CNC机床在线测量系统校准方法研究

目前CNC机床在线测量系统的校准方法在国内有用激光干涉仪、标准量块等一些用于企业的针对性方法,缺少适用于计量校准机构的校准方法,本文根据该系统的工作原理,对CNC机床在线测量系统的校准方法进行研究,提出几项计量特性参数,并结合实际情况设计了校准方案,研制了校准用计量标准器,分析了数据的处理方法.经研究表明,本文的校准方...     

Synthesis of the measurement system on the machine tool

The design methodology of a 2½-dimensional measurement and inspection system realized on a machine tool using a touch trigger probe and measuring G codes is studied in this paper. The reliability of measuring results, the agility of measurement, and user friendliness are synthesized in the design process. Algorithms for calibration and compensation of measuring errors are proposed to ensure the measuring accuracy by using a laser interferometer and ring gauges. Classification of probing feedrates and a collision-check algorithm can reduce measuring time and implement stylus-fracture-free measurements. To improve the previous onmachine measurement processes, all functions required for measurement and inspection processes are constructed as measuring G codes with similar forms of machining G codes. The interactive measuring program generating tool, which can automatically generate measuring G codes, is developed and potted in a ROM of a CNC, and can be called to perform an operation by the CNC without interfacing with personal computers. The validity and effectiveness of the developed system are verified on a horizontal machining centre with a Fanuc 15MA.     

线性运动平台多自由度几何运动误差测量技术

线性运动平台是精密制造和测量的基础,其定位精度直接影响着制造和测量的精度。由于制造和装配误差的影响,运动平台存在六个自由度的运动误差,将影响运动平台的定位精度。为了提高运动平台的定位精度,需要准确地测量各项运动误差。传统的测量方法只能对单一误差进行测量,并且测量仪器体积较大,无法集成在运动平台中进行实时误差测量。本文提出了一系列成本低、体积小、易集成的高精度多自由度几何运动误差同时测量技术,可以根据测量需求选择测量系统的自由度,在提高测量精度的同时,还可以实现在线测量,为提高线性运动平台运动精度起到重要作用。     

高速激光切割机床数控加工态势识别系统

当前方法设计的系统对机床数控加工态势进行识别时,没有对噪声进行回放,对切割平面度、切割定位精度、机床平稳性进行识别时,识别结果不准确,存在识别准确率低的问题。该文提出高速激光切割机床数控加工态势识别系统设计方法,首先,通过运动控制卡,伺服控制模块及加工态势识别模块构成高速激光切割机床数控加工态势识别系统的架构;其次,在加工态势识别模块中设计系统初始化、态势识别、自动诊断报警、运动控制、图形转码和G代码编译等子模块,在此基础上,通过噪音采集、噪音回放和信号分析等方法提高加工态势识别的准确率;最后,采用HMM算法构建高速激光切割机床数控加工态势识别模型,实现加工态势识别。实验结果表明,加工态势设计方法设计的系统可有效识别机床的切割平面度、切割定位精度和机床平稳性,识别准确率较高。     

数控机床在线测量系统校准技术研究

数控机床在线测量技术广泛应用于薄型、复合材料等大型加工工件的在线测量,以确保工件的加工质量符合要求。针对目前数控机床在线测量系统校准工作中存在的工作现场环境条件干扰和校准过程耗时较长问题,本文根据实际工作中的技术要求,采用双频激光干涉仪、成组球规等标准器组成校准系统,提出一种适用于企业内部的数控机床在线测量系统校准技术,结合补偿技术提供单位间距的修正量,确保轴线长度示值误差符合技术要求。经实验证明,该校准方法准确性好,工作效率高,具有技术推广价值。     

Intelligent tool path correction for improving profile accuracy in CNC turning

This paper presents the development of an intelligent predictive tool for improving the accuracy of parts produced on CNC turning centers. Actual dimensions and shape (form) produced on components during machining differ from the nominal dimensions commanded in the CNC program. These dimensional and form errors on parts depend on a variety of factors such as tool/work deflections, machine tool accuracy, machining conditions etc. These errors, if predicted, can be used to correct the ideal CNC code and thus improve the part accuracy in CNC machining. In the present work artificial neural networks are used to capture the complex relationship between the errors on the component and the input process conditions. Significant improvement in part accuracy has been obtained using the corrected CNC code during machining.     

