Development of practical postprocessor for 5-axis machine tool with non-orthogonal rotary axes

In order to develop a practical postprocessor for 5-axis machine tool,the general equations of numerically controlled(NC) data for 5-axis configurations with non-orthogonal rotary axes were exactly expressed by the inverse kinematics,and a windows-based postprocessor written with Visual Basic was developed according to the proposed algorithm.The developed postprocessor is a general system suitable for all kinds of 5-axis machines with orthogonal and non-orthogonal rotary axes.Through implementation of the developed postprocessor and verification by a cutting simulation and machining experiment,the effectiveness of the proposed algorithm is confirmed.Compatibility is improved by allowing exchange of data formats such as rotational total center position(RTCP) controlled NC data,vector post NC data,and program object file(POF) cutter location(CL) data,and convenience is increased by adding the function of work-piece origin offset.Consequently,a practical post-processor for 5-axis machining is developed.

Development of tool-path generation module for 5-axis control machining of impellers

An impeller is difficult to machine because of severe collision due to the complex shape,overlapping and twisted shape of the impeller blades.So,most computer aided manufacturing(CAM)software companies have developed CAM module for manufacturing impeller according to their CAM software.But these dedicated modules are difficult to use for inexperienced users.The purpose of this work is to develop a tool-path generation module for impellers.For this purpose,it is based on Visual Basic language and used CATIA graphical environment.The result of simulation for generated tool-path by the module is satisfactory.And it has slow processing speed compared to other commercial modules,but it is easy to use.

Parameters Optimization of a Novel 5-DOF Gasbag Polishing Machine Tool

The research on the parameters optimization for gasbag polishing machine tools, mainly aims at a better kinematics performance and a design scheme. Serial structural arm is mostly employed in gasbag polishing machine tools at present, but it is disadvantaged by its complexity, big inertia, and so on. In the multi-objective parameters optimization, it is very difficult to select good parameters to achieve excellent performance of the mechanism. In this paper, a statistics parameters optimization method based on index atlases is presented for a novel 5-DOF gasbag polishing machine tool. In the position analyses, the structure and workspace for a novel 5-DOF gasbag polishing machine tool is developed, where the gasbag polishing machine tool is advantaged by its simple structure, lower inertia and bigger workspace. In the kinematics analyses, several kinematics performance evaluation indices of the machine tool are proposed and discussed, and the global kinematics performance evaluation atlases are given. In the parameters optimization process, considering the assembly technique, a design scheme of the 5-DOF gasbag polishing machine tool is given to own better kinematics performance based on the proposed statistics parameters optimization method, and the global linear isotropic performance index is 0.5, the global rotational isotropic performance index is 0.5, the global linear velocity transmission performance index is 1.012 3 m/s in the case of unit input matrix, the global rotational velocity transmission performance index is 0.102 7 rad/s in the case of unit input matrix, and the workspace volume is 1. The proposed research provides the basis for applications of the novel 5-DOF gasbag polishing machine tool, which can be applied to the modern industrial fields requiring machines with lower inertia, better kinematics transmission performance and better technological efficiency.

MOTION ERROR ESTIMATION OF 5-AXIS MACHINING CENTER USING DBB METHOD

In order to estimate the motion errors of 5-axis machine center, the double ball bar （DBB） method is adopted to realize the diagnosis procedure. The motion error sources of rotary axes in 5-axis machining center comprise of the alignment error of rotary axes and the angular error due to various factors, e.g. the inclination of rotary axes. From sensitive viewpoints, each motion error is possible to have a particular sensitive direction in which deviation of DBB error trace arises from only some specific error sources. The model of the DBB error trace is established according to the spatial geometry theory. Accordingly, the sensitive direction of each motion error source is made clear through numerical simulation, which is used as the reference patterns for rotational error estimation. The estimation method is proposed to easily estimate the motion error sources of rotary axes in quantitative manner. To verify the proposed DBB method for rotational error estimation, the experimental tests are carried out on a 5-axis machining center M-400 （MORISEIKI）. The effect of the mismatch of the DBB is also studied to guarantee the estimation accuracy. From the experimental data, it is noted that the proposed estimation method for 5-axis machining center is feasible and effective.

