High Speed Machining Research Articles

Convection Heat Transfer Coefficient Regression Models Construction for Fast High-Speed Motor Thermal Analysis

This article proposes a computationally efficient thermal study method that substitutes computational fluid dynamics (CFDs) with a finite-element analysis (FEA) involving minimal loss of accuracy and omission of the increased computational load. The suggested technique contributes toward the realization of multiphysics optimization of high-speed electrical machines that effectively includes critical thermal evacuation phenomena. The strategy is regression-based and succeeds in constructing convection coefficient regression models that typically involve many variables and small training datasets. The proposed scheme is verified in high-loss density and high-speed outer rotor surface-mounted permanent magnet (SMPM) motor geometries that an optimization algorithm typically encounters during execution. The reference target specifications correspond to 20 kW output power, 15k r/min rotating speed, and 2 kHz electrical frequency.

Laser Beam Machining of Tungsten Alloy: Experimental and Numerical Analysis

Laser beam machining of various materials has found wide applications in the industry due to its advantages of high-speed machining, no tool wear and no vibration, precision and accuracy, low cost of machining, etc. Investigations into the laser beam machining of uncommon alloy are still limited and more research is needed in this field. In this paper, an analysis of the laser beam machining of tungsten alloy was performed, for cutting and drilling machining processes. First, an experimental analysis of microhardness and microstructure on the laser-cut samples was performed, and then the numerical simulation of the laser beam drilling process and its experimental validation was carried out. The experiments were carried out on a tungsten alloy plate of two different thicknesses, 0.5 and 1 mm. No significant changes in the microhardness, nor in the microstructure characteristics in the heat-affected zone (HAZ), were observed for the cutting conditions considered. A two-dimensional axisymmetric mathematical model for the simulation of the laser beam drilling process is solved by a finite volume method. The model was validated by comparing numerical and experimental results in terms of the size of HAZ and the size and shape of the drilled hole. Experimental and numerical results showed that HAZ is larger in the 0.5-mm-thick plate than in the 1-mm-thick plate under the same drilling conditions. Good agreement was observed between the experimental and numerical results. The developed model improves the understanding of the physical phenomena of laser beam machining and allows the optimization of laser and process parameters.

Modeling of the cutting front profile in abrasive water jet machining based on the energy balance approach

High-speed abrasive water jet machining (AWJM) is a universal tool for manufacturing engineering materials. However, the application of AWJM is greatly limited due to the jet lag value caused by the cutting front profile. This paper proposes a new method to predict jet lag values at different cutting depths. The novelty is that a simplified mathematical model of the cutting front profile is developed based on the energy balance theory. Two groups of experiments were conducted to investigate the influences of process parameters on the jet lag value and the dissipated energy during cutting. The numerical regression method is adopted to obtain the energy dissipation function, which has taken the key parameters such as material property, cutting depth, traverse speed, and the initial water jet energy into consideration. The predicted curves are compared with experimental results under different operating situations with the least value of R2 = 0.9136 and the maximum deviation in percent of 16% at the jet exit point. The proposed method contributes to further research on product distortion in abrasive water jet cutting.

Modeling of Traction Drive in Elastohydrodynamic Lubrication Contact and Traction Coefficient Enhancement Using Surface Texture Under High-Speed Conditions of up to 50,000 rpm

Abstract A high-speed electric motor with a small reducer that has high-power transmission efficiency can be used to realize a high-power-density powertrain system because electric motors can be miniaturized to increase the rotational speed. A traction drive has low vibration noise due to its lack of meshing vibration, making it suitable as a transmission element for high-speed reducers. However, the traction coefficient, which greatly affects transmission performance, decreases with increasing rotational speed. In this study, to increase the traction coefficient using a surface texture, a model that takes into account transient temperature changes under high-speed conditions and the effects of micro-surface geometry was developed. The traction coefficient was measured using a high-speed test machine capable of operating at a maximum speed of 50,000 rpm. The model was able to predict the experimental values with an error of at most 6%. The high-pressure rheological properties of the oil were examined to develop design guidelines for the surface texture and a model was used to optimize the texture parameters. The designed texture was manufactured and evaluated. Experimental results show that the traction coefficient can be improved by up to 19%.

Dynamic Splitting Tensile Behaviour of Concrete Confined by Natural Flax and Glass FRP.

