With the advancement of information technologies such as the Internet of Things and artificial intelligence, cyber-physical systems are being introduced into society. At the core of these systems is the digital twin, a computer model (twin) of a physical entity built in cyberspace for simulation-based prediction.

Currently, the digital twin mainly targets artificial objects, such as aircraft engines and factories. However, if it can be extended to humans, it could lead to the realization of human-machine cooperative systems and health promotion services, thereby solving social issues stemming from the aging of society. However, humans are the weakest link in the system, and many technical problems remain to be solved, such as realizing the measurement, modeling, and prediction of human behavior, if the human digital twin is to become reality.

This special issue contains 9 papers on developing essential technologies for the human digital twin and constructing human-machine systems for specific applications. The topics covered include learning algorithms, motion measurement and analysis techniques, human perception, system development, and platform software for system development. These clearly show that cross-disciplinary efforts are essential to the realization of the human digital twin.

We thank the authors of the papers submitted for this special issue. We are confident that the information provided by the authors is suggestive and informative for both specialists and non-specialists alike. We also sincerely appreciate the efforts of the reviewers. Their contributions helped to make this special issue possible. We hope that this special issue will catalyze sharing across the boundaries of research fields along the path to realizing a human digital twin.

Artificial intelligence (AI) techniques have been behind disruptive innovations in every industry. Based on AI techniques, large amounts of data can be converted into actionable insights and predictions. Manufacturers have frequently faced different kinds of challenges, such as unexpected machinery failures or defective product deliveries. Still, the adoption of AI techniques is expected to improve operational efficiency, enable the launch of new products, customize product designs, and plan future financial actions. Recently, manufacturers have been using AI techniques to improve the quality of their products, achieve greater speed and visibility across supply chains, and optimize inventory management.

Given that the attention and interest in AI techniques has been growing rapidly, it is time that the current state of the art of their practical applications be presented. The main aim of this special issue is to bring together the latest AI research and practical case studies of AI techniques in production engineering.

This special issue features 10 papers related to not only operation automation but also sophisticated skill transfer in manufacturers. Their subjects cover various advancements, such as failure diagnosis, product estimation, process planning, operation planning, and workpiece fixturing in the area of machining. Moreover, the authors boldly strive to apply AI technologies even to complex systems in manufacturing fields such as laser-assisted incremental forming, injection molded direct joining, and parts assembling.

We thank the authors for their interesting papers submitted for this special issue, and we are sure that both general readers and specialists will find the information the authors provide both interesting and informative. Moreover, we deeply appreciate the reviewers for their incisive efforts. Without these contributions, this special issue would not have been possible. We truly hope that this special issue triggers further research on AI techniques in production engineering.

Abrasive processing technologies support both the creation of new products and progressive production processes as finishing processing in various industries, such as the automotive, telecommunications, semiconductor, healthcare, energy, and aerospace industries. In this era of major changes, known as the Fourth Industrial Revolution, advanced abrasive processing technologies that produce cutting-edge devices, machinery, and equipment for a smart society are needed. The subjects related to abrasive processing are extremely diverse, including function generation processing and ICT fusion processing, in addition to the continuing basic subjects, including high-efficiency processing, difficult-to-cut material processing, ultra/high-precision processing, etc. The field of abrasive processing has recently been expanding from removal processing to additional types of processing, such as additive manufacturing. As a result, its importance is increasing as a technology indispensable for advanced industries such as healthcare and the production of power semiconductors, cutting-edge semiconductors, etc. On the other hand, new abrasive processing technologies, such as grinding wheel surface property analysis and highly efficient surface finishing methods, have developed along with the advancement of the elemental technologies that support abrasive processing using the latest measurement methods and ultra-precision technology. Furthermore, new research, such as work on energy-assisted or reaction-assisted grinding, has been conducted through the fusion of the materials science and physical chemistry fields. This special issue contains seven papers that cover the following topics.

- Abrasive jet processing

- Analysis of the surface profile of a grinding wheel

- Drilling of glass with a diamond tool

- Reaction-assisted grinding

- Barrel finishing

- High-speed polishing

We deeply appreciate the authors for their careful work and thank the reviewers for their incisive efforts in producing this special issue. We hope that it will help readers understand the latest research on abrasive pro...<more>

The award ceremony for the Best Paper Award and the Special Paper Award was held virtually on September 27, 2022. Since the influence of COVID-19 pandemic is still ongoing, the winners and IJAT committee members who took part in the selection process attended online. The award-winning papers were carefully selected from among the 85 papers published in Vol.15 (2021). The award winners were granted a certificate and a honorarium. We congratulate the winners and sincerely wish them success in the future.

This is the sixth special issue on Design and Manufacturing for Environmental Sustainability. As the first special issue on this topic was issued in 2009, the topic has thirteen years of history in this journal. Environmental sustainability was recognized as important for manufacturing even at that time. This is why the special issue was started in this journal. The seriousness of this topic has been increasing not only in Europe but also in Japan and other countries. One critical trend as of late has been the way that the attitude of companies regarding this issue, including their positions on carbon neutrality, circular economy, and biodiversity, has come to determine the value of the company in the eyes of, for example, environment, society, and governance (ESG) finance. Nowadays, we cannot say sustainability or business; we should pursue businesses that contribute to sustainability.

