平头端铣刀三轴联动自适应等参数曲线法加工自由曲面

曲面参数线法是多轴数控加工中生成刀具轨迹的主要方法，但是对等参数曲线分布不均匀的情况不适应。平头端铣刀在数控多轴加工中相对于球头铣刀来说，有加工精度高，经济性好的特点，其刀具轨迹的生成方法越来越引起人们的注意。本文针对曲面参数线法的缺点作了相应的改进，提出了适应平头端铣刀的刀具轨迹生成算法，同时用局部检查的方法进行干涉校验，消除了局部干涉。本算法适应于三轴联动以下的机床。     

用密切曲率法加工自由曲面

采用中凹盘铣刀取代传统的球头铣刀，在每一行程中让刀具运动形成的包络面与被加工表面之间在垂直于进给方向的法向截面中达到三阶密切，从而大大减少走刀次数，增加切削宽度，提高加工效率，本文给出了边界不受限制的单张曲面的刀位及刀具轨迹的计算方法。     

平头端铣刀三轴联动自适应等参数曲线法加工自由曲面

曲面参数线法是多轴数控加工中生成刀具轨迹的主要方法，但是对等参数曲线分布不均匀的情况不适应．平头端铣刀在数控多轴加工中相对于球头枕刀来说，有加工精度高、经济性好的特点，其刀具轨迹的生成方法越来越引起人们的注意．本文针对曲面参数线法的缺点作了相应的改进，提出了适应平头端铣刀的刀具轨迹生成算法，同时用局部检查的方法进行干涉校验，消除了局部干涉．本算法适应于三轴联动以上的机床。     

基于密切曲率法的加工理论及算法研究

采用中凹的盘形铣刀取代传统的球头铣刀,在每一行程中让刀具运动形成的包络面与被加工表面之间存在垂直于进给方向的法截面中达到三阶密切,从而大幅度减少了走刀次数,增加了切削宽度,提高了加工效率。文中给出了边界不受限制的单张曲面的刀位及刀具轨迹的计算方法。     

用密切曲率法加工边界受限制的曲面

采用端面中凹的端铣刀取代传统的球头铣刀，在每一行程中让刀具运动形成的包络面与被加工表面之间在垂直于进给方向的法截面中达到三阶密切。在约束边界处，调整铣刀的姿态以便把曲面完整地加工出来。     

四自由度数控铣削异形螺杆关键技术研究

基于高效盘铣刀无瞬心包络理论，提出四自由度刀具，变安装角数控铣削复杂异形螺杆的螺旋曲面；由于刀具在切削中不断地变化安装角，为了寻求有效轨迹计算模型，把迭代计算算法引入到轨迹计算中，建立计算模型。从空间啮合和干涉中考虑问题，使切削轨迹计算准确性大大提高，避免了先前刀具定安装角切削方法的不足，大大提高螺杆铣削加工精度和表面质量，也扩大了加工螺杆的范围。     

巧用程序输入补偿值（G10）指令加工倒角

用数控铣削加工倒角或倒圆角比较困难,通常使用铣刀进行逐层拟合成型加工,因在加工过程中刀具的中心轨迹和曲线轮廓的相对位置要不断变化,即刀尖的轨迹与被加工曲面轮廓不重合,影响加工精度。为了有效解决以上的问题,从而引入程序输入刀具补偿值（G10）。     

大模数直齿轮数控精铣削方法的研究

针对大模数齿轮加工采用盘形、指状铣刀存在着加工效率低,专用刀具造价昂贵的问题,提出了用普通铣刀数控加工大模数齿轮的方法,涉及走刀方式、走刀步长的确定、切削关键点的处理。依据提出的方法建立了齿轮毛坯与刀具运动关系的数学模型,推导了渐开线上点以及刀位点在该模型中的轨迹方程以及刀具与工件之间运动关系方程。该数学模型在齿轮参数已知的情况下能够计算出刀位点以及刀心按照齿轮渐开线齿廓运动的一系列轨迹,利用MATLAB的数据可视化功能,通过刀位点的轨迹方程计算出刀位点,依据齿轮参数绘制出齿轮基圆以及渐开线齿廓,选择合适的刀具半径绘制刀具轮廓,令刀具轮廓跟随刀位点产生一系列刀具轮廓,从而形象直观的对该数学模型进行验证,在理论上分析了该方法的可行性。     

