【作者】 杨健；

【导师】 肖世德；

【作者基本信息】 西南交通大学 ， 机械电子工程， 2003， 硕士

【摘要】 本文以实现在小型三坐标二联动立式加工中心TH5632C上加工曲面的计算机辅助编程为目的。对于二轴联动的数控加工中心，实现加工曲面的方式一般是采用球头铣刀，通过把曲面剖切成平行于某轴的平面曲线，再用直线、圆弧、抛物线去拟合该平面曲线，最终对每一条曲线加工集合成曲面。 结合国内外的应用现状，论文综合分析了在数控加工中，用直线段及圆弧段来拟合和逼近非圆曲线及列表曲线的常用处理方法及算法，在此基础上，对于平面非圆曲线的加工预处理，提出用等误差直线逼近非圆曲线的近似算法——逐点逼近法、伸缩步长法；而对于列表曲线的加工预处理，则先采用累加弦长三次参数样条曲线拟合列表曲线，再以双圆弧来逼近三次参数样条曲线，最终求得列表曲线的节点坐标。在满足加工精度和实时性要求的条件下，本文采用C语言实现上述算法。 论文的开始对数控编程中数值计算的内容和要求作了简要介绍，其中节点坐标数据的计算是数值计算中最烦琐、最复杂的计算。逼近误差δ≤δ_允以及加工实时性要求是针对任何平面轮廓曲线寻找其最佳的节点算法的重要依据和必要条件。 用直线段逼近非圆曲线的算法总体来说有以下三种，即：等间距法—使每段逼近直线在X轴上的投影相等；等弦长法—使每段逼近直线的长度相等；等误差法—使每段逼近直线与轮廓曲线的最大误差相等。本文用C语言实现了以上算法的计算机程序，该程序可完成抛物线，椭圆和双曲线三种常用曲线的计算机插补节点计算，同时给出使用说明。 用圆弧段逼近非圆曲线，目前常用的方法有曲率圆法，三点圆法和相切圆法等。本文主要探讨采用双圆弧法逼近非圆曲线，并给出其算法流程。 对于列表曲线，本文采用三次参数样条函数对列表曲线进行第一次拟合，然后用双圆弧样条进行第二次逼近的算法，并用C语言结合实例给出了计算程序和计算结果。 本文还通过旋转曲面零件的数控加工实践，对二坐标联动加工时直线插补步长、行距及球刀半径的选择进行了探讨。更多还原

【Abstract】 The thesis aims to design the computer-aided program for the curved face machining based on the small three coordinate axes vertical machine center. In the two axes linked numerical control machine center, the spherical cutter is firstly used to subdivide the curved face to a plane curve that is parallel to one axis. Then the line, the arc and the parabola are adopted to form a fitted curve. Finally, the curved face is aggregated by each curve.Based on the analysis of the present domestic and overseas situation, the thesis discusses the normal techniques and arithmetic of fitting and approaching non-circularity curves and tabulate curves by line and arc in the numerical control milling. For the pretreatment of the plane non-circularity curve, the thesis then points out the approximate arithmetic of non-circularity curve, namely the point-to-point approaching and the flexible steps method, by using equal error line approaching. While for the pretreatment of the tabulate curves, the first step is to approach tabulate curves with accumulating cube parameter style curves. Then the double-arc is adopted to fit the cube parameter style curve. Finally the coordinate of nodes on the tabulate curve is calculated. Meeting the requirement of cut accuracy and real-time control, the thesis aims at achieving the above algorithm with C Language. Meanwhile, the summary of the advantages and disadvantages of each the algorithm lays the foundation for its implementation in the numerical control system and plotting system.Therefore, the thesis has been organized in the following way.Firstly, it will summarize the contents and requirements of numerical computation in the numerical program, in which the calculation of nodes coordination may be the most complicated. The approaching error δ≤δ允 and the real-time control are important and necessary during the selection of optimum nodes algorithm for configuration.There are three algorithms in the approaching non-circularity curve with line, namely the equal interval algorithm, the equal arc algorithm and the equal error algorithm. In the thesis, the computer programs of these algorithms will be realized with C Language. Furthermore, these programs can realize the computer interpolate nodes algorithm of three normal curves, including parabola, ellipse andhyperbola.There are also three algorithms in the approaching non-circularity curve with arc, namely the circum flexion algorithm, the three-point circle method and the tangency circle algorithm. In the thesis, the double-arc algorithm and its flowchart will be mainly discussed in approaching non-circularity curve.For the tabulate curve, the cube parameter style curve will be firstly adopted to fit the curve. Then the double-arc style curve will be implemented. The computer program and the running results with C Language will be included in this section based on examples. Finally, the thesis will discuss the selection of step length, string space and radius of spherical cutter in the three coordinate axes and two axes linked machining center based on the practice of NC machining for revolution surface parts.更多还原