工件旋转与刀轴摆动数控加工关键技术研究

研究工件旋转与刀轴摆动五轴联动数控加工过程中,进给轴之间的协调、插补方式的选取、刀轴矢量与转角和摆角间的换算、刀位点从工件坐标系向工作坐标系转换的坐标变换关系、刀轴摆动导致基准点与刀位点之间的位置补偿、后处理器开发和刀位文件的后处理等关键技术,为多轴联动数控加工编程技术提供了参考.     

基于UG/CAM模块固定轴曲面轮廓数控铣的研究

UG/CAM模块固定轴曲面轮廓铣操作用于对表面轮廓进行数控加工,其后处理模块可以生成指定机床能够识别的NC程序,利用其可视化功能可以直观地仿真加工过程,检验NC程序的正确性.本文提出了UG NX/CAM模块中固定轴曲面轮廓铣削的CAM及NC程序生成的思路、方法.通过一具体实例讨论了固定轴曲面轮廓铣数控加工中工艺设计与规划的方法,研究了固定轴曲面轮廓铣数控加工中参数的合理设置方法及其误差的有效控制手段.     

五轴联动数控加工进给率规划方法

针对五轴联动数控加工中恒定机床进给率下加工刀尖点速度波动的问题,提出了同时考虑机床坐标系和工件坐标系下运动学性能约束的进给率规划方法.首先推导了机床坐标系和工件坐标系之间的运动学变换关系,然后综合考虑了机床各轴运动速度和加速度约束条件,以及刀尖点与工件相对运动速度与加速度约束条件,对各程序段中的机床进给速度进行规划.将该方法主要应用于后置处理,仿真结果表明,规划进给率后,加工时间比恒定进给速度下缩短了32.9%,加工速度更为平滑.     

五轴联动的曲面编程与后处理

1五轴联动的编程方法 最初的五轴编程方法是编程员根据零件图样和有关加工工艺要求,用一种专用的数控编程语言来描述整个零件的加工过程,即零件的源程序.然后将源程序输入计算机中,由计算机进行编译、计算,最后再由与所用数控机床相对应的后置处理程序处理后,自动生成相应的数控加工程序.     

基于VERICUT的车铣复合IT100建模和数控仿真研究

针对车铣复合IT100机床机构复杂、程序繁琐、刀轴运动灵活,在实际加工过程中很难人为判断程序的正确性以及刀轴是否会与零件、工作台、夹具等发生碰撞、干涉等问题。提出首先在UG软件中根据机床各部件的实测尺寸进行建模,然后将其建好模型导入VERICUT软件中,并根据各部件的相对运动关系组建虚拟的仿真机床。在此虚拟的仿真机床上对诱导轮进行模拟仿真加工,最后通过在车铣复合IT100上对诱导轮的实际加工验证了其模拟仿真的正确性和实用性,同时也为其他多轴联动数控机床的数控仿真提供了一定的经验。     

五轴联动加工中进给速度的控制算法

目的研究刀具进给速度平稳性对五轴联动加工中复杂自由曲面表面粗糙度、轮廓精度的影响。方法首先对五轴联动机床运动过程中的空间线性插补原理进行了分析,推导出插补周期内各轴的分解速度数学模型。根据数控系统中不同的速度指令方式以及刀具在空间的实际运动距离,分端铣和侧铣两种情况,分别建立了刀具空间运动的实际速度计算模型,然后根据机床各轴的最高速度及加速度约束条件,对各轴分速度、分加速度进行校核处理,最终求得刀具实际的合成速度。最后,基于后置处理技术,用开发的专用后置处理软件进行刀位源代码后置处理,采用某叶轮试件进行了验证,并对实验结果进行了分析。结果在复杂曲面加工中,稳定的表面进给速度会获得较高的表面质量及轮廓精度,曲面曲率变化越大,速度变化对加工质量的影响越大。在同等条件下切削,刀具采用恒表面速度与采用恒进给速度相比,获得的叶片进出汽边轮廓误差值由0.1 mm减小为0.04 mm。结论在五轴联动加工中,越稳定的表面进给速度,越能获得较高的表面质量和轮廓精度,对于曲率变化较大的复杂曲面,需要严格控制刀具的进给速度,尽量获得稳定的表面速度以减少过切值,从而提高零件表面质量。     

