复杂曲面网格模型的直接数控加工刀具轨迹生成与实验

发布时间：2018-06-19 16:11

本文选题：三角网格 + CL路径法　；参考：《广东工业大学》2017年博士论文

【摘要】：近年来,随着航空航天、汽车、模具及消费产品等行业的快速发展,复杂曲面零件得到了越来越多的应用。三角网格模型可用于曲面零件的外观表达,具有快速灵活及拓扑适应能力强的优点,在增材制造、质量检测、再设计与再制造工程等相关技术领域得到了广泛应用。基于三角网格模型的直接数控加工可避免反求曲面模型的繁琐操作、误差控制及曲面质量等问题,是实现快速制造的一个重要途径。然而,三角网格模型仅由网格面片组成,在数控代码生成、加工精度及加工质量等方面仍存在问题,并有待于进一步的研究。本论文针对三角网格模型直接数控加工中的刀具轨迹生成方法,开展较为深入的研究。基于CL路径法的三角网格模型实验加工与缺陷分析,提出一种面向复杂曲面网格模型的刀具轨迹生成新方法,其中包括网格模型的顶点偏置方法、离散误差补偿的刀位点生成算法及双向插值的刀具轨迹生成算法,开发复杂曲面网格模型的直接数控加工系统,生成复杂曲面网格模型的刀具轨迹,实现三角网格模型的直接数控加工。本论文的主要研究内容包括以下几个方面:(1)深入调研复杂曲面网格模型的直接数控加工方法,了解该领域的国内外研究现状,分析目前三角网格模型刀具轨迹生成的CL路径法,指明当前三角网格模型刀具轨迹生成中存在的关键技术问题,确定本论文的研究内容与实施方案。(2)基于模型文件的格式描述,分析网格模型的质量问题对刀具轨迹生成的影响,提出模型数据的拓扑重构方法,为网格模型的刀具轨迹生成提供有效的模型数据。基于网格模型的CL路径法,实现粗细两种网格模型的实际加工,分析加工零件的表面质量,发现网格模型加工表面出现的凸面凹坑、凹面凹槽及区域三角化缺陷问题,明确目前网格模型CL路径法的关键技术问题。(3)研究网格模型的顶点偏置方法,提出基于边界顶点相邻网格面片补齐的边界顶点法矢修正算法及基于相邻面片偏置误差加权的顶点偏置距离补偿算法,有效改善三角网格模型的偏置效果。针对边界顶点法矢计算偏差所引起的加工过切问题,通过边界顶点相邻网格面片补齐的边界顶点法矢修正计算,消除边界区域的实际加工问题。基于偏置模型的实际偏置距离,分析模型偏置距离不足造成加工过切问题,通过基于相邻面片偏置误差加权的顶点偏置距离补偿,减小偏置模型的偏置误差。(4)研究偏置模型的刀位点生成方法,提出基于近似曲面轮廓曲线截平面求交的离散误差补偿刀位点生成算法,避免三角网格模型离散误差造成的刀位点计算精度问题。在走刀方式选择及残留高度计算的基础上,详细研究偏置模型刀位点生成的截平面求交法,探讨截平面与网格面片的位置关系,给出截面交点的计算方法。详细分析三角网格模型离散误差对截面交点计算精度的影响,重点研究网格模型加工零件表面的缺陷机理,通过刀位点的离散误差补偿,改善刀位点的计算精度。(5)研究刀位点的刀具轨迹生成方法及刀具轨迹的插补算法,提出双向插值的刀具轨迹生成算法,实现刀具轨迹的光滑处理。采用三次非均匀B样条曲线插值的方法,实现截平面方向的刀具轨迹生成及光顺处理。通过刀位点的双向插值,解决垂直于截平面方向的刀具轨迹连接问题。基于走刀步长与逼近误差的几何关系,分析样条曲线的插补方法,通过等参数直线逼近的方法,实现刀具轨迹的插补点坐标计算。(6)基于三角网格模型的刀具轨迹生成方法,开发了复杂曲面网格模型的直接数控加工系统,实现了本论文提出的面向复杂曲面网格模型刀具轨迹生成新方法。通过多个实例模型的加工实验与结果分析,对刀具轨迹生成新方法的有效性进行了验证,为复杂曲面网格模型的直接数控加工提供了有效的理论依据。最后,进行全文的总结,并总结展望在复杂曲面网格模型的直接数控加工方法研究中存在和需进一步解决的若干问题。
[Abstract]:In recent years, with the rapid development of aerospace, automobile, molds and consumer products, complex surface parts have been more and more applied. Triangular mesh model can be used to express the appearance of surface parts. It has the advantages of rapid flexibility and strong topological adaptability. It is used in the manufacturing of timber, quality detection, redesign and remanufacture engineering, etc. The field of related technology has been widely used. Direct numerical control machining based on triangular mesh model can avoid the complicated operation of reverse surface model, error control and surface quality. It is an important way to realize rapid manufacturing. However, triangular mesh model is composed of mesh only, the NC code is generated, the machining accuracy and the addition are added. There are still problems in the work quality and other aspects, which need further research. In this paper, the tool path generation method in the triangular mesh model direct numerical control machining is studied. The tool path of the complex surface mesh model is proposed by the experimental processing and defect analysis of the triangular mesh model based on the CL path method. The new method is generated, including the vertex offset method of grid model, the algorithm for generating the tool locus of the discrete error compensation and the tool path generation algorithm of the bidirectional interpolation, developing the direct numerical control machining system of the complex surface mesh model, generating the tool track of the complex surface mesh model, and realizing the direct numerical control machining of the triangular mesh model. The main research contents of this paper include the following aspects: (1) in-depth investigation of the direct numerical control processing method of complex surface mesh model, understanding the current research status at home and abroad in this field, analyzing the CL path method of cutting tool path generation in the triangular mesh model, and pointing out the key technologies in the tool path generation of the current triangular mesh model. The research content and implementation plan of this paper are determined. (2) based on the format description of the model file, the influence of the quality of the grid model on the tool path generation