A Real-time NURBS Surface Interpolator for 5-axis Surface Machining

A real-time non-uniform rational B-spline （NURBS） surface interpolator is proposed and 5-axis machining method with a flat-end cutter is discussed. With the Taylor expansion and the coordinate transformation, the algorithms of NURBS interpolation, cutter effective machining radius, cutter offsetting and.inverse kinematics are deduced and implemented, respectively. Different from the conventional free-form surface machining, the proposed interpolator can real-time generate the motion commands of computer numerical control （CNC） machines with CC feedrate, rather than that of CL. An example part surface is demonstrated and the results of simulation show that the proposed method can be applied in actual 5-axis surface machining.

Real-Time Data and Visualization Monitoring of Computer Numerical Control Machine Tools Based on Hyper Text Markup Language 5

In order to ensure the safety,quality and efficiency of computer numerical control(CNC)machine tool processing,a real-time monitoring and visible solution for CNC machine tools based on hyper text markup language(HTML)5 is proposed.The characteristics of the real-time monitoring technology of CNC machine tools under the traditional Client/Server(C/S)structure are compared and analyzed,and the technical drawbacks are proposed.Web real-time communication technology and browser drawing technology are deeply studied.A real-time monitoring and visible system for CNC machine tool data is developed based on Metro platform,combining WebSocket real-time communication technology and Canvas drawing technology.The system architecture is given,and the functions and implementation methods of the system are described in detail.The practical application results show that the WebSocket real-time communication technology can effectively reduce the bandwidth and network delay and save server resources.The numerical control machine data monitoring system can intuitively reflect the machine data,and the visible effect is good.It realizes timely monitoring of equipment alarms and prompts maintenance and management personnel.

Realization Methodology of a 5-axis Spline Interpolator in an Open CNC System

By making use of the advantages of non-uniform rational B-spline （NURBS） curves to represent spatial curves, an instruction format with double NURBS curves suitable for 5-axis coordinated real-time interpolation is presented to replace the current 5-axis coordinated linear interpolation method defective in low-speed, low-accuracy and enormous numerical control （NC） files in sculptured surface machining. A generation procedure of the NC files with the presented format is introduced and the method to realize the interpolation in an open computer numerical control （CNC） system is developed by ourselves. These illustrated the feasibility of the proposed method and its capability of avoiding all the shortages of 5-axis linear interpolation method.

A Tentative Study on Dynamics of a New Parallel NC Machine Tool with Long Travel, Large Rotating Angle and High Moving Speed

In view of the structure of traditional five-coord in ate machine tool, the work-piece and machine tool often move along their respec tive guides simultaneously on the whole. In this kind of machine structure, the total mass of moving parts including work-pieces, fixtures, rotating table, wor king table and so on is often very large. Besides, the elastic reform of transmi ssion and the viscous friction force of the guide can not be ignored. As a resul t, the machine tool can not move with high velocity and acceleration, and can no t meet the needs of modern fast and efficient production. The emergence of virtual-axis machine tool has provided a new approach for the solution of the above problems. The kernel of the virtual-axis machine tool is the parallel mechanism. So far, research of parallel mechanism in the world has achieved many results and various applied equipments based on parallel mecha nism have been worked out, but the research generally focuses on the working spa ce and kinematics analysis, dynamics are rarely considered. To meet the requirements of the modern fast and efficient production, reduce the cost and promote the machine tool’s acceleration character, not only should we analyze the kinematics of machine tool, but also we should study its dynamics a nd optimize the structure on the basis of analysis. In this paper, the kinem atics and dynamics of a 5-DOF (degrees of freedom) machine tool with novel para llel mechanism that has three moving DOF and one rotating DOF are studied by Rob ot-Wittenberg method. The dynamics character of the parallel robotic machine is analyzed and used to guide the structure design of machine tool. At last, the c orrectness is verified through a numerical simulation of 5-DOF. Hence, the dyna mics model can generally solve the problems existing in the parallel and hybrid machine tools. The dynamics character of the parallel robotic machine is studied and analyzed in quantity. The dynamics equation of the system can be written as This is a set of differential equations of four DOF system. Theoretically, the c losed solution of the forward and inverse problems can be gained by solving the above equations. The system equations quite suit to program at the computer. Whe n the forces are given, the state variables’ numerical solution can be gain ed through integral; and when the dynamics parameters are given, the forces can also be solved. But the multiple valued phenomena can not be avoided. We have developed simulation software based on the dynamics model presented by t his paper. The different effects of the structure parameters can be given by numerical simulation.