This sixth special issue includes eighteen well-written papers, with one more paper to follow. This series of special issues has focused on topics related to ecodesign, recycling, remanufacturing, low-energy and low-emission manufacturing, and circular economy. The papers in this special issue are also deeply related to these topics. As a result of the thirteen-year history of the special issue, we have been able to learn some viewpoints specific to the series in this journal. This has led this special issue to consist of four subcategories, although they are not explicitly represented in the table of contents. The first subcategory consists of seven papers, from the first paper by K. Halada et al. to the seventh paper by A. Yoshimura et al. These papers are related to design, including evaluation, business, remanufacturing, and materials. Among others, the important viewpoint common to these papers is the “flow” of product lifecycles and materials. The second category starts with the eighth paper by C. Ye et al. and ends with the eleventh paper by Y. Yamashita et al. These papers deal with manufacturing issues in the context of the environmental sustainability. For example, the eighth paper deals with the crushing of ...<more>

The continued effects of the global spread of COVID-19 have reaffirmed that restrictions on the movement of people and products have geopolitical consequences. In addition, the impacts involved in the decarbonization of the global environment have further strengthened the growing demand for the building of a sustainable society. These factors have had no small impact on the global economy and on global manufacturing as well. In this context, the demand for the realization of new manufacturing technologies that can respond to changes in social and economic environments has been growing.

This special issue focuses on recent advances in manufacturing technologies that maximize product quality and reduce costs, with an emphasis on the machinery industry. This special issue of the IJAT contains 12 papers. These include works on cutting technology, machining metrology, advanced machine tools, gear manufacturing technology, additive manufacturing, and more. The first five papers are proposals for new cutting technologies and elucidations of cutting phenomena. The next three papers are new proposals for machining measurements. The next two papers are on precision positioning technologies and a rack gear compensation technology. The last two papers are theoretical investigations into the basic phenomenon of additive manufacturing and its applications.

These papers were originally presented at the 10th International Conference on Leading Edge Manufacturing in the 21st Century (LEM21), held in Kitakyushu, Japan in 2021. The papers have been revised and expanded at the request of the editors.

The editors would like to thank all authors for their comprehensive efforts in making this special issue possible, and would like to thank the anonymous reviewers for their hard work. We wish them all the best in their future research in this field of manufacturing technology.

Actuators are components that are essential to the moving, manipulating, or deforming of objects. Historically, conventional electromagnetic motors as well as pneumatic and hydraulic actuators have been developed to sophistication. In the past several decades, however, many other kinds of actuators based on novel principles have also been proposed. These have employed physical or/and chemical effects, such as piezoelectric, electrostatic, or giant magnetostrctive effects, as well as thermal expansion, phase transformation, or ion mobility in polymers. Not only the novel actuators but also conventional ones have been continually evolving in astounding ways. These actuators have been embedded not only in conventional machines but also in smart ones, such as artificial muscles for robots and power assist systems, electric vehicles, and machine tools. By combining the actuators with the Internet of Things (IoT), they are also used to test equipment. In addition, there is no doubt that the technologies involved in the development of novel actuators and the improvement of their efficiency are key to the achievement of Sustainable Development Goals (SDGs), as actuators currently consume a huge aggregate amount of energy. In sum, actuators have the potential to be central to the development of innovative machines.

This special issue features one review, six research papers, and three technical papers on the most recent advances in various types of actuators. These papers cover topics that include magnetic levitation technologies for precision motion control, electromagnetic motors, fluid power actuators, electrostatic actuators embedded in micro-electromechanical systems, and an ultrasonic motor, plus their applications.

All the papers were refereed through careful peer reviews. I believe that this special issue will help the readers to enhance their understanding and knowledge of actuators and their applications. I would like to express my sincere appreciation to the excellent contributions of all the authors, and I appreciate the incisive efforts of reviewers in producing this special issue.

A Fourth Industrial Revolution has been proposed, and various research and development activities geared toward the realization of smart factories have become extremely active. In smart factories developed individually within companies, the direction of the development activities is changing drastically. Regarding common technologies, research activities and feasible case study activities that are collaborations among industry, academia, and government and that show consideration and awareness of ecosystems are becoming active.

It has been five years since the IJAT last published a special issue on smart manufacturing. Smart factory technologies are becoming more and more important in the industrial world, not as a temporary boom, but as a steady development. Research on smart factory technologies is progressing, as they are considered to be important technologies in the industrial world, along with Digital Transformation (DX) technologies, among others.

This special issue addresses the latest in advanced research on smart factories. We have received many submissions from researchers at universities, public research institutes, and companies, and we are pleased to publish eight papers. The latest research being published mainly concerns the following five topics:

- Smart and digital twinning of machine tools

- Smart and digital twinning of production systems

- Optimization of production systems using scheduling algorithms

- Optimization of production systems including worker operations

- Optimization of energy consumption for production systems

The results of these studies will serve as a reference for further smart factory technologies in the future.