基于ADAMS的端铣齿轮动力学特性研究

采用端铣加工方法加工渐开线齿轮,运用UG软件对某大模数齿轮轴进行刀具轨迹仿真,并通过数据转换将齿轮和刀具模型导入动力学仿真软件ADAMS中。在ADAMS中建立刀具齿轮铣削系统仿真模型,对端铣刀粗加工切削过程进行动力学分析,得到刀具和工件的位移、速度及加速度变化曲线以及主轴转速和进给速度对切削加工及振动影响的变化规律,为实现端铣齿轮加工技术的实际应用提供参考。     

数控加工石材时加工参数对金刚石铣刀耐磨性影响实验研究

为确定合理的加工参数,提高加工效率,采用正交法设计实验参数,在数控机床上研究了铣削石材时各加工参数对金刚石刀具磨损量的影响.金刚石铣刀采用热压成型法制造,金刚石铣刀磨损表面采用 Leica MZ95 体式显微镜分析.结果表明,影响金刚石铣刀磨损量的主要加工参数是切割深度,其次是进给速度,刀具主轴转速影响最小.刀具底面的磨损比侧面严重,底面金刚石主要以脱落为主,侧面金刚石磨损以冲击破碎为主.     

Adaptive tool-path generation on point-sampled surfaces

In this paper, we present a new approach to generate tool paths for machining point sampled surfaces using a direct projection algorithm, which is based on generating tool paths along planar intersection curves. In our implementation, a guide surface, with simple geometry like planes or cylinder surfaces, is first created according to the bound volume of the point cloud and initial tool paths are planned on it in terms of the motion pattern of the cutters. For each point of the initial tool paths, then, the corresponding cutter contact point (CC) of the point set surface is located by projecting the point onto the point cloud using the direct projection algorithm. In order to obtain adaptive cutter location points (CL), a least squares-based curve fitting method is applied to approximate the CC points using piecewise cubic Bezier, and a numerical method derived to estimate the length of the curve is used to adjust the position of the points along the curve, and make them evenly spaced on the curve with equal arc lengths. In addition, considering that offset curves or surfaces are necessary for locating CL points in many applications, such as machining using ball end milling cutter, torus ended milling cutters, an offset strategy for cubic Bezier curves is also studied. By testing the proposed method on several point clouds, it has been demonstrated to be promising.     

基于人工鱼群和粒子群优化混合算法的侧铣刀轴轨迹规划

针对圆锥刀侧铣加工非可展直纹面的刀轴轨迹规划问题,采用两点偏置法确定初始刀轴矢量,为评价单个刀位,提出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锥面的距离差值的平方和最小。为解决每个刀位下的位姿寻优问题,提出了基于人工鱼群（AFS）和粒子群优化（PSO）混合算法的优化方案。仿真结果表明,所提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。     

球头铣刀刀具磨损建模与误差补偿

针对刀具磨损度量方式和模型建立的问题,以球头刀具为研究对象,提出球头铣刀刀具磨损的度量方式,建立球头刀具磨损模型.以复映磨损在硬度较软加工材料上的方式测量球头刀具磨损,确定刀具磨损模型系数,给出刀具磨损模型系数确定的具体实现方法.加工试验验证球头刀具磨损度量方式的合理性和所建立刀具磨损模型的正确性,同时针对数控铣削加工中球头铣刀刀具磨损引起的误差提出离线仿真误差补偿算法,给出离线仿真误差补偿算法的具体实现步骤,通过建立的刀具磨损引起的加工误差模型仿真获得加工走刀步的误差.对于误差超差的走刀步,预先修改数控加工(Numerical control,NC)程序,保证实际加工零件满足精度要求.误差补偿验证试验表明所提出的离线仿真误差补偿算法的正确性和有效性.     

面向并联机床的后置处理方法

为了解决并联机床的后置处理问题，克服现有方法开发的难度和工作量大的缺点，提出了直接转化传统数控机床数控代码，得到并联机床数控代码的方法。对5-虎克铰-移动副-球铰／移动副-转动副-移动副-虎克铰并联机床和刀具双摆动5轴数控机床进行运动学分析，得出并联机床动平台的两个可变化的姿态角具有与刀具双摆动5轴数控机床中两个摆动转角相同的性质；然后直接利用智能制造后置处理软件进行后置处理得到刀具双摆动5轴数控机床的数控程序；再经过适当的变换，得到并联机床的数控程序。曲面加工的计算机模拟结果表明，该方法正确、有效。     

