High-speed Machine Tools Research Articles

Design and damping characterization of sandwich composite made of particle-filled hollow spheres and steel sheets

Sandwich composites made of particle-filled hollow sphere structures (PHSS) and steel sheets offer excellent lightweight and damping properties, ideal for high-speed machine tool components under dynamic loads. Previous research has focused on single particle-filled hollow sphere (PHS) and small PHSS, leaving a gap understanding of PHSS/steel sandwich composites. In this study a test rig was developed, and Design of Experiments and Response Surface Analysis were used to investigate the effects of sheet and core thickness (design parameters), filling ratio, and particle size (particle parameters) on the damping performance of PHSS/steel sandwiches. The results indicate that the design parameters have a significant influence on damping performance. The interaction between design and particle parameters also substantially affects damping. Minimizing particle size, increasing filling ratio, thinning the face layer, and thickening the core layer significantly improve structural damping. To address manufacturing tolerances, a finite element (FE) model-based optimization was developed to accurately determine PHSS material parameters. These parameters were used in an FE model of the PHSS-steel composite, with identified contact parameters minimizing measurement and simulation differences. The homogenized material model and the linear model using global damping parameters accurately reproduce the dynamic properties of the PHSS-steel sandwich composite in low vibration modes.

A Review of Machine Tool Motorized Spindle Variable Pressure Preload Technology Research

High-precision spindles are a vital study topic because of the growing demand for highspeed, high-precision, reliable, and long-lasting machine tools. Bearing preload is the primary means of improving the accuracy of the spindle rotor system. This study aims to summarize the research results, systematically analyze and evaluate the machine tool motorized spindle variable pressure preload technology, and provide a scientific basis for the practical application of the motor spindle variable pressure preload technology. This study is an in-depth analysis of the basic principles of the electric spindle preloading technology, the study of its influence mechanism on the thermal deformation, stiffness, slewing error, and life of the spindle system, and a discussion of the current shortcomings in the field of spindle preloading to provide a reference for the subsequent optimization. In the spindle system, the performance of rolling bearings and the design of bearing preload have an important impact on the spindle's accuracy and stability. The traditional preload method has yet to meet the requirements of modern high-speed machine tools. Real-time controllable preload has become the new direction of development, but the current preload technology still has certain limitations and needs to be further improved. In the future, the spindle bearing variable pressure preload technology will be more efficient and intelligent.

High-Speed Steel Technology Substitution in Mining Machinery – an Experimental Study

The growth of mineral extraction in countries with a developed mineral resource sector under conditions of external restrictions requires the modernization of the domestic mining machinery – an indispensable condition of which is the replacement of technologies for the production of high-speed steels and machine tools. This research was aimed at experimental studies of microstructure, phase composition and microhardness distribution in the surface layer of the R6M5 high-speed steel samples after laser cutting, cold treatment and laser tempering. It was demonstrated that after laser cutting in the surface layer of the cut there was the carbide dissolution and enrichment of the metal matrix with carbon and alloying components, resulting in an increase of residual austenite content up to 50...60 %. After the cold treatment in liquid nitrogen the content of residual austenite decreased up to 7...9 %. The laser cut surface microhardness increased up to 1000...1100 MPa. At further laser tempering the dispersion hardening processes took place, as a result the V2C carbides appeared in the steel structure amounting to 4.7 %. The microhardness increased up to 10400...10600 MPa. The study showed the possibility of using the high-speed steel laser cutting not only as a separating operation, but also as a hardening treatment. The findings contribute to the technological support for the development of domestic mining machinery in terms of replacing imported high-speed steels and machine tools.

Methodic of design of technological complexes. Design of tools for high-speed machining

Within the framework of the developed methodic for designing of non-stationary technological complexes, a further decomposition of the tool development block is carried out with the workup of its structural design for the slipway processing of grooves for welding in the hull structures of underwater shipbuilding products. Keywords:non-stationary technological complexes, groove for welding, mathematical model, design methodology, components of cutting forces, tool diagram s.rusanovskiy@narfu.ru, m.khudyakov@narfu.ru

Coupling Study on Quasi-Static and Mixed Thermal Elastohydrodynamic Lubrication Behavior of Precision High-Speed Machine Spindle Bearing with Spinning

