High-speed Spindle System Research Articles

Research on the nonlinear resonance response of the high-speed spindle system supported by preloaded ball bearings

Research on the nonlinear resonance response of the high-speed spindle system supported by preloaded ball bearings

Digital twin–driven causal diagnosis mechanism for life health of high-speed spindle system

Digital twin–driven causal diagnosis mechanism for life health of high-speed spindle system

Analysis and experimental research of transient temperature rise characteristics of high-speed cylindrical roller bearing

In this paper, on one hand, the time-varying characteristics of the heat source and thermal boundary conditions of the high-speed spindle system were analyzed considering the thermal-structural coupling effect. And a transient bearing temperature field prediction method combining the thermal network method and finite element method was proposed. Furthermore, the relationships between time step, calculation efficiency and calculation results were analyzed. On the other hand, a online real-time monitoring system of the transient temperature of the cylindrical roller bearing inner ring for maximum speed of 13,000 r/min was designed and implemented using fibre optic sensing technology. Comparing with the conventional static thermal analysis results, it is verified that the simulation method proposed in this paper has higher accuracy. This paper provides a new approach for analysing and testing the thermal characteristics of high-speed spindle system.

Thermal Property Analysis of Precision Machinery and Its Thermal Error Compensation

The machining error caused by the thermal deformation of machines or tools accounts for half or even more in the total error, and the machining precision could be improved by stabilizing the heat balance of the process system. However, few of the existing studies have concerned about the thermal deformation law caused by the high-speed self-feed spindle system that could meet the performance requirements of high-speed cutting in precision machining, therefore, it’s of great necessity to study the thermal properties of precision machinery. For this reason, this paper took the precision machinery with a high-speed self-feed spindle system as the subject to study its thermal properties and thermal error compensation. At first, this paper introduced the composition of the precision machining control system and analyzed the thermal properties of the subject. Then, the heat source and heat exchange forms of the precision machinery were analyzed, the thermal intensity of the internal and external heat sources during the machining process was calculated, and the corresponding thermal boundary conditions were given. After that, this paper divided the heat sources of the subject during high-speed cutting into two types: internal heat source and external environment heat source, and carried out analysis. Moreover, this paper gave the structure of a thermal error and temperature synchronous measurement system for precision machinery, integrated the features of the thermal error data of two groups of high-speed cutting process, and built a thermal error compensation model based on the Bayesian network. At last, experimental results verified the effectiveness of the model.

An improved thermal performance modeling for high-speed spindle of machine tool based on thermal contact resistance analysis

The temperature field distribution has a significant influence on structural performance, thermal deformation, and thermal error compensation. To improve the prediction accuracy of the temperature distribution of the spindle system, a comprehensive model considering the contact thermal resistance (TCR) of the interfaces was established to analyze the thermal performance of the high-speed spindle system in the present work. An elastoplastic contact model was used to calculate the contacting areas and loads of interfaces, which were employed to establish the contact thermal resistance model of the primary interfaces of the spindle, such as bearing rings and tool holders. Based on the TCR parameters, a finite element analysis (FEA) model was proposed to analyze the temperature distribution of the spindle system. And a temperature test experiment was set up to verify the accuracy of the FEA model. The results show that the relative errors of representative test points were all less than 5%, which means the established model can appropriately reflect the temperature field distribution of the spindle.

An analysis of a thermally affected high-speed spindle with angular contact ball bearings

This paper discusses thermal effects on bearing stiffness, and consequently, the natural frequencies of a high-speed spindle system. Heat is generated due to friction torque at the contacts between the raceways and the balls of the angular contact ball bearings. In our experimental spindle system, the heat sources included six bearings and a built-in motor. Five-by-five bearing stiffness matrices were computed based on the thermal-mechanical parameters. The stiffness matrices were used as inputs for a finite element model generated in the ANSYS Workbench environment, in which the bearings were simulated as bushing joints, to compute frequency response numerically. The simulated results showed that the third natural frequencies decreased with increasing temperature and were in good agreement with the experimentation.

