A review on spindle thermal error compensation in machine tools

Li, Yang; Zhao, Wanhua; Lan, Shuhuai; Ni, Jun; Wu, Wenwu; Lu, Bingheng

doi:10.1016/j.ijmachtools.2015.04.008

Cited by 260 publications

(87 citation statements)

References 104 publications

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“…Machine tools that are capable of correcting for displacements of the Tool Centre Point (TCP) caused by thermal expansion are a promising approach for high precision manufacturing (other approaches involve, e.g., design modification or thermal-error control) [1]. Most machine tools these days are "intelli- 5 gent" and employ sensors to measure temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Despite only re-30 solving one machine part and employing a time-averaged heat source instead of a full coupling, Galant et al report a computation time of around 5 hours to simulate a milling machine with 16,626 degrees-of-freedom over 16 hours using ANSYS (corresponding to η = 3.2). To the best of the authors' knowledge, there are no reports of simulations solving in real-time the fully coupled tran-35 sient FEM problem for a machine with moving parts without simplifications.Recent review papers also make no mention of such efforts [1,3,9]. A combination of finite differences and FEM, called FDEM, has been proposed that reduces computational effort but still relies on the use of macro elements to reduce the size of the solved system [2].…”

mentioning

confidence: 99%

“…Recent review papers also make no mention of such efforts [1,3,9]. A combination of finite differences and FEM, called FDEM, has been proposed that reduces computational effort but still relies on the use of macro elements to reduce the size of the solved system [2].…”

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confidence: 99%

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Toward transient finite element simulation of thermal deformation of machine tools in real-time

2018

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Finite element models without simplifying assumptions can accurately describe the spatial and temporal distribution of heat in machine tools as well as the resulting deformation. In principle, this allows to correct for displacements of the Tool Centre Point and enables high precision manufacturing. However, the computational cost of FEM models and restriction to generic algorithms in commercial tools like ANSYS prevents their operational use since simulations have to run faster than real-time. For the case where heat diffusion is slow compared to machine movement, we introduce a tailored implicit-explicit multi-rate time stepping method of higher order based on spectral deferred corrections. Using the open-source FEM library DUNE, we show that fully coupled simulations of the temperature field are possible in real-time for a machine consisting of a stock sliding up and down on rails attached to a stand. 15 though accurate specification of boundary conditions can be a challenge [4]. Accurate transient finite element models are very useful as they can provide spatially and temporally resolved temperature fields for machines with complex designs and geometries [3,5]. In contrast to empirical approaches [6, 7], the parameters in FEM are physical quantities that can, at least theoretically, be 20 measured. Since reduced models are typically machine-specific, their derivation also comes with a high cost in terms of person hours. In contrast, the mesh for FEM models can be generated automatically, e.g. from CAD files, even for machines with complex geometries.The disadvantage of FEM models is their high computational cost, which 25 is why often reduced models are employed, sacrificing accuracy or generality for speed. Running full time-dependent FEM models is considered too computationally expensive to be possible in real-time: "application of the original FE-models without any simplifications [...] for model-based control-integrated correction is very time-consuming and thus impractical" [8]. Despite only re-30 solving one machine part and employing a time-averaged heat source instead of a full coupling, Galant et al. report a computation time of around 5 hours to simulate a milling machine with 16,626 degrees-of-freedom over 16 hours using ANSYS (corresponding to η = 3.2). To the best of the authors' knowledge, there are no reports of simulations solving in real-time the fully coupled tran-35 sient FEM problem for a machine with moving parts without simplifications.Recent review papers also make no mention of such efforts [1,3,9]. A combination of finite differences and FEM, called FDEM, has been proposed that reduces computational effort but still relies on the use of macro elements to reduce the size of the solved system [2]. With respect to FDM and FEM, in a 40 review from 2017, Cao et al. state that "[...], due to the low efficiency, the computational models were rarely used in online thermal error compensation" [10], mentioning only approaches that rely on steady-state FEM models [11,12].A key reason is probably...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Toward transient finite element simulation of thermal deformation of machine tools in real-time

2018

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“…The device not only provides motion error measurements, but can also be used for spindle thermal expansion monitoring. (16)(17)(18)(19) However, the proposed measurement method cannot be used for on-line or real-time measurement. (20) 2.…”

Section: Introductionmentioning

confidence: 99%

Three Degrees-of-Freedom Optical Spindle Error Motion Measurement Device

2017

Sensors and Materials

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An inexpensive optical measurement device for spindle error measurement, which has three degrees of freedom (3DOF) and is integrated with the Internet of things (IoT), is presented. The device uses an artificial standard sphere, which is set on the spindle to be measured, and two optical measurement modules. Each module includes an aspherical lens, a laser diode, a beam splitter and a quadrant position-sensing detector, and the autocollimator principle of measurement is used. After the calibration of the device, the residual error and resolution are about 1 and 0.1 μm, respectively. The experiment results show errors of measurement, caused by the roughness of the standard sphere, as periodic noise with an amplitude of 10 μm. After the noise has been eliminated, the error motion of the spindle, which includes radial, axial, and synchronous and asynchronous errors, can be observed. The proposed device can also be used for the measurement of spindle thermal expansion.

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“…Thermal errors caused by the uneven distribution of the temperature field are the most significant factors influencing the machining accuracy of computer numerical control (CNC) machine tools and account for about 70% of total errors resulting from various errors, and the more sophisticated the machine tool, the greater the proportion of thermal errors. [1][2][3] Besides, the mapping relationship between thermal error and temperature field distribution is strongly nonlinear, resulting in the difficulty in thermal error modeling and compensating. Thus, eliminating thermal error of high-speed spindle systems is an effective way to improve the machining accuracy of CNC machine tools.…”

Section: Introductionmentioning

confidence: 99%

Thermal error compensation based on genetic algorithm and artificial neural network of the shaft in the high-speed spindle system

Zhao

Mei

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part B:

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To improve the accuracy, generality and convergence of thermal error compensation model based on traditional neural networks, a genetic algorithm was proposed to optimize the number of the nodes in the hidden layer, the weights and the thresholds of the traditional neural network by considering the shortcomings of the traditional neural networks which converged slowly and was easy to fall into local minima. Subsequently, the grey cluster grouping and statistical correlation analysis were proposed to group temperature variables and select thermal sensitive points. Then, the thermal error models of the high-speed spindle system were proposed based on the back propagation and genetic algorithmback propagation neural networks with practical thermal error sample data. Moreover, thermal error compensation equations of three directions and compensation strategy were presented, considering thermal elongation and radial tilt angles. Finally, the real-time thermal error compensation was implemented on the jig borer's high-speed spindle system. The results showed that genetic algorithm-back propagation models showed its effectiveness in quickly solving the global minimum searching problem with perfect convergence and robustness under different working conditions. In addition, the spindle thermal error compensation method based on the genetic algorithm-back propagation neural network can improve the jig borer's machining accuracy effectively. The results of thermal error compensation showed that the axial accuracy was improved by 85% after error compensation, and the axial maximum error decreased from 39 to 3.6 mm. Moreover, the X/Y-direction accuracy can reach up to 82% and 85%, respectively, which demonstrated the effectiveness of the proposed methodology of measuring, modeling and compensating.

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A review on spindle thermal error compensation in machine tools

Cited by 260 publications

References 104 publications

Toward transient finite element simulation of thermal deformation of machine tools in real-time

Toward transient finite element simulation of thermal deformation of machine tools in real-time

Three Degrees-of-Freedom Optical Spindle Error Motion Measurement Device

Thermal error compensation based on genetic algorithm and artificial neural network of the shaft in the high-speed spindle system

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