结构热变形对机床进给系统热误差的影响分析

以某企业生产的T-500B高速钻铣加工中心为研究对象,利用有限元仿真软件对机床实际工况下丝杆进给系统的热特性进行模拟分析,寻找出进给系统与结构铸件间的整体热变形规律,同时还根据丝杆的热变形规律,分别通过考虑结构铸件变形与否这两种不同情况,建立起机床进给系统相应的热误差模型并进行模拟验证分析,最终得出了两种情况下丝杆在有效行程范围内的热误差曲线,提高了热误差模型的准确性,对机床热误差预测模型的构建具有一定的参考价值。     

应对龙门机床横梁热变形的结构分析与改进

分析了一种消除定梁龙门机床横梁热变形伸缩结构的基本原理和特点,并对某专利结构的不足之处进行了分析,提出了一种新的应对定梁龙门机床横梁热变形伸缩的结构。     

加工过程热动态建模与数学模型分析

以某生产厂家的一种车削加工中心为研究对象 ,通过对机床加工过程中热误差模态 (或称热动态模型 )的分析 ,以一种非常简便的热变形计算方法 ,即结构部件整体分元法 ,给出了该机床的热误差数学模型 ,并提出了热误差链具有封闭特性这一概念。实验证明 ,该方法正确且简便实用     

五轴数控机床热误差检测案例分析

对机床热误差的检测是为了解机床热误差规律、寻找数据支撑,从而进行误差补偿或减少热误差发生,提高机床精度。通过数控机床的主轴热误差检测案例,简单介绍热误差检测方法及在实际中的运用。案例表明机床不同的热误差源的性质不同,对机床精度的影响也不同,因此实现误差补偿所需建立的模型也就不同,需要热误差检测方法也将不同。机床热误差检测方法的研究为热误差补偿技术的研究提供了前提和基础。     

立式数控机床主轴热态精度检测

利用电容式位移传感器和电阻式温度传感器对立式数控机床主轴进行高精度测量,试验获取主轴端径向和轴向热位移,以及主轴系统热敏感位置的温升。对于机械式主轴,主轴前后轴承和减速器因高速滚动摩擦发热,使得主轴的发热量很大,造成的热变形会严重影响机床的加工精度。对于结构稳定、技术成熟的数控机床,提高数控机床的热态精度最有效的措施是改进机床的主轴润滑方式或者对主轴轴承进行强制冷却。     

基于ANSYS Workbench的机床热结构与热平衡分析

机床热误差是影响机床加工精度的主要因素,目前对热误差的控制主要采取补偿的方法,即通过采集机床热平衡时的温度以及热变形误差来建立数学模型,实现热误差的补偿。通过对XK7132数控铣床进行热边界条件分析,提出了利用ANSYS Workbench软件对机床整机进行稳态热结构分析以及对主轴进行热平衡分析,得到了机床的稳态热变形及主轴温升平衡曲线。由分析结果可知,稳态热变形主要发生在主轴的X轴和Z轴方向,而达到热平衡时所需时间大约为40～50 min,为机床热误差补偿时传感器的布置提供了理论依据。     

MHCES机床热特性试验方案决策专家系统

以普通车床、精密磨床、镗床的热变形试验为研究对象,把专家系统技术应用到机床热特性的研究,构造了机床热特性研究专家系统的结构。重点介绍了基于框架推理和规则推理相结合的热变形试验方案决策专家系统。     

机床主轴热设计研究综述

机床的热态性能已成为影响高速机床工作性能的最重要的因素之一。主轴是机床的关键功能部件,其热态特性在很大程度上决定了机床的切削速度和加工精度,是影响机床精度提升的最重要因素。因此,在主轴的设计阶段减少机床热误差的影响,对于提高机床的热态特性十分重要。在过去的近一个世纪时间中,国内外众多学者针对主轴热设计方法开展了研究探索,基于热设计的过程可以分成三部分内容:热态特性分析方法,热设计与优化方法和热态特性试验方法。先通过主轴热态特性(如温度场分布、热变形、热平衡时间等)建模与分析获取必要的参数,然后以此为基础开展主轴结构设计优化、材料设计优化和冷却系统设计等热设计措施,获得较佳的主轴热态特性,最后通过热态特性试验来校验分析和设计优化的结果,整个过程循环直至达到满意结果为止。本文以此为脉络展开,分别探讨了三部分内容的国内外典型研究现状、主要研究内容和所存在的优缺点,并对未来的研究趋势进行了展望。     

