球头铣刀柔性铣削力建模与仿真

本文建立了球头铣刀柔性铣削力模型,研究了任意进给方向的球头铣刀铣削力模型,在模型建立过程中考虑了刀具偏心、刀具变形和刀具振动物理影响因素,推导出了综合物理因素影响下的瞬时切屑厚度表达式.在此基础上对球头铣刀瞬时铣削力进行仿真对比分析,验证了建立模型的正确性.     

微径球头铣刀铣削表面误差建模与仿真

以微细铣削表面误差为研究对象,考虑尺度效应,建立了微径球头铣刀铣削力模型.将刀具简化为阶梯状悬臂梁,运用虚位移原理结合机床-工件系统变形获得刀具在铣削力作用下的变形量,并将其耦合到切削刃轨迹中,最终建立了综合主轴径向跳动、最小切削厚度、刀具弹性变形及机床-工件系统变形等因素的铣削过程表面创成物理模型.在此基础上,提出了微径球头铣刀铣削表面误差三维仿真算法,并通过仿真算例分析了各因素对工件铣削表面误差的影响.最后通过实验验证了该算法的有效性和可行性.     

切削用量对球头铣刀加工铝合金零件表面粗糙度的影响

本文通过对球头刀铣削(包含平面和斜面的零件表面粗糙度)进行理论和试验研究。建立了两种零件粗糙度经验模型,并分析了铣削加工中表面粗糙度的影响因素。研究发现,刀具每齿进给量是影响零件表面粗糙度的主要因素,增大每齿进给量、切削深度和切削宽度对表面质量不利。在两种经验模型中,指数模型拟合效果好于多项式模型,为实际生产中预测表面粗糙度合理安排工艺方案提供了参考。     

基于MasterCAM的自由曲面多轴数控加工的行距分析与控制

一般曲面零件的数控加工通常采用球头铣刀.球头铣刀加工曲面时多按行切法加工,即铣刀沿坐标轴方向或参数轴方向对曲面一行一行进行加工,每加工完一行后,铣刀移动一个行距,直至将整个曲面加工完毕.     

可编程数据输入指令G10在数控加工中的应用

在数控铣削加工过程中,通常会遇到轮廓周边的倒圆和孔口倒角类零件,对于这种类型的零件,一般有两种加工方法:其一是使用成形铣刀铣削,简单方便,但是同一把成形刀只能用于相同尺寸的工件倒角,使用范围窄,并且成形刀具成本高,因此,在小批量的工件加工中较少使用;其二是使用球头铣刀或立铣刀,逐层拟合成形,采用这种方法倒角与倒圆时,适用范围广,同一把刀具能用于不同的倒圆与倒角加工。     

立铣加工过程中的微元铣削力建模分析

针对单纯通过高速切削技术制造某些大型飞机零件过程中,存在难以控制的加工变形和较强表面残余拉应力分布等突出问题,以直齿和螺旋齿立铣加工过程为研究对象,基于微元切削机理,通过对刀齿铣削过程的分析,建立动态铣削加工仿真模型,导出铣削面积、铣削力、主轴扭矩、铣削功率与切削用量的关系.数值模拟结果与试验值较吻合,表明该模型可以实现动态铣削力预测,优化切削用量.     

薄壁筒段件机器人铣削系统

航空航天领域常用薄壁筒段件的铣削存在工件装夹困难、铣削设备单一且成本高、常规工艺参数不适用等难点，为解决这些问题，提出了一种基于六自由度工业机器人的解决方案。结合薄壁筒段件的结构特点与铣削工艺需求，开发了组成末端执行器的框架单元、铣削单元、检测单元、运动单元和清理单元。采用球头铣刀分别在模拟件和试验件上铣圆弧槽以验证该设备的可行性并检验其铣削性能，先用模拟件试切以研究不同工艺参数对铣削过程和铣槽质量的影响，然后根据模拟件的试验结果确定走刀方案并在试验件上试切以预测该设备对实际薄壁筒段件的铣削效果。试验结果表明该设备的铣削效果良好，试验件槽深平均值偏差为0.014 mm,可达到IT8精度等级，表面粗糙度(Ra)范围为1.038～6.079μm,证明了该设备具备铣削薄壁筒段件的能力，可以用于实际加工生产。     

数控加工中加工误差预测模型的研究

提出了一个在球头端铣加工中预测复杂曲面加工误差的理论模型.在理论模型的基础上,计算出了曲面各个部分的由刀具变形引起的加工误差.对影响加工误差的诸如切削模式、铣削位置角、曲面几何形状等各种切削状况进行了研究.最后,使用加工中心,在各种加工状况下.通过一系列实验对理论模型进行了验证.并利用计算机图形学工具对二者进行了建模仿真,结果显示理论值与实验值非常吻合.恰好证明了趣论模型在预测表面加工误差方面的适应性非常好.     