Dual Drive Curve Tool Path Planning Method for 5-axis NC Machining of Sculptured Surfaces

The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.

Systematic Geometric Error Modeling for Workspace Volumetric Calibration of a 5-axis Turbine Blade Grinding Machine

A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine. This machine is designed to serve a specific purpose to attain high accuracy and high efficiency grinding of turbine blades by eliminating the hand grinding process. Although its topology is RPPPR （P： prismatic; R： rotary）, its design is quite distinct from the competitive machine tools. As error quantification is the only way to investigate, maintain and improve its accuracy, calibra- tion is recommended for its performance assessment and acceptance testing. Systematic geometric error modeling technique is implemented and 52 position dependent and position independent errors are identified while considering the machine as five rigid bodies by eliminating the set-up errors of workpiece and cutting tool. 39 of them are found to have influential errors and are accommodated for finding the resultant effect between the cutting tool and the workpiece in workspace volume. Rigid body kinematics techniques and homogenous transformation matrices are used for error synthesis.

HEM-500U型五轴数控机床旋转中心精度校准方法探究

多轴数控加工涉及空间角度变换,为保证机床本身能够准确反映旋转运动导致的坐标变化从而确保加工工件的高精度,数控系统控制算法能根据机床运动结构变换链计算工件坐标系的相应变换并控制运动轴进行相应动作。该运动变换链的设定参数通常在机床设计和机床制造商调试机床时确定。随着用户使用场合的不同,环境温变等因素对机床的精度会产生很大影响,因此定期调试校对保证五轴数控机床加工精度很有必要。

Tool Orientation Optimization and Path Planning for 5-Axis Machining

Tool path generation is a fundamental problem in 5-axis CNC machining, which consists of tool orientation planning and cutter-contact(CC) point planning. The planning strategy highly depends on the type of tool cutters. For ball-end cutters, the tool orientation and CC point location can be planned separately;while for flat end cutters, the two are highly dependent on each other. This paper generates a smooth tool path of workpiece surfaces for flat end mills from two stages: Computing smooth tool orientations on the surface without gouging and collisions and then designing the CC point path. By solving the tool posture optimization problem the authors achieve both the path smoothness and the machining efficiency. Experimental results are provided to show the effectiveness of the method.

5-UPS/PRPU并联机床工作空间分析

介绍了新型5-UPS/PRPU五自由度并联机床的运动学反解,分析了其工作空间。以刀尖点为参考点对机床进行了运动学反解分析和工作空间的搜索。定义了灵活刀具倾斜角,使得只用一个参数就能够实现对工作空间的降维描述。对机床工作空间进行了以刀尖点为参考点的三维描述,并对影响机床工作空间大小的几何约束条件进行了分析。根据机床的实际结构参数对工作空间进行了算例分析,并以三维图形形式直观方便地描述了机床的工作空间。机床的最大可达工作空间为800×300的圆柱体,灵活工作空间为400×300的圆柱体,最大灵活刀具角为25°,分析结果与机床的实际运行情况基本一致。

