究及实现 总被引:25,自引:3,他引:25
选择性激光烧结(Selective laser sintering,SLS)快速成形技术是近10年来发展起来的一种先进制造技术,采用此项技术可以显著地缩短产品投放市场的周期,降低成本,提高产品质量,增强企业的竞争能力。而扫描方式是SLS成形过程中的一项关键技术,在分析了现有扫描方式及其对SLS制件精度、强度以及成形速度影响的基础上,指出了现有扫描方式的缺陷。为了克服这种缺陷,特提出并实现了一种新的分区变向扫描方式及其分区算法,它通过将扫描线段进行分组,以避开截面内孔和凹槽。这种新的分区变向扫描方式及其算法已经成功地应用到华中科技大学开发的HRPS系列SLS系统中。实际应用表明:这种新型扫描方式能大幅度地提高烧结成形效率和减小烧结体的翘曲变形量。 相似文献
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快速原型制造技术实质上是分层制造、层层叠加的过程。本文应用阿克玛算法对切片轮廓进行拟合, 并采用自适应插补技术来提高 R P制件的精度。 相似文献
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快速原型制造技术实质上是分层制造、层层叠加的过程。本文应用阿克玛算法对切片轮廓进行拟合,并采用自适应插补技术来提高RP制件的精度。 相似文献
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现有金属激光沉积成形工件是根据几何模型按照设定扫描路径层层叠加而成,不可避免造成局部热量累积,导致成形工件内部温度梯度大,产生局部应力集中,易引起工件变形开裂。对成形过程温度进行实时检测并实现动态扫描路径规划是解决工件变形开裂的根本途径。在研究不同基体温度对熔宽、熔高影响规律基础上,提出基于层面温度分区的激光沉积成形扫描路径生成方法。采用红外热像仪对沉积层面温度进行实时采集,提取不同温度分区轮廓;提出温度分区轮廓规则化方法,消除局部轮廓尖角,避免过熔覆;改进Weiler-Atherton算法,快速实现分层轮廓与温度分区轮廓的求交运算;针对不同温度分区采用适应性间距生成扫描路径,实现激光沉积成形动态扫描路径规划。试验结果表明:该扫描路径可有效提高成形工件质量。 相似文献
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E. Cerit I. Lazoglu 《The International Journal of Advanced Manufacturing Technology》2011,56(1-4):319-327
A wide range of rapid prototyping (RP) methods are available commercially. Even though the hardware and production materials of these RP methods differ, their production techniques are built on the same idea: layer-by-layer material additive manufacturing. Whatever the material is used, it is deposited, vulcanized, or melted by following a pre-determined path, and each layer is stowed on the previous one to create the 3D model which is designed by using a computer-aided design program. The path which is followed while creating the model is very crucial. In this paper, a novel idea for path generation for RP processes is introduced. This new method is based on computer numerical controlled milling operation. Although the RP process and the milling process are completely opposite of each other since one of them is an additive and the other one is a subtractive method, the paths which are followed for these operations are very similar and based on the same idea: The progress goes on layer by layer. In this novel method, cutter location source files are used to create paths for RP processes. Examples of the prototypes produced by using this new method are also presented in the paper. 相似文献
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Mohammad T. Hayasi Bahram Asiabanpour 《The International Journal of Advanced Manufacturing Technology》2009,45(1-2):170-180
This paper explains a new machine path generating system that its output is compatible with different rapid prototyping processes. The basis of this system is direct slicing from design-by-feature solid model. Slicing a computer-aided design (CAD) model through intersecting the model with the XY-plane at each Z increment is a well-known method of path generation. Slicing a CAD model is currently conducted through stereolithography (STL) file slicing, direct slicing, and additive direct slicing. A direct slicing approach inside a design-by-feature solid modeler is proposed. Autodesk Inventor solid modeler, as a design-by-feature solid modeler, is used for 3D solid modeling. The proposed system is implemented by Visual Basic codes inside Inventor. In this approach, first protrusion and subtractive features that form a model are extracted. Then, the intersection of each feature and the XY-plane is identified. Then, the internal and external loops are found. Depending on the specific rapid prototyping (RP) process requirements, internal or external hatch are also computed, respectively. Finally, a continuous path in required format is generated. The system reported in this paper has been successfully tested on several complex 3D models created in Inventor. The system offers customized output for different RP processes that need external or internal hatch pattern. The proposed approach for generating RP machine path through feature recognition inside design-by-feature solid modeler overcomes with the problems that are caused by imperfect STL files. Also, this system is capable of generating code compatible with major rapid prototyping processes. 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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You-Min Huang Hsiang-Yao Lan 《The International Journal of Advanced Manufacturing Technology》2006,27(11-12):1101-1112
The rapid prototyping (RP) process is the fastest and most feasible method for prototype construction. However, with the use of any material or build method the phenomenon of volume shrinkage is unavoidable. It is known that volume shrinkage and curl distortion are the major causes that lead to poor accuracy of the built prototype. Subsequently, in order to improve the precision of dimension and volume shrinkage, more expensive equipment is used on the market. Also, it is expensive and inefficient to obtain better process parameters through trail and error in the RP process. In order to improve the precision of dimension, reduce the processing cost and the frequency of trail and error, this study first induces the concept of computer-aided engineering (CAE) into the processing of RP, which uses a dynamic finite element simulation code to simulate the photopolymerization process, so as to reduce the time for selecting the processing parameters and obtain the distortion data. Second, by means of reverse distortion compensation to obtain a new CAD model, then it is sent to a RP machine for the actual prototyping processes, so as to obtain a more accurate precision. Finally, in order to confirm this method and restriction in experimental equipment, the stereolithography process and simple laser scanning path are chosen as examples. The results of the simulation and experiment prove that the method proposed herein is effective. It not only can reduce the cost of equipment but also obtain a better precision of dimension on final-parts at the same time. Besides, it is believed that this research method can be promoted to other materials or build methods in RP fabrication . 相似文献
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《Computer Integrated Manufacturing Systems》1998,11(4):337-350
This paper discusses automatic tool path generation for five-axis filleted end mill finish-surface machining. A new method of automatic five-axis tool path generation is introduced called Grind-Free (GF) tool path generation. GF surfaces result from tool paths that avoid gouging and have scallops that are within the surface profile or waviness tolerances. New algorithms are presented for determining tool forward step and tool path step-over that produce a GF surface. Gouge-free tool paths can be generated directly from CAD data based solely on local and global machining constraints. The proposed methodology for GF tool path generation has been implemented in the C language using the CODE/Robline system. Surfaces were machined on a Boston Digital 505 five-axis milling machine to confirm this method. 相似文献