基于临界约束的四轴数控加工刀轴优化方法

针对自由曲面四轴加工中复杂刀具运动导致的干涉和刀具运动不连续等现象,提出一种基于临界约束的刀轴优化方法。基于刀具与工件约束曲面之间的相对位置关系,利用曲线上的点搜索算法确定切触点处的临界刀轴矢量,并计算当前切触点刀轴摆动的可行域;以切削行内所有切触点的刀轴可行域为基础,建立当前切削行内无干涉且相邻刀轴变化最小的刀轴矢量优化模型,实现了自由曲面四轴加工无干涉刀轴矢量的光顺控制。整体叶盘四轴加工试验表明,利用此方法获得的刀轴矢量可以显著改善机床运动的连续性,并避免刀具干涉的产生,提高了加工质量。     

数控轮廓铣削的切入和切出程序

在数控铣削轮廓加工中,铣刀从起始位置快速移动到即将以工作进给速度开始切削位置的程序,称为切入程序。因此,切入程序的终点就是开始切削的程序的起点,这一点称为切入点。切削完毕后,铣刀应返回起始位置。铣刀由切削终了时的位置返回起始位置的程序,称为切出程序。编制数控铣削轮廓加工程序时,必须合理地安排切入和切出程序。一、切入程序的编制切入程序要把刀具从起始位置调到开始切削的位置,为切削加工做好准备。而刀具开始切削的位置与其切入工件的方式有关。加工中,为了避免在工件加工表面的切入处留下刀痕,所以当加工表面质量要求较高时,应使铣刀沿工件轮廓的切线方向或工件轮廓     

滚齿机床热变形对加工精度的影响

滚刀与工件的相对位置是由工件与刀具的有关参数确定的。滚齿加工时，滚削热的作用造成机床的床身和立柱产生变形，进而使刀具与工件的相对位置和转角产生误差。刀具与工件间相对位置的变化，必然对加工的齿轮精度产生影响。掌握机床热误差对刀具与工件间的相对位置的影响规律，对于从硬件上改善机床设计，或从软件上利用数控补偿的方法减小加工误差，有着重要的理论和实际意义。     

基于可视锥理论的五轴加工刀具碰撞检验方法

针对复杂曲面数控加工中刀具与工件的碰撞问题,提出一种基于可视锥理论的刀具碰撞检验方法。根据点的可视性特点推导点的可视锥算法,对任意采样点进行可视锥模型构建,通过刀轴矢量与可视锥的布尔运算判断刀具与工件的碰撞,由此计算刀轴避免碰撞时应转过的最小夹角,并对旋转后的新刀轴矢量是否在机床刀轴可加工范围内进行检验。通过将该方法应用于整体叶轮加工中,可快速检验出发生碰撞的区域并对刀轴矢量进行修正,有效地解决了刀具在数控加工中的碰撞检测问题,为刀具路径规划提供了有效的检验方法。     

GTX4E数控系统刀具半径补偿方法

1．问题的提出 在数控铣削加工中,由于刀具半径不为零,导致刀具中心轨迹与工件轮廓不重合,为此现代数控铣床的数控系统均配备了刀具半径补偿功能。按其补偿功能,只需按零件的轮廓进行编程,并在控制面板上手工输入刀具半径值,数控系统应当自动地计算出相应刀具的中心轨迹,并按刀具中心轨迹运动。即执行刀具半径补偿后,刀具自动偏离工件轮廓一个刀具半径值,从而加工出所要求的工件轮廓。具体操作时还可以用同一个加工程序,通过改变刀具半径的偏移量,     

复杂曲面五轴侧铣加工的运动学优化方法

针对五轴侧铣加工中刀轴的运动可能导致加工材料过切与效率低下的问题,提出采用多约束自适应的刀轴运动学优化方法来解决该问题。建立球头铣刀在刀具路段上的运动学模型,通过分析刀轴运动对刀刃微元去除材料的影响,确定刀轴运动优化的约束条件。在虚拟环境中仿真复杂曲面五轴侧铣加工过程,通过自适应控制器调整刀轴运动速度,使机床在多约束加工条件下最大限度地发挥其工作潜能。整个刀轴运动规划过程随刀具与工件接触区域的变化而不断优化,最后将优化结果存储在每个刀位点上。仿真与实验结果表明,刀轴自适应控制的运动学优化方法有效可行,为五轴侧铣加工过程提供了有力的分析工具。     

