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A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 21256

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Prof. Dr. Yuanliu Chen

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State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China
Interests: precision manufacturing and metrology
Special Issues, Collections and Topics in MDPI journals

Dr. Yang Zhang

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Department of Mechanical Engineering, Technical University of Denmark, Produktionstorvet, 427A, 2800 Kgs. Lyngby, Denmark
Interests: soft tooling; injection molding; laser machining; surface microstructuring
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Precision manufacturing and intelligent machine tools are of great importance in current and future industries. Precision manufacturing is an advanced manufacturing technique that can be used to produce parts composed of a variety of materials with high accuracy and surface/subsurface integrity to meet the requirements of astronomy, semiconductor, biomedicine, precision optics, etc. In the precision manufacturing of today and the future, both the achievable precision/accuracy and the productivity are of concern. The integration of manufacturing processes with intelligent sensors, software, and even intelligent algorithms, which form the basis for intelligent machine tools, provides the possibility of developing manufacturing processes with improved productivity and process capability. This developing trend has continuously enriched precision manufacturing. In this Special Issue of Applied Sciences, we will consider papers that present new technologies and significant contributions for the promotion of precision manufacturing and intelligent machine tools.

We are interested in contributions that focus on topics such as:

Micro/nanomachining and ultraprecision machining;
Precision replication processes;
Modeling and simulation for precision manufacturing;
Process planning for precision manufacturing;
Sensors for precision manufacturing;
Process monitoring and quality control for precision manufacturing;
Designing and building intelligent machine tools;
Intelligent manufacturing systems;
Innovative machine systems;
Atomic- and close-to-atomic-scale manufacturing.

Prof. Dr. Yuanliu Chen
Dr. Yang Zhang
Guest Editors

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Published Papers (13 papers)

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Research

19 pages, 6070 KiB

Open AccessArticle

A Hybrid Deep Learning Model as the Digital Twin of Ultra-Precision Diamond Cutting for In-Process Prediction of Cutting-Tool Wear

by Lei Wu, Kaijie Sha, Ye Tao, Bingfeng Ju and Yuanliu Chen

Appl. Sci. 2023, 13(11), 6675; https://0-doi-org.brum.beds.ac.uk/10.3390/app13116675 - 30 May 2023

Cited by 2 | Viewed by 1218

Abstract

Diamond cutting-tool wear has a direct impact on the processing accuracy of the machined surface in ultra-precision diamond cutting. It is difficult to monitor the tool’s condition because of the slight wear amount. This paper proposed a hybrid deep learning model for tool wear state prediction in ultra-precision diamond cutting. The cutting force was accurately estimated and the wear state of the diamond tool was predicted by using the hybrid deep learning model with the motion displacement, velocity, and other signals in the machining process. By carrying out machining experiments, this method can classify diamond-tool wear condition with an accuracy of more than 85%. Meanwhile, the effectiveness of the proposed method was verified by comparing it with a variety of machine learning models. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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16 pages, 6349 KiB

Open AccessArticle

Investigation of Angle Measurement Based on Direct Third Harmonic Generation in Centrosymmetric Crystals

by Kuangyi Li, Jiahui Lin, Zhiyang Zhang, Ryo Sato, Hiroki Shimizu, Hiraku Matsukuma and Wei Gao

Appl. Sci. 2023, 13(2), 996; https://0-doi-org.brum.beds.ac.uk/10.3390/app13020996 - 11 Jan 2023

Cited by 2 | Viewed by 1581

Abstract

This paper proposed angle measurement methods based on direct third harmonic generation (THG) in centrosymmetric crystals. The principles of the intensity-dependent and the wavelength-dependent angle measurement methods were illustrated. In this study, three prospective centrosymmetric crystals and two different phase-matching types were investigated in a wavelength range from 900 nm to 2500 nm. For the intensity-dependent method, a dispersion-less wavelength range was found from 1700 nm to 2000 nm for α-BBO and calcite. Compared with rutile, α-BBO and calcite had relatively better measurement performance based on the angle measurement sensitivity calculation. The wavelength-dependent method was considered in a dispersive range of around 1560 nm. The results suggested that α-BBO and calcite were also suitable for wavelength-dependent measurement. In addition, the effects of focusing parameters were considered in the simulation, and the optimized focal length (f = 100 mm) and the focused position (in the center of the crystal) were determined. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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12 pages, 10666 KiB