We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts. Without these contributions, this special issue could not have been created. We also hope that this special issue will trigger leading to further advances in smart factories.

The concept of Self-Optimizing Machining Systems (SOMS) has been proposed against the background of Industry 4.0 and the Digital Twin concept, based on cyber-physical systems. In order to improve manufacturing productivity, quality, and efficiency, each component technology related to the machining process, such as CAD/CAM, process modeling/simulation, process monitoring/control, and workpiece assessment, as well as the machine tools themselves, has been developed independently to date. However, series of processes, including the interactions among these component technologies, have finally determined the machining performance and the quality of the products. SOMS deals with the information links among these components comprehensively and plays the important role of combining these links and functionalities to optimize the overall machining system. Nevertheless, an intensive implementation and combination of these technologies has yet to become state-of-the-art in industry, while further research and development for SOMS is required for Industry 4.0 and Digital Twin.

This special issue focuses on the research trends of SOMS, especially the interaction links among machine tools, process monitoring, and work assessment. From researchers who are active on the front lines of manufacturing engineering, the latest achievements related to the development of SOMS are presented in 6 papers. On one hand, the development of sensor-integrated components is indispensable for SOMS to monitor the status of a process and feed it back to a related component in order to control the machining process and its environment. On the other hand, it can be said that visual simulation, virtual metrology, and other epoch-making, on-machine technologies for evaluating machined surfaces, as well as process optimization based on machined surface information, are strongly required.

We hope this special issue will contribute to future research and development for researchers and engineers in the field of manufacturing and machining systems.

Demand for the high-precision and high-efficiency machining of hard ceramics, such as silicon carbide for semiconductors and hardened steel for molding dies, has significantly increased for optical and medical devices as well as for powered devices in automobiles. Certain types of hard metals can be machined by deterministic precision-cutting processes. However, hard and brittle ceramics, hardened steel for molds, and semiconductor materials have to be machined using precision abrasive technologies, such as grinding, polishing, and ultrasonic vibration technologies that use diamond super abrasives. The machining of high-precision components and their molds/dies using abrasive processes is very difficult due to their complex and nondeterministic natures as well as their complex textured surfaces. Furthermore, the development of new cutting-edge tools or machining methods and the active use of physicochemical phenomena are key to the development of high-precision and high-efficiency machining.

This special issue features 11 research papers on the most recent advances in precision abrasive technologies. These papers cover the following topics:

- Characteristics of abrasive grains in creep-feed grinding

- Quantitative evaluation of the surface profiles of grinding wheels

- ELID grinding using elastic wheels

- Nano-topographies of ground surfaces

- Novel grinding wheels

- Grinding characteristics of turbine blade materials

- Polishing mechanisms

- Polishing technologies using magnetic fluid slurries

- Application of ultrasonic vibration machining

- Turning and rotary cutting technologies

This issue is expected to help its readers to understand recent developments in abrasive technologies and to lead to further research.

We deeply appreciate the careful work of all the authors, and we thank the reviewers for their incisive efforts.

“The digital transformation can be understood as the changes that the digital technology causes or influences in all aspects of human life” (definition by Prof. Erik Stolterman). In order to manufacture high value-added products and create a sustainable society, the digital transformation, based on advanced precision engineering, will be an urgent task within manufacturing systems.

This special issue consists of eight excellent research papers that focus on advanced precision engineering in manufacturing systems. All research papers were presented at the 18th International Conference on Precision Engineering (ICPE2020). The ICPE2020 covered various topics, including digital design, CAD/CAM technology, traditional cutting/grinding, non-traditional additive manufacturing, machine tools, measurement, robotics, control, and others. Held during the COVID-19 pandemic, it was a virtual conference that saw 189 papers presented in the oral session and 38 papers presented in poster session. The COVID-19 pandemic demands the innovation of current manufacturing systems with new concepts and methodologies, and the editors hope that the research papers in this special issue give us valuable information for the digital transformation of manufacturing systems.

All papers were refereed through careful peer reviews. The editors deeply appreciate the efforts and excellent work of all the authors and anonymous reviewers in realizing this special issue. Finally, we hope that future research on precision engineering in manufacturing will further contribute to the achievement of the Sustainable Development Goals (SDGs) of our global society.

The industrial robot is more precisely an “automatically controlled, reprogrammable, multipurpose manipulator, programmable in three or more axes, which can be either fixed in place or mobile” (ISO 8373:2012). According to the International Federation of Robotics, by 2018, more than 400,000 new units were being installed annually, and the global average robot density in the manufacturing industry was 99 robots per 10,000 employees. More than 30% of all installed robots were in the automotive industry, the biggest customer for robots.

Research on measuring and calibrating, modeling, programming and controlling, and integrating systems has been conducted to give robotic manipulators a wider variety of industrial applications. This special issue covers technical and academic efforts related to new technologies that improve the accuracy and facilitate the implementation of robotic manipulators in industrial applications.

The first paper, by Ibaraki et al., outlines technical issues and future research directions for the implementation of model-based numerical compensation schemes for industrial robots. The random forest method is used by Kato et al. to construct a calibration model for positioning errