Editorial

3 pages, 196 KiB

Open AccessEditorial

Editorial for the Special Issue on Advances in Ultra-Precision Machining Technology and Applications

by Benny C. F. Cheung and Jiang Guo

Micromachines 2022, 13(12), 2093; https://doi.org/10.3390/mi13122093 - 28 Nov 2022

Cited by 1 | Viewed by 1275

Ultra-precision machining technology has been widely used in the manufacture of many mission-critical components for various industrial areas, such as the advanced optics, photonics aerospace, automotive, telecommunications, biomedical and energy and environmental sectors, among others [...] Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

Research

Jump to: Editorial

14 pages, 6631 KiB

Open AccessArticle

Experimental Research and Multi-Physical Field Coupling Simulation of Electrochemical Machining Based on Gas–Liquid Two-Phase Flow

by Zhaolong Li, Wangwang Li and Ye Dai

Micromachines 2022, 13(2), 246; https://doi.org/10.3390/mi13020246 - 01 Feb 2022

Cited by 5 | Viewed by 1496

Abstract

In this paper, the forming mechanism of cooling hole electrolytic machining is studied using multi-physical field coupled simulation and experimental observation. A multi-physical field coupled simulation model was established to obtain the gas–liquid two-phase distribution law inside the machining gap, and a mathematical [...] Read more.

In this paper, the forming mechanism of cooling hole electrolytic machining is studied using multi-physical field coupled simulation and experimental observation. A multi-physical field coupled simulation model was established to obtain the gas–liquid two-phase distribution law inside the machining gap, and a mathematical model of gas–liquid two-phase flow was established to analyze the change law of the size and morphology of cooling hole electrolytic machining under different process parameter conditions. The simulation and experimental results show that the size of the inlet of the cooling hole is larger, the size of the outlet is smaller, and the middle section is more stable; machining voltage and electrode feed speed have a significant influence on the size and shape of heat dissipation holes. Compared with the experimental data, simulation accuracy is good. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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23 pages, 10247 KiB

Open AccessArticle

Analysis of Main Error Sources for the Error Motion Measurement of a Precision Shafting Using a T-Type Capacitive Sensor

by Kui Xiang, Wen Wang and Zichen Chen

Micromachines 2022, 13(2), 221; https://doi.org/10.3390/mi13020221 - 29 Jan 2022

Cited by 1 | Viewed by 1549

Abstract

As a key indicator reflecting the working accuracy of rotary functional units, the error motions of the precision shafting are very necessary to be measured. In this paper, the main error sources for the error motion measurement of a precision shafting using a [...] Read more.

As a key indicator reflecting the working accuracy of rotary functional units, the error motions of the precision shafting are very necessary to be measured. In this paper, the main error sources for the error motion measurement of a precision shafting using a T-type capacitive sensor were investigated. The theoretical modeling error due to the approximate simplification for the output capacitance expressions was firstly analyzed. By means of the 3D-FEA method, the influence of fringe effects was subsequently investigated. Finally, the analysis of electrode installation errors was emphasized on the tilt error of the cylindrical electrode and coaxiality error of the fan-shaped electrode by establishing mathematical models and numerical simulation. Based on the theoretical analysis and simulation results, the methods of decreasing the approximate error and the nonlinear error caused by fringe effects were subsequently proposed; for the installation errors, the tilt error of cylindrical electrode only makes the solution of phase angle have a certain deviation and has almost no effect on solving the radial displacement, especially for the measurement range less than 0.1 mm; the measurement of the rotor tilt displacement was basically not affected by the coaxiality error of the fan-shaped electrode. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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10 pages, 5009 KiB

Open AccessArticle

Integration of Multifocal Microlens Array on Silicon Microcantilever via Femtosecond-Laser-Assisted Etching Technology

by Bao-Xu Wang, Jia-Xin Zheng, Jin-Yong Qi, Ming-Rui Guo, Bing-Rong Gao and Xue-Qing Liu

Micromachines 2022, 13(2), 218; https://doi.org/10.3390/mi13020218 - 29 Jan 2022

Cited by 7 | Viewed by 2279

Abstract

Micro-opto-electromechanical systems (MOEMSs) are a new class of integrated and miniaturized optical systems that have significant applications in modern optics. However, the integration of micro-optical elements with complex morphologies on existing micro-electromechanical systems is difficult. Herein, we propose a femtosecond-laser-assisted dry etching technology [...] Read more.

Micro-opto-electromechanical systems (MOEMSs) are a new class of integrated and miniaturized optical systems that have significant applications in modern optics. However, the integration of micro-optical elements with complex morphologies on existing micro-electromechanical systems is difficult. Herein, we propose a femtosecond-laser-assisted dry etching technology to realize the fabrication of silicon microlenses. The size of the microlens can be controlled by the femtosecond laser pulse energy and the number of pulses. To verify the applicability of this method, multifocal microlens arrays (focal lengths of 7–9 μm) were integrated into a silicon microcantilever using this method. The proposed technology would broaden the application scope of MOEMSs in three-dimensional imaging systems. Full article

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11 pages, 3539 KiB

Open AccessArticle

Numerical Modeling of the Effect of Cutting-Edge Radius on Cutting Force and Stress Concentration during Machining

by Peng Li and Zhiyong Chang

Micromachines 2022, 13(2), 211; https://doi.org/10.3390/mi13020211 - 28 Jan 2022

Cited by 9 | Viewed by 2374

Abstract

Cutting is the primary method of material removal, and the quality of machined parts depends on the geometry of cutting tools. In this paper, a new cutting force coefficient model is established, revealing the influence of cutting-edge radius on the cutting process. The [...] Read more.

Cutting is the primary method of material removal, and the quality of machined parts depends on the geometry of cutting tools. In this paper, a new cutting force coefficient model is established, revealing the influence of cutting-edge radius on the cutting process. The effects of cutting-edge radius on the shear angle and cutting force components are analyzed by finite element simulations. A series of simulations is conducted, and the results show that with increased cutting-edge radius, the shear angle decreases nonlinearly, and the cutting force increases gradually. Additionally, the growth rate of the feed force caused by increasing the cutting-edge radius is higher than that of the tangential force. Furthermore, the stress concentration area of the machined surface extends from the surface to the subsurface as the cutting-edge radius increases. The results of this research show that changing the cutting edge affects the cutting force component, shear angle, and stress concentration range during the cutting process. These results provide a theoretical reference for predicting the residual stress in parts. Full article

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17 pages, 5354 KiB

Open AccessArticle

A Novel Updated Full-Discretization Method for Prediction of Milling Stability

by Junjin Ma, Yunfei Li, Dinghua Zhang, Bo Zhao, Geng Wang and Xiaoyan Pang

Micromachines 2022, 13(2), 160; https://doi.org/10.3390/mi13020160 - 21 Jan 2022

Cited by 8 | Viewed by 2103

Abstract

This paper presents an updated full-discretization method for milling stability prediction based on cubic spline interpolation. First, the mathematical model of the time-delay milling system considering regenerative chatter is represented by a dynamic delay differential equation. Then, in a single tooth passing period, [...] Read more.

This paper presents an updated full-discretization method for milling stability prediction based on cubic spline interpolation. First, the mathematical model of the time-delay milling system considering regenerative chatter is represented by a dynamic delay differential equation. Then, in a single tooth passing period, the time is divided into a finite time intervals, the state item and the time-delay item are approximated in each time interval by cubic spline interpolation and third-order Newton interpolation, respectively. Afterward, a transition matrix is constructed to represent the transfer relationship of the teeth in a period. Finally, based on Floquet theory, the milling stability lobes can be obtained. Meanwhile, in order to improve computational efficiency, an optimized method is proposed based on the traditional algorithm and the proposed method has high precision without losing high efficiency. Finally, several milling experiments are conducted to verify the accuracy of the proposed method, and the results show that the predicted results agree well with the experimental results. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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19 pages, 6154 KiB

Open AccessArticle

Influence of Some Microchanges Generated by Different Processing Methods on Selected Tribological Characteristics

by Gheorghe Nagîț, Laurențiu Slătineanu, Oana Dodun, Andrei Marius Mihalache, Marius Ionuț Rîpanu and Adelina Hriţuc

Micromachines 2022, 13(1), 29; https://doi.org/10.3390/mi13010029 - 26 Dec 2021

Cited by 5 | Viewed by 1991

Abstract

Different processing methods can change the physical–mechanical properties and the microgeometry of the surfaces made by such processes. In turn, such microchanges may affect the tribological characteristics of the surface layer. The purpose of this research was to study the tribological behavior of [...] Read more.