HPM 1850U虚拟机床的构建与多轴数控加工仿真验证

HPM 1850U机床是一种能进行高速高精度加工的五轴联动加工中心,由于其结构复杂,主轴灵活且还可进行立卧转换,所以在数控加工过程中存在无法人为判断数控程序的正确性和刀轴的干涉碰撞等问题。为解决此问题,利用三维软件搭建了1850U机床实测尺寸模型,并在数控虚拟仿真加工软件VERICUT中构建该机床的虚拟仿真环境,以某叶轮为例,验证了该虚拟仿真环境的正确性。结果表明:该机床的虚拟仿真环境可实现数控加工过程动态仿真,也可以验证刀具轨迹和数控程序的正确性,并同时检验刀轴干涉的碰撞,从而缩短产品生产周期,提高生产效率,并且为其他同类型多轴机床虚拟仿真提供技术支持,也为数字化集成制造提供了虚拟仿真机床和技术。     

叶片螺旋铣加工刀位计算研究

研究了航空发动机叶片叶身部分的螺旋铣数控加工过程，推导出了用于多坐标数控铣加工的叶片刀位点计算公式。根据叶片特征和数控加工理论，详细讨论了叶片前后缘头加工过程中的刀位计算方法和缘头边界判别方法，有效地避免了缘头处的刀具啃切和刀轴晃动现象。本文的刀位计算方法在叶片螺旋铣加工实践中取得了良好效果，提高了叶片生产效率，降低了生产成本。     

轧辊的铣削原理及进给速度修正问题研究

本文讨论了在具有第四轴(旋转轴)的数控铣床上，铣削轧辊的原理及数控编程方法，应用“对应圆柱”这一概念对铣削进给速度的修正问题进行了分析。为了实现高效率加工，需要对编程进给速度进行必要的修正，并给出了速度修正的计算方法。     

基于速度前瞻控制的五轴NURBS曲线插补方法

在分析了最大加速度、进给速度约束以及曲线曲率变化等因素对数控加工过程影响的基础上,提出了一种基于速度前瞻控制的五轴NURBS曲线插补方法.该方法将五轴NURBS曲线插补划分为预处理和实时插补两个阶段,预处理阶段用于样条曲线表达式的计算、刀心点样条曲线按曲率变化的分段以及分割点处期望速度的计算,以减少实时插补阶段的计算量,使其能够满足数控系统对实时性的要求;实时插补阶段利用预处理阶段所得到的信息进行进给速度实时规划,以确保到达曲率较大或曲率突变点之前提前减速.最后对所设计的插补方法进行了仿真验证,验证结果表明本文所提出的方法可在保证加速度不超出限制的条件下保证加工的精度.     

An investigation of workpiece temperature variation in end milling considering flank rubbing effect

Better prediction about the magnitude and distribution of workpiece temperatures has a great significance for improving performance of metal cutting process, especially in the aviation industry. A thermal model is presented to describe the cyclic temperature variation in the workpiece for end milling. Owing to rapid tool wear in the machining of aeronautical components, flank rubbing effect is considered. In the proposed heat source method for milling, both the cutting edge and time history of process are discretized into elements to tackle geometrical and kinematical complexities. Based on this concept, a technique to calculate the workpiece temperature in stable state, which supposes the tool makes reverse movement, is developed. And a practicable solution is provided by constructing a periodic temperature rise function series. This investigation indicates theoretically and experimentally the impact of different machining conditions, flank wear widths and cutter locations on the variation of workpiece temperature. The model results have been compared with the experimental data obtained by machining 300M steel under different flank wear widths and cutting conditions. The comparison indicates a good agreement both in trends and values. With the alternative method, an accurate simulation of workpiece temperature variation can be achieved and computational time of the algorithm is obviously shorter than that of finite element method. This work can be further employed to optimize cutting conditions for controlling the machined surface integrity.     