The influence of rolling bearing parameters on the nonlinear dynamic response and cutting stability of high-speed spindle systems

Abstract In modern industry, thinner, lighter, curved and complex-surface work-pieces are playing a more and more important role in mechanical assemblies. Therefore, the quality and the machining precision requirements of the work-pieces are also getting higher and higher. In order to get higher machining accuracy and stability, the simplified nonlinear factors should be considered. In this paper, a five-degrees-of-freedom (five-DOF) model of angular contact ball bearings and a complete high-speed dynamic model with the combination of spindle-holder-tool joints are established. The laws of bearing characteristic parameters changing with pre-load and bearing speed are analyzed including contact angle, normal contact force and axial deformation. Finally, the nonlinear characteristic influences of high speed on angular contact ball bearings are introduced into the whole spindle system in the form of bearing parameters, furthermore, the nonlinear dynamic responses and stability influences of high-speed spindle system at bearing and tool point are studied. The results provide a theoretical basis and an evaluating criterion for nonlinear stability prediction and product surface quality improvement.

Thermally affected stiffness matrix of angular contact ball bearings in a high-speed spindle system

Bearing stiffness directly affects the dynamic characteristics in a high-speed spindle system and plays an important role in terms of manufacturing quality. We developed a new approach for predicting the thermal behavior of a high-speed spindle, calculated the thermal expansion, and generated a bearing stiffness matrix for angular contact ball bearings. The heat convection of spindle housing in air, the balls in lubricant, the spindle shaft in quiescent air, and the bearing inner ring surfaces were determined. Heat sources such as bearing friction, and the heat contributed by the built-in motor, were simulated using an analysis systems (ANSYS) steady-state thermal model. The results were imported into a static ANSYS structural model. Ball thermal expansion was calculated based on changes in the coordinates of nodal points on the ball surface. Finally, a thermally affected bearing stiffness matrix was generated by applying the Newton–Raphson technique. Decreases in the bearing radial, axial, angular, and coupling stiffness values as rotational spindle speed increased were calculated. Also, the stiffness coefficients at a specific speed increased significantly caused by the thermal effects. Finally, for validation, the bearing stiffness was compared to that calculated using an earlier thermal network approach.

Prediction of Temperature Distribution of the Spindle System by Proposed Finite Volume and Element Method

High-speed machining is one of the emerging cutting processes possessing tremendous potential in the arena of increased metal removal rates as well in achieving improved surface finish, burr-free edges, dimensional accuracy and a virtually stress-free component after machining. However, as known the performance of a machine tool depends on a number of factors of which the most important is the thermal behavior of the high-speed spindle. Thus, the temperature rise and the displacement due to temperature variation in the spindle components will severely affect the thermal characteristics of high-speed motorized spindle. Hence, it is significant to study its thermal behavior, and so in this paper, a coupled fluid–thermal (CFT) of a high-speed spindle is developed to simulate fluid-structural conjugate heat transfer. Based on the proposed model, the thermal characteristic of the high-speed spindle system is studied. The investigation revealed that the proposed CFT analysis for the motor cooling path has shown a minimum deviation in spindle temperature approximating to 7.6% when compared with that of attained experimental results at high speed.

Thermal-structure interaction characteristics of a high-speed spindle- bearing system

Abstract The neglection of thermal-structure interaction of high-speed spindle system may lead to the modeling error of the thermal characteristics. To improve the modeling accuracy, the thermal-structure interaction mechanism was analyzed and the closed-loop iterative modeling method of thermal characteristics was proposed to modify the heat sources and thermal boundary conditions of the spindle system in each substep. The heat generation of bearings and built-in motor, the convective coefficients and the thermal contact resistances (TCRs) of bearing joints were computed. The heat generation of bearings was calculated by the SKF bearing thermal model and the results were compared with that obtained by integral method. The heat generation of bearings was modified by considering the combined effect of the lubricant viscosity variation and thermally-induced preload of bearings. Moreover, a novel geometrical-mechanical-thermal model for TCRs was proposed by characterizing the rough surface morphology and by establishing the multi-scale contact mechanics of joint surfaces. To validate the effectiveness of the proposed method, the thermal characteristic experiments of the spindle system were conducted under different rotational speeds. The results showed that the modeling errors in the temperature field and thermal deformation are reduced significantly and that this model has the ability of thermal error compensation.