铣削加工中心对刀方案及刀具长度补偿措施

数控程序控制机床用刀具对工件加工之前,不仅要定义刀具参考基准相对工件的位置,还必须定义刀具刀位点相对工件的位置。文章分析了不同对刀方案的对刀原理及操作方法、刀具长度补偿措施及应用特点。     

万能压板的结构设计与应用

加工工件时,为了达到所需的形位精度和尺寸精度,在加工前必须要先确保工件的被加工面相对刀具有准确的位置,同时由于工件定位后,在加工过程中还要受到切削力、惯性力以及工件自重的作用,使工件产生位移,从而破坏工件已定好的位置。为了使工件在加工过程中始终保证被加工面与刀具之间的相对准确位置,必须保证工件在加工过程中相对机床工作台的位置不发生变动。     

外刊文摘

本文介绍了一种用于回转零件精密加工的新工艺方法——高速车铣。这种工艺综合了车削与铣削的特点,加工时,工件和刀具均绕各自的轴线作旋转运动。按照工件与刀具轴线的相对位置关系,可以分为垂直车铣和平行车铣。车铣加工的切削速度是工件与刀具的速度之和,容易实现高速切削,因而,车铣     

工作台回转与刀轴摆动五轴联动数控加工编程技术研究

研究了工作台回转与刀轴摆动五轴联动数控加工编程中的刀轴矢量与转动角度之间的转换;刀位点在工件坐标系与工作坐标系之间的位置变换;刀轴摆动导致的基准点与刀位点之间的位置补偿等关键技术,为多轴联动数控加工编程技术提供参考.     

带边界约束叶片的螺旋加工轨迹规划

通过采用通道加工原理实现的螺旋加工方法成功解决了叶片螺旋加工中刀具与叶片橼板之间的干涉问题,讨论了确定走刀步长的保证条件,求证出相邻两刀具切触点法矢夹角与刀轴摆角之间的关系。结果表明,采用提出的方法能够有效解决叶根处的干涉问题,为提高叶片的加工效率找到了一种新的解决方案。     

A manufacturing model of helical groove on rotary burr and a universal post processing method

A systematic machining theory and precision method to determine cutter location in a grinding system is presented for rotary burr. First, the helical cutting edge on various kinds of revolving surfaces is built. Then, based on the geometry model of the helical cutting edge, the smooth spiral rake surface with constant normal rake angle and flank surface can been formed during the one-pass grinding process by this method. No interference between the grinding wheel and workpiece happens by the wheel special rotation. The method has the characteristic of detaching the grinding wheel path solution from specified machining conditions. The grinding wheel path is suitable for different NC machine tools through post processing. Meanwhile, a mechanism kinematic model of the NC machine tool is built, and a generalized algorithm for post-processing of multi-axis NC machine tools is presented. This model is applied to arbitrary configuration of NC machine tool, and the motion value for each axis will be generated by the inputting structure and motion parameters of the machine tool. The model, together with the machining method mentioned in this paper, make the calculation and generation of the grinding wheel path simpler and universal. At last, the validity of the method given in the paper is identified by an example of grinding.     

Study on discrete form algorithm of cutter location surface in CNC milling of freeform surface