Open AccessArticle

Finite Element Analysis and Experimental Investigation of Tool Chatter in Ultra-Precision Diamond Micro-Milling Process

by Haijun Zhang, Shijin Lu, Chunyu Zhang, Guo Li, Fei Teng, Junjie Zhang and Tao Sun

Appl. Sci. 2022, 12(23), 11968; https://0-doi-org.brum.beds.ac.uk/10.3390/app122311968 - 23 Nov 2022

Cited by 1 | Viewed by 1133

Abstract

Ultra-precision milling with an aerostatic high-speed spindle and a single-crystal diamond micro-tool is promising for the fabrication of miniaturized complex parts. While tool chatter occurring in milling processes has a substantial effect on the machined surface formation, a fundamental understanding of the tool chatter behavior in ultra-precision milling is essentially required for achieving an ultra-high surface finish. In this paper, through a combination of finite element simulations and experimental validations, the machining mechanisms of the ultra-precision diamond micro-milling of a copper workpiece are revealed, in which the tool chatter behavior and its correlation with the machined surface morphology are emphatically studied. Specifically, the correlation between the tool chatter and the transient depth of cut is analytical established. Subsequently, we first establish a finite element model of diamond micro-milling with the consideration of milling tool deformation and material removal to reveal the tool chatter behavior during the milling process. Furthermore, a corresponding micro-milling experiment is also conducted to validate the simulation results in terms of the milling force, chip profile and morphology of machined surfaces. Finally, the effect of spindle speed on the milling process in particular tool chatter is investigated by FE simulations, through which a linear relationship between the spindle speed and microscopic roughness Rz of a machined surface is obtained. The research findings provide a theoretical basis for understanding the origination of tool chatter in the diamond micro-milling process, as well as the rational selection of machining parameters for suppressing the tool chatter. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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14 pages, 14461 KiB

Open AccessArticle

Research on Electrochemical Controllable Machining Technology of Small-Sized Inner Intersecting Hole Rounding

by Guibing Pang, Zhaobin Yan, Xiaofei Zhu and Shuangjiao Fan

Appl. Sci. 2022, 12(20), 10666; https://0-doi-org.brum.beds.ac.uk/10.3390/app122010666 - 21 Oct 2022

Viewed by 1307

Abstract

Small-sized inner intersecting holes are a common structure for large engine nozzles, hydraulic valves, and other parts. In order to ensure the uniform and stable fluid state in the intersecting hole, it is necessary to process the fillet at the intersecting line and accurately control the fillet radius. Limited by the structure and size, the rounding of the small-sized inner intersecting hole is a technical problem, and the traditional machining methods have problems, in terms of efficiency and accuracy. In order to solve this problem, electrochemical machining technology was applied to the rounding of small-sized inner intersecting holes. According to the structure of inner intersecting holes, an electrochemical rounding processing scheme with built-in fixed cathode was designed. The electric field distribution of different cathode shapes was analyzed using finite element method software. The influence of processing voltage and processing time on the current density distribution was studied for different cathode shapes, to determine the most reasonable cathode shape. Taking the inner intersecting hole with a diameter of 2 mm as the research object, and according to the analysis of the influence of processing voltage on the processing effect, a suitable control factor for controlling the rounding was processing time, and the optimal processing voltage was obtained. The formulas of fillet radius and processing time were obtained by regression analysis and verified using machining examples. The results provide a feasible method for the accurate and controllable machining of small-sized inner intersecting hole rounding. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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20 pages, 5558 KiB

Open AccessArticle

A Deformation Force Monitoring Method for Aero-Engine Casing Machining Based on Deep Autoregressive Network and Kalman Filter

by Haonan Guo, Yingguang Li, Changqing Liu, Yang Ni and Kai Tang

Appl. Sci. 2022, 12(14), 7014; https://0-doi-org.brum.beds.ac.uk/10.3390/app12147014 - 12 Jul 2022

