自由曲面五轴加工刀具轨迹规划技术的研究进展

利用五坐标设备进行自由曲面的数控加工是提高加工质量和加工效率的有效途径,自由曲面形状和五坐标机床运动的复杂性导致其刀具轨迹规划技术十分困难。针对自由曲面五坐标端铣加工、侧铣加工以及碰撞干涉分析中的关键技术,综述了近年来自由曲面五坐标数控加工领域刀具轨迹规划技术的研究进展和现状。结合自由曲面数控加工的工程实用性要求,分析了当前研究中存在的不足,指出目前的研究成果在通用性、稳定性和有效性方面尚不能完全满足工程应用,认为自由曲面五坐标数控加工刀具轨迹规划技术的研究应从三维的角度出发,在更为广域的刀具影响空间研究刀具同自由曲面之间的几何啮合关系,同时需要考虑机床的运动学和动力学特性以实现五坐标机床的高速和高效运行。     

五轴加工中基于局部几何条件的刀具势态优化

文中给出了五轴加工中环形刀具势态优化的两个条件，并根据牡潘标线的几何意义，分析了加工曲面和刀具曲面的局部几何特性。在此基础上提出了一个刀具势态优化的新方法，从而使五轴加工的效率得到进一步提高。     

五轴联动激光淬火路径规划

研究了基于五轴多功能激光加工机床激光淬火的工艺特点,提出了用于复杂型面五轴联动激光淬火路径规划的方法,实现了针对于五轴多功能激光加工机床激光淬火的前计算,为使五轴联动激光淬火应用于实践奠定了一定的基础。该方法主要是在考虑了以下3个约束条件的基础上提出的:(1)在淬火的过程中要保证激光光斑相对于工件表面的扫描速度恒定;(2)在激光淬火过程中要保证工件表面激光光斑的大小不变;(3)在进行激光扫描时要使插补时产生的弦误差最小。通过保证这3个约束条件,进而保证工件表面淬火质量。     

A New Tool-Path Generation Method Using a Cylindrical End Mill for 5-Axis Machining of a Spatial Cam with a Conical Meshing Element

The geometry of a spatial cam is normally generated using a form-milling cutter and a special multi-axis machine and software. The general purpose CAD/CAM software can generate the cutter location file of this class of product only by the sculpturing method. Because of the limited choice of cutting tool when using the generating method, this paper presents a new toolpath generating method which combines the advantages of the generating and sculpturing methods for machining a spatial cam. In the machining process, the cutter location is derived for rough and finish machining using a cylindrical end mill. The guidelines for choosing cutter diameter for the machining process are discussed. To avoid interference, the principal curvatures and the principal induced normal curvatures are analysed. The mathematical errors including chordal deviation and scallop height are used as the basis for generating appropriate tool-paths. Cutting simulation of a solid model was performed to verify the proposed tool-path generation method.       

Optimising Tool Positioning for End-Mill Machining of Free-Form Surfaces on 5-Axis Machines for both Semi-Finishing and Finishing

End-milling of free-form surfaces on 5-axis NC machine tools is a complex problem which has been studied by a large number of research scientists. When end-milling non-convex surfaces there is a risk of interference between the tool and the surface. Using a 5-axis NC machine tool enables the tool to be oriented in any spatial direction to access a given point. This means interference can be avoided and the position of the tool can be optimised so as to minimise residual material. Here, a new method is presented for tool positioning in end-milling of free-form surfaces based on evaluating the interference for a set of test points distributed around the circumference of the tip of the tool. Distinction is made between the cases of semi-finishing and finishing which can be performed using a large diameter flat-end tool and a toroidal tool, respectively. Further, all developments are implemented for interactive use in a CAD/CAM software environment.     

典型五轴零件的数控加工工艺分析与编程加工

文中在典型五轴零件的结构分析和工艺分析基础上,基于传统的三轴数控加工工艺,融合前沿的五轴加工策略,使用CAXA制造工程师设计了典型五轴零件的刀路,并完成了五轴零件的数控编程和加工,获得了满足要求的加工效果。     

五轴数控加工奇异点问题研究

研究了五轴数控加工奇异点问题,分析了奇异现象及产生的原因。在对前人工作分析的基础上,提出了在刀轨规划时避免奇异现象的方法。该方法通过监测刀轴与旋转轴的夹角,找出产生奇异的刀位点,并以上一刀位点对当前刀位点进行优化。结果显示机床各运动轴能平缓通过奇异区域,证明该方法切实可行。     

面向特征的整体叶轮五轴数控加工技术

基于特征制定整体叶轮数控加工工艺,同时兼顾叶轮的工作要求和加工刚度,利用UGNX3.0提供的Interpolate方式规划流道特征的开粗加工和精加工轨迹,Swarf方式规划叶片特征的侧铣加工轨迹.经过仿真验证加工轨迹的合理性,最后使用配有HNC-22M数控系统的五轴加工中心VMC-1100成功加工了整体叶轮.     