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.     

五轴侧铣加工3D刀具半径补偿研究

为了解决五轴联动侧铣加工3D刀具半径补偿的难题,建立了三维空间刀具半径补偿模型;通过对刀具空间不同位姿的异面法矢的最佳补偿点的求取,避免了空间投影造成的误差,解决了五轴轨迹空间转角的半径补偿问题.论文提出的空间半径补偿算法已集成在五轴联动数控系统中,通过加工实验进行了验证.     

Time domain prediction of milling stability according to cross edge radiuses and flank edge profiles

This article proposes a time domain model for predicting an end milling stability considering process damping caused by a variety of cross edge radiuses and flank profiles. The time domain model of calculating indentation areas, as well as regenerative dynamic uncut chips, is formulated for the prediction of the stabilizing effect induced by interference areas between the edge profiles and undulation left on a workpiece. The interference area generates forces against the vibration motion, which acts as a damping effect. In the model, the present and previous angular position of cross radiuses and flank edge profiles are located to calculate the dynamic uncut chip as well as indentation area based on a time history of the dynamic cutter center position. The phenomenon that chatter is damped according to cross edge radiuses and flank edge profiles is successfully simulated with the proposed dynamic model and validated through the extensive experimental tests.     

UG／CAM在汽车模具加工中的应用

介绍了UG／CAM数控编程的基本过程,以第三横梁成形模中的凹模镶件为例,重点分析了不同加工方法对加工质量的影响。     

A three-dimensional analytical cutting force model for micro end milling operation

In the present day manufacturing arena one of the most important fields of interest lies in the manufacturing of miniaturized components. End milling with fine-grained carbide micro end mills could be an efficient and economical means for medium and small lot production of micro components. Analysis of the cutting force in micro end milling plays a vital role in characterizing the cutting process, in estimating the tool life and in optimizing the process. A new approach to analytical three-dimensional cutting force modeling has been introduced in this paper. The model determines the theoretical chip area at any specific angular position of the tool cutting edge by considering the geometry of the path of the cutting edge and relates this with tangential cutting force. A greater proportion of the helix face of the cutter participating in the cutting process differs the cutting force profile in micro end milling operations a bit from that in conventional end milling operations. This is because of the reason that the depth-of-cut to tool diameter ratio is much higher in micro end milling than the conventional one. The analytical cutting force expressions developed in this model have been simulated for a set of cutting conditions and are found to be well in harmony with experimental results.     

金属切削加工中铣刀及切削参数的选择

文章介绍了铣削加工中铣刀及其几何参数的合理选用,切削用量的选择、切削功率的计算及常见问题的解决方法.     

深孔加工的新方法——钻铣法

传统的深孔加工方法,如接柄麻花钻,机械夹固硬质合金钻头,单刃深孔钻,BTA深孔钻长期以来已在不同的范围内广泛地应用,但是这些方法至今未能解决钻孔时的零切削速度区问题。钻铣法在钻头上加装铣刀,切削时铣刀自转并连同钻头一起公转或钻头不转工件旋转,成功地解决了深孔钻削时的零切削区问题,为较大孔径的深孔加工提供了一种可供选择的新型加工方法。     

模具平面铣削刀具的选择方法

根据模具平面铣削的要求,就铣刀刀体选择、铣刀片的选择、顺铣和逆铣3个方面具体进行了分析,为模具平面铣削刀具的选择提供了参考。     

激光铣削玻璃的试验研究

采用Nd:YAG脉冲激光器对普通玻璃进行铣削加工.系统地研究了工艺参数对铣削量和铣削面质量的影响规律,并利用优化的铣削工艺对玻璃进行多种形状无裂纹铣削加工试验.