SolidCAM 2012车铣复合上下刀塔同步加工设置

车铣复合机是利用铣刀旋转和工件旋转的合成运动来实现对工件的切削加工,使工件在形状精度、位置精度和已加工表面完整性等多方面达到使用要求的一种先进切削加工方法。车铣复合加工不是单纯地将车削和铣削两种加工手段合并到一台机床上,而是利用车铣合成运动来完成各类表面的     

基于模型预测控制的飞机蒙皮铣削方法研究

针对飞机蒙皮铣削精度低的问题,提出一种考虑铣削力的模型预测控制铣削方法。首先,构建以机械臂为工具的自动化铣削系统,利用矢量法推导机械臂正反解运动学模型。其次,提取飞机蒙皮三维轮廓,采用离散法进行曲线偏移,规划铣削加工路径;在此基础上,利用五阶B样条曲线拟合路径得到加工轨迹。然后,建立铣刀与工件接触数学模型,以铣削力与速度比、轨迹误差与控制输入为目标函数,采用预测模型反馈校正控制跟踪轨迹。最后,利用激光跟踪仪测量蒙皮修切精度。修切的重复定位精度与绝对定位精度分别在±0.1 mm和±0.3 mm以内。相较于传统基于激光跟踪仪测量的铣削方法,采用本方法可获得到较高的铣削加工精度。该方法可用于机器人铣削加工以及其他自动化加工任务。     

柔性螺旋立铣刀数控铣削表面形貌物理仿真模型

以圆柱螺旋立铣刀铣削过程物理特性为研究对象 ,考虑机床主轴偏心和刀杆静态、动态变形等因素的影响 ,建立了一种新的柔性螺旋立铣刀数控铣削过程表面创成物理模型 ;在此基础上 ,给出一种数控铣削三维表面形貌高效仿真算法和仿真算例     

5-axis flank milling free-form surfaces considering constraints

A new tool path generation method of flank milling considering constraints is proposed for ball-end cutters in this paper. It will not only reduce the machining error range but also meet the following two constraints: (a) The ball end of the milling tool is tangential to the constraint surface; (b) There is no overcut and the minimum error is zero, which is called nonnegative-error constraint. The two constraints are very useful in some situations of engineering applications, such as flank milling impeller blades. Based on the proposed method, two types of cutter will be used to generate tool paths for the same designed surface and constraint surface. The effectiveness and accuracy of the proposed method will be finally proved with some examples.     

球面铣刀修磨几何模型研究

文中给出球面铣刀的制造模型,探讨了运用同一机构磨制邻近规格的不同球面铣刀的可行性问题。为了充分利用现有的磨制机构,提出了斜等距曲面的概念及相应公式,介绍了它在球面铣刀修磨模型中的应用,并给出与制造相关的几何模型,最后用实例验证了模型的可行性与可靠性。该模型为实现复杂刀具的ＣＡＤ／ＣＡＭ提供了方法模型。     

A mathematical model for simulating and manufacturing ball end mill

The performance of ball end mill cutters in cutting operations is influenced by the configuration of the rake and clearance faces in the ball component. From the mathematical design of a cutting edge curve, the rake face can be defined by the rake angle and the width of the rake face at each cross section along the cutting edge. We propose the fundamental conditions that must govern the engagement between the grinding wheel and the designed rake face in order to avoid interference while machining a ball end mill. As a result, a new mathematical model for determining the wheel location and a software program for simulating the generation of the rake face of a ball end mill are proposed. In addition, methods for grinding the clearance face in both concave and flat-shapes are introduced. The flute surface generated by a disk wheel during the grinding process is determined on the basis of a tangency condition. The results of the experiment and the simulation are compared to validate the proposed model.     

Influence of ball milling parameters on blue phosphor for cathode ray tube

A series of experiments have been conducted to examine ball milling parameters, such as the size of beads, ball milling time, the ratio of beads/phosphor/water, and the material composition of the ball milling beads to optimize the milling conditions for phosphor powders. It is concluded that longer time, smaller size of Φ2 Al₂O₃ beads, and higher ratio of beads/phosphor/water = 2:1:0.5 can produce phosphor powder with higher dispersibility which in turn creates a densely packed coating of phosphor particles on the screen, a necessity for high resolution and high cathodoluminescence. When harder material with higher density are applied in the disagglomeration process or lower density beads which have undergone a longer ball milling time, the dispersion result is more effective. Nevertheless, the brightness of phosphor powder may deteriorate, a side effect which is undesirable for high quality phosphor powders. The concept of dispersibility is also proposed by evaluating the sediment volume, hardness, and ratio of water absorption.     

