五轴数控加工无干涉刀具轨迹规划研究

发布时间：2018-06-20 15:56

本文选题：五轴加工 + 可行域构造　；参考：《湘潭大学》2017年硕士论文

【摘要】：随着现代工业化的飞跃式发展,对制造业也提出了更高的要求——产品性能优、制造方法新、加工精度高及生产周期短。五轴加工以高速高精度高效率等特点被广泛的应用于自由曲面的加工,虽然五轴加工给制造业带来了一种创新的、高优势的制造方法,但也因为其相对于普通数控机床外加了两个额外旋转轴,给加工中的工艺规划带来不少难点。本文在系统地研究了五轴加工相关理论和国内外研究进展的基础上,以提高自由曲面加工误差精度与加工效率为目的,针对环形刀五轴加工自由曲面刀具轨迹规划算法进行了基础研究。通过对切削模型和干涉现象的分析,在刀轨规划时将刀具干涉问题考虑在内,并以此为前提规划出等弓高、等最大残高刀具轨迹曲线。本文的主要内容如下:首先,针对五轴加工中的单刀触点在某刀具姿态下的干涉检测问题,提出一种基于投影法与映射理论的干涉检测算法,该算法可以有效地避免两曲面间、线与曲面间的相交判断计算。其思路为:根据环形刀的几何形状对其进行分解并建立数学表达式,通过投影得到可能发生干涉的曲面待测点,进行干涉检测时将待测点的工件坐标值按映射理论反代入到环形刀各个数学表达式中,通过对比待测点与刀具表面映射点在Z轴方向的取值间接进行干涉判断。为后续的无干涉刀具姿角可行域构造奠定了基础。其次,提出了一种基于定向距离理论的等弓高、等最大残高刀具轨迹规划算法。该算法能够有效的减少因近似处理所带来的规划误差,在容许误差范围内最大限度地减少刀触点和刀轨总数量。其规划过程包括初步规划与精确修正两个步骤:首先根据圆弧近似法和微分几何法对进给步长与侧向行距进行初步计算,然后以基于定向距离理论的弓高、残高误差计算模型对进给步长与侧向行距进行精确修正,最后通过递推计算得到覆盖整个工件曲面的刀轨曲线。该算法能够有效的减少因近似处理所带来的规划误差。最后,根据对五轴机床运动学原理、各联动轴间相互关系的分析,提出了针对双回转工作台AC型五轴机床刀轨刀位数据转换计算方法,并在UG NX8.0/Post Builder系统中构造临时刀轨后置处理器。其后在Vericut软件和Mikron UCP800 Duro五轴加工中心中分别进行加工仿真和实际加工,并与传统算法及商用软件MasterCAM 9.0的结果进行对比。实验结果表明,采用本文算法进行刀轨规划,既能有效地避免加工中干涉现象的发生,又能在满足加工质量的基础上大大地提高加工效率。
[Abstract]:With the rapid development of modern industrialization, higher requirements have been put forward to the manufacturing industry, such as excellent product performance, new manufacturing method, high processing precision and short production cycle. Five-axis machining is widely used in free-form surface processing with the characteristics of high speed, high precision and high efficiency, although five-axis machining has brought an innovative, high-advantage manufacturing method to the manufacturing industry. But because of the addition of two additional rotating shafts to the NC machine tools, it brings many difficulties to the process planning. On the basis of systematically studying the theory of five-axis machining and the research progress at home and abroad, the purpose of this paper is to improve the accuracy and efficiency of free-form surface machining. In this paper, the basic research on tool path planning algorithm for free form surface machining with annular cutter is carried out. Based on the analysis of cutting model and interference phenomenon, the tool interference problem is taken into account in the tool path planning, and the tool trajectory curve of equal arch height and equal residual height is obtained on this premise. The main contents of this paper are as follows: firstly, an interference detection algorithm based on projection method and mapping theory is proposed to detect the interference of a single pole contact in five-axis machining under a tool attitude. The algorithm can effectively avoid the interference between two surfaces. Calculation of the intersection between lines and surfaces. The idea is to decompose the annular knife according to its geometric shape and establish its mathematical expression, and obtain the points to be measured by projecting the surface that may interfere. In the process of interference detection, the coordinate value of the workpiece to be measured is inversely inserted into the mathematical expressions of the ring cutter according to the mapping theory, and the interference judgment is made indirectly by comparing the values of the mapping points between the measured points and the mapping points of the tool surface in the Z axis direction. It lays a foundation for the construction of the feasible region of the pose angle of the non-interference cutting tool. Secondly, a tool path planning algorithm based on directional distance theory is proposed for equal bow height and equal maximum residual height. The algorithm can effectively reduce the planning error caused by approximate processing and minimize the total number of cutter contacts and tracks within the allowable error range. The planning process includes two steps: first, according to the arc approximation method and differential geometry method, the feed step size and the lateral distance are calculated, and then the bow height based on the directional distance theory is used. The calculation model of residual height error corrects the feed step size and the lateral distance accurately. Finally, the tool track curve covering the whole workpiece surface is obtained by recursive calculation. This algorithm can effectively reduce the planning error caused by approximate processing. Finally, according to the kinematics principle of the five-axis machine tool and the analysis of the interrelation between the linkage shafts, a method for calculating the tool path position data conversion of the AC type five-axis machine tool with double rotary table is presented. In UG NX 8.0 / Post Builder system, the post processor of temporary cutter rail is constructed. Then the machining simulation and actual machining were carried out in Vericut software and Mikron UCP800 Duro five-axis machining center, respectively, and compared with the results of traditional algorithm and commercial software MasterCAM 9.0. The experimental results show that the proposed algorithm can not only effectively avoid the interference in machining, but also greatly improve the machining efficiency on the basis of satisfying the machining quality.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG659

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