侧铣加工刀位轨迹优化算法研究

针对非可展直纹面侧铣精加工刀轴矢量计算中存在的问题,侧铣加工误差几何模型分析圆柱铣刀加工非可展直纹面误差产生的原因。以两点偏置法和三点偏置法等基本算法为基础,提高非可展直纹面类零件的加工精度,文章提出一种定点旋转寻求最优刀轴矢量组的计算方法,并且采用密切法进一步优化。通过优化算法使加工误差趋于最小,最终得到整体最优的刀轴轨迹。此方法与已有方法进行加工实验对比,从仿真结果可以看出明显提高了加工精度,对非可展直纹面侧铣加工提供一定的参考意义。     

基于GA—NOA优化算法的侧铣刀轴轨迹规划

针对非可展直纹面的圆柱刀侧铣加工,提出了一种基于遗传算法(GA)和非线性规划(NOA)混合算法的优化方法。首先,采用两点偏置法确定初始刀轴矢量,在此基础上,引入了单刀位下的误差度量函数,即刀轴上各点到非可展直纹面的距离与对应各点到圆柱面的距离差值的平方和最小来实现单刀位的优化结果。进而对整体刀位优化问题,提出了基于遗传算法和非线性规划混合算法进行整体刀位。仿真计算结果表明,该方法在单刀位下的优化过程简单,结果精度高,优化后位姿集合形成的刀具包络误差小,对非可展直纹面侧铣加工有一定的实际意义。     

数控电解-机械精密切割加工直纹面的算法

为了精密切割加工整体叶轮的叶片型面,进行了数控电解一机械精密切割加工直纹面的算法研究。研究了复合阴极加工时的实际运动轨迹,得到了电解一机械精密切割加工机床的5个坐标计算公式。在建立叶片型面型值点数据库的基础上,完成了叶片型面拟合、插值加密、边界处理的计算机程序,并计算出5轴联动机床加工时的各轴运动参数,最后实现了整体叶轮叶片数控电解一机械切割加工程序的自动编程。整个处理过程集成在一个C＋＋应用程序中,程序运行可靠,操作界面友好,且便于扩展。该算法避免了求解非线性微分方程组的难题,具有构思巧妙、运算简单和编程方便等特点,可推广到其他领域应用。     

直纹面型叶轮五坐标数控铣削原理的研究

本文详细分析了三元叶轮的几何造型，计算了进行叶轮数控加工的全部参数，给出了直纹面型叶轮加工的一般方法，为编制通用的三元叶轮ＣＡＤ／ＣＡＭ一体化软件打下了良好基础     

基于误差分析的复杂曲面可侧铣判定方法研究

基于复杂曲面侧铣加工误差计算,提出了一种曲面能否通过侧铣实现高精度加工的判定方法,该方法适用于任意直纹和非直纹曲面。侧铣加工误差为待加工理论曲面与刀具运动包络曲面之间的距离,在此基础上,应用整体最优刀具路径下的最大几何偏差进行曲面可侧铣判定依据。数值仿真算例表明:该方法不仅能够有效地判定曲面能否侧铣,同时能够输出满足误差要求的最优刀具路径,加工实验也表明该方法能够极大地提高加工效率。     

电火花线切割机数控装置的直纹面编程与插补

为解决加工直纹面模具的难题，本文提出考虑使用高速走丝电火花线切割机，并给出其数控装置的直纹面编程方法和插补原理，且结合上圆下方体实例进行了说明。     

鼓形刀密切法加工复杂曲面刀位轨迹生成

复杂曲面加工的刀具路径规划以往多是针对圆柱刀,圆锥刀等外形相对简单的刀具。与此相比,鼓形刀曲率可以很大,位姿变换较为灵活。为扩展其在凹形曲面等直纹面侧铣加工中的应用,基于密切法加工模型构架,引入鼓形刀侧圆弧半径和纬线半径,推导鼓形刀侧铣加工刀轴矢量、刀心位置的公式表达。根据密切法加工适应判别条件,由刀具几何性质论证了鼓形刀密切法加工条件不仅与曲面曲率有关,还受刀具姿态本身影响。通过算例验证了鼓形刀密切法加工刀位轨迹生成的可行性。     