Different processing methods can change the physical–mechanical properties and the microgeometry of the surfaces made by such processes. In turn, such microchanges may affect the tribological characteristics of the surface layer. The purpose of this research was to study the tribological behavior of a test piece surfaces analyzing the changes on the values of the coefficient of friction and loss of mass that appear in time. The surfaces subjected to experimental research were previously obtained by turning, grinding, ball burnishing, and vibroburnishing. The experimental research was performed using a device adaptable to a universal lathe. Mathematical processing of the experimental results led to the establishment of power-type function empirical models that highlight the intensity of the influence exerted by the pressure and duration of the test on the values of the output parameters. It was found that the best results were obtained in the case of applying ball vibroburnishing as the final process. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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13 pages, 4185 KiB

Open AccessArticle

Study on the Mechanism of Solid-Phase Oxidant Action in Tribochemical Mechanical Polishing of SiC Single Crystal Substrate

by Wanting Qi, Xiaojun Cao, Wen Xiao, Zhankui Wang and Jianxiu Su

Micromachines 2021, 12(12), 1547; https://doi.org/10.3390/mi12121547 - 12 Dec 2021

Cited by 11 | Viewed by 2397

Abstract

Na₂CO₃—1.5 H₂O₂, KClO₃, KMnO₄, KIO₃, and NaOH were selected for dry polishing tests with a 6H-SiC single crystal substrate on a polyurethane polishing pad. The research results showed that [...] Read more.

Na₂CO₃—1.5 H₂O₂, KClO₃, KMnO₄, KIO₃, and NaOH were selected for dry polishing tests with a 6H-SiC single crystal substrate on a polyurethane polishing pad. The research results showed that all the solid-phase oxidants, except NaOH, could decompose to produce oxygen under the frictional action. After polishing with the five solid-phase oxidants, oxygen was found on the surface of SiC, indicating that all five solid-phase oxidants can have complex tribochemical reactions with SiC. Their reaction products are mainly SiO₂ and (SiO₂)x. Under the action of friction, due to the high flash point temperature of the polishing interface, the oxygen generated by the decomposition of the solid-phase oxidant could oxidize the surface of SiC and generate a SiO₂ oxide layer on the surface of SiC. On the other hand, SiC reacted with H₂O and generated a SiO₂ oxide layer on the surface of SiC. After polishing with NaOH, the SiO₂ oxide layer and soluble Na₂SiO₃ could be generated on the SiC surface; therefore, the surface material removal rate (MRR) was the highest, and the surface roughness was the largest, after polishing. The lowest MRR was achieved after the dry polishing of SiC with KClO₃. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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16 pages, 9624 KiB

Open AccessArticle

Modeling and Simulation of the Surface Generation Mechanism of a Novel Low-Pressure Lapping Technology

by Ninghui Yu, Lihua Li and Chea-su Kee

Micromachines 2021, 12(12), 1510; https://doi.org/10.3390/mi12121510 - 04 Dec 2021

Cited by 1 | Viewed by 2026

Abstract

Aluminum alloy (Al6061) is a common material used in the ultraprecision area. It can be machined with a good surface finish by single-point diamond turning (SPDT). Due to the material being relatively soft, it is difficult to apply post-processing techniques such as ultraprecision [...] Read more.

