【作者】 姬俊锋；

【导师】 周来水；

【作者基本信息】 南京航空航天大学 ， 航空宇航制造工程， 2009， 博士

【摘要】 整体叶轮是航空发动机和各类透平机械的关键部件,随着发动机性能要求的提高,整体叶轮的形状也更趋复杂,其特点是:叶片薄,扭曲大,叶片间隔小。这给整体叶轮的制造加工带来了极大的困难。五坐标数控铣削加工柔性好,加工效率高,适用广泛,是整体叶轮加工常用的方法之一。本文研究了整体叶轮五坐标数控加工中的一些关键技术。以一类开式整体叶轮为例,提出了一套适合于整体叶轮数控加工编程的核心算法,解决了一些关键技术问题。论文主要内容及成果如下:研究了五坐标数控加工编程基础算法。分析了五坐标数控加工中非线性误差产生的原因,建立了适用于五坐标数控加工的非线性误差计算模型。针对五坐标数控加工中刀轴矢量的转动会产生非线性误差及刀轴矢量受机床转动行程限制的问题,提出了满足允许加工误差的五坐标数控加工刀具轨迹计算方法。提出了一种五坐标数控编程过程中刀轴矢量平滑处理方法:根据刀轨特征,在一条刀具路径上设置数个无干涉关键刀轴矢量,通过两阶段三次B样条函数插值,建立平滑过渡刀轴矢量函数,将刀轴矢量与刀具路径上的刀位点一一对应起来,实现了刀轴矢量的平滑过渡。改进弦截法计算走刀步长,获得刀位数据。研究了裁剪曲面叶片刀具轨迹计算方法。首先根据裁剪曲面叶片特征,将裁剪后叶片曲面参数域重新映射到一个规范化参数域,从而可以在该规范化参数域上方便地规划与叶片边界相匹配的刀具轨迹。在此基础上,根据自由曲面叶片点铣加工要求,提出了满足允许加工误差的等参数螺旋刀具轨迹计算方法。提出了整体叶轮数控加工无干涉平滑过渡刀轴矢量计算方法。选取叶片若干截面等参线,在每个截面等参线上的关键位置设置指向流道开口处的无干涉关键刀轴矢量并建立平滑过渡刀轴矢量函数,然后沿叶高参数方向再进行插值,最终得到整体叶轮无干涉平滑过渡刀轴矢量。提出了整体叶轮叶片数控加工刀具进给速度平滑处理方法。针对叶片前后缘处曲率大、刀轴矢量转角大、加工质量难以保证的问题,提出对叶盆、叶背加工进给速度采用S型曲线规划,实现了叶盆、叶背及前后缘加工进给速度的平滑过渡,同时实现了刀轴矢量转动速度的平滑过渡,有利于提高叶片加工质量。研究了整体叶轮叶片粗加工刀轨计算方法。根据整体叶轮干涉碰撞情况,给出了两种母线生成方式。以叶片截面偏置线为准线,得到整体叶轮叶片粗加工刀轨直纹驱动面,最终计算得到整体叶轮叶片粗加工刀轨。提出了一种整体叶轮轮毂曲面刀具轨迹计算方法:根据轮毂曲面特征,在保证残留高度满足允许加工误差前提下,首先计算出所需刀具轨迹数目,然后推导出轮毂曲面刀触点轨迹的参数方程,以此为依据计算轮毂曲面加工刀轨。针对整体叶轮的变半径叶根圆角曲面,根据该曲面成型原理,可计算得到叶根圆角曲面的最小曲率半径,由此可选择加工刀具。在其基础上,结合曲面几何条件及加工要求计算得到叶根圆角曲面的加工刀轨。采用本文提出的一系列关键技术,在UGNX4.0平台上开发了整体叶轮数控加工专用编程模块。采用该软件模块对某企业整体叶轮零件编制了数控加工程序,并进行了加工试验。加工试验表明本文的研究成果是可行有效的。更多还原

【Abstract】 The integral impeller is the key part of the aero engine and all kinds of turbine machine. With the increase of the engine capability, the integral impeller becomes more and more complex. The blade becomes thinner and more twisted and the tunnel is narrower. This brought the manufacture of the impeller more barriers. The 5-axis NC machining is flexible, efficient and widely adopted. So it is one of the frequently used manufacturing methods of the integral impeller.This thesis investigates the 5-axis NC machining technique of the integral impeller. Taking an open integral impeller as an example, a set of key algorithms for the integral impeller NC programming is proposed and some key techniques are resolved. The main content and the research result of this thesis are as follows:The foundation algorithms of the 5-axis NC programming are investigated. The peculiar non-linear error in the 5-axis NC machining is analyzed and the non-linear error computation model for general 5-axis NC machines is proposed. Due to the non-linear error in the 5-axis NC machining and the limitation to the tool orientation range by the real NC machine, the tool path computing method for the 5-axis NC machining with meeting the prescribed tolerance is proposed. The smoothing technique of the tool orientations in the 5-axis NC programming is proposed. With considering the tool path character, several key tool orientations are set at a tool path. By the two-phrase interpolation technique, the smooth tool orientation function is built. With this function, the tool orientation and the CL point at the tool path are associated and the smoothed tool orientations are achieved. Finally, the improved secant method is adopted to compute the tool step and the CL files can be obtained.The planning method for the trimmed blade surface is studied. According to the character of the trimmed blade, the remained parameter field is mapped to a normalized one and it is convenient to plan the tool path according the normalized parameter field. Based on the proposed method, the algorithm of the error-meeting isoparamter spiral tool path is presented with adopting the point milling method. The computation method of the integral impeller tool orientations is proposed. Several isoparamter curves along the section direction are selected. The interference-free key tool orientations pointing to the opening of the tunnel at each isoparamter curve are set and the smooth tool orientation function is built. The interpolation along the radial direction of the blade is taken and the global smoothed tool orientations of the integral impeller can be obtained. Due to the large curvature and the rotation angle of the tool orientation around the edges of the blade, it is difficult to ensure the machining quality. The S-shape federate-setting method is proposed to set the federate and the tool transits from the middle of the blade to the edges smoothly and the tool orientation rotating speed is also smoothed. This can increase the quality of the machining of the blade.The rough machining tool path computation method of the blade of the integral impeller is studied. According to the interference of the integral impeller, two kinds of generatrix computation method are given. The offset of the blade section is taken as the directrix and the ruled driven surface for the rough machining of the blade of the integral impeller is constructed. With the ruled surface, the rough machining tool path can be gained. One tool path planning method for the NC machining of the hub of the integral impeller is proposed. According to the feature of the hub, the number of the tool path is obtained and the parameter function of the CC tool path is deduced with the scallop under the specified error. The tool path planning method for the variable radii bend surface is studied. According to the feature of the variable radius bend surface, the minimal bending radius is obtained and the machining tool can be selected. Then, the toolpath of the bend surface can be obtained with considering the geometric conditions and the machining demand.The customized programming modular embedded in UGNX4.0 for the NC machining of the integral impeller is developed by the UPopen apis with the proposed techniques in this thesis. The NC programs are obtained with the modular and applied to the machining test of an integral impeller. The machining test shows that the proposed techniques are validated.更多还原