Flax fibre has been used to reinforce concrete composite, but its dynamic properties have not been thoroughly studied. This study investigates the dynamic splitting tensile properties of plain concrete (PC) confined by flax-fibre-reinforced polymer (FFRP) and glass-fibre-reinforced polymer (GFRP). The dynamic splitting tensile tests were carried out on PC, FFRP-PC, and GFRP-PC cylinder specimens by the high-speed servo-hydraulic machine, with the impact-induced strain rates ranging from 0.1 to 58 s−1. The effect of the FRP confinement, FRP thickness and strain rate on the dynamic splitting tensile behaviour were assessed. The results indicated that similar confinement effectiveness of FFRP and GFRP is observed. The dynamic tensile strength of 1- and 2-layer FFRP-PC increased by 29% and 67%, and the one- and two-layer GFRP-PC increased by 32% and 84%, respectively. FFRP-PC and GFRP-PC cylinders showed less sensitivity to the strain rate compared with PC. The empirical relationship between the tensile DIF and strain rate for PC, FFRP-PC and GFRP-PC was proposed based on experimental data. The proposed model was developed to predict the dynamic splitting tensile strength. The results suggested the potential of FFRP composites applied into concrete structures under extreme dynamic loadings.

유한요소해석 모델을 이용한 스핀들 유닛의 열변형 예측

High-speed machining is essential in the manufacturing field, and it involves the removal of material through rotational and translational tool motion. Existing methods used for simulating the thermomechanical behavior of spindle systems in machining require extensive calculations owing to the geometry complexity and thermomechanical properties. This article presents a simplified model of an angular contact ball bearing and a simulation method for predicting the thermomechanical behavior of a spindle system. A commercially available software, ANSYS, was used to analyze the coupled behavior. The Matrix27 element was adopted to substitute the stiffness/damping characteristics of the angular contact ball bearing. Validated values of the thermal contact conductance for the contact option were adjusted to match the measured thermal characteristics of angular contact ball bearings. Experimental measurements of the temperature and deformation of a spindle were used to verify the simulated results for several preload conditions.

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.

Analysis and Performance Evaluation of a Novel Adjustable Speed Drive with a Homopolar-Type Rotor

The use of a magnetic adjustable speed drive is a popular choice in industrial settings due to its efficient operation, vibration isolation, low maintenance, and overload protection. Most conventional magnetic adjustable speed drives use various forms of the permanent magnets (PMs). Due to the PMs, this type of machine has continuous free-wheeling losses in the form of hysteresis and induced eddy currents. In recent years, the homopolar-type rotor has been widely used in high-speed machines, superconducting machines, and in the application of flywheel energy storage. This study proposes a new application of the homopolar-type rotor. A novel adjustable speed drive with a homopolar-type rotor (HTR-ASD), which has obvious advantages (no brush, no permanent magnet, and no mechanical flux regulation device), is designed and analyzed in this study. Its speed and torque can be adjusted only by adjusting the excitation current. Firstly, in this study, the structure, operation principles, and flux-modulated mechanism of the HTR-ASD are studied. The homopolar-type rotor has a special three-dimensional magnetic circuit structure with the same pole. The 3D-FEM is usually used to calculate its parameters, which is time consuming. In this study, an analytical method is developed to solve this issue. To analytically calculate the torque characteristics, the air gap magnetic flux density, and the winding inductance parameter, the equivalent circuit and the air gap permeance are researched to simplify the analysis. Then, the key parameters of the HTR-ASD are calculated. Finally, the performance of the HTR-ASD is comparatively studied using the analytical method and finite element method, and a comparison of the results is carried out. The comparison indicates that the analytical method is in good agreement with simulation results, and that it is very helpful for designing homopolar-type rotor machines. According to the analysis, the proposed adjustable speed drive displays a great performance in relation to the operating characteristics of a flexible mechanical speed drive.

Microstructure and Mechanical Properties of Steel and Ni-Based Superalloy Joints for Rotors of High-Speed Electric Motors.

High-speed electric motors, e.g., axially laminated anisotropic synchronous reluctance motors (ALA-SynRM), use a solid rotor manufactured by joining alternating layers of magnetic and non-magnetic metallic sheets. The strength of the dissimilar metallic joints is critical for the rotor’s ability to withstand the operating conditions of the high-speed electrical machine. In this work, various dissimilar metallic joint configurations that can be used in high-speed ALA-SynRM rotors are studied by analyzing the shear strength, microstructure, hardness, and composition of the joints. Metallic joints of structural steels and Inconel® alloys fabricated by vacuum brazing and hot isostatic pressing (HIP) are studied. Finite element analysis (FEA) was performed to calculate the maximum shear stress of the joints that were subjected to various high speed operating conditions. The shear strength of the test specimens was measured and compared with FEA results. The microstructure and chemical composition of the joints were studied by using optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) on SEM. The results show that the hot isostatic pressed S1100MC-IN718 joint achieved the highest ultimate shear strength (233.3 MPa) followed by vacuum brazed S355MC-IN600 joint (230.1 MPa) and HIP S355-IN718 (203.5 MPa), thereby showing that vacuum brazing and HIP can be viable manufacturing methods to fabricate a high-speed ALA-SynRM rotor.