Aluminum alloy (Al6061) is a common material used in the ultraprecision area. It can be machined with a good surface finish by single-point diamond turning (SPDT). Due to the material being relatively soft, it is difficult to apply post-processing techniques such as ultraprecision lapping and ultraprecision polishing, as they may scratch the diamond-turned surface. As a result, a novel low-pressure lapping method was developed by our team to reduce the surface roughness. In this study, a finite element model was developed to simulate the mechanism of this novel lapping technology. The simulation results were compared with the experimental results so as to gain a better understanding of the lapping mechanism. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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17 pages, 45084 KiB

Open AccessArticle

Simulation, Modeling and Experimental Research on the Thermal Effect of the Motion Error of Hydrostatic Guideways

by Pengli Lei, Zhenzhong Wang, Chenchun Shi, Yunfeng Peng and Feng Lu

Micromachines 2021, 12(12), 1445; https://doi.org/10.3390/mi12121445 - 25 Nov 2021

Cited by 3 | Viewed by 1840

Abstract

Hydrostatic guideways are widely applied in ultra-precision machine tools, and motion errors undermine the machining accuracy. Among all the influence factors, the thermal effect distributes most to motion errors. Based on the kinematic theory and the finite element method, a 3-degrees-of-freedom quasi-static kinematics [...] Read more.

Hydrostatic guideways are widely applied in ultra-precision machine tools, and motion errors undermine the machining accuracy. Among all the influence factors, the thermal effect distributes most to motion errors. Based on the kinematic theory and the finite element method, a 3-degrees-of-freedom quasi-static kinematics model for motion errors containing the thermal effect was established. In this model, the initial state of the closed rail as a “black box” is regarded, and a self-consistent setting method for the initial state of the guide rails is proposed. Experiments were carried out to verify the thermal motion errors simulated by the finite element method and our kinematics model. The deviation of the measured thermal vertical straightness error from the theoretical value is less than 1 μm, which ensured the effectiveness of the model we developed. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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19 pages, 5958 KiB

Open AccessArticle

Knowledge-Driven Manufacturing Process Innovation: A Case Study on Problem Solving in Micro-Turbine Machining

by Dong Zhang, Gangfeng Wang, Yupeng Xin, Xiaolin Shi, Richard Evans, Biao Guo and Pu Huang

Micromachines 2021, 12(11), 1357; https://doi.org/10.3390/mi12111357 - 03 Nov 2021

Cited by 2 | Viewed by 2093

Abstract

Micromachining techniques have been applied widely to many industrial sectors, including aerospace, automotive, and precision instruments. However, due to their high-precision machining requirements, and the knowledge-intensive characteristics of miniaturized parts, complex manufacturing process problems often hinder production. To solve these problems, a systematic [...] Read more.

Micromachining techniques have been applied widely to many industrial sectors, including aerospace, automotive, and precision instruments. However, due to their high-precision machining requirements, and the knowledge-intensive characteristics of miniaturized parts, complex manufacturing process problems often hinder production. To solve these problems, a systematic scheme for structured micromachining process problem solving and an innovation support system is required. This paper presents a knowledge-based holistic framework that enables process planners to achieve micromachining innovation design. By analyzing innovation design procedures and available knowledge sources, an open multi-source Machining Process Innovation Knowledge (MPIK) acquisition paradigm is presented, including knowledge units and a knowledge network. Further, a MPIK network-driven structured process problem-solving and heuristic innovation design method was explored. Subsequently, a knowledge-driven heuristic design system for machining process innovation was integrated in the Computer-Aided Process Innovation (CAPI) platform. Finally, a case study involving specific process problem-solving and innovation scheme design for micro-turbine machining was studied to validate the proposed approach. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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15 pages, 6865 KiB

Open AccessArticle

Theoretical Modeling and Experimental Analysis of Single-Particle Erosion Mechanism of Optical Glass

by Zhongchen Cao, Shengqin Yan, Shipeng Li and Yang Zhang

Micromachines 2021, 12(10), 1221; https://doi.org/10.3390/mi12101221 - 06 Oct 2021

Cited by 5 | Viewed by 1618

Abstract

The study of the single-particle erosion mechanism is essential to understand the material removal mechanism in the non-contact polishing process and ultimately ensure the high-efficiency, non-damage, and ultra-smooth processing of optical glass. In this study, the theoretical model of smoothed particle hydrodynamics (SPH) [...] Read more.

