A computer simulation approach to machining complicated shapes, on an orthogonal 6-rod machine tool

A computer simulation approach to machining a gear and cam by using a virtual orthogonal 6-rod machine tool is presented. First, based on Stewart's parallel mechanism, a virtual 3D orthogonal 6-rod machine tool with 6 degrees of freedom is created with advanced CAD software. Secondly, a 3D spur gear base and cam base are constituted. Thirdly, the gear base and cam base are assembled into a virtual orthogonal 6-rod machine tool with some auxiliary links and a new virtual 1-degree of freedom mechanism is created. Finally, using reversing motion analysis, the kinematic curves of the 6 rods and the feeding process are simulated and analyzed.     

Design of a generic five-axis postprocessor based on generalized kinematics model of machine tool

This paper presents a generic five-axis postprocessor system for various five-axis machine tools. The generalized kinematics model of common five-axis machines is constructed by combining two rotational degrees of freedom on the fixture table and two rotational degrees of freedom on the spindle. The complete analytical equations for NC data are obtained through homogeneous coordinate transformation matrix and inverse kinematics. The derived five-axis NC code expression is a general form suitable for all kinds of five-axis machine tools with three orthogonal linear axes and two orthogonal rotational axes. A window-based postprocessor software written by Borland C++ Builder and OpenGL has been developed according to the presented algorithm. The wireframe model of the configured five-axis machine tool can be promptly shown and rotated/zoomed dynamically on the screen to assist the user to input relevant parameters correctly and efficiently. Through the implementation of the developed postprocessor and the verification by the solid cutting simulation software as well as the real machining experiment, the effectiveness of the proposed scheme was confirmed.     

三自由度混联机床的机构误差分析与仿真

文章提出了一种新的三自由度混联机床构型,基于Solidworks建立其三维实体模型.利用误差独立作用原理,建立了误差分析数学模型.通过矩阵分析方法结合运动学徽分方程,分析了并联机床静态误差,得到固定平台校链点位里误差、驱动杆长度误差与运动平台位里误差的映射关系,并对机构误差在工作空间内的分布规律进行了仿真,为混联机床的误差补偿提供了理论基础.     

虚拟仿真技术在多轴机床后处理定制中的应用

对FIDIA五轴立式加工中心后处理的定制过程进行研究,并利用虚拟仿真技术对后处理的正确性进行验证。通过NX软件的后处理构造器定制了适用于FIDIA C1系统的后处理。为了验证后处理的正确性,在NX中建立简化的机床几何模型,将机床各部件以STL格式文件导出至VERICUT软件中,在VERICUT中进行相应的配置,完成虚拟仿真环境的构建;以鼠标模型作为加工对象,在NX加工模块中创建刀具轨迹,通过定制好的后处理将刀轨源文件转换为机床能够识别的NC代码,在虚拟仿真环境中进行模拟加工,验证无误后传输至机床进行零件的实际加工。结果表明:虚拟仿真技术可以有效避免由于后处理定制不当而导致的机床碰撞,确保机床安全、高效地运行。     

基于螺旋理论的并联机床虚拟概念设计及运动分析

提出了并联机床虚拟概念设计的设计过程,采用基于虚拟样机技术的商业软件ADAMS实现了并联机床虚拟样机模型的建立及仿真分析.提出以螺旋理论为指导、以"虚拟样机"技术为验证手段的空间并联机构运动性质分析方法,并用该方法对并联机构自由度的正确求解、机构驱动副选取合理性的判别以及并联机构的型综合等问题进行了研究.     

三自由度工业机器平台机电液一体化仿真

提出了一种通过液压系统控制的三自由度工业机器平台,着重介绍了三自由度机器平台的机械结构及性能指标参数。通过ADAMS、AMESim、Matlab/Simulink软件间的协同仿真技术开展了该机器平台的机电液一体化的仿真分析,确定所设计的三自由度机器人能够较好地跟踪给定的目标指令,满足系统设计要求。通过虚拟仿真,提高了机电液复杂系统分析的效率,仿真方法对于复杂机电液系统具有普遍的适应性。     

三自由度串联式快速刀具伺服刀架的研究

快速刀具伺服金刚石车削被认为是针对光学自由曲加工方法中非常有发展潜力的超精密加工技术。针对目前三自由度快速刀具伺服刀架在X、Y、Z3个方向上存在运动耦合、导致在刀具路径规划困难以及影响刀具使用寿命的问题,提出一种新型三自由度串联式快速刀具伺服刀架,通过将X、Y、Z3个方向的运动串联,避免了X、Y、Z 3个方向运动解耦困难;通过分析三自由度快速刀具伺服刀架应具备的要求,确定柔性铰链截面形状、材料以及尺寸;运用ANSYS对该三自由度串联式快速刀具伺服刀架进行有限元分析,得到X、Y、Z3个方向柔性铰链最大应力均远小于材料的许用应力,前6阶振型共振频率远高于伺服刀架的工作频率。结果表明,该刀架满足实际车削过程中的内应力和共振频率要求。     