In this work, a modified numerical algorithm that couples the quasi-static theory with the mixed thermal elastohydrodynamic lubrication (mixed-TEHL) model is proposed to examine the mechanical properties and lubrication performance of the spindle bearing that is used in a high-speed machine tool with spinning. The non-Newtonian fluid characteristics of the lubricant and the non-Gaussian surface roughness are also considered. Moreover, the mechanical properties and lubrication state of the bearing are examined in various service environments. The results indicate that the temperature reduces the lubrication efficiency, which in turn exerts a significant impact on the mechanical properties. The lubrication that either behaves in the manner of Newtonian or non-Newtonian fluid has a relatively negligible influence on the bearing working state, while the non-Gaussian surface roughness significantly alters the oil film thickness and temperature. Calculations with different operating conditions demonstrate that the operating parameters (i.e., axial load, rotation speed) will directly affect the performance of the bearings via the changes in the oil film thickness and the temperature.

Recent Patents on Motorized Spindle Cooling Strategies

Abstract: High-speed motorized spindle is the core component of high-speed machining machine tools, and thermal error is the main factor affecting the machining accuracy of the motorized spindle. Reducing thermal error has become the most important research topic in the case of motorized spindles. The development status of the cooling strategy of the motorized spindle is explored, and the methods to improve the cooling efficiency of the motorized spindle are discussed. Some representative research results of the cooling strategy of motorized spindles at home and abroad are reviewed. Based on summarizing the related research results on cooling strategies for the core components, such as the stator, rotor and bearing of the motorized spindle, this paper analyzes the advantages and disadvantages of various cooling strategies and their applicable working conditions, and the future development direction of motorized spindle cooling strategies is discussed. The combination of various channel structures and the cooling strategy of the stator outer ring of the motorized spindle will improve the cooling efficiency of the motorized spindle, and research on the motorized spindle core cooling will become more and more important. In addition, the cooling system of the motorized spindle bearing, stator, and rotor can be improved at the same time, and the heating problem of the motorized spindle can be solved.

Research on High-Speed Vibration and Structure Optimization of Multiwire Sawing Machine

To improve the sawing stability and slicing quality of an existing multi-wire saw under severe vibrations using a high wire speed, its structure is optimized to improve its structural stiffness, so that it can still maintain good operation stability under higher wire speed. First, a finite element simulation model is established based on the shape, structural and material characteristics of the multi-wire saw, and then a transient dynamic simulation calculation is carried out using finite element software to obtain the vibration characteristics of the machine, which is verified with the measured data. The results show that the error between the calculated and the measured value is less than 11.46%, which verifies the accuracy of the simulation. On this basis, a multi-objective optimization design method based on the response surface is used to optimize the structure of the whole machine, and the optimized model is simulated again to evaluate its optimization effect. The results show that the amplitude of the optimized machine at a 2400 m/min wire speed is equivalent to that of the original machine at a 1500 m/min wire speed, and the wire speed is increased by 60% year-on-year with the same operation stability, which can guide research on high-speed multi-wire saws and machine tool vibration control strategies.

Design of a High-Speed Rotary Ultrasonic Machining Machine Tool for Machining Microstructure of Brittle Materials.

Aiming at the problems of low machining accuracy and more serious tool wear in the traditional diamond grinding machining (DGM) microstructure of hard and brittle materials, this paper proposes high-speed rotary ultrasonic machining (HRUM) technology and develops a HRUM machine tool. The hardware part of the machine tool mainly includes the spindle module, micro-motion system module, ultrasonic machining tank module, and data acquisition (DAQ) system module. The LabView-based controlled machining control system, including motion selection, initialization, coarse tool setting, constant force tool setting, control machining, and coordinate display module, is developed. Comparative experimental research of the HRUM and DGM of small holes in Al2O3 ceramics is carried out in the developed HRUM machine tool. The results demonstrate that HRUM effectively reduces axial cutting forces, reduces binder adhesion, and suppresses slippage while improving tool-cutting ability and extending tool life compared to DGM under the same machining parameters. This technology has essential research significance for the high-precision and efficient machining of microstructures in hard and brittle materials.

Evaluation of the Vibration Signal during Milling Vertical Thin-Walled Structures from Aerospace Materials.