The study of the single-particle erosion mechanism is essential to understand the material removal mechanism in the non-contact polishing process and ultimately ensure the high-efficiency, non-damage, and ultra-smooth processing of optical glass. In this study, the theoretical model of smoothed particle hydrodynamics (SPH) is established to reveal the dynamic removal process of a single particle impacting the optical glass. The single-particle erosion mechanisms, which include ductile–brittle transition, crack initiation, and propagation, are discussed in detail through theoretical simulation. A series of particle impact experiments are designed to validate the correctness of the SPH model. The experimental data show good agreement with the simulation results in terms of the depth and width of the eroded craters. Thereafter, the SPH simulation is conducted by studying the effect of various impact parameters, such as impact speed, impact angle, and abrasive diameter, on the material removal process. With the gradual increase of impact velocity and particle size, the material removal mode changes from plastic removal to brittle removal. Although the large impact velocity and particle size increase the material removal rate, they lead to the occurrence of brittle removal and reduce the surface and sub-surface quality. When the impact angle is between 45° and 75°, the material removal rate is the largest, and the increase of the material removal rate does not cause damage to the subsurface layer of the material. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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23 pages, 5440 KiB

Open AccessArticle

Dynamic Performance of Partially Orifice Porous Aerostatic Thrust Bearing

by Muhammad Punhal Sahto, Wei Wang, Ali Nawaz Sanjrani, Chengxu Hao and Sadiq Ali Shah

Micromachines 2021, 12(8), 989; https://doi.org/10.3390/mi12080989 - 20 Aug 2021

Cited by 2 | Viewed by 2098

Abstract

The aerostatic thrust bearing’s performance under vibration brings certain changes in stiffness and stability, especially in the range of 100 to 10,000 Hz, and it is accompanied by significant increase in fluctuations due to the changes in frequency, and the size of the [...] Read more.

The aerostatic thrust bearing’s performance under vibration brings certain changes in stiffness and stability, especially in the range of 100 to 10,000 Hz, and it is accompanied by significant increase in fluctuations due to the changes in frequency, and the size of the gas film damping. In this research work, an analysis is carried out to evaluate the impact of throttling characteristics of small size orifice on stiffness and stability optimization of aerostatic thrust bearings. There are two types of thrust bearing orifices such as: partial porous multiple orifice and porous thrust bearings and their effects on variations in damping and dynamic stiffness are evaluated. A simulation based analysis is carried out with the help of the perturbation analysis model of an aerostatic thrust bearing simulation by using FLUENT software (CFD). Therefore, two models of aerostatic thrust bearings—one with the porous and other with partial porous orifice are developed—are simulated to evaluate the effects of perturbation frequencies on the damping and dynamic stiffness. The results reveal a decrease in the amplitude of dynamics capacity with an increase in its frequency, as well as a decrease in the damping of partial porous aerostatic thrust bearings with an increase in the number of orifices. It also reveals an increase in the radius of an orifice with an increment of damping of bearing at the same perturbation frequency and, with an increase in orifice height, a corresponding decrease in the damping characteristics of bearings and in the dynamic stiffness and coefficient of damping of bearing film in the frequency range less than 100 Hz. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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18 pages, 5637 KiB

Open AccessArticle

Research on Multi-Physics Coupling Simulation for the Pulse Electrochemical Machining of Holes with Tube Electrodes

by Zhaolong Li, Bingren Cao and Ye Dai

Micromachines 2021, 12(8), 950; https://doi.org/10.3390/mi12080950 - 11 Aug 2021

Cited by 8 | Viewed by 2325

Abstract

Electrical parameters of the power supply are significant factors affecting the accuracy and stability of the electrochemical machining (ECM). However, the electric field, flow velocity and temperature in the machining area are difficult to measure directly under the influence of the power supply. [...] Read more.

