Numerical and experimental modeling of thermal errors in a five-axis CNC machining center

This work aims at the establishment of methodology to model and analyze the thermal errors of a five-axis CNC machining center, from an estimated temperature field, to finally model an artificial neural network (ANN) algorithm to accurately predict with robustness the thermal error. The thermoelastic behavior of the machining center was modeled through two different approaches: experimental (or data-driven) model and numerical (or physical) model. The thermal behavior of the machine was first modeled using finite element method (FEM) techniques based on theory of friction heat and convection heat and validated with the various experimentally raised temperature fields using temperature sensors and thermal imaging. The main machine subsystems were initially validated, such as ball screw system, linear guides, and spindle, which allowed for validating of the thermal behavior of the entire machine for five different duty cycles obtaining a maximum error of less than 8% when comparing the numerical results with the experimental results. The components of the thermal errors in X, Y, and Z directions were obtained through FEM by measuring the displacement of the spindle tip in relation to the reference bushing located on the worktable. The same procedure was experimentally performed using a touch probe system clamped in the spindle, and the results were compared obtaining a maximum deviation of 17 μm. The validation of the finite element model allowed for the use of the results obtained by the simulation to train and validate an ANN for predicting the thermal errors of the machining center. The relative errors between the thermal errors predicted by the ANN and the FEM simulation results were less than 1% indicating that the methodology developed in this work that combines the use of physical models with data-driven models is an accurate and robust tool to predict the thermal errors of the machine for various working conditions, even with the machine moving at different speeds or alternating the movement of the axles.

[1]  Christian Brecher,et al.  Thermal issues in machine tools , 2012 .

[2]  Xu Min,et al.  An improved thermal model for machine tool bearings , 2007 .

[3]  Sung-Ki Lyu,et al.  Thermal error forecast and performance evaluation for an air-cooling ball screw system , 2011 .

[4]  Michael M. Khonsari,et al.  Experimental testing and thermal analysis of ball bearings , 2013 .

[5]  Chun-Hong Park,et al.  Effect of frictional heat generation on the temperature distribution in roller linear motion rail surface , 2017 .

[6]  Chun-Hong Park,et al.  Friction experiment of linear motion roller guide THK SRG25 , 2014 .

[7]  Enming Miao,et al.  Robustness of thermal error compensation modeling models of CNC machine tools , 2013 .

[8]  Cheng-Chi Wang,et al.  Real-Time Compensation for Thermal Errors of the Milling Machine , 2016 .

[9]  M. H. Attia,et al.  A generalized modelling methodology for optimized real-time compensation of thermal deformation of machine tools and CMM structures , 1999 .

[10]  Hui Liu,et al.  Study on the effects of changes in temperature-sensitive points on thermal error compensation model for CNC machine tool , 2015 .

[11]  Jun Ni,et al.  Accuracy enhancement of a horizontal machining center by real-time error compensation , 1996 .

[12]  Andrew Honegger,et al.  Analysis of thermal errors in a high-speed micro-milling spindle , 2010 .

[13]  A. Palmgren.  Ball and roller bearing engineering , 1945 .

[14]  Xuesong Mei,et al.  Investigation into effect of thermal expansion on thermally induced error of ball screw feed drive system of precision machine tools , 2015 .

[15]  T. A. Harris,et al.  Rolling Bearing Analysis , 1967 .

[16]  Takamasa Suzuki,et al.  Real-Time Estimation of Ball-Screw Thermal Elongation Based upon Temperature Distribution of Ball-Screw , 2004 .

[17]  M A. Donmez,et al.  A Novel Cooling System to Reduce Thermally-Induced Errors of Machine Tools☆ , 2007 .

[18]  Hui Liu,et al.  Robust modeling method for thermal error of CNC machine tools based on ridge regression algorithm , 2017 .

[19]  Zhijun Wu,et al.  THERMAL STRUCTURE DESIGN AND ANALYSIS OF A MACHINE TOOL HEADSTOCK , 2013 .

[20]  Hongqi Li,et al.  Integrated Dynamic Thermo-Mechanical Modeling of High Speed Spindles, Part 1: Model Development , 2004 .

[21]  Yang Jianguo,et al.  Simulation of thermal behavior of a CNC machine tool spindle , 2007 .

[22]  Haitong Wang,et al.  A Temperature Sensor Clustering Method for Thermal Error Modeling of Heavy Milling Machine Tools , 2017 .

[23]  T. A. Harris,et al.  Tribological Performance Prediction of Aircraft Gas Turbine Mainshaft Ball Bearings , 1998 .

[24]  Alexander Verl,et al.  Correlation between feed velocity and preloading in ball screw drives , 2010 .

[25]  Jean-Pierre Kruth,et al.  Linear regression and neural net models applied to thermal error compensation in machine tools , 1999 .

[26]  Hui Jiang,et al.  Machine tool thermal error modeling and prediction by grey neural network , 2012 .

[27]  Marnix Nuttin,et al.  Compensation of thermal deformations in machine tools with neural nets , 1995 .

[28]  Sun-Kyu Lee,et al.  Effect of thermal deformation on machine tool slide guide motion , 2003 .

[29]  John C. Ziegert,et al.  Neural network thermal error compensation of a machining center , 2000 .

[31]  Jun Ni,et al.  Dynamic neural network modeling for nonlinear, nonstationary machine tool thermally induced error , 2005 .

[32]  Yuliang Wu,et al.  Physically based modeling method for comprehensive thermally induced errors of CNC machining centers , 2018 .

[33]  Chun-Hong Park,et al.  Estimation of friction heat in a linear motion bearing using Box–Behnken design , 2017 .

[34]  James B. Bryan,et al.  International Status of Thermal Error Research (1990) , 1990 .

[35]  Jie Zhu,et al.  Robust Thermal Error Modeling and Compensation for CNC Machine Tools. , 2008 .

[36]  Jeffrey L. Stein,et al.  Model error compensation for observer design , 1998 .

[37]  Eckart Uhlmann,et al.  Thermal Modelling of a High Speed Motor Spindle , 2012 .

[38]  Hossam A. Kishawy,et al.  Effect of coolant strategy on tool performance, chip morphology and surface quality during high-speed machining of A356 aluminum alloy , 2005 .

[39]  Tiejun Zhu,et al.  Modeling and compensation for spindle's radial thermal drift error on a vertical machining center , 2016 .