The main functions of thin-walled structures-widely used in several industries-are to reduce the weight of the finished product and to increase the rigidity of the structure. A popular method for machining such components, often with complex shapes, is using milling. However, milling involves undesirable phenomena. One of them is the occurrence of vibrations caused by the operation of moving parts. Vibrations strongly affect surface quality and also have a significant impact on tool wear. Cutting parameters, machining strategies and tools used in milling constitute some of the factors that influence the occurrence of vibrations. An additional difficulty in milling thin-walled structures is the reduced rigidity of the workpiece-which also affects vibration during machining. We have compared the vibration signal for different approaches to machining thin-walled components with vertical walls made of Ti6Al4V titanium alloy and Inconel 625 nickel alloy. A general-purpose cutting tool for machining any type of material was used along with tools for high-performance machining and high-speed machining adapted for titanium and nickel alloys. A comparison of results was made for a constant material removal rate. The Short-Time Fourier Transform (STFT) method provided the acceleration vibration spectrograms for individual samples.

Intelligent Servo Tuning of High-Speed Machine Tools Using Circular Test

PID control and multi-loop control schemes are widely used in machine-tool computer numerical control servo systems. However, fast and efficient tuning methods for solving mismatches are uncommon. Servo mismatch is an important source of error owing to its effect on positioning accuracy. A circular test using a double ball-bar is used to access such errors. This study proposed a simple, model-free, and inexpensive approach without add-on measurement to solve the servo mismatch system by measurement of simultaneous movements in two axes. Based on the proposed features, our approach is established by iterative tuning using Lagrange interpolation polynomials for the position and velocity loops parameters. The system performance can be improved to iteratively minimize the mismatch of servo systems by tuning the servo parameters of multi-axis feed drive systems. The proposed approach is based on the linear scale signals of iterative circular tests, which avoids using expensive measurement instruments. The experimental results demonstrate the accuracy of feed drive system diagnosis and the performance improvement (mismatch is improved from 0.67 to 0.01ms).

A comparative study on structural analysis of 3-PRS Tri-Glide, 3-PRR and 3-PRS Tripod parallel kinematic machines for angular drilling applications

Parallel kinematic machines are a result of intensive research and development in the area of high speed machining (HSM). The high stiffness and low inertia characteristics of the parallel kinematic architecture make it suitable for high speed machine tool. This research aims to compare the structural characteristics of 3-DOF Tri-Glide and Tripod Parallel Kinematic Machines (PKMs) by varying the geometrical parameters of their links. Both solid and hollow tube structures are considered to evaluate the stiffness of the PKMs. Initially, mild steel is used for this comparative study. Later, mild steel is replaced by aluminium alloy due to its high strength to weight ratio. The 3PRS Tri-Glide, 3PRS and 3PRR Tripod models are modeled and analyzed using the Finite element software package ANSYS. Based on the structural analysis the results are compared and summarized.

Transient formation theory of air-microbubble oil and testing its oil-spraying mechanism

In oil–air lubrication systems, large numbers of air microbubbles are often included in the oil phase. However, the principles of microbubble formation in oil–air annular flow and their influencing factors remain uncertain, and previous conclusions regarding the effects of microbubbles on the viscosity properties of the lubricant oil are inconsistent. Thus, there is an urgent need for experimental verification. In this paper, a transient force balance model is established and used to ascertain the formation of air microbubbles in oil (AB-oil) for an oil–air annular flow. The stability of these microbubbles is analyzed using the Rayleigh–Plesset equation. Theoretical analysis shows that the microbubble radius is the key factor affecting the force balance and stability of microbubbles in oil. Experiments are conducted based on this theoretical analysis, and the void fraction of AB-oil is determined through image analysis to verify the principles and influencing factors of AB-oil formation in oil–air lubrication systems. The viscosity properties of AB-oil are then tested using a rheometer. The experimental results indicate that the formation of AB-oil is affected by oil viscosity, pipe range, oil feeding rate, and air pressure. AB-oil exhibit different viscosity properties at different shear rates and void fractions. Finally, the relationship between the void fraction and viscosity at different shear rates is determined from the experimental data. The outcomes of this research provide insights into the characteristics of oil–air lubrication systems for high-speed machine tool spindles.

Tool wear and surface roughness evaluation of mill insert tools in high-speed machining of Ti-6Al-4 V

The experiment carried out using high-speed machining (HSM) in this study is primarily focused on producing high-quality products and lowering the cost of production. To increase tool life and surface quality, HSM is a metal cutting method that priorities quick speeds and feed rates. Determining the appropriate machining and cutting settings that can produce the best results in terms of tool performance and surface qualities becomes essential in this way. Experiments using the L9 orthogonal array were conducted to determine the ideal responses for the Ti grade −5 alloy using a variety of variables, including cutting speed, feed rate, depth of cut, and stepover. By machining at a fast speed, the ultimate goal is to provide a superior surface finish and lengthen the tool life. According to the results of the machining, the cutting speed and stepover have a significant impact on the machining outcome. The optimal value of surface roughness Ra = 0.51 m is achieved with the following parameters: speed = 450 m/min, feed rate = 2100 mm/min, depth of cut = 0.3 mm, and stepover = 60 %. Confirmatory tests with a value of less than 10 % have verified the results. The conclusion being drawn that it is in strong agreement with the experimental results. The findings of this research reveal that the Taguchi technique is capable of analysing the advanced features of boundaries in HSM. This demonstrates the validity of the Taguchi methodology as a specialized model for addressing the issue of high-speed machining settings for titanium grade 5 alloy.