Electrical parameters of the power supply are significant factors affecting the accuracy and stability of the electrochemical machining (ECM). However, the electric field, flow velocity and temperature in the machining area are difficult to measure directly under the influence of the power supply. Therefore, taking the film cooling hole as an example, the multi-physics coupling simulation analysis of the ECM is performed on the basis of Faraday’s law and fluid heat transfer mathematical model. The machining characteristics of the direct current and pulse ECM are compared through simulation. The results show that the pulse ECM improves the distribution of temperature and current density in the machining area. The period has little effect on the temperature, current density and side removal rate. The side removal rate increases with the increase of the duty ratio and lateral gap. Increasing of the duty ratio and decreasing of the lateral gap will increase the temperature and current density. Increasing the inlet pressure accelerates the frequency of renewal of heat and electrolysis products, which can reduce the single side gap. The experience of the ECM holes verifies the results of the simulation. The accuracy and stability of the ECM of holes are enhanced by optimizing the duty ratio, lateral gap and inlet pressure. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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14 pages, 4436 KiB

Open AccessArticle

Interaction Mechanism of Thermal and Mechanical Field in KDP Fly-Cutting Process

by Chenhui An, Ke Feng, Wei Wang, Qiao Xu, Xiangyang Lei, Jianfeng Zhang, Xuelian Yao and Haibo Li

Micromachines 2021, 12(8), 855; https://doi.org/10.3390/mi12080855 - 21 Jul 2021

Cited by 4 | Viewed by 1660

Abstract

As an important nonlinear optical material, potassium dihydrogen phosphate (KDP) crystal is used in high-power laser beams as the core element of inertial confinement fusion. It is the most general method of single point diamond fly-cutting (SPDF) to produce high precision and crack-free [...] Read more.

As an important nonlinear optical material, potassium dihydrogen phosphate (KDP) crystal is used in high-power laser beams as the core element of inertial confinement fusion. It is the most general method of single point diamond fly-cutting (SPDF) to produce high precision and crack-free KDP surfaces. Nevertheless, the cutting mechanism of such material remains unclear, and therefore needs further analysis. Firstly, the stress field, cutting force and cutting temperature under different working conditions are calculated by a KDP crystal cutting simulation model. Then, the rules and the cause of change and interaction mechanisms of force and temperature are analyzed by comparing the measurement experiments with simulations. Furthermore, the causes of chip formation and micro-cracks on the machined surface are analyzed based on thermo-mechanical coupling and chip morphology. The conclusion can be deduced: Although the temperature has not reached the phase transition temperature during the finishing process, under high cutting speeds and large unformed chip thickness, such as semi-finishing and roughing, the temperature can reach up to 180 °C or higher, and KDP crystals are very likely to phase transition—chip morphology also verifies this phenomenon. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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14 pages, 4690 KiB

Open AccessArticle

High-Precision Machining Method of Weak-Stiffness Mirror Based on Fast Tool Servo Error Compensation Strategy

by Zelong Li, Yifan Dai, Chaoliang Guan, Jiahao Yong, Zizhou Sun and Chunyang Du

Micromachines 2021, 12(6), 607; https://doi.org/10.3390/mi12060607 - 24 May 2021

Cited by 3 | Viewed by 2033

Abstract

Weak-stiffness mirrors are widely used in various fields such as aerospace and optoelectronic information. However, it is difficult to achieve micron-level precision machining because weak-stiffness mirrors are hard to clamp and are prone to deformation. The machining errors of these mirrors are randomly [...] Read more.

Weak-stiffness mirrors are widely used in various fields such as aerospace and optoelectronic information. However, it is difficult to achieve micron-level precision machining because weak-stiffness mirrors are hard to clamp and are prone to deformation. The machining errors of these mirrors are randomly distributed and non-rotationally symmetric, which is difficult to overcome by common machining methods. Based on the fast tool servo system, this paper proposes a high-precision machining method for weak-stiffness mirrors. Firstly, the clamping error and cutting error compensation strategy is obtained by analyzing the changing process of the mirror surface morphology. Then, by combining real-time monitoring and theoretical simulation, the elastic deformation of the weak-stiffness mirror is accurately extracted to achieve the compensation of the clamping error, and the compensation of the cutting error is achieved by iterative machining. Finally, a weak-stiffness mirror with a thickness of 2.5 mm was machined twice, and the experimental process produced a clamping error with a peak to valley (PV) value of 5.2 µm and a cutting error with a PV value of 1.6 µm. The final machined surface after compensation had a PV value of 0.7 µm. The experimental results showed that the compensation strategy proposed in this paper overcomes the clamping error of the weak-stiffness mirror and significantly reduces cutting errors during the machining process, achieving the high precision machining of a weak-stiffness mirror. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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16 pages, 3159 KiB

