【作者】 杨家强；

【导师】 何国金；

【作者基本信息】 广西大学 ， 机械制造及自动化， 2001， 硕士

【摘要】 本文在全面总结和分析目前制造领域中反向工程的研究现状、基本理论及技术、应用领域的基础上，结合电风扇叶片和某型号电话机听受话筒型面的反向工程，对复杂零件曲面的反向工程的全过程及其关键技术进行了研究和探索，内容包括数据测量、数据处理、曲面重构和数控加工编程。该论文主要完成了以下工作： 1、对目前反向工程的常用数据测量工具三坐标测量机的自动测量模式及自动编程模式进行了分析和比较。通过扫描测量电风扇叶片和某型号电话机听受话筒的曲面数据，论述了测头类型的选择、测杆长度校正、测头定义和测球半径的校正、零件测量坐标系建立的具体步骤和方法。同时指出了测头半径的选择原则，提出了利用测量机工作台面和零件边界三个标记点建立形状不规则零件的测量坐标系的新方法，解决了形状不规则零件的测量坐标系不好建立的问题。根据测量零件的几何拓扑关系，探索出沿生成线方向测量曲面的最佳测量规划，在能测量出正确几何形状的条件下，提高了扫描测量的效率，减少了扫描的数据点。 2、阐述了反向工程数据处理的方法：数据格式转换及补偿、噪声点剔除、数据多视图拼合、数据点精化、数据点加密、数据点排序和数据点分割的概念及其原理。通过对电风扇叶片和电话机听受话筒的扫描数据的处理，从中摸索出一种快速剔除噪声点的3D边界法。这种方法是以测得的零件3D边界为参考，只要定义一个多边形包围住所要剔除的“点云”数据，多边形内部的“点云”就可以被剔除。这种剔除方法既可以快速剔除3D边界外噪声点，又可保留3D边界内的有效点，去除噪声的效率较高。另外，提出了“点云”数据分割凹凸性一致的原则，即进行“点云”数据分割时，在分割处曲面的凹凸性要求一致，且曲面比较平缓。强调了在数据处理时必须进行“点云”数据排序，这是曲面重构前必不可少的步骤。 3、对曲面重构的基本理论和方法进行了论述。探索出用Cimatron软件对“点云”数据进行曲面重构的过程：扫描线的生成、扫描线的排序、曲面裁剪和曲面的拼接直至曲面的构成，这是进行曲面重构的一条捷径。经过比较研究得知平面法是生成3D扫描线的最佳方法，用3D边界作为约束可使曲面重构方便快捷，这是重构出高精度的NURBS曲面 — —豆—— 广西大学硕士学位论文 摘要的有效方法。对于两块以上的曲面拼接，本文提出了先平面裁剪和后拼接融合的方法，此方法能使曲面光滑地连接成为一体。 4、分析比较了复杂曲面数控加工编程的各种加工方法、切削用量、加工余量、走刀方式、进退刀方式、编程零点和加工坐标系确定等。总结出层切法比较适合于粗加工。推导出用残留刀痕高度法来控制加工步长的关系式，用这种方式控制加工步长可获得粗糙度非常均匀的加工表面。在Cimatron环境下，提出了先按曲面大小和后按输人坐标值建立任意大小矩形编程毛坯的方法，使编程毛坯和实际的加工毛坯大小一致，很有实际意义。本文还研究出对平缓型的曲面用“WCUT”进行粗、精加工；对凹凸型的曲面先用“WCUT”进行粗加工，再用“SgyPKT”进行精加工的一种新方法，这种方法既可提高加工效率，又可获得较好的表面加工质量。更多还原

【Abstract】 The reverse engineering and its key technique of complex part抯 surface are researched and explored in this paper, which by the reverse engineering of electric fan vane and hear-accept mike and based on that the basic theory, research status, application field, technique of reverse engineering in the manufacture field at present are analyzed and summarized, including data measuring, and data processing, and surface reconstruction, and numerical control machining program. The mostly harvest as following: 1. Automation measuring mode and automation programming mode of three-CMM which is the common measure tool in reverse engineering are analyzed and compared. By scanning measure the surface of electric fan vane and hear-accept mike, The concreting step and method of the probe choice, and calibration of probe head length, and define probe and calibration of probe radius, and establish part measure reference frame are discussed. At the same time, the principle of choice probe radius is pointed out and a new method of establish abnormal shape part measure reference frame is put forward, using work table-board of CMM and three marked points of part boundaiy. So abnormal shape part抯 measure reference frame can be established by this method. The best measuring surface layout along creating line is explored. This layout can increase efficiency of scanning measure and decrease scanning data point. 2. The conception and theory of data processing in reverse engineering are discussed, including transforming data format and offsetting, and eliminating yawp points, and putting many data points view together, and simplifying data points , and densfying data points, and ordering data points, and clipping data points. By processing scanning data the surface of electric fan vane and hear-accept mike, a 3D boundary method that can eliminate yawp points speedily is explored. This method defines a polygon to surround the 揷loud?data that need to be eliminated; taking part 3D boundary measured as reference, so the 揷loud?data can be eliminated in the polygon. The method eliminates yawp points speedily outside 3D boundary as well as keeps the real points inside 3D boundary, and improves efficiency of eliminating yawp points. In addition, the principle of the same concave and protruding nature is put forward at the clipping loud?data. That to say, the surface has the same concave and protruding nature, and relatively flat where loud?data are clipped. At last, the author emphasizes that 揷loud? data must be ordered, this is indispensability step of surface reconstruction. ?III ? 3. The basic theory and method of surface reconstruction are discussed. The process of surface reconstruction of 揷loud?data by Cimatron software is explored. First, to create scanning lines; second to order scanning lines; third to trim surface by a plane; last to adjoin some surfaces, it is a short cut of surface reconstruction. The plane method is the best method of creating 3D scanning line by research. The method that high precision NURBS surface is reconstructed by 3D boundary is studied out. It makes surface reconstruction conveniently and quickly. The method of trimming surface by a plane first and then adjoining is put forward. Some surface can be adjoined smoothly by this method. 4.更多还原