基于热误差神经网络预测模型的机床重点热刚度辨识方法研究

为了合理分配机床热刚度并为机床零部件的热刚度优化提供依据,提出一种基于热误差神经网络预测模型的机床重点热刚度辨识方法.该方法针对机床不同零部件的热刚度对整机热刚度的影响具有不完全相同的特征,定义一种机床重点热刚度的概念.根据机床温度和热误差试验数据,利用径向基神经网络建模精度高和泛化能力强的特点,建立一种机床热误差神经网络预测模型.以机床不同零部件达到热平衡后产生的单位温升为热误差预测模型的输入矢量,计算热误差变化值作为机床重点热刚度的辨识依据,在此基础上阐述机床重点热刚度辨识方法的原理和实施步骤.将该方法应用在一台高架桥式龙门加工中心的重点热刚度辨识上,辨识结果与验证试验得到的结果相一致.     

BFPC填充结构机床立柱设计及其性能分析

为探索提高机床静、动、热态性能和轻量化从而满足机械制造向着高效率、高精度和高自动化程度方向发展需求的新途径,以某立式加工中心的立柱为研究原型,以满足刚度要求和轻量化为约束条件,设计了玄武岩纤维树脂混凝土(BFPC)填充结构机床立柱。利用ANSYS软件对两种结构立柱的静、动、热态性能进行仿真分析,对其轻量化及所需铸铁量进行计算。并将其结果进行对比分析,结果表明,BFPC填充结构机床立柱可在保证轻量化的同时提高机床静、动及热态性能,并有利于实现机床制造的节能减排和绿色环保。     

零传动滚齿机热特性的试验研究

在零传动滚齿机中,工件主轴的径向热变形严重影响工件的齿向加工精度,而滚刀主轴的轴向和径向热变形对工件的齿距偏差和齿向偏差都产生很大的影响。从试验的角度研究工件主轴和滚刀主轴的热变形,最后根据试验提出从结构优化和热误差补偿两方面来研究机床热变形的控制技术。     

数控机床热变形误差研究及补偿应用

热变形误差是影响机床加工精度的重要因素之一,通过误差补偿的方法可以提高机床的加工精度。研究了通过实时补偿热变形误差提高数控机床加工精度的方法,阐述了热误差的基本原理,介绍了热误差的测量方法。采用模糊聚类的方法来布置测温点,利用多元线形回归方法建立了机床热变形与温升之间的数学模型。在PLC补偿系统的作用下,在加工过程中对XH718数控机床进行实时补偿。实验结果表明补偿效果很好。     

A real-time thermal inaccuracy compensation method on a machining centre

The errors which affect the processing precision of a machining tool are due to the built in volumetric errors in the machine structure, and also the thermal displacement of the machine tool during cutting. In this paper, a new technique is developed to compensate for these errors in machine tools. The work demonstrates that the thermal effect is quite different in air-cutting conditions and real-cutting conditions. An IC type thermometer is designed to detect the temperature variation at specific components of the machine tool. These thermal displacements are measured on-line with a touch trigger probe. A mathematical model is then built, based on the sensed temperature variation and the thermal displacements by multivariable regression analysis. Finally, these errors are reduced on the machine by sending a feedback signal to the CNC controller to improve the processing precision of the machine tool. In this research, the errors are successfully reduced to within 4 µm for general cutting.     

Thermal error compensation of a 5-axis machine tool using indigenous temperature sensors and CNC integrated Python code validated with a machined test piece

Achieving high workpiece accuracy is the long-term goal of machine tool designers. There are many causes for workpiece inaccuracy, with thermal errors being the most common. Indirect compensation (using prediction models for thermal errors) is a promising strategy to reduce thermal errors without increasing machine tool costs. The modelling approach uses transfer functions to deal with this issue; it is an established dynamic method with a physical basis, and its modelling and calculation speed are suitable for real-time applications. This research presents compensation for the main internal and external heat sources affecting the 5-axis machine tool structure including spindle rotation, three linear axes movements, rotary C axis and time-varying environmental temperature influence, save for the cutting process. A mathematical model using transfer functions is implemented directly into the control system of a milling centre to compensate for thermal errors in real time using Python programming language. The inputs of the compensation algorithm are indigenous temperature sensors used primarily for diagnostic purposes in the machine. Therefore, no additional temperature sensors are necessary. This achieved a significant reduction in thermal errors in three machine directions X, Y and Z during verification testing lasting over 60 h. Moreover, a thermal test piece was machined to verify the industrial applicability of the introduced approach. The results of the transfer function model compared with the machine tool's multiple linear regression compensation model are discussed.     