A novel discrete form algorithm of cutter location surface is proposed to produce 3D tool paths in computer numerical control (CNC) 3-axis milling of freeform surface. As compared with the normal form algorithm, it can be applied to the complex curve surface and irregular shape cutter. The research objective is to identify the discrete form algorithm of cutter location surface. First, the cutter working surface and the machined curve surface were dispersed to be two-point clouds, respectively. Next, the tangency mode of their point clouds was established to produce the cutter location surface. Then, CNC milling experiments were carried out to identify the machined form errors for discrete and normal form algorithms. Finally, the effects of discrete form parameters and workpiece surface posture were investigated on the discrete form accuracy. Experimental results show that the machined form errors for the discrete form algorithm is identical to that for normal form algorithm, but its large form errors are mainly distributed on the large workpiece slope location. On decreasing searching interval and lattice grid size, the discrete form accuracy increases. Moreover, the workpiece surface posture greatly influences the discrete form accuracy, but there exists such a workpiece surface posture that the best discrete form accuracy may be achieved. It is concluded that the discrete form algorithm is feasible to produce the cutter location surface for CNC milling of freeform surface by controlling lattice grid size and searching interval and choosing a suitable workpiece surface posture.     

Local interference detection and avoidance in five-axis NC machining of sculptured surfaces

The tool interference problem is the most critical problem faced in sculptured surface machining. This paper presents a methodology for interference detection and avoidance in five-axis NC machining of sculptured surfaces with a filleted-end cutter. The surfaces to be machined are divided into convex and non-convex regions. There is no local interference inside the convex regions. For the non-convex regions, based on the analysis of the different local interference, local gouging is first detected and avoided by determining optimal cutter orientations. Rear gouging detection and avoidance algorithms are then proposed for simple smooth surfaces and complex shaped surfaces, respectively. The techniques presented in this paper can be used to generate interference-free tool paths. The realistic results indicate that the proposed method is feasible and reliable .     

高速铣削用机械阻尼器铣刀模型的建立及其减振规律的分析

高速铣削加工过程中,刀具颤振会对机床、刀具和工件表面产生不良影响。提出增加机械阻尼器来抑制铣刀颤振的方法;通过对建立的铣刀模型进行理论分析,讨论了阻尼耗散功率随着刀指内径、刀指数目、刀指初始安装角变化而变化的规律。     

高速铣削铝合金时切削力和表面质量影响因素的试验研究

对高速铣削典型铝合金框架结构工件时的切削力和加工表面质量进行了试验研究。在高速进给铣削时 ,当进给方向发生改变 ,机床的加减速特性将导致在拐角处进给量减小、铣刀切入角增大 ,从而引起切削力增大和加工振动。在恒切削效率条件下高速铣削铝合金的试验结果表明 ,高速铣削时宜采用较小的轴向切深和较大的径向切深 ,以减小铣削力、提高加工表面质量 ;刀具动平衡偏心量是高速铣削时引起轴向振纹的主要原因     

Improved Tools for the Turning of Complex Surfaces

The low cutter productivity in the turning of complex discontinuous surfaces is analyzed. New tools with composite cutters are proposed. Thanks to the cutter configuration with respect to the machined surface, the consequences of tool impact on insertion in the workpiece may be minimized.     

A study on the five-axis end milling for sculptured surfaces

The direction vector of milling cutter for CL-data of five-axis milling is obtained by the fact that the bottom part of the milling cutter rides on free-form surfaces using the z-map method. Since the direction vector is known, CL-data can be transformed to the NC-code with regard to the geometry of the five-axis machine and post-processing. For uniform surfaces, the tool path is created from the prediction of cusp heights. After generating the NC-code, a sculptured surface was machined by five-axis end milling and cusp heights on the machined surface were measured by a three-dimensional CMM with laser scanner. From this machining test, it was found that this machining method is effective.     

Machining and dimensional inspection of spatial cams on 5-axis machine tools

An analytical methodology is developed for NC data generation to produce and measure spatial cams on 5-axis machine tools. The Denavit-Hartenberg notation is used for expressing the ability function of the employed machine tool and in the generation of the desired cutter/measuring-probe location. NC data equations are determined by equating the corresponding elements of the machine tool's ability function to the desired tool location matrices. To validate this methodology, a designed cam was machined and its surfaces were measured by an online measurement system equipped with a touch-trigger probe on a 5-axis machine tool. The resultant cutting speed and material-removal rate during machining are also investigated. This methodology is a general one and is applicable to various spatial cams. It also combines the activities of design, manufacturing, and measurement, thus making the production process more flexible, automatic, and controllable.