Simulation of Toolpaths Using 3D Method Strategies for Complex Shape in Milling Application

Several strategies can be used for machining complex 3D shapes on a 3-axis CNC vertical milling machine in Autodesk Inventor Professional software. However, it is challenging to determine suitable strategies without guidance. Among the strategies involved are Scallop, Radial, Spiral, and Morphed Spiral. The purpose of this study is to compare the toolpaths strategy in terms of machining time by using high-speed machining parameters. A hemisphere shape and a fillet feature in the part are considered complex shapes due to their convex and concave surfaces. There are two step machining processes involved, which are roughing and finishing. Comparison time is focused on finishing the process using those strategies. Actual fixed machining parameters like tool diameter, feed rate, spindle speed, stepover, and cutting depth are used to make simulations of the toolpaths. Based on the simulation, the radial strategy has the shortest machining time and cutting length by more than fifty percent (50%) compared to other strategies. This is due to the fact that this technique generates passes along the arc's radii, which are subsequently projected down on the surfaces. The passes can be linked in a zig-zag pattern between the outer and inner radius, either from inside to outside or outside to inside. However, collisions between the cutting tool and the workpiece must be closely monitored. As a result, cutting length must also be addressed when deciding to use this strategy. In conclusion, high-speed machining with the right machining strategy is essential for increased productivity.

Automatic Foreground Detection at 784 FPS for Ultra-High-Speed Human–Machine Interactions

Human-machine interactive systems show increasing demand for analysing fast moving objects in high-frame-rate videos. Robust foreground detection, which is able to reduce large amount of redundant background data from high-frame-rate video, becomes the essence to achieve ultra-high-speed human-machine interactions. This paper proposes a local spatial propagation based background model generation, a local linear illumination correction based background model update, and a regional central coordinates and edge keypoints constrained foreground region reselection. The three proposals make up a robust and hardware-friendly foreground detection method. Experimental results prove that the proposed hardware-friendly algorithm achieves high accuracy and robustness on various kinds of challenging cases. Meanwhile, the hardware implementation utilizes little hardware resources and achieves realtime processing of high-frame-rate (784 frame/second) video with the delay less than 1 ms/frame in image processing core. In addition, a practical system is implemented by combing a PC, a high-speed camera and a field programmable gate array (FPGA) for realworld applications. This work will significatively promote the development and application of high-speed human machine interaction. A demo of the proposed vision system working at 784 FPS is available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://wcms.waseda.jp/em/5f84f75136a6</uri> . Note to Practitioners—This paper was motivated by the problem of high-frame-rate video contains large amount of redundant background pixels which makes ultra-high-speed human-machine interactions inaccessible. Existing approaches are mainly focused on designing complex background models, but processing speed, which is the most important issue for ultra-high-speed human-machine interactions, has received relatively little attention. This paper suggests a robust and hardware-friendly foreground detection algorithm which has been implemented as a hardware system by using an FPGA, a high-frame-rate camera, and a PC. We show that the hardware implementation utilizes less hardware resources and achieves real-time processing speed of 784 FPS with the delay less than 1 ms/frame in the image processing core. This work is a pioneering attempt of ultra-high-speed foreground detection, which will significatively speed up the wide applications of ultra-high-speed human machine interactions.

고속 모터의 토크 리플 및 효율 개선을 위한 고정자 구조에 대한 연구

Recently, the demand for electric motors for high-speed operation is increasing due to the development of hydrogen vehicles using fuel cells as well as electric vehicles. In particular, the Air Blower Motor is receiving a lot of attention as an electric motor for hydrogen vehicles, and there is a need for performance improvement research on high-power, high-speed machines. In this paper, a coreless model with stator tooth removed was studied and designed to design a high-performance, high-speed motor. The purpose of this study was to increase the specific power of the motor by reducing the core usage and improve the efficiency by reducing the loss by improving the iron loss. It was verified that the torque ripple and loss of the coreless model were improved through the Finite Elements Method (FEM).