Three dimensional modeling and finite element simulation of a generic end mill

The geometry of cutting flutes and the surfaces of end mills is one of the crucial parameters affecting the quality of the machining in the case of end milling. These are usually represented by two-dimensional models. This paper describes in detail the methodology to model the geometry of a flat end mill in terms of three-dimensional parameters. The geometric definition of the end mill is developed in terms of surface patches; flutes as helicoidal surfaces, the shank as a surface of revolution and the blending surfaces as bicubic Bezier and biparametric sweep surfaces. The proposed model defines the end mill in terms of three-dimensional rotational angles rather than the conventional two dimensional angles. To validate the methodology, the flat end milling cutter is directly rendered in OpenGL environment in terms of three-dimensional parameters. Further, an interface is developed that directly pulls the proposed three-dimensional model defined with the help of parametric equations into a commercial CAD modeling environment. This facilitates a wide range of downstream technological applications. The modeled tool is used for finite element simulations to study the cutting flutes under static and transient dynamic load conditions. The results of stress distribution (von mises stress), translational displacement and deformation are presented for static and transient dynamic analysis for the end mill cutter flute and its body. The method described in this paper offers a simple and intuitive way of generating high-quality end mill models for use in machining process simulations. It can be easily extended to generate other tools without relying on analytical or numerical formulations.     

An innovative approach to NC programming for accurate five-axis flank milling of spiral bevel or hypoid gears

To transfer power, a pair of spiral bevel or hypoid gears engages. From beginning to end of two tooth surfaces engaging with each other: for their rigid property, they contact at different points; and for their plastic property, they contact at small ellipses around the points. On each surface, the contact line (or called as contact path) by connecting these points and the contact area by joining these ellipses are critical to driving performance. Therefore, to machine these surfaces, it is important to machine the contact line and area with higher accuracy than other areas. Five-axis flank milling is efficient and is widely used in industry. However, tool paths for flank milling the gears, which are generated with the existing methods, can cause overcuts on the contact area with large machining errors. To overcome this problem, an innovative approach to NC programming for accurate and efficient five-axis flank milling of spiral bevel or hypoid gears is proposed. First, the necessary conditions of the cutter envelope surface tangent with the designed surface along a designed line are derived to address the overcut problem of five-axis milling. Second, the tooth surface including the contact line and area are represented using their machining and meshing models. Third, according to the tooth surface model, an optimization method based on the necessary conditions is proposed to plan the cutter location and orientation for flank milling the tooth surface. By using these planned tool paths, the overcut problem is eliminated and the machining errors of contact area are reduced. The proposed approach can significantly promote flank milling in the gear manufacturing industry.     

Research on the directionality of end dynamic compliance dominated by milling robot body structure and milling vibration suppression

The end dynamic characteristics dominated by the milling robot's body structure play a crucial role in vibration control and chatter avoidance in robotic milling. As the excitation source, the milling force may exist in any direction under different process parameters. Consequently, investigating the directional distribution of the end dynamic characteristics becomes essential for studying the direction-dependent dynamic response of a milling robot. In this paper, firstly, the directionality of the end modal vibration is proved based on the body structure mode shape of the milling robot. Subsequently, combined with the multi-body dynamics model of milling robots, the distribution of the end dynamic compliance with the excitation direction in the robot mode is modeled and found to be double-sphere, which is verified experimentally. A convenient method for acquiring the double-sphere dynamic compliance (DSDC) is given and its portability is shown. Then, two application cases of the DSDC in milling vibration suppression are given. In Case 1, based on the DSDC, the milling vibration amplitude is found to be distributed as an eccentric ellipse with a non-orthogonal basis with the feed angle in a robot mode, wherein a feed direction selection method for reducing milling vibration without traversal calculation is given with experimental validation. Case 2 shows that according to the guidance of the DSDC, the tuned mass damper can significantly suppress the milling vibration. It is worth noting that the directionality of the end modal vibration and DSDC constitute fundamental dynamic properties of milling robots, which may provide a new theoretical basis for the research related to the robotic end dynamic characteristics (such as frequency response function identification, mode coupling chatter mechanism and its suppression, etc.), which are well worth exploring.