Determination of Cutter Orientation for Five-Axis Sculptured Surface Machining with a Filleted-End Cutter

In this paper, an accurate and efficient method is proposed for determining filleted-end cutter orientation based on surface analysis. With this method, the surface geometry is first analysed and classified according to its shape. Different kinds of surface shape require different treatments with regard to cutter orientation, so that the local geometry of the filleted-end cutter is matched with that of the surface as closely as possible without gouging the surface in the local region of the cutter contact points. The proposed method has been successfully implemented using the visual C ++ language and the ACIS geometric modeller. Finally, some illustrative examples are given. ID="A1"Correspondance and offprint requests to: Dr T. Chen, CAD Centre, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China. E-mail: tc29@chinese.com     

Geometrical Error Analysis and Control for 5-axis Machining of Large sculptured surfaces

One of the important tasks in five-axis machining of large sculptured surfaces is to control and reduce the machined errors. This paper presents the methods to control geometrical errors based on the establishment of the link between geometrical errors and the parameters of tool path planning. Nonlinear errors, which are the majority of geometrical errors during five-axis machining, are is strictly analysed and formulated. An adaptive step length method is proposed to control effectively the cutter contact path error. The measures to reduce the scallop error in machining of the large sculptured surfaces are discussed also. With the combination of this research with CAM software, both large Kaplan and Francis hydroturbine blades have been successfully machined. It shows that the machined errors can be controlled effectively and the machining efficiency can be improved in the machining of the large sculptured surfaces by the proposed methods.     

直驱式高速龙门五轴加工中心横梁的设计

以一种直驱式高速龙门五轴加工中心的横梁为研究对象,介绍了龙门式横梁的载荷特点,对焊接横梁和铸造横梁进行了对比分析,对应用于直驱式高速龙门五轴加工中心横梁的筋板结构、截面形式、导轨和直线电机的布置形式进行了分析,指出焊接横梁更适用于直驱式高速龙门五轴加工中心.     

高速加工及在线测量在挤压分流模精加工中的应用

利用高速加工中心及在线测量的高效、精密制造工艺,使铝型材挤压分流模的加工精度由±0.02mm提高到±0.008mm。     

铣头可自动交换的高速龙门五轴加工中心设计研究

介绍了一种铣头可自动交换的桥式高速龙门五轴加工中心的总体设计方案,对国内外现有的类似机床的性能指标作了详细的对比,其中,主要阐述了机床的机械结构、特点和关键零部件的设计及选型,对三个直线轴驱动方式、两个摆动轴的驱动方式以及数控操作系统的的设计选型作了深入的分析探讨,重点介绍了大推力直线电机的应用和双摆铣头可自动交换技术的应用;为大推力直线电机的应用以及高速龙门机床的设计研究提供了重要的理论依据和实践经验。     

GS5200高速精密五轴联动龙门加工中心关键技术研究

结合 GS5200 型机床的研制情况,详细介绍了高速精密五轴联动龙门加工中心的应用及研发的关键技术.     

针对VDF-850四轴立式加工中心的UG后置处理设计

介绍了利用NX后处理构造器(Post Builder)针对VDF-850四轴立式加工中心及HNC-22M数控系统定制专用后置处理程序的方法,并通过产品加工实例,验证了该专用后置处理器的正确性和实用性。     

大型螺旋桨五轴加工中基于方向包围盒层次树的全局干涉碰撞检测

针对大型螺旋桨五轴加工中重叠区存在的全局干涉碰撞，构建了一种基于动态OBB层次树的检测算法：建立螺旋桨和特殊铣刀头的方向包围盒层次树，利用多刚体系统的运动学理论，获得螺旋桨和特殊铣刀头在每个加工位置处包围盒的动态坐标变换矩阵，根据分离轴理论，实现每个加工位置的全局干涉碰撞检测。通过包围盒分组以及运动趋势判断，提高了全局干涉碰撞检测算法的效率。     

大型叶片五坐标数控加工进给速度优化

针对大型叶片数控加工中存在加工余量分布不均匀的现象 ,本文在建立叶片毛坯曲面模型的基础上 ,提出了一种基于恒切削量的进给速度优化算法 ,在计算刀位轨迹、生成 NC代码的过程中实现了进给速度的优化。实践表明 ,这种方法能够提高大型叶片的五坐标数控加工效率 ,降低刀具磨损 ,改善叶片表面加工质量。     

Three-half and half-axis patch-by-patch NC machining of sculptured surfaces

Despite the inbuilt advantages offered by five-axis machining, the manufacturing industry has not widely adopted this technology due to the high cost of machines and insufficient support from CAD/CAM systems. Companies are used to three-axis machining and their shop floors are not yet ready for five-axis machining in terms of training and programming. The objective of this research is to develop and implement a machining technique that uses the simplicity of three-axis tool positioning and the flexibility of five-axis tool orientation, to machine sculptured surfaces. This technique, 3½½-axis, divides a sculptured surface into patches and then machines each patch using a fixed tool orientation. This paper presents the surface partitioning scheme and the method of selecting an optimum number of sub-divisions along with actual machining experiments. For the example surface utilized in this study, the proposed hybrid method led to shorter machining time compared to traditional three-axis machining and comparable to simultaneous five-axis machining.     

Three-half and half-axis patch-by-patch NC machining of sculptured surfaces

Despite the inbuilt advantages offered by five-axis machining, the manufacturing industry has not widely adopted this technology due to the high cost of machines and insufficient support from CAD/CAM systems. Companies are used to three-axis machining and their shop floors are not yet ready for five-axis machining in terms of training and programming. The objective of this research is to develop and implement a machining technique that uses the simplicity of three-axis tool positioning and the flexibility of five-axis tool orientation, to machine sculptured surfaces. This technique, -axis, divides a sculptured surface into patches and then machines each patch using a fixed tool orientation. This paper presents the surface partitioning scheme and the method of selecting an optimum number of sub-divisions along with actual machining experiments. For the example surface utilized in this study, the proposed hybrid method led to shorter machining time compared to traditional three-axis machining and comparable to simultaneous five-axis machining .     

五轴联动机床的圆度测试与同步龙门轴调整

针对应用西门子840D数控系统的五轴联动数控机床,阐述了它基于软件的圆度测试过程,对可能出现的测试结果给出了具体的分析与解决方案。讨论了同步龙门轴的调整过程以及相应参数的设置方法。实验结果表明了文中所述方法的有效性。