Cited by 4 | Viewed by 1351

Abstract

Aero-engine casing is a kind of thin-walled rotary part for which serious deformation often occurs during its machining process. As deformation force is an important physical quantity associated with deformation, the utilization of deformation force to control the deformation has been suggested. However, due to the complex machining characteristics of an aero-engine casing, obtaining a stable and reliable deformation force can be quite difficult. To address this issue, this paper proposes a deformation force monitoring method via a pre-support force probabilistic decision model based on deep autoregressive neural network and Kalman filter, for which a set of sophisticated clamping devices with force sensors are specifically developed. In the proposed method, the pre-support force is determined by the predicted value of the deformation force and the equivalent flexibility of the part, while the measurement errors and the reality gaps are reduced by Kalman filter via fusing the predicted and measured data. Both computer simulation and physical machining experiments are carried out and their results give a positive confirmation on the effectiveness of the proposed method. The results are as follows. In the simulation experiments, when the confidence is 84.1%, the success rate of deformation force monitoring is increased by about 30% compared with the traditional approach, and the final impact of clamping deformation of the proposed method is less than 0.003 mm. In the real machining experiments, the results show that the calculation error of deformation by the proposed method based on monitoring the deformation force is less than 0.008 mm. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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21 pages, 6885 KiB

Open AccessArticle

Accurate Inner Profile Measurement of a High Aspect Ratio Aspheric Workpiece Using a Two-Probe Measuring System

by Peng Hu, Xin Xiong, Wen-Hao Zhang, Bing-Feng Ju and Yuan-Liu Chen

Appl. Sci. 2022, 12(13), 6628; https://0-doi-org.brum.beds.ac.uk/10.3390/app12136628 - 30 Jun 2022

Cited by 1 | Viewed by 1387

Abstract

This paper presents a novel method for inner profile measurement and geometric parameter evaluation, such as the radius of the bottom, steepness and straightness of the steep sidewall of a high aspect ratio aspheric workpiece, by utilizing a two-probe measuring system, which includes a lateral displacement gauge for the inner steep sidewall profile measurement and an axial displacement gauge for the inner deep underside profile measurement. To qualify the measurement accuracy, the systematic errors associated with the measurement procedure, including the miscalibration, misalignment and the roundness error of the gauge probes, as well as the slide motion error of the four-axis motion platform, are all evaluated and separated from the measurement results. A point cloud registration algorithm is employed to stitch the evaluated inner sidewall profile and the inner underside profile to form an entire inner profile of the workpiece. To verify the performance of the newly proposed method, the inner profile of a high aspect ratio aspheric workpiece, which has a tapered cone shape with a maximum inner radius of 40 mm, a maximum inner depth of 140 mm and a steep sidewall angle approaching 85°, is measured in experiments. The measurement result is compared with that of a coordinate measuring machine (CMM), and the comparison verifies the feasibility of the proposed measurement system. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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16 pages, 6061 KiB

Open AccessArticle

Intelligent Air Cutting Monitoring System for Milling Process

by Shih-Ming Wang, Chun-Yi Lee, Hariyanto Gunawan and Ren-Qi Tu

Appl. Sci. 2022, 12(9), 4137; https://0-doi-org.brum.beds.ac.uk/10.3390/app12094137 - 20 Apr 2022

Cited by 2 | Viewed by 1377

Abstract

This research proposes a method for auto-monitoring the air cutting condition of a machining process, so the air cutting time can be further improved to enhance the machining efficiency. A two-way data communication module with a CNC controller was established to achieve real-time monitoring and control function via TCP/IP protocol. The module enables the identification of the executing NC block and the cutting time during machining. The spindle load current and cutting vibration signals were used to on-line diagnose the cutting state (effective cutting or air cutting), and their associated NC codes were identified and recorded at the same time, based on the executing NC block in the CNC controller. An algorithm adopting this state change information to determine effective cutting time and air cutting time was developed and used to build an intelligent air cutting monitoring system, with a friendly human–machine interface. The system can detect air cutting time, effective cutting time, machine idle time, as well as the total machining time to improve the air cutting time to enhance the machining efficiency. Verification experiments were conducted, and the results showed the proposed method can accurately detect the air cutting occurrence and its associated NC blocks in the NC program. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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10 pages, 733 KiB

Open AccessArticle

Uniform Accuracy Lifetime Principle and Optimal Design Methods for Measurement Systems

by Zhenying Cheng, Liying Liu and Ruijun Li

Appl. Sci. 2022, 12(8), 3961; https://0-doi-org.brum.beds.ac.uk/10.3390/app12083961 - 14 Apr 2022