电火花线切割机数控装置的直纹面编程与插补

为解决加工直纹面模具的难题，本文提出考虑使用高速走丝电火花线切割机，并给出其数控装置的直纹面编程方法和插补原理，且结合上圆下方体实例进行了说明。     

侧铣不可展直纹面模具原理性加工误差计算方法

分析了侧铣不可展直纹面模具的原理性加工误差的来源及特点，提出通过计算被加工表面各点到刀具旋转轴扫掠面的距离以确定误差分布，为刀位主动补偿和后续加工提供了依据。采用有限次离散和平面替代的方法求取点到曲面之间的距离，根据求解精度要求确定曲面最小离散次数，提高了计算效率，平面替代法将问题简化为可精确求解的点到平面的距离问题。实例通过与三坐标测量结果的对比验证了算法的可靠性。     

基于双NURBS曲线的叶轮叶片工业机器人GMAW增材制造

以双NURBS曲线获得的直纹面广泛存在于各行业复杂零件中,如何实现复杂直纹面的增材制造一直是增材制造领域中极为关心的问题。以双NURBS曲线描述叶片模型,进一步获得直纹面,采用优化工艺参数,以GMAW方法实现了叶轮叶片的增材制造,增材获得的叶片完整,成形良好,表明以GMAW工艺实现双NURBS曲线叶片增材制造是可行的。为叶片模型构建、复杂形状叶片的电弧增材制造提供了新方法,对复杂形状零件增材制造过程控制具有借鉴意义。     

Machining accuracy improvement in five-axis flank milling of ruled surfaces

The aim of this study is to develop a new adjustment method for improving machining accuracy of tool path in five-axis flank milling of ruled surfaces. This method considers interpolation sampling time of the five-axis machine tools controller in NC tool path planning. The actual interpolation position and orientation between G01 commands are estimated with the first differential approximation of Taylor expansion. The tool swept volume is modeled using the envelope surface and compared with the design surface to determine the deviation, which corresponds to the machining error induced by the linear interpolation. We propose a feedrate adjustment rule that automatically controls the tool motion at feedrate-sensitive corners based on a bisection method, thus limiting the maximum machining errors and improving the machining accuracy. Experimental cuts are conducted on different ruled surfaces to verify the effectiveness of the proposed method. The result shows that it can enhance the machining quality in five-axis flank milling in both simulation and practical operation.     

Optimized tool path generation based on dynamic programming for five-axis flank milling of rule surface

This paper presents a computation scheme that generates optimized tool path for five-axis flank milling of ruled surface. Tool path planning is transformed into a matching problem between two point sets in 3D space, sampled from the boundary curves of the machined surface. Each connection in the matching corresponds to a possible tool position. Dynamic programming techniques are applied to obtain the optimal combination of tool positions with the objective function as machining error. The error estimation considers both the deviation induced by the cutter at discrete positions and the one between them. The path planning problem is thus solved in a systematic manner by formulizing it as a mathematical programming task. In addition, the scheme incorporates several optimization parameters that allow generating new patterns of tool motion. Implementation results obtained from simulation and experiment indicate that our method produces better machining quality. This work provides a concise but effective approach for machining error control in five-axis flank milling.     