Toolpath interpolation with novel corner smoothing technique

• Propose a novel filter-based corner smoothing with double filter technique for CNC machining. • Derive analytical formulations for contour errors with satisfying kinematic constraints. • Design filter order and corner speed to ensure that acceleration, jerk and contour error. • Achieve higher machining efficiency and contour accuracy as compared to the state-of-art technique. In this study, a novel filter-based corner smoothing with double filter (FCSDF) technique is proposed to generate interpolated trajectories for high-speed machine tools. The technique uses a double filter to smooth segment junctions and limit axial jerk. The novelty of this study is to derive an analytical formulation for corner contour error and to find the relationship between corner speed and contour error. The FCSDF algorithm provides a systematic way to design filter order and to determine the corner speed to ensure that acceleration, jerk and contour error are confined. As a result, the technology can achieve both high machining accuracy and efficiency and is easy to implement in real time. Finally, the FCSDF is validated using a multisegment trajectory, and the experimental results verify the effectiveness in improving the contouring performance and cycle time.

Proposal of novel chatter-free milling strategy utilizing extraordinarily numerous flute endmill and high-speed high-power machine tool

This paper proposes a novel chatter-free milling strategy that utilizes the infinite stable area, i.e., area below the high-speed part of the 0-th lobe, which has not been generally utilized to date. In the conventional methodology, the stable pockets are utilized to realize a high axial depth of cut. However, these pockets tend to shift, e.g., due to long-term deterioration of the spindle, and hence they sometimes cannot be utilized effectively. The proposed strategy combines an extraordinarily numerous flute endmill, e.g., 20 flutes, and a high-performance spindle, e.g., capable of a spindle speed of 33000 min−1, installed on a high-speed high-power machine tool. By increasing the number of flutes, the stability lobes shrink in inverse proportion to that number against the spindle speed and the depth of cut, and the infinite stable area can be utilized in the practical spindle speed zone of recent machine tools. A design method is proposed for the cutting tool and the cutting conditions to utilize this area effectively. Analyses and experiments are conducted to verify the effectiveness of the proposed milling strategy. In the experiments, the material removal rate reaches 2904 cc/min at the spindle speed of 33000 min−1 and the axial depth of cut of 110 mm with no chatter vibration. The infinite stable area is capable of much higher stability and machining ability than the conventionally utilized stable pockets.

General-purpose controller for multiple types of magnetic bearing rotor systems

With the increasingly widespread application of magnetic bearings (MBs) in high-speed motors, turbomachinery, and machine tools, the development of magnetic bearing controllers (MBCs) is becoming increasingly significant. Conventional MBCs are designed specifically for a particular type of MB and have poor generality. Given this, an MBC with a digital signal processor (TMS320F28377S) as the core is developed. Meanwhile, a generality calculation method for the circuit module is proposed. The displacement conditioning circuit designed in this paper can match most MB displacement sensors, and the generality is improved to 91.66%. The designed power amplifier can realize the switching of two-level and three-level pulse width modulation (PWM). It can also realize the switching of unidirectional and bidirectional power amplifier control. Therefore, it can apply to most MB rotor systems, and the generality is improved to 66.67%. In addition, the proposed dual closed-loop control strategy based on linear active disturbance rejection control (LADRC) makes the system’s anti-interference capability, robustness and self-adaptive capability enhanced, further improving the generality of the controller. Simulation and experimental results show that the MBC is highly general and has good dynamic performance, and the electrical control system of the MB is optimized.