Viewed by 1164

Abstract

The accuracy of measurement instruments, as well as that of their components, gradually declines as time goes on. Due to different loss mechanisms and the allowable accuracy loss values, the accuracy lifetimes of a whole system and its components are generally nonuniform, which lead to the waste of resources and costs. In this paper, a novel design method based on the uniform accuracy lifetime principle is presented to avoid the waste of resources. After giving and determining the uniformity and accuracy loss weights, optimal design models are established, and the sequential quadratic programming (SQP) method is employed to solve the models. A design example is presented to verify the effectiveness of the design model and the solution method. Using this method, the minimum accuracy lifetime of the whole system extends from 73.07 weeks to 200 weeks, and the uniformity improves from 0.75 to 0.96. The proposed method can be used in practice to achieve the target of uniform accuracy lifetimes for measurement systems because it is easy for manufacturers to obtain the average loss velocities of different components. The implementation of the optimization method will greatly help to save resources and improve the utilization efficiency of instruments or equipment. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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13 pages, 5274 KiB

Open AccessArticle

Accuracy Improvement of a Laser Diode-Based System for Measuring the Geometric Errors of Machine Tools

by Yindi Cai, Yinghao Gao, Kedi Yin, Qin Fu and Kuangchao Fan

Appl. Sci. 2022, 12(7), 3479; https://0-doi-org.brum.beds.ac.uk/10.3390/app12073479 - 29 Mar 2022

Cited by 1 | Viewed by 1572

Abstract

Active methods are proposed to improve the measurement accuracy of a compact laser diode-based (LD-based) system, which is designed to measure the geometric errors of machine tools. The LD has some advantages, such as a small size, low cost and high efficiency. However, the laser spot of the LD is elliptical and the stability in the output power of the LD is low, which limits the accuracy of the measurement system, where the LD is used as the laser source. An active shaping method is proposed to shape the elliptical laser spot of the LD without adding additional optical elements. In addition, the laser beam drifts, including the linear drift and angular drift, are compensated in real-time by a proposed improved active error compensator, which consists of two drift feedback units and a Backpropagation Neural Networks-based PID controller, during the long-distance measurement. A series of experiments were conducted to verify the effectiveness of the proposed methods and the capability of the constructed LD-based system. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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14 pages, 21419 KiB

Open AccessArticle

Fabrication of an Anti-Icing Aluminum Alloy Surface by Combining Wet Etching and Laser Machining

by Annan Xia, Lei He, Shihang Qie, Jingchen Zhang, Hanlong Li, Ning He and Xiuqing Hao

Appl. Sci. 2022, 12(4), 2119; https://0-doi-org.brum.beds.ac.uk/10.3390/app12042119 - 17 Feb 2022

Cited by 5 | Viewed by 1704

Abstract

The phenomenon of icing on the surface of the fuselage while aircraft pass through clouds has an impact on flight safety. This aircraft icing may adversely affect metrological conditions and cause aerodynamic mechanical effects, resulting in a threat to flight safety. This research aims to fabricate an anti-icing surface on a 2524 aluminum alloy material by combining laser machining and wet etching. The microstructure surfaces were obtained by laser, the nanostructured surfaces were obtained by wet etching, and the hierarchical structures were prepared through a combination of these two processes. The contact angle, icing delay performance, icing adhesion, and dynamic water repellency of three kinds of textured surfaces and smooth surface were tested and compared comprehensively through experiments. The experimental findings have shown that the hierarchical surface has the best superhydrophobic properties, and the freezing time of droplets on the hierarchical surface can be extended 10 times. In addition, the ice adhesion on the surface of the hierarchical structure decreased by approximately 75% compared to the untreated samples. The surface of the hierarchical structure showed the best dynamic water repellency. The proposed hybrid laser machining–wet etching fabricating method has the potential to avoid aircraft icing. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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23 pages, 18442 KiB

Open AccessArticle

Improvement of Position Repeatability of a Linear Stage with Yaw Minimization

by Doo-Hyun Cho, Hyo-Chan Kwon and Kwon-Hee Kim

Appl. Sci. 2022, 12(2), 657; https://0-doi-org.brum.beds.ac.uk/10.3390/app12020657 - 10 Jan 2022