is analyzed, and the topology reconstruction method of the model data is proposed, which provides the effective model data for the tool path generation of the grid model. The CL path method based on the grid model is implemented. The actual processing of two kinds of mesh models is used to analyze the surface quality of the machined parts. The problem of convex concave pits, concave grooves and regional triangulation defects on the surface of the mesh model is found, and the key technical problems of the current grid model CL path method are clearly defined. (3) the vertex offset method based on the boundary vertex is proposed. The boundary vertex normal vector correction algorithm and the vertex offset distance compensation algorithm based on the weighting error of the adjacent face offset error can effectively improve the bias effect of the triangular mesh model. The boundary vertex method is used to solve the cutting problem caused by the deviation of the boundary vertex normal vector. The vector correction calculation eliminates the actual machining problem in the boundary area. Based on the actual bias distance of the bias model, the analysis of the offset distance is not enough to cause the cutting problem, and the offset error is reduced by the offset distance compensation based on the weighted offset error of the adjacent face offset error. (4) the tool loci generation side of the bias model is studied. Method based on the discrete error compensation tool site generation algorithm based on the intersection of approximate curved surface contour curve, which avoids the precision problem of the knife site calculation caused by the triangular mesh model discretization error. On the basis of the selection of the cutter and the calculation of the residual height, the cross section intersection method is studied in detail. The relation between the surface and the position of the mesh surface, the calculation method of cross section intersection is given. The influence of the discrete error of the triangular mesh model on the calculation precision of cross section intersection is analyzed in detail. The mechanism of the defect on the surface of the part is studied by the grid model. The calculation precision of the knife site is improved by the discrete error compensation of the knife site. (5) the knife site knife is studied. With the path generation method and the interpolation algorithm of tool path, the tool path generation algorithm of bidirectional interpolation is proposed to realize the smooth processing of the tool path. The tool path generation and smoothing of the cutting plane direction are realized by using the three inhomogeneous B spline curve interpolation method. Through bidirectional interpolation of the knife site, the vertical to the cutting plane square is solved. Based on the geometric relationship between the tool path length and the approximation error, the interpolation method of the spline curve is analyzed. The interpolation point coordinates of the tool path are calculated by the method of equal parameter straight line approximation. (6) the direct numerical control of the complex surface mesh model is developed based on the tool path generation method based on the triangular mesh model. In this paper, a new method of tool path generation for complex surface mesh model is realized. The effectiveness of the new method of tool path generation is verified by the processing experiments and results of multiple example models, which provides an effective theoretical basis for the direct numerical control machining of the complex surface mesh model. Finally, A summary of the whole paper and a summary of some problems that need further solution in the study of direct NC machining methods for complex curved surface mesh models are given.
【学位授予单位】：广东工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG659

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