Open AccessArticle

An Investigation of the High-Frequency Ultrasonic Vibration-Assisted Cutting of Steel Optical Moulds

by Canbin Zhang, Chifai Cheung, Benjamin Bulla and Chenyang Zhao

Micromachines 2021, 12(4), 460; https://doi.org/10.3390/mi12040460 - 19 Apr 2021

Cited by 9 | Viewed by 2087

Abstract

Ultrasonic vibration-assisted cutting (UVAC) has been regarded as a promising technology to machine difficult-to-machine materials such as tungsten carbide, optical glass, and hardened steel in order to achieve superfinished surfaces. To increase vibration stability to achieve optical surface quality of a workpiece, a [...] Read more.

Ultrasonic vibration-assisted cutting (UVAC) has been regarded as a promising technology to machine difficult-to-machine materials such as tungsten carbide, optical glass, and hardened steel in order to achieve superfinished surfaces. To increase vibration stability to achieve optical surface quality of a workpiece, a high-frequency ultrasonic vibration-assisted cutting system with a vibration frequency of about 104 kHz is used to machine spherical optical steel moulds. A series of experiments are conducted to investigate the effect of machining parameters on the surface roughness of the workpiece including nominal cutting speed, feed rate, tool nose radius, vibration amplitude, and cutting geometry. This research takes into account the effects of the constantly changing contact point on the tool edge with the workpiece induced by the cutting geometry when machining a spherical steel mould. The surface morphology and surface roughness at different regions on the machined mould, with slope degrees (SDs) of 0°, 5°, 10°, and 15°, were measured and analysed. The experimental results show that the arithmetic roughness

S_{a}

of the workpiece increases gradually with increasing slope degree. By using optimised cutting parameters, a constant surface roughness

S_{a}

of 3 nm to 4 nm at different slope degrees was achieved by the applied high-frequency UVAC technique. This study provides guidance for ultra-precision machining of steel moulds with great variation in slope degree in the pursuit of optical quality on the whole surface. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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19 pages, 6443 KiB

Open AccessArticle

Multi-Field Coupling Dynamics Modeling of Aerostatic Spindle

by Guoda Chen and Yijie Chen

Micromachines 2021, 12(3), 251; https://doi.org/10.3390/mi12030251 - 01 Mar 2021

Cited by 10 | Viewed by 2887

Abstract

The aerostatic spindle in the ultra-precision machine tool shows the complex multi-field coupling dynamics behavior under working condition. The numerical investigation helps to better understand the dynamic characteristics of the aerostatic spindle and improve its structure and performance with low cost. A multi-field [...] Read more.

The aerostatic spindle in the ultra-precision machine tool shows the complex multi-field coupling dynamics behavior under working condition. The numerical investigation helps to better understand the dynamic characteristics of the aerostatic spindle and improve its structure and performance with low cost. A multi-field coupling 5-DOF dynamics model for the aerostatic spindle is proposed in this paper, which considers the interaction between the air film, spindle shaft and the motor. The restoring force method is employed to deal with the times varying air film force, the transient Reynolds equation of the aerostatic journal bearing and the aerostatic thrust bearing is solved using ADI method and Thomas method. The transient air film pressure of aerostatic bearings is obtained which clearly presents the influence induced by the tilt motion of the spindle shaft. The motion trajectory of the spindle shaft is obtained which shows different stability of the shaft under different external forces. The dynamics model shows good performance on simulating the multi-field coupling behavior of the aerostatic spindle under external force. which is quite meaningful and useful for the further research on the dynamic characteristics of the aerostatic spindle. Full article

(This article belongs to the Special Issue Advances in Ultra-Precision Machining Technology and Applications)

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