侧铣加工空间刀具半径补偿技术实现

通过对侧铣加工空间刀具半径补偿算法的研究,建立刀具和工件模型,并对其进行了求解和公式推导。对任意侧铣加工曲面进行偏置计算,生成带有刀具半径补偿的侧铣偏置曲面,从而解决了侧铣加工中曲面偏置位置的问题,实现了侧铣加工空间刀具半径补偿,该方法的应用为数控系统研究侧铣空间刀具半径补偿提供了参考。     

铝基复合材料铣削加工过程参数的预测与优化(英文)

研究了LM25Al/SiCp复合材料的铣削加工特征。将获得的相关试验数据采用响应面方法建立了一个数学模型来描述各种加工参数对后刀面磨损率的影响。采用标准的响应面方法来设计实验。方差分析结果表明,在实验研究范围内,所建立的数学模型能够很好地描述铣削加工各参数的影响。采用优化组合参数得到了最小的后刀面磨损率。     

5-Axis adaptive flank milling of flexible thin-walled parts based on the on-machine measurement

Deformation of the part and cutter caused by cutting forces immediately affects the dimensional accuracy of manufactured parts. This paper presents an integrated machining deviation compensation strategy based on on-machine measurement (OMM) inspection system. Previous research attempts on this topic deal with deformation compensation in machining of geometries in 3-axis machine tools only. This paper is the first time that concerned with 5-axis flank milling of flexible thin-walled parts. To capture the machined surface precision dimensions, OMM with a touch-trigger probe installed on machine׳s spindle is utilized. Probe path is planned to obtain the coordinate of the sampling points on machined surface. The machined surface can then be reconstructed. Meanwhile, the cutter׳s envelope surface is calculated based on nominal cutter location source file (CLSF). Subsequently, the machining error caused by part and cutter deflection is calibrated by comparing the deviation between the machined surface and the envelope surface. An iteration toolpath compensation algorithm is designed to decrease machining errors and avoid unwanted interference by modifying the toolpath. Experiment of machining the impeller blade is carried out to validate the methodology developed in this paper. The results demonstrate the effectiveness of the proposed method in machining error compensation.     

5-Axis tool path smoothing based on drive constraints

In high speed machining, the real feedrate is often lower than the programmed one. This reduction of the feedrate is mainly due to the physical limits of the drives, and affects machining time as well as the quality of the machined surface. Indeed, if the tool path presents sharp geometrical variations the feedrate has to be decreased to respect the drive constraints in terms of velocity, acceleration and jerk. Thus, the aim of this paper is to smooth 5-axis tool paths in order to maximize the real feedrate and to reduce the machining time.Velocity, acceleration and jerk limits of each drive allow to compute an evaluation of the maximum reachable feedrate which is then used to localize the areas where the tool path has to be smoothed. So starting from a given tool path, the proposed algorithm iteratively smoothes the joint motions in order to raise the real feedrate. This algorithm has been tested in 5-axis end milling of an airfoil and in flank milling of an impeller for which a N-buffer algorithm is used to control the geometrical deviations. An important reduction of the measured machining time is demonstrated in both examples.     

宏指令加工立体曲面的研究与实践

文章详细地介绍了在华中ZJK7532A数控铣床上利用宏指令编程加工圆弧面和圆锥面,比较了加工圆弧面和圆锥面的几种刀具轨迹生成方法,阐明了提高规则立体曲面加工质量的方法.     

Geometrical deviations versus smoothness in 5-axis high-speed flank milling

The paper deals with the Generation of Optimized 5-aXis Flank milling trajectories. Within the context of 5-axis High-Speed Machining, oscillatory trajectories may penalize process efficiency. The control of the trajectory smoothness is as essential as the control of geometrical deviations. For this purpose the Geo5XF method based on the surface representation of the tool trajectory has been developed. In flank milling, this surface, also called the Machining Surface (MS), is the ruled surface locus of the tool axes defining the trajectory. Based on a first positioning, the method aims at globally minimizing geometrical deviations between the envelope surface of the tool movement and the designed surface by deforming the MS while preserving trajectory smoothness. The energy of deformation of the MS is used as an indicator of the smoothness. Hence, in most cases, results obtained using Geo5XF show that minimum energy tool paths lead to minimal machining time. As geometrical deviations are not minimized for minimum energy tool paths, a compromise must be reached to find the best solution.