Performance of Multilayered Nanocoated Cutting Tools in High-Speed Machining: A Review

In machining processes, cutting tools play a dominant role in producing quality products. The quality of finished goods is directly related to the cutting tool condition. Several types of research have been carried out in cutting tool condition monitoring. On the other hand, the manufacturing industries should be aware of the cutting tool selection, operating conditions, and performance of cutting tools. This article emphasizes the performance of coated cutting tools and tool materials for various machining operations. Nowadays, the nanocoating of CNC tool inserts increases the wear resistance, vibration emissions, metal removal rate, etc. These coating techniques influence the manufacturing industry to increase the productivity and quality of the finished goods and reduce the machining cost. The performance of thin film multilayered coatings such as TiN, TiAlN, AlTiN, Ti, and TiCN on plain silicon carbide tool inserts is revealed by the researchers to guide the manufacturing industry for proper tool selection and standard machining inputs for metal removal operation. The influence of coating material such as TiBN, TiN, TiAlN, and CrAlSiN in cutting tools leads to increase the life time of the cutting tools, which decreases the material sticking and cutting forces. Titanium carbo nitride is wear-resistant and corrosion-resistant. Compared to TiCN, TiAlN is harder due to the higher hardness of 32 GPa. This article concludes the material selection based on the work piece material which yields good metal removal with less cutting forces. The article concludes the cutting material selection based on the work piece for machining operations.

A hybrid remaining useful life prediction method for cutting tool considering the wear state

Accurate cutting tool remaining useful life (RUL) prediction is of significance to guarantee the cutting quality and minimize the production cost. Recently, physics-based and data-driven methods have been widely used in the tool RUL prediction. The physics-based approaches may not accurately describe the time-varying wear process due to a lack of knowledge for underlying physics and simplifications involved in physical models, while the data-driven methods may be easily affected by the quantity and quality of data. To overcome the drawbacks of these two approaches, a hybrid prognostics framework considering tool wear state is developed to achieve an accurate prediction. Firstly, the mapping relationship between the sensor signal and tool wear is established by support vector regression (SVR). Then, the tool wear statuses are recognized by support vector machine (SVM), and the results are put into a Bayesian framework as prior information. Thirdly, based on the constructed Bayesian framework, the tool wear model parameters are updated iteratively by the sliding time window and particle filter algorithm. Finally, the tool wear state space and RUL can be predicted accordingly using the updating tool wear model. The validity of the proposed method is demonstrated by a high-speed machine tool experiment. The results show that the presented approach can effectively reduce the uncertainty of tool wear state estimation and improve the accuracy of RUL prediction.

Developing a Ball Screw Drive System of High-Speed Machine Tool Considering Dynamics

In order to provide guidance and reference for developing a ball screw drive system of the high-speed machine tool, this article investigates three basic issues with consideration of dynamics, including mechanical characteristics, inertia matching problem, and driving torque characteristics. The axial stiffness and natural frequency of the system are first calculated to verify the correctness of mechanical parts selection, and the stability of the system is ensured by designing an appropriate gain. vvNext, the inertia matching problem between the servo motor and load is analyzed based on the two-inertia-system, and the range of the inertia ratio is determined as an important principle in developing a ball screw drive system. The speed–torque characteristics are further discussed, and a graphical method is proposed to quickly and accurately determine a suitable servo motor. Finally, a complete flow is described, and the ball screw drive systems of a high-speed machine tool for aeroengine casing manufacturing are developed as an application. The actual test results of speed, accuracy, cutting ability, and machining performance indicate that the developed ball screw drive systems have a satisfactory performance, which validate the effectiveness of the comprehensive study.

Effects of oil recess structural parameters on comprehensive tribological properties in multi-pad hydrostatic thrust bearing for CNC vertical processing equipment based on low power consumption

Hydrostatic thrust bearings have been applied in high speed and heavy load machine tools because they provide superior characteristics such as higher positional accuracy, greater stability, and lower friction. The energy consumption of the fluid system exceeds 40% of the total energy consumption of the machine tools To reduce the energy consumption, it is usually necessary to optimize comprehensive tribological properties of multi-pad hydrostatic thrust bearing in CNC vertical processing equipment from the perspective of the oil recess structure. Effects of oil recess structural parameters on comprehensive tribological properties in multi-pad hydrostatic thrust bearing are investigated using CFD (Computational Fluid Dynamics) and lubrication theory. Focusing on this problem, this study comprehensively investigates the effects of oil recess shape, oil recess depth, land width on the tribological properties of hydrostatic thrust bearing using numerical simulation method. The relationships between the optimal comprehensive tribological properties and structural parameters are determined. An experimental rig is set up to verify the correctness of the numerical simulation method. The results indicate that to get an optimal comprehensive performance from hydrostatic bearing based on low power consumption, it is necessary to choose a proper of oil recess structural parameters.