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题名: 紫外光固化快速成型中的工艺规划方法研究
其他题名: Research on Process Planning of the UV Stereolithography
作者: 赵吉宾
导师: 王越超 ; 刘伟军
分类号: TH166
关键词: 快速成型 ; 工艺规划 ; 多目标优化 ; STL数据模型 ; 加工路径
索取号: TH166/Z44/2004
学位专业: 机械电子工程
学位类别: 博士
答辩日期: 2004-06-27
授予单位: 中国科学院沈阳自动化研究所
学位授予地点: 中国科学院沈阳自动化研究所
作者部门: 先进制造技术研究室
中文摘要: 快速成型技术技术是八十年代发展起来的一种基于材料累加思想的新型制造技术,涉及机械、CAD、控制、光学、材料科学等多学科多领域。它可以实现直接从CAD模型到三维实体模型的制作,而不需要任何刀、卡具,从而实现对产品设计进行快速评价、修改及功能实验,有效缩短了产品的研发周期。但目前该技术还存在许多有待于进一步研究和解决的问题,如成型精度和表面质量较差,零件的成型速度较慢,常用的数据接口STL文件经常出现错误等。本文紧紧围绕这些问题,从数据处理的角度对紫外光快速成型中的工艺规划方法进行了深入的研究,并利用所研制的快速成型系统对一些工艺规划方法进行了实验验证。 设计了紫外光固化快速成型机,并分析了设备各个子系统的结构和功能;根据快速成型机控制系统的功能需求,设计并实现了一种基于Windows的单机型实时控制系统。通过设计定时器的虚拟设备驱动程序、多线程和提高控制线程的优先级的方法,达到了控制系统的实时性能。对快速成型技术中的数据接口STL和CLI文件的进行了详细的介绍,并讨论了STL文件格式的优缺点。通过分析STL文件中的缺陷,提出了对间隙、顶点错误、覆盖和分离等几种常见错误的检测和修正算法。为了解决快速成型机对大尺寸零件制作的限制,提出了一种对STL文件的分割算法。 在光固化快速成型技术中,零件的制作方向关系到零件制作的精度及效率,甚至成败。制作方向的优化是一个涉及由台阶效应引起的体积误差、悬臂面积和制作时间的多目标优化问题,本文首次将基于广义满意度原理的多目标优化方法引入零件制作方向优化中,合理地解决了零件制作方向的优化问题。 CAD模型的分层是快速成型数据处理中的核心,对零件制造的精度有十分重要的影响。本文提出一种基于STL文件的智能分层算法,通过分析STL文件的拓扑关系,建立了三角形面片的之间的加权有向图,采用递归方法实现了快速分层。然后,对该算法进行了改进,在分层处理过程中,利用所谓信息继承技术获得每个截面轮廓要切割的第一个三角形面片,加快了分层速度;同时在切割这个三角形面片时,直接确定轮廓的正确走向,节省了对分层轮廓的后处理;提出了一种截面轮廓的适应性计算方法,有效地解决了由台阶效应造成的零件的变形。对分层后的截面轮廓进行了误差分析,并采用了三次NURBS曲线对截面轮廓进行了拟合,提高了截面轮廓的精度。 提出了一种轮廓扫描路径的生成算法,该算法对尖角的情况,进行了特殊的处理;对补偿轮廓中经常出现的自交环现象,提出了一种基于单调链自交点的求解算法和自交环的剔除方法,有效提高了补偿轮廓的正确性。提出了一种改进的分区填充扫描路径生成算法,提高了算法的执行效率。研究表明,填充扫描的方向对加工效率有重要影响,因此本文提出了一种基于遗传算法的填充扫描方向的优化方法,实验证明,该算法能够有效减少扫描矢量的数目。实现了一种的OFFSET填充扫描路径的生成算法,解决了往复扫描薄壁零件时,需多次跳转的问题。 对紫外光固化的快速成型机理进行了系统的研究,研究表明,紫外光源下的光敏树脂的固化符合非线性阈值模型和Beer-Lambert规则;通过理论分析建立了扫描速度、扫描间距、紫外光功率和树脂参数之间的相互关系的数学模型,并通过实验研究了固化宽度和固化深度的变化规律。研究了工艺参数对成型效率的影响。对制作高度与零件制作时间的关系进行了实验研究,结果表明,降低零件的制作高度能够明显减少零件的制作时间。通过理论分析和实验研究得出了扫描矢量数与零件制作时间之间的关系模型,实验证明,通过扫描方向优化得到扫描路径明显提高了加工效率。分析了对成型系统精度的影响因素,通过实验研究了制作工艺对成型零件精度的影响。
英文摘要: Rapid Prototyping & technology is one kind of new manufacturing technology based on material increasing which emerged in the 1980’s. It integrates in Mechanical Engineering, CAD, Numerical Control, optics and material science. This technology is widely used in the product design and rapid evaluation, modification and function test, which effectively reduced the period of research and design. However there still exit some problems which should be further research and solved, such as poor parts’ accuracy and surface finish, and low productivity, and excessive errors in STL (Stereolithography) File etc. Aimed exactly at the problems, the thesis covers a comprehensive study on the process planning of UV stereolithography from the data process points of view. At last, we experimentally testify some process planning by the rapid prototyping system developed. The UV Stereolithography rapid prototyping machine is designed, and the structure and function of all subsystems is analyzed. A single-stage control system is designed and implemented according to the function requirement of control system for rapid prototyping machine. The real-time of control system is gained by designing virtual device driver of timer, multiple threads and arising priority of the control threads. The data interface STL and CLI file of RP is introduced in detail, and the merits and flaws of STL file format are discussed. After analyzed the error of STL file, an algorithm for diagnosis and modification of STL file is proposed to deal with the gaps, vertex error, overlapping facets etc. The par-building orientation in stereolithogrphy affects part’s accuracy and efficiency, even success and failure. The optimization of part-building orientation is a multi-objective optimizing problem involved in volume error from staircase effects, support area and building time. Multi-objective optimization based on the generalized satisfactory degree is firstly introduced in optimization of fabricating orientation, and the method effectively solved the problem. The slicing of CAD model is the core of data process for rapid prototyping, which significant influences part-building accuracy. An intelligent slicing algorithm based on STL file is presented. After analysis the topology relation of triangle facets of STL file, a weighted directional graph for triangle facets is created. A rapid slicing is obtained by a recursive algorithm. And then, the algorithm is improved. The first triangle facet to be sliced is gained by a technology so called information inheriting, which effectively accelerated the slicing. Mean while, decision the right direction of the sectional contour is made by the first triangle. For the part deformation stem from staircase, an adaptive computing method of sectional contours is put forward. A contour-scanning path generation algorithm is presented, which specially deal with the sharp angle. A self-intersection searching algorithm based on monotone chain and self-loop removal algorithm are presented. The algorithm effectively improves the validity of compensated contours. An improved zoning fill-scan path generation algorithm is presented, which improved the execution efficiency. Research shows, the direction of fill-scanning can evidently affect the productivity. So an optimization method of fill-scanning direction is presented. Experiment test, the method can effective reduce the number of scan vectors.
语种: 中文
产权排序: 1
内容类型: 学位论文
URI标识: http://ir.sia.cn/handle/173321/9581
Appears in Collections:工业信息学研究室_先进制造技术研究室_学位论文

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Recommended Citation:
赵吉宾.紫外光固化快速成型中的工艺规划方法研究.[博士学位论文].中国科学院沈阳自动化研究所.2004
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