DOE-FEM based design improvement to minimize thermal errors of a high speed spindle system

Thermal error caused by the thermal deformation is one of the most important concerns influencing the accuracy of machine tools. In this investigation, a thermal-structure model is developed by the finite element method (FEM) to effectively simulate thermal characteristics for predicting the transient temperature field and thermal deformation of a high speed spindle system. The FEM predictions were then compared against the measured temperatures and deformations at the tool center point (TCP) for model validation. Since the machining error must be estimated to achieve high quality and precision of machining products, this study applied the design of experiment (DOE) method to predict machining errors. The Pearson’s correlation analysis showed that the temperatures measured from the specific detection points were more significant than those from other points on the machining errors. The regression model was satisfactory to forecast the response variables formed by MATLAB. Alternatively, the significance of factors and the fitness of the designed model were verified by the ANOVA and residual analyses in conjunction with the collinearity diagnostics. The implementation of this model in the machine tool under study is expected to greatly reduce its thermally induced deformation up to 96.5% in composite working conditions for a spindle system.

Thermal energy balance control model of motorized spindle system enabling high-speed dry hobbing process

High-speed dry hobbing has been confirmed as a dominant advanced technique for gear machining due to its outstanding performance in terms of high productivity and environmental friendliness. The motorized spindle system is the key component of the high-speed dry hobbing machine, and its thermal stabilization is of significant importance for the machining precision. However, due to the integration of motor and spindle, the adoption of high cutting speed and the heavy cutting load, thermal energy will accumulate in the motorized spindle system and result in thermal deformation and stability degeneration, which eventually affects the consistency of hobbing accuracy. In this paper, an analytical model is proposed to control the thermal energy balance of a high-speed dry hobbing spindle system by optimizing the thermal energy accumulation with the hob rotation speed, hob axial feed rate, cooling water flow rate and the compressed air temperature. The optimal solution is obtained by solving the proposed optimization model with the simulated annealing method. A motorized spindle system is introduced as a case study and the experimental results indicate that the maximum value of the average temperature of the motorized spindle system is reduced from 39.6 °C to 35.0 °C, an 11.6% margin, and the material removal time is reduced from 2.07 min to 1.06 min, a 48.8% margin, under the optimal condition. Moreover, the average runout value of a hobbed workpiece is effectively controlled, by a 15.7% margin. Therefore, the presented optimization model can give a reference for the selection of suitable process parameters for thermal stability control and higher machining productivity and accuracy.

Online Dynamic Balance Technology for High Speed Spindle Based on Gain Parameter Adaption and Scheduling Control

Unbalance vibration is one of the main vibration forms of a high speed machine tool spindle. The overlarge unbalance vibration will have some adverse effects on the working life of the spindle system and the surface quality of the work-piece. In order to reduce the unbalance of a high speed spindle system, a pneumatic online dynamic balance device and its control system are presented in the paper. To improve the balance accuracy and adaptation of the balance system, the gain parameter adaption and scheduling control method are proposed first, and then the different balance effects of the influence coefficient method and the gain scheduling control method are compared through many dynamic balance experiments of the high speed spindle. The experimental results indicate that the gain parameters can be changed timely according to the transformation of the speed and kinetic parameters of the spindle system. The balance accuracy can be improved for a high speed spindle with time-varying characteristics, based on the adaptive gain scheduling control method.

Thermal error compensation of high-speed spindle system based on a modified BP neural network

The accuracy, convergence performance, and robustness of the thermal error model based on traditional artificial neural networks (ANNs) are poor because the model is sensitive to the training data. To improve these performances, the genetic algorithm (GA) and particle swarm optimization (PSO) were used to optimize the parameters of ANNs with back propagation (BP) algorithm, such as the number of neurons in the hidden layer, initial weights, and thresholds. Moreover, the fuzzy cluster grouping and correlation analysis were combined to group and optimize the typical temperature variables to guarantee the robustness of the thermal error models based on BP, GA-BP, and PSO-BP neural networks. Then, thermal error compensation experiments were conducted on the spindle system of a precision jig borer, and the machining accuracy was increased from 67 to 78 % for the GA-BP model and 89 % for the PSO-BP model, respectively. To validate the effectiveness of the thermal error measurement, modeling, and compensation methods, the test samples were machined and the surface quality of the machined parts was measured. By measuring the dimension error and the surface quality of the machined parts, the results showed that the machining error can be reduced and that the surface quality can be improved by the thermal error compensation. Moreover, the accuracy, convergence performance, and robustness of the thermal error model based on the traditional BP neural network can be improved greatly by GA and PSO.