并联机床振动仿真分析

以三平动非对称并联机床(3-2SPS)为研究对象,研究单支链各个机构的振动模型,并推导出整条支链的等效振动模型,建立单支链以及机床整机的多自由度振动系统的微分运动方程,运用MATLAB软件对多自由度无阻尼振动的多阶固有频率进行仿真分析,得到机床在工作空间内前两阶固有频率,为机床后续的优化设计和加工生产提供了参考。     

Sculptured surface machining of spiral bevel gears with CNC milling

Gears are crucial components for modern precision machinery as a means for the power transmission mechanism. Due to their complexity and unique characteristics, gears have been designed and manufactured by a special type of machine tools, such as gear hobbing and shaping machines. In this paper, we attempt to manufacture the spiral bevel gear (SBG: the most complex type among the gear products) by a three-axis CNC milling machine interfaced with a rotary table. This consists of (a) geometric modeling of the spiral bevel gears, (b) process planning for NC machining, (c) a tool path planning and execution algorithm for both 4-axis and 3/4-axis (three out of four axes) controls. Experimental cuts were made to ascertain the validity and effectiveness of the presented method with a CNC milling machine controlled by the 3/4-axis control mode.     

Enhanced virtual machining for sculptured surfaces by integrating machine tool error models into NC machining simulation

Sculptured surface machining is a time-consuming and costly process. It requires simultaneously controlled motion of the machine axes. However, positioning inaccuracies or errors exist in machine tools. The combination of error motions of the machine axes will result in a complicated pattern of part geometry errors. In order to quantitatively predict these part geometry errors, a new application framework ‘enhanced virtual machining’ is developed. It integrates machine tool error models into NC machining simulation. The ideal cutter path in the NC program for surface machining is discretized into sub-paths. For each interpolated cutter location, the machine geometric errors are predicted from the machine tool error model. Both the solid modeling approach and the surface modeling approach are used to translate machine geometric errors into part geometry errors for sculptured surface machining. The solid modeling approach obtains the final part geometry by subtracting the tool swept volume from the stock geometric model. The surface modeling approach approximates the actual cutter contact points by calculating the cutting tool motion and geometry. The simulation results show that the machine tool error model can be effectively integrated into sculptured surface machining to predict part geometry errors before the real cutting begins.     

螺旋锥齿轮数控铣齿加工过程几何仿真研究

利用面相对象技术和CAD系统的三维建模功能及其ObjectARX技术，根据螺旋锥齿轮的加工原理，提出了CNC铣齿机、齿坯和刀具三维模型的构建方法以及基于全局光照明的加工环境光照计算的具体方法。利用齿坯实体模型和刀具实体模型做布尔减运算，来实现模拟工件材料的去除过程；同时，采用全局光照明模型建立了具有真实感的数控加工虚拟现实环境。实际应用表明，该系统不但实现了螺旋锥齿轮的计算机辅助铣齿，提高了加工效率，降低了加工成本；而且还提供了非常真实的仿真效果。所获仿真结果可为齿面接触分析、有限元应力分析、齿轮的数控加工等提供精确的三维几何模型。     

A Nanometre-precision, Ultra-stiff Plezostepper Stage for ELID-grinding

The extremely high machine stiffnesses required for a successful Implementation of ELectrolytic in-process Dressing (ELID) grinding cannot be obtained win conventional technologies. In this paper, an Innovative drive concept is presented, where the actuation and guiding functions in three degrees of freedom are combined in one functional unit, using an original plezo-stepping technology. The stage is actively positioned by a set of six ‘feet’ giving it an infinite static stiffness in all six degrees of freedom. The drive motions in x-, y- and C-directions are obtained by rolling the feet over the base surface in a three-by-three feet gait pattern. The stepping resolution can be as low as 2.5 nm. Hammering is avoided by force-controlled stepping. The x and y stage positions are interferometrically measured. Thermal errors are minimised by a symmetrical design.     

并联机床的运动仿真研究

利用三维建模软件UG对并联机床进行了实体建模,并完成了整个机构的参数化建模与并联机床的虚拟装配。完成了并联机床的运动仿真研究,并针对机床加工中螺旋线加工轨迹进行了仿真,解决了加工过程中曲率变化较大情况下的仿真问题,可以进一步提高机床的整体设计质量以及缩短机床的研发周期。     

A three-dimensional CAD/CAM/CAE integration system of sculpture surface die for hollow cold extrusion

In this paper, a CAD/CAM/CAE integration system for a sculptured surface die for hollow cold extrusion has been developed by using C language for Windows. A sculptured surface model with variable control points is incorporated with a general three-dimensional velocity field to analyze the extrusion process. The profiles of the product and the billet are generated in the CAD module. The fitting points are generated to interpolate the profiles of the product and the billet. The initial guess of control points are created by using the offset of corresponding fitting points in the axial direction. The control points are varied automatically to obtain the optimum die surface by using the upper-bound method and optimization procedure. The CAM module generates the cutter locations by using the optimized die surface model. The gouging areas of the tool path are detected and removed. The calculated cutter locations are verified through the tool path simulation. The NC codes are generated automatically by using the gouging-free cutter locations and then sent directly to a three-axis CNC machine centre to manufacture the EDM electrodes. The extrusion die cavity is made by using an EDM process. Extrusion experiments have verified the proposed CAD/CAM/CAE integration system is successful.     