Machinability and Chip Morphology Study of Inconel 740H and Haynes 282 for Advanced-Ultra Supercritical Applications

Abstract: High speed machining of Nickel based alloys has gained a lot of research interest since the last decade owing to their applications in areas like power generation, aerospace, marine propulsion, and nuclear reactors. For the realization of an advanced ultra-supercritical (A-USC) thermal plant, operating at service temperatures of about 700 to 760oC and pressures of around 24 MPa, the use of Nickel-based super alloys is indispensable. Some these parts used for the application may be required to be machined before use, although the machinability of these materials is relatively poor. Chip morphological studies are performed for better understanding of cutting force and surface finish of the alloys. In this work, authors have tried to study the effect of machining parameters like cutting speed, feed rate, rake angle, and nose radius on chip morphology like peak height, valley height, tooth height, tooth pitch, and segmentation frequency. The results of chip morphology studies indicate the need for saw tooth chips for better machining. Accordingly, Inconel 740H is found to have better machinability than Haynes 282 for the used range of machining parameters. Moreover, higher cutting speeds, lower feed rates, and positive rake angles are found to yield optimum conditions for an improved machinability

Linear Tool Path-Smoothing Method in High-Speed Machining Based on Error Feasible Area and Curvature Optimization

Linear tool path is widely used in high-speed NC machining. However, the geometrical discontinuity of the corner between the linear tool paths will lead to fluctuations in speed, acceleration and jerk, which can excite machinery vibration and reduce the machining efficiency and surface quality. To solve these problems, a novel corner smoothing method based on error feasible area and curvature optimization is proposed in this paper. Compared with most traditional corner smoothing methods using higher-order curves with all control points lying in the straight segment and inside of the tool path, the proposed method constructs B-spline transition curves with smaller curvatures to smooth the corners by reasonably distributing the curve control points inside and outside the straight line segment of the tool path (i.e., error feasible area). Furthermore, the corner transition curve is optimized by the minimum curve curvature extreme to improve the smoothness of the corner transition curve and reduce fluctuation in the kinematic profiles while respecting the G3 continuity (i.e., curvature-smooth), transition length limits and the uniqueness of curvature extremum. Finally, the simulation results show that the proposed method can reduce the curvature value and improve the smoothness of the curve and the minimum transitional velocity of the corner, which means that it can enhance machining efficiency and weaken machining vibration. The feasibility and effectiveness of the method are also verified.

Analysis of alternating flux density harmonics inside the rotor of a 1 MW high-speed interior permanent magnet synchronous machine used for flywheel energy storage systems

With the popularization of renewable distributed energy generation in the power grid, flywheel energy storage systems (FESS) with fast response and high power density are gradually becoming popular for achieving fast frequency modulation. Generally, the rotor of high-speed permanent magnet synchronous machine (HSPMSM) used for FESS rotates in a vacuum to reduce air friction loss, which concurrently makes it difficult to dissipate heat in the rotor. For reducing rotor iron loss and preventing demagnetization of the PM due to high temperature, effective measures need to be applied. In this study, a 1 MW 10,500 r/min high-speed interior PMSM (HSIPMSM) is proposed for an FESS. As rotor iron loss is caused by alternating flux density harmonics (FDH) inside the rotor, the causes and characteristics of alternating FDHs are analyzed. Then, the finite element analysis (FEA) is combined with two-dimensional fast Fourier transform (2D-FFT) to obtain the alternating frequencies and amplitude variation trends of alternating FDHs in the designed rotor. The analytical results indicate that the amplitudes of alternating FDHs on the PM surface are effectively reduced due to bypass of the rotor core at the outside of the PM to alternating FDHs, which helps to restrain the rotor iron loss from the source. This provides a design idea for mitigating the high temperature of high-power high-speed PM rotors.

Multi-Response Optimization during the High-Speed Drilling of Composite Laminate Using the Grey Entropy Fuzzy Method (GEF)

The machining of glass-fiber-reinforced composites is complex due to their heterogeneous structures. Research has indicated that high-speed machining, at high spindle speeds and feed rates, not only increases productivity but also reduces drilling defects, such as delamination. However, there are several challenges with high-speed machining, such as the heat generated during drilling between the drill tool and chip contact surfaces that can result in hole size errors. Therefore, it is essential to determine the optimum drilling parameters. This paper presents an innovative hybrid optimization approach called Grey Entropy Fuzzy. This approach is a combination of entropy-based weight integrated Grey Relation analysis and fuzzy logic. With the consideration of all responses simultaneously, an optimum machining combination was obtained at a spindle speed of 12,000 rpm and a feed rate of 0.02 mm/rev using a drill bit with a point angle of 118° and a drill diameter of 6 mm.