新型5自由度并联机床运动学自标定研究

为提高并联机床的运动精度,提出了一种新的运动学自标定方法。该方法基于冗余传感器测出的动平台全部位姿信息,利用运动学反解公式,建立了标定数学模型,并应用遗传算法进行参数辨识,避免了大量的偏导计算。标定后机床X轴定位精度由标定前的±0.06 mm提高到±0.03 mm,Y轴定位精度由标定前的±0.43mm提高到±0.07 mm,Z轴定位精度由标定前的±0.94 mm提高到±0.07 mm。该方法为改善并联机床的运动精度提供了一种有效手段,并为并联机床的闭环控制奠定了基础。

适合多种机床结构的数控系统5坐标变换库

研究了适合多种结构布局形式的统一坐标变换方法,开发出数控系统5坐标变换函数库,并作为坐标变换控制模块集成到数控系统中.分析了5坐标数控机床运动学模型,归纳出12种5坐标数控机床结构布局,并推导了对应的坐标变换数学算法.通过结构分析和数学变换将12种算法扩展归纳到3类基础算法,并基于3类基础算法开发出适合多种机床结构布局的5坐标变换库.利用机床三维仿真系统验证了5坐标变换库的可行性,并将该坐标变换库集成到北京航空航天大学开发的CH-2010开放式数控系统中.

5轴叶轮粗加工过切与碰撞综合检测修正研究

针对复杂多曲面叶轮的5轴粗加工刀轨自动生成问题,提出一种基于使用平头立铣刀的无过切,干涉的刀具轨迹生成算法。通过对整体叶轮5轴加工中可能出现刀具与叶片干涉的问题,提出了一种干涉检测方法。依据检测结果对干涉进行处理,从而避免实际加工时干涉的发生。方法考虑了刀具运动路径上全部刀位点与叶轮的位置关系,计算量小,对于叶轮数控加工编程中大量刀位数据的干涉检查,可以显著地节省计算机运算时间。

新型5-UPS/PRPU 5自由度完全并联机床

介绍了一种新型5自由度完全并联机床。该机床具有5个驱动分支和1个约束分支,可以实现3维移动和2维转动。该机床结构设计采用了多种新型构件,运动控制系统采用开放式、模块化设计,实现了机床的运动伺服控制、位姿实时检测等功能。加工试验表明,该机床具有良好的运动稳定性和较高的位置精度,可实现5坐标加工。

基于空间模型技术的新型正交5-DOF并联机床的运动学传递性能分析

提出了一种新型正交5-DOF并联机床,研究了这种新型机床的运动传递性能.推导出这种机床的运动传递平衡方程,定义了运动传递性能评价指标、速度各向同性性能评价指标及各全域性能评价指标,应用空间模型技术,绘制了各全域性能图谱,为这种新型正交5-DOF并联机床的参数优化奠定理论基础.这种新型正交5-DOF并联机床具有结构简单、承载能力强、初始装配位姿解耦、工艺性好等优点,适用于空间曲面(磨具、叶片等)零件的加工及气囊抛光等领域.

新型5自由度并联机床运动控制算法研究

在分析 5 UPS/PRPU 5自由度并联机床机构的基础上 ,介绍了并联机床运动控制的基本原理 ,确定了具体的运动控制算法 ,将输入控制系统的数控刀位数据转化为驱动轴的控制指令 ,从而实现对机床加工过程中刀具位姿的控制。根据该算法编制的数控软件已成功地应用于实际的并联机床控制 ,取得了较好的效果。

5-UPS/PRPU五自由度并联机床静力学分析

介绍了 5 -UPS/PRPU五自由度并联机床机构 ,通过对该机构进行静力学分析 ,建立了该机床的静力平衡方程和静力传递矩阵。对机床加工过程中的受力进行了具体分析 ,根据作用在动平台上的外力负载 ,可以得到 5个驱动杆的受力大小和中间分支所承受的力偶矩大小 ,为该机床的结构设计。