Experimental and simulation study on the thermal characteristics of the high-speed spindle system

High-speed spindles often suffer from degeneration in its machining accuracy caused by the uneven distribution of temperature field. In order to improve the machining accuracy of high-speed spindles, a three-dimensional (3D) finite element analysis (FEA) model, which considered the combined effect of thermal contact resistance (TCR) and the change in heat power and stiffness caused by thermal displacements of bearing components on the accuracy of simulation results, was proposed to conduct transient thermal-structure analysis of high-speed spindles. The predictive model for TCR was proposed based on the fractal theory to characterize the rough surface morphology with disorder, self-affinity and non-stationary random features. And a contact mechanics model was developed to consider the influence of asperities’ deformation on TCR. The thermal-structure model of bearing was proposed to calculate the heat power and stiffness based on the quasi-static mechanics analysis. The FEA model proposed in this paper was used to simulate the temperature field distribution and thermal deformations of the high-speed spindle system. Then thermal characteristic experiments were conducted to validate the effectiveness of this model. The results showed that the FEA model was much more accurate than the traditional model which ignored the above two important factors. The temperature field and thermal errors of the spindle system were analyzed.

Non-contact electromagnetic exciter design with linear control method

A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations: constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.

Effect of recess configuration on the performances of high-speed hybrid journal bearing

Purpose The purpose of this paper is to study the influences of recess configurations on the performances of high-speed hybrid journal bearing. Hybrid journal bearing earns increasing attention in high-speed machine tool spindle owing to its intrinsic outstanding performances of low temperature rise and high stability. Design/methodology/approach To investigate the coupled effects of temperature, turbulence and the interaction between lubricant and journal/bearing bush, a thermal fluid-structure interaction approach is presented and validated by the experimental results. Findings Ladder-type recess has excellent tribological characteristics in decreasing temperature rise, improving stability and inhibiting cavitation, which are all beneficial to improve the performances of high-speed spindle system. Originality/value This work can be a valuable guide for the future high-speed hybrid journal bearing design.

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

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 algorithm–back 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 µm. 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.

Stability-based selection of cutting parameters to increase material removal rate in high-speed machining process

The reasonable selection of cutting parameters is of great significance to improve the productivity in high-speed machining process. In this article, a stability-based selection method of cutting parameters is proposed to increase material removal rate in high-speed machining process. First, the coupled dynamics of the high-speed spindle system and machining process is modeled. Then, the interaction mechanism between the spindle-tool system and the cutting process is investigated. Based on the process stability and surface quality of workpiece, a cutting parameter selection method is proposed from the perspective of machining stability. In order to select reasonable spindle speed and depth of cut, the lower bound of chatter stability lobe diagram and surface finish are taken as constraints, and the maximum material removal rate is set as the target. The proposed method is applied to the machining of the front face of a gearbox cover, which is made of Aluminum-7050. The axial depth of cut and spindle speed are chosen reasonably with the increase in machining efficiency by about 133%.

Simulation and experimental study on the thermally induced deformations of high-speed spindle system

In order to avoid the degeneration of high-speed spindle's machining accuracy in actual machining caused by the uneven distribution of temperature field at the design stage, a three-dimensional (3D) finite element analysis (FEA) model, which considered the combined influence of thermal contact resistance (TCR) and bearing stiffness on the accuracy of simulation results, was proposed to conduct transient thermal-structure interactive analysis of motorized spindles. And the method to calculate the boundary conditions used in the FEM model were discussed in detail, such as the heat loads, convective heat transfer, TCR and bearing stiffness. Based on the quasi-static mechanics analysis of rolling bearing, the transfer relationships among multiple variables in the equilibrium equation set of bearings were analyzed. Newton–Raphson algorithm, which regarded the contact angle as the iteration variable, was proposed to calculate the heat power and stiffness of bearings and improve the convergence of the algorithm, and the termination criteria of contact angle's searching trial calculation was proposed to improve the accuracy of the algorithm. The Weierstrass–Mandelbrot (W–M) function in fractal geometry was used to characterize the rough surface morphology of bearing rings. The fractal parameters were identified by the power spectrum method, and a contact deformation model of asperities was developed to calculate the contact parameters used in the TCR modeling. Then, the predictive model for TCR, which considered the combined effect of the morphology of bearing rings and the contact deformation of asperities, was proposed. Thermal equilibrium experiments were conducted to demonstrate the validity of the model. The results showed that the FEA model can accurately simulate the temperature field and thermal deformation of the spindle system and that the FEA model was much more accurate than the traditional thermal model of the high-speed spindle system which ignored TCR and bearing stiffness.