A transient cutting temperature prediction model for high-speed ultrasonic vibration turning

As a precision machining method, ultrasonic vibration cutting is widely applied for cutting difficult-to-machine materials due to the phenomena of cutting force and the decrease of cutting temperature when coolant is applied. However, the cutting efficiency is limited due to the existence of critical cutting speed of ultrasonic vibration cutting. Therefore, a high-speed ultrasonic vibration cutting (HUVC) method is proposed to realize high-efficiency machining with tool life prolongation and surface quality improvement. The key issue of these advantages is the decrease of cutting temperature within the cutting interfaces. Therefore, it is necessary to figure out the temperature decrease principles when ultrasonic vibration is added. In this paper, a transient cutting temperature prediction model is built to further investigate the mechanism of HUVC. In spite of the average cutting temperature, this model is mainly focused on the transient process. Firstly, the kinematics of HUVC is analyzed, based on which a cutting force model is built. Then, cutting heat is divided into heat generation in cutting duration and heat transfer in noncutting duration, which are then calculated respectively. After calculating the transient cutting heat, cutting temperature in the cutting interfaces is calculated through numeric iteration and integration in the time and space domain. At last, the accuracy of the proposed model is validated by measuring the average cutting temperature through a self-developed tool-workpiece thermocouple. The results demonstrate that the maximum error of this model is no larger than 14 %. Both cutting speed and duty cycle are key factors influencing the increase of cutting temperature in cutting duration and the decrease of it in noncutting duration. In this regard, this model is significant for cutting and vibration parameter setup to obtain an optimal tool life in high-speed machining by restraining the heat generation and enlarging the heat decrease.

Research on high-speed and high-precision laser processing algorithm based on macro-micro platform

Aiming at the problem that XY motion platform cannot realize high-speed and high-precision machining simultaneously, a high-speed and high-precision laser processing algorithm is proposed based on the macro-micro structure of laser cutter with a laser galvanometer scanner. The velocity planning of macro platform and composite motion is carried out by applying finite impulse response (FIR) filters three times, and velocity planning of micro platform is obtained by vector subtraction method. The motion decomposition of the macro-micro platform is realized accurately. The macro platform is responsible for large-format movement, and the micro platform is responsible for fast-speed turning. Velocity overlap of adjacent segments is employed to improve the machining efficiency. The constraints are established to determine the overlapping time, so that the algorithm can realize high-speed machining without introducing contour error, and ensure that the velocity, acceleration, and jerk of the macro platform can be processed within the limit range. Experiment and simulation analysis show that compared with using only the XY platform, the total machining time of using the macro-micro platform with the algorithm proposed in this paper is reduced by more than 35%.

Mathematical Modeling of Heating and Strain Aging of Steel during High-Speed Wire Drawing

In this article, a mathematical model of the wire’s average temperature change in the process of multiple drawing on high-speed straight-line drawing machines has been developed. The calculation results showed that the average temperature of the wire during a drawing at a speed of up to 45 m/s on straight-line drawing machines could reach 400 °C. Deformation heating of the wire during drawing does not exceed 60 °C, and heating due to sliding friction can reach 300 °C, depending on the friction coefficient, which ranges from 0.05 to 0.15. The average strain rates under the conditions of the modern high-speed drawing process reach 7000 s−1. Over the course of the research, it was found that there are no conditions for the occurrence of dynamic deformation aging due to impurity atoms of carbon, nitrogen and oxygen. At the same time, at the temperature and speed parameters of the high-speed wire drawing, conditions are created for the onset of the dynamic strain aging of steel in the presence of hydrogen atoms. Therefore, during heat treatment and pickling, it is necessary to exclude the hydrogenation of steel. It has been established that in order to exclude static strain aging of steel during drawing, it is necessary to prevent heating the wire above 180–200 °C.

Comparison of Heat Transfer Characteristics of the Hollow-Shaft Oil Cooling System for High-Speed Permanent Magnet Synchronous Machines

The rotor cooling poses a significant challenge for high-speed permanent magnet synchronous machines. This article presents a recirculating hollow-shaft oil cooling structure. Through the computational fluid dynamics (CFD) method, its convective heat transfer characteristics are studied in depth. Besides, the recirculating hollow-shaft cooling (RHSC) is compared with the direct-through hollow-shaft cooling (DHSC). Based on the CFD analysis, it is found that the convective heat transfer coefficient (CHTC) of the RHSC is higher than that of the DHSC, which can be as high as 58%. Furthermore, the advantage of the RHSC is most prominent at low rotational speed and small flow rate due to its relatively large oil friction loss at a high rotational speed. Moreover, the explanation for the fluctuation of the CHTC before the critical rotational speed, as well as the law of its variation with rotational speed and flow rate, are revealed in this study. The correctness of the simulation analysis is verified by experiments implemented on a rotor setup. In order to summarize the convective heat transfer law of the RHSC better, a dimensionless empirical equation is fitted finally.