Cited by 1 | Viewed by 1748

Abstract

Recently, due to the miniaturization of electronic products, printed circuit boards (PCBs) have also become smaller. This trend has led to the need for high-precision electrical test equipment to check PCBs for disconnections and short circuits. The purpose of this study is to improve the position repeatability of the platform unit up to ±2.5 μm in linear stage type test equipment. For this purpose, the causes of the position errors of the platform unit are analyzed. The platform unit holding the PCB is driven by a single-axis linear ball screw drive system offset from its geometric center due to design constraints. The yaw rotation of the platform is found to have a dominant effect on position repeatability. To address this problem, adding balancing weights to the platform unit and adjusting the stiffness of the LM Guides are proposed. These methods reduce the yaw rotation by moving the centers of mass and stiffness closer to the linear ball screw actuator. In the verification tests, the position repeatability was decreased to less than ±1.0 μm. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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14 pages, 3642 KiB

Open AccessArticle

Positioning Errors Measurement of CNC Machine Tools Based on J-DBB Method

by Tao Sun, Wen Wang, Zhanfeng Chen, Yewen Zhu, Kaifei Xu, Haimei Wu, Zhiqian Sang, Keqing Lu and He Yang

Appl. Sci. 2021, 11(24), 11770; https://0-doi-org.brum.beds.ac.uk/10.3390/app112411770 - 10 Dec 2021

Cited by 3 | Viewed by 2262

Abstract

Due to the errors of the servo system and the errors of the ball screw drive system, the positioning errors inevitably occur in the process of CNC machine tools. The measurement of traditional equipment is limited by a fixed measurement radius and a single degree of freedom, which can only be measured within a fixed plane. In this paper, four different positioning errors of CNC machine tools are first measured at full scale by using J-DBB (a modified double ball bar with one spherical joint connecting two bars) method. The J-DBB device uses a three-degree-of-freedom spherical joint as a connecting part, which realizes that the measurement radius can be continuously changed, and the measurement space is a spatial sphere. First, the principle of the J-DBB method is briefly introduced. Next, four typical positioning errors of CNC machine tools are analyzed and examined, which contain the uniform contraction error of ball screw and linear grating, periodic error of the ball screw and linear grating, interference of measurement devices error, and opposite clearance error. In the end, the trajectories of the CNC machine tool spindle with a single positioning error are simulated by using the J-DBB method. The results reveal that this method can be used for the positioning error of machine tools, which helps to better understand the spatial distribution of CNC machine tool errors and provides guidance for the reasonable selection of working areas to improve the machining accuracy of parts. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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11 pages, 42987 KiB

Open AccessArticle

Fabrication of Sinusoidal Microstructures on Curved Copper Surface by Ultra-Precision Diamond Cutting with a Rotary B-Axis and Fast Tool Servo System

by Xuesen Zhao, Haiping Du, Wenda Song, Qiang Zhang, Zhenjiang Hu, Junjie Zhang and Tao Sun

Appl. Sci. 2021, 11(21), 10302; https://0-doi-org.brum.beds.ac.uk/10.3390/app112110302 - 02 Nov 2021

Cited by 2 | Viewed by 1835

Abstract

While curved surface microstructures have wide applications in optical components and devices, how to achieve high machining accuracy of the microstructures is crucial for their applications. In the present work, we fabricate sinusoidal modulation microstructures on a curved copper surface by ultra-precision diamond cutting, with the combination of a rotary B-axis and a fast tool servo system. Specifically, tool path planning, together with the consideration of a curved, sinusoidal surface meshing and tool tip arc segmentation compensation, is carried out. Preliminary cutting experiments are firstly carried out on a homemade four-axis ultra-precision lathe, which demonstrates the advantages of additionally applying the rotary B-axis in suppressing burr formations and over-cutting phenomenon over the sole utilization of the fast tool servo system. Subsequent experiments are carried out to evaluate the effects of feed rate and the number of sampling points on the machining accuracy of the microstructures under the combination of a rotary B-axis and a fast tool servo system. With the optimized machining parameters, sinusoidal modulation microstructures, which have a wavelength of 700.6 μm, a peak-to-valley of 18.7 μm, a surface roughness of 18.9 nm and a deviation of profile tolerance of 4.326 μm, are successfully fabricated on a curved copper surface with a face radius of 10 mm and a curvature radius of 500 mm. Full article

(This article belongs to the Special Issue Precision Manufacturing and Intelligent Machine Tools)

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