A solid modeler based ball-end milling process simulation

A system for geometric and physical simulation of the ball-end milling process using solid modeling is presented in this paper. A commercially available geometric engine is used to represent the cutting edge, cutter and updated part. The ball-end mill cutter modeled in this study is an insert type ball-end mill and the cutting edge is generated by intersecting an inclined plane with the cutter ball nose. The contact face between cutter and updated part is determined from the solid model of the updated part and cutter solid model. To determine cutting edge engagement for each tool rotational step, the intersections between the cutting edge with boundary of the contact face are determined. The engaged portion of the cutting edge for each tool rotational step is divided into small differential oblique cutting edge segments. Friction, shear angles and shear stresses are identified from orthogonal cutting data base available in the open literature. For each tool rotational position, the cutting force components are calculated by summing up the differential cutting forces. The instantaneous dynamic chip thickness is computed by summing up the rigid chip thickness, the tool deflection and the undulations left from the previous tooth, and then the dynamic cutting forces are obtained. For calculating the ploughing forces, Wu's model is extended to the ball-end milling process [21]. The total forces, including the cutting and ploughing forces, are applied to the structural vibratory model of the system and the dynamic deflections at the tool tip are predicted. The developed system is verified experimentally for various up-hill and down-hill angles.     

Exact Tool Sizing for Feature Accessibility

This paper presents an algorithm for calculating the volume of a 2D-profile, accessible by a given diameter of milling cutter. The method is independent of the generation of cutter tool paths, and exploits facilities commonly found in kernel modellers. Exact results are obtained despite the simplicity of the procedure. As a proof of the concept, the algorithms have been implemented in the Heriot-Watt University feature recogniser as a pre-processor for a part programming system. The aim of these algorithms is to assist and optimise the selection of multiple tools for the machining of complex components. The methodology has applications in process planning research where it is currently common to assume that a single tool will machine each feature. Although cutter selection is a critical step in planning the manufacture of components, computer-aided process planning (CAPP) systems rarely make any attempt to analyse the trade-offs involved. Perhaps this is because, traditionally, exact tool accessibility calculations have been viewed as a side effect of generating a cutter tool path. Consequently, accessibility calculations are not carried out explicitly but they appear implicitly in the results of a complex geometric algorithm (i.e. cutter path generation). Because this implicit checking of tool accessibility is carried out, downstream from the higher-level reasoning about set-up and sequencing, the results are generally available only after a detailed process plan has been generated.     

曲面铣削过程加工路径对切削力和磨损的影响研究

针对不同走刀路径下的复杂曲面加工过程进行球头铣刀铣削Cr12MoV加工复杂曲面研究,分析不同走刀路径下铣削力和刀具磨损的变化趋势。试验结果表明:通过对比分析直线铣削和曲面铣削过程中的最大未变形切屑厚度,可以得出单周期内曲面铣削的力大于直线铣削过程的力,铣削相同铣削层时环形走刀测得的切削力普遍大于往复走刀测得的切削力;以最小刀具磨损为优化目标,运用方差分析法分析得出不同走刀路径的影响刀具磨损的主次因素,同时利用残差分析方法建立球头铣刀加工复杂曲面刀具磨损预测模型,并通过试验进行验证。     

Redesigned Surface Based Machining Strategy and Method in Peripheral Milling of Thin-walled Parts

Currently, simultaneously ensuring the machining accuracy and efficiency of thin-walled structures especially high performance parts still remains a challenge. Existing compensating methods are mainly focusing on 3-aixs machining, which sometimes only take one given point as the compensative point at each given cutter location. This paper presents a redesigned surface based machining strategy for peripheral milling of thin-walled parts. Based on an improved cutting force/heat model and finite element method(FEM) simulation environment, a deflection error prediction model, which takes sequence of cutter contact lines as compensation targets, is established. And an iterative algorithm is presented to determine feasible cutter axis positions. The final redesigned surface is subsequently generated by skinning all discrete cutter axis vectors after compensating by using the proposed algorithm. The proposed machining strategy incorporates the thermo-mechanical coupled effect in deflection prediction, and is also validated with flank milling experiment by using five-axis machine tool. At the same time, the deformation error is detected by using three-coordinate measuring machine. Error prediction values and experimental results indicate that they have a good consistency and the proposed approach is able to significantly reduce the dimension error under the same machining conditions compared with conventional methods. The proposed machining strategy has potential in high-efficiency precision machining of thin-walled parts.