An NC tool path translator for virtual machining of precision optical products

In this paper, a virtual machining system (VMS) for the ultra-precision diamond turning is presented, and the NC tool path translator function module of the VMS is discussed. The developed VMS is based on the NC program not as some commercial CAD/CAM software which is based on the cutter location DATA file. In the VMS, the virtual machine tool is controlled through the NC program used by the actual machine tool. The NC tool path translator consists of accidence analysis, lexical-analyzer, grammar and semantic parse, driving code generator, etc. The manufacture of a mould insert for a diffractive lens was used as a case study to illustrate the performance of the developed VMS.     

Spiral cutting operation strategy for machining of sculptured surfaces by conformal map approach

Although compound surfaces and polyhedral models are widely used in manufacturing industry, the tool path planning strategies are very limited for such surfaces in five-axis machining and high speed machining. In this paper, a novel conformal map based and planar spiral guided spiral tool path generation method is described for NC machining of complex surfaces. The method uses conformal map to establish a relationship between 3D physical surface and planar circular region. This enables NC operation to be performed as if the surface is plat. Then through inversely mapping a planar spiral defined by a mathematical function into 3D physical space, the spiral cutter contact paths are derived without inheriting any corners on the boundary in the subsequent interior paths. The main advantage of the proposed method is that a smoother, longer and boundary conformed spiral topography tool path is developed. Therefore, the machined surface can be cut continuously with minimum tool retractions during the cutting operations. And it allows both compound surfaces and triangular surfaces can be machined at high speed. Finally, experimental results are given to testify the proposed approach.     

Cartesian compliance model for industrial robots using virtual joints

Industrial robots represent a promising, cost-saving and flexible alternative for machining applications. Due to the kinematics of a vertical articulated robot the system behavior is quite different compared to a conventional machine tool. The robot’s stiffness is not only much smaller but also position dependent in a non-linear way. This article describes the modeling of the robot structure and the identification of its parameters with focus on the analysis of the system’s stiffness. Therefore a method for the calculation of the Cartesian stiffness based on the polar stiffness and the use of the Jacobian matrix is introduced. Furthermore, so called virtual joints are used. With this method it is possible to model each joint of the robot with three degrees of freedom. Beside the gear stiffness the method allows the consideration of the tilting rigidity of the bearing and the link deformations to improve the model accuracy. Based on the results of the parameter identification and the calculation of the Cartesian stiffness the experimental model validation is done.     

Accuracy test of five-axis CNC machine tool with 3D probe–ball. Part I: design and modeling

The error model of CNC machine tool describes the relationship between the individual error source and its effects on the overall position errors. A practical problem in applying this technique to five-axis machine tool is that the predicted position errors cannot be justified. This paper, the first in a set of two, presents a new measurement device, the probe–ball, which can be used to measure the overall position errors of five-axis machine tools directly. To perform the accuracy test, a three-degree-of-freedom (3D) measuring probe is installed in the main spindle and a base plate is fixed on the turntable. The kinematic chain of the five-axis machine tool is then closed through connecting the central ball on the base plate with the extension bar of the probe. To generate simultaneous axes motion under the condition of closed kinematic chain, the central ball is defined as origin of the workpiece coordinate frame and the probe is driven along a path on a spherical test surface with the central ball as center. The overall position errors are measured with the 3D measuring probe. A theoretical model is derived to explain the nature of the probe–ball error measurements.     

基于激光三角法的自由曲面零件测量

针对超细长螺旋曲面工件廓形误差脱机测量所用测量设备不能满足工件长度和工件稳定旋转等方面要求的难题,提出了一种基于激光三角法的自由曲面零件测量系统,该系统通过利用机床对工件的定位、夹紧、支撑以及有关运动和控制机构,增配激光检测系统,增配运动部件实现的。构建完成了在机激光检测硬件技术平台;通过对采集所得的点云数据进行分析处理,绘制出被测工件的截面廓形。结果表明:该系统提高了检测的效率和准确性,提高了细长螺旋曲面零件的精度,从而实现了螺旋曲面廓形的精确测量。     

一种三平移并联激光加工机床的运动学研究及仿真

结合并联机构与激光技术的特点,提出一种三自由度平移并联激光加工机床.介绍了并联激光加工机床的组成部分,并应用机器人机构拓扑理论计算其自由度,进行了并联机构的运动学逆解分析.通过运动学仿真,模拟了机床的运动轨迹,验证了并联激光加工机床运动学性能与设计的合理性.