Scanning strategies and spacing effect on laser fusion of H13 tool steel powder using high power Nd:YAG pulsed laser

Layered manufacturing technologies have been used to produce complex parts of diversified materials through different physical/chemical manufacturing principles. Nevertheless only a few materials are commercially available to build parts suitable for engineering applications. In this paper, the powder fusion of H13 tool steel is investigated. A high power Nd:YAG pulsed laser source on a CNC machine was used to fuse the powder, layer by layer, building solid cubes for further analysis. Four different laser vector scanning strategies were evaluated by comparing the results of porosity and layer distortion. The complexity of the laser/powder interaction shows that a complex strategy must be used to avoid porosity and distortion.     

复合进给电解加工机床控制系统设计与测试

为解决航空制造领域复杂零件的加工难题，针对研制的复合进给电解加工机床，开发了基于PC（ personal computer，个人计算机）和PMAC（programmable multi-axles controller，可编程多轴控制器）运动控制卡的开放式数控系统。基于虚拟仪器技术及其开发环境LabVIEW平台，遵循模块化设计思路，采用ActiveX自动化技术和CLF (call library function，调用库函数)节点设计了复合进给电解加工机床控制系统的人机交互界面，通过调用PMAC运动控制卡中的服务程序PmacServer，实现上位机与PMAC运动控制卡之间的功能交互。为了验证该控制系统的可靠性和运行稳定性，使用激光干涉仪进行了实验测试。实验结果显示，该控制系统响应迅速，运行稳定，人机交互界面易于操作；机床运动误差控制在-5~5 μm内，重复定位误差小于2.3 μm，能够满足航空发动机叶片的电解加工精度要求。研究结果在电解加工领域具有重要工程应用价值，可以为新一代高性能电解加工机床的设计提供参考。     

Multimode machine tools—a concept that improves operations of flexible manufacturing systems

Modern flexible manufacturing systems offer certain benefits when compared to conventional stand-alone systems, but have problems associated with high capital outlays, system integration difficulties and lower than expected utilization because of characteristics of their component machine tools. These problems are addressed in this paper, which introduces a conceptual computer controlled multimode machine tool that can be programmed to execute conventional machining operations. Characteristics of hypothetical manufacturing systems built with these machines, are compared to those of conventional flexible manufacturing systems using established criteria, where it it is shown that these multimode machine tools enhance the operation of flexible manufacturing systems.     

基于状态空间模型的机床加工精度分析

伺服进给系统的机电耦合特性直接影响数控机床的加工精度，单独针对伺服系统或机械系统建立的模型不足以准确分析系统参数对机床整机加工精度的影响。因此，综合考虑机床伺服系统与机械结构之间的耦合关系，建立伺服进给系统机电耦合动力学模型具有重要意义。首先，为保证伺服进给系统建模精度，利用状态空间法建立了机床机电耦合状态空间方程。其次，建立了伺服进给系统机电耦合Simulink模型，在此基础上采用复合控制提高系统的响应速度和加工精度。随后，利用多体动力学软件建立机床进给系统的刚柔耦合动力学模型，添加摩擦、阻尼等非线性因素，并导入Simulink与伺服系统建立耦合关系。最终，建立了卧式加工中心伺服进给系统的刚柔-机电耦合仿真加工平台，通过模拟机床加工轨迹以验证机电耦合状态空间模型的可靠性。结果表明：该状态空间模型能准确描述系统内部参数和系统输入输出的耦合关系；采用复合控制结构能有效提高系统的响应速度和加工精度。研究结果为数控机床的仿真建模和提高加工精度提供理论依据，为机床机电系统的设计提供有效指导。     

Thermal characteristics of composite sandwich structures for machine tool moving body applications

The thermal deformation affects the accuracy of a precision machine tool. There are various heat sources in machine tools such as motors, spindle units, and friction in LM-guide systems. In this work, the thermal characteristics of composite sandwich structures for machine tool parts were investigated both by FEM analysis and experiment. Then the machine tool slide of a high speed CNC milling machine was designed and manufactured with composite sandwich structures combined with a welded steel structure––a hybrid machine tool structure. In addition, the reliability of adhesive joints between the composite sandwich and the steel structure was investigated in terms of adhesive joint strength and thermal stress induced by heat generation of linear motors.     

Modeling and identification of the multi-axis drive system using support vector machine and granular computing

Advanced manufacturing technology requires high-precision capability in multi-axis computer numerical control (CNC) machine tools. At present, the modeling and identification for the drive system of CNC machine tools has some defects. In order to solve the problem, some interdisciplinary theories and methods, such as support vector machines, granular computing, artificial immune algorithms, and particle swarm optimization algorithms, have been used to model and identify multi-axis drive systems for CNC machine tools. An identification method using a support vector machine, based on granular computing, is presented to identify a multi-axis servo drive system model for improving the precision of model identification, and an immune particle swarm optimization algorithm, based on crossover and mutation functions, is proposed to optimize the structure parameters of the support vector machine based on granular computing. The proposed identification method was evaluated by experiments using the multi-axis servo drive system. The experimental results showed that the proposed approach is capable of improving modeling and identification precision.     

Kinematic error modeling and error compensation of desktop 3D printer

Desktop 3D printers have revolutionized how designers and makers prototype and manufacture certain products.Highly popular fuse deposition modeling(FDM)desktop printers have enabled a shift to low-cost consumer goods markets,through reduced capital equipment investment and consumable material costs.However,with this drive to reduce costs,the computer numerical control(CNC)systems implemented in FDM printers are often compromised by poor accuracy and contouring errors.This condition is most critical as users begin to use 3D-printed components in load-bearing applications or to perform mechanical functions.Improved methods of low-cost 3D printer calibration are needed before their open-design potential can be realized in applications,including 3D-printed orthotics and prosthetics.This paper applies methodologies associated with high-precision CNC machining systems,namely,kinematic error modeling and compensation coupled with standardized test methods from ISO230-4,such as the ballbar for kinematic and dynamic error measurements,to examine the influence and feasibility for use on low-cost CNC/3D printing platforms.Recently,the U.S.Food and Drug Administration's"Technical considerations for additive manufactured medical devices"highlighted the need to develop standards specific to additive manufacturing in regulated manufacturing environments.This paper shows the benefits of the methods described within ISO230-4 for error assessment,alongside applying kinematic error modeling and compensation to the popular kinematic configuration of an Ultimaker 3D printer.A Renishaw ballbar QC10 is used to quantify the Ultimaker's errors and thereby populate the error model.This method quantifies machine errors and populates these in a mathematical model of the CNC system.Then,a post-processor can be used to compensate the printing code.Subsequently,the ballbar is used to demonstrate the dramatic impact of the error compensation model on the accuracy and contouring of the Ultimaker printer with 58%reduction in overall circularity error and 90%reduction in squareness error.     

数控刀具材料的研究进展

数控刀具是数控加工技术中的重要基础装备之一,在保证制造技术的有效实施方面有着十分重要的作用。本文主要介绍数控机床刀具的分类、数控刀具材料的现状和发展趋势。     

A control algorithm for improving the accuracy of five-axis machine tools

An algorithm for reducing the influence of geometrical, thermal, kinematic and stiffness errors in five-axis machine tool components on the desired tool position and orientation is given. This new algorithm is based on the calculation of the cutting tool error matrix for orthogonal machine tools. In the new model of this matrix, all angular errors of the machine links are considered as infinitesimal rotations. The error matrix is a function of the commanded machine component positions and the errors in these positions. To correct errors in the three translational and two angular tool positions, a matrix of commanded tool position and orientation is multiplied by the inverse error matrix in every period of the tool trajectory interpolation. This corrected matrix of the tool position and orientation provides the inverse kinematics used for calculation of the successive links positions required for achieving the given tool trajectory. The control algorithm for five-axis machine tools with the error compensation is implemented both in the CNC system and in the postprocessor. The proposed algorithm is applied on a vertical five-axis turning centre with two translational and three rotational axes. Twenty-four errors that could cause inaccurate machining are recognised on this machine. The machine links and their coordinate frames are denoted using the Denavit–Hartenberg parameters.     

数控机床热误差的建模与预补偿

研究了数控机床热误差的预补偿方法。建立了基于主轴转速的热误差自回归模型,从而不需要测量机床的温度场就可以预测热误差。在加工前通过修改工作的数控加工程度即可进行补偿,大大简化了误差补偿过程。可应用于中等精度的数控机床。     

用激光干涉仪检测双丝杠驱动加工中心的方法与评定

介绍了使用激光干涉仪检测双丝杠驱动加工中心时,选择测量轴线的有效位置,能够真实地反映加工中心轴线的运动定位状态;提出检测双丝杠驱动加工中心定位精度和重复定位精度的方法,通过调整激光干涉仪和位移镜组件的安装位置,获得数控机床及加工中心的检测精度,并根据自动采集获得的测量数据进行有效地补偿,以提高和恢复数控机床及加工中心的最佳定位精度.     

Heuristic optimization system for the determination of index positions on CNC magazines with the consideration of cutting tool duplications

This paper presents a meta-heuristic optimization system developed for the determination of optimal index positions of cutting tools on the tool magazines (automatic tool changer (ATC) or turret magazine, etc.) of CNC (computerized numerical control) machine tools. The selection of index positions is performed using a simulated annealing (SA) algorithm that takes the following as the input: (1) a list of cutting tools assigned to certain machining operations; (2) the number of copies of each cutting tool available in the workshop; (3) total number of index positions on the tool magazines; (4) the indexing time of a tool magazine of a CNC machine tool specified by manufacturer. Then, the SA algorithm determines index locations of cutting tools on the tool magazines. Dereli et al. and Dereli and Filiz previously studied the present problem by using genetic algorithms (GAs). However, the duplication of cutting tools was not taken into account in their works, although it can reduce the total tool-indexing time and therefore improve the productivity considerably. Nevertheless, the consideration of the ‘tool duplications’ makes the problem much harder to model and to solve. In this paper, a novel solution representation-scheme based on the SA, which enables easy manipulation during feasible neighbourhood solution generation, is proposed for the determination of the index positions of cutting tools on the CNC magazines with the consideration of ‘tool duplications’. Example problems are solved to present the implementation and merits of the proposed optimisation system. It is shown that it is possible to allocate the cutting tools in an efficient manner on the CNC magazines with the developed system.     

Design of Vibration Monitoring System of CNC Machine

CNC machine have a fast development and is widely used in China. Generally, CNC machine tool, includs CNC lathes and CNC milling machine. CNC machine tool is a necessary tool for machining. It plays an important role in the mechanical design and machining fields. CNC machine tool is mainly composed of two parts of the machine body and the computer control system. Mechanical equipment failures usually related information such as vibration, sound, pressure, temperature performance. CNC machine tool vibration monitoring system with piezoelectric accelerometer, the eddy current displacement sensor, signal amplifier, signal conditioning modules. We can take an advantage of the CNC machine tool vibration monitoring system for vibration monitoring and fault diagnosis of CNC machine tools.