数控机床主轴热变形伪滞后研究及主轴热漂移在机实时补偿

为研究数控机床热变形规律,实现数控机床误差在机实时补偿,进行数控机床主轴热变形理论及试验分析,结果表明,数控机床主轴热变形与主轴温变在距热源约1/3位置存在近似线性关系,即主轴热变形存在伪滞后现象,这一结果为数控机床测温点优化布置及热误差鲁棒建模提供理论依据。为验证机床热变形伪滞后现象,对VM850加工中心主轴热漂移误差在机实时检测并建模,通过自主研发数控机床误差在线实时补偿系统对主轴热漂移误差进行实时补偿,经补偿,机床主轴热漂移误差减少90%以上,有效提高了数控机床主轴精度。     

车磨复合机床主轴系统的温度场建模与仿真

影响现代高速机床加工精度的主要因素是热误差。机床主轴系统的热特性直接影响到机床的精度进而影响零部件精度,因此有必要对主轴系统进行热分析,了解其热特性,以便进一步分析和改进。车磨复合机床主轴回转系统结构设计及性能要求很高,应具有足够的强度、刚度、抗振性、韧性和抗疲劳性能。分析主轴热源,计算发热量,确定边界条件,利用有限元软件ANSYS建立了主轴系统的温度场模型并进行了数字模拟仿真,为类似主轴系统的热应力及热变形设计提供了参考。     

基于HEIDENHAIN数控系统主轴轴向热变形补偿技术

分析HEIDENHAIN数控系统实现机床热变形误差补偿的原理,介绍将其应用于数控机床主轴轴向热变形误差补偿的方法和步骤,以及一种自行设计PLC控制程序,识别温度变化过程,自动计算补偿值的原理和方法。经过在某大型加工中心上应用验证,证实基于数控系统的主轴轴向热变形补偿具有显著效果,并且通过识别温度变化过程控制补偿值计算方法具有更加稳定的效果。     

Thermal Error Measurement and Real Time Compensation System for the CNC Machine Tools Incorporating the Spindle Thermal Error and the Feed Axis Thermal Error

Thermally induced errors have been significant factors affecting machine tool accuracy. In this paper, the thermal spindle error and thermal feed axis error have been considered, and a measurement/compensation system for thermal error is introduced. Several modelling techniques for thermal errors are also implemented for the thermal error prediction; i.e. multiple linear regression, neural network, and the system identification methods, etc. The performances of the thermal error modelling techniques are evaluated and compared, showing that the system identification method is the optimum model having the least deviation. The thermal error model for the feed axis is composed of geometric terms and thermal terms. The volumetric errors are calculated, combining the spindle thermal error and feed axis thermal error. In order to compensate for the thermal error in real-time, the coordinates of the CNC controller are modified in the PMC program. After real-time compensation, the machine tool accuracy improved about 4–5 times. ID="A1" Correspondence and offprint requests to: Dr H. J. Pahk, School of Mechanical and Aerospace Engineering, Seoul National University, San 56–1, Shinlim-Dong, Kwanak-Ku, Seoul 151–742, Korea. E-mail: hjpahk@plaza.snu.ac.kr     

基于动态反馈神经网络模型的数控机床热误差实时预报补偿

分析了数控机床热误差对制造加工精度的影响及影响数控机床热误差的关键因素,对采用神经网络模型预报数控机床热误差进行了深入分析,提出了具有反馈输入环节的动态神经网络模型.讨论了建立模型的关键技术问题,并对基于该模型的数控机床热误差的智能预报进行了计算机仿真分析.     

Compensation of machine tool thermal deformation in spindle axis direction based on decomposition method

One of the fundamental areas in high precision cutting is represented by the machine's thermal state monitoring. Understanding of this state gives significant information about the overall machine condition such as proper performance of cooling system as well as software compensation of machine's thermal deformation during manufacturing. This paper presents a method focused on compensation of machine's thermal deformation in spindle axis direction based on decomposition analysis. The machine decomposition is performed with the help of specially developed measuring frame, which is able to measure deformation of machine column, headstock, spindle and tool simultaneously. Compensation is than calculated as a sum of multinomial regression equations using temperature measurement. New placements of temperature measurement like spindle cooling liquid or workspace are used to improve the accuracy of this calculation. Decomposition process allows describing each machine part's thermal dynamic more precisely than the usual deformation curve usually used one deformation curve for the complete machine. The residual thermal deformation of the machine is considerably reduced with this cheap and effective strategy. The advantage is also in the simplicity of presented method which is clear and can be used also on older machines with slower control systems without strong computing power.