【作者】 黄常标；

【导师】 徐西鹏； 江开勇；

【作者基本信息】 华侨大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 目前典型的分层RP工艺由于原理性的缺陷使得原型的制造精度、强度、成形效率等都不尽如人意。分段注射/雕刻快速原型制造工艺(Decomposed Injection Sculpturing, DIS)是一种离散/堆积成形方法与数控切削加工复合的新型RP工艺。该工艺同时具有离散/堆积成形的柔性和机械加工的高精度。为了促进DIS工艺的深入研究,加快该工艺投入应用的进程,本文就基于STL模型的数据前置处理、异地RP制造中网络协同机制的若干关键问题进行了深入研究,完成的研究内容主要包括以下几个方面:(1) DIS系统软件的总体分析设计:在分析了DIS工艺及其设备的原理与特点的基础上,对DIS系统软件进行了功能分析和总体设计,包括模块化的体系结构、高效的数据结构;设计了建立STL模型拓扑信息的算法、扩展式面片搜索算法等新算法及其软件实现;(2)实体模型三维离散技术研究:提出了三轴加工中零件CAD模型三维离散的基本理论以及DIS工艺三维离散的基本原则;针对DIS工艺原理,提出了几种不同的STL实体模型三维离散分解算法,其中包括基于扩展Z-Buffer的离散算法、基于有向极值轮廓线的离散算法、两段分解算法、平面截分法等等,并详细研究了各种算法的具体实现;(3)三角面片模型细节特征处理研究:基于DIS工艺以及STL模型,对零件模型的特征进行了分类和定义;提出了DIS工艺中零件细节特征的描述和识别方法;然后对零件细节特征的可加工性进行了分析,提出了验证细节特征可加工性的轮廓偏置验证算法;最后针对几种具有代表性的细节特征,进行工艺规划优化。(4)三角面片模型等高线刀具轨迹的生成研究:目前对于STL模型的刀具轨迹主要为平行刀具轨迹的生成研究。针对DIS工艺的需要,提出了STL模型的等高线刀具轨迹两次偏置生成算法。等高线刀具轨迹两次偏置算法主要包括STL模型的等距偏置、各种条件下的过渡轨迹生成方法、切割偏置模型获得中间轨迹、中间轨迹的二次偏置、刀具轨迹中干涉部分的消除等内容。(5) RP系统软件异地协同实现研究:在对完整的协同过程及其信息传输进行分析的基础上,提出了一种复合式RP协同体系结构,其中异地异步协同信息通过B/S结构进行传输,而异地同步协同信息则通过嵌入网页中的协同网络插件与专门的协同服务器进行类似C/S结构的传输;研究了具有文档/视图界面的网络插件的开发、同步协同操作消息的实时可靠传输、同步协同过程的回放等。本文的创新点主要体现在:1.零件模型的三维离散实现了真正意义的变层厚、曲面离散;2.在对零件几何细节特征的分类、识别和可加工性验证的基础上,提出了DIS工艺的特殊工艺规划,增强了DIS工艺的成型能力;3.针对通用的环形刀具模型,提出了STL模型的等高线刀具轨迹两次偏置生成算法,可简化算法、提高计算效率。更多还原

【Abstract】 The precision, strength, and efficiency of the prototype manufactured by the Rapid Prototyping processes based on the layered manufacturing are not fully up to expectations because of the limitation of their prototyping theory. Decomposed Injection Sculpturing (DIS) is a novel RP process, which combines the discrete/additive process and Numerical Control (NC) machining. DIS possesses the characteristics of both the flexibility of RP and the high precision of NC machining. In order to promote the further study of DIS and to accelerate the process of putting DIS into practice, several key problems are studied, which are mainly relevant to the development of software for the pretreatment of the STL model used in DIS and for the distributed collaboration in distributed RP manufacturing. The finished work is as follows:(1) General analysis and design for DIS system software: On the base of analysis of the process and equipment of DIS, the functional analysis and general design for DIS system software are accomplished, which include the modularized architecture and efficient Data Structures. Two new algorithms are presented respectively for rebuilding the topological information of STL and searching the adjacent facets under the given conditions.(2) Research on the three-dimensional decomposition of the triangular mesh: The basic theory of the 3-dimensional decomposition of CAD model for 3-axis NC machining and the basic principle of 3D decomposition for DIS are presented. Several algorithms are put forward for the 3D decomposition of STL, which include the 3D decomposition algorithm based on Extended Z-Buffer model, the algorithm based on the silhouettes with direction, the algorithm for the model which can be decomposed into two sub-parts, and the decomposition algorithm using plane. The details about the implements of these algorithms are keenly studied.(3) Research on processing local features in the triangular mesh: The analysis, definition and classification for the feature of STL used in DIS are given, and the presentation and recognition method for the local feature is presented. The machining feasibility of the local feature is discussed, and the verifying algorithm based on the offset of contour line is presented. And some special process plannings are demonstrated for some typical local features which can’t be manufactured directly.(4) Research on the generation of Contour Tool Path from the triangular mesh: The research on generation of the tool path from STL is insufficient at present, and the existing research is mainly about the parallel tool path. The algorithm for the generation of contour tool path from STL is presented, which consists of twice offsets. The algorithm comprises the offset of STL, the generation of the transition line, the slicing of the offset STL model, the second offset of the temporary path, and the elimination of the interference in the tool path.(5) Research on the realization of the distributed collaboration in the RP software: A hybrid architecture for the distributed collaboration in RP is put forward based on the analysis of the entire procedure of the RP collaboration and the information transportation. The asynchronous information of collaboration is transported by B/S. And synchronous information is transported between the IE control embedded in the web page and the special collaborative server, just like C/S. Some work are accomplished such as the development of the ActiveX control with Document/View frame, menu, tool bar and status bar, the realization of the synchronous information transportation, the replay of the synchronous collaboration.The innovations in this paper mainly include such as follows: 1. The decomposition of CAD model is truly 3-dimension according to the geometrical characteristics of part models; 2. Based on the classification, recognition and machining feasibility verification of local features on the CAD model, the special process plannings are presented for enhancing the prototyping capability of DIS; 3. An algorithm including twice offsets is presented for the generation of contour tool path from STL for bull mill, which can simplify the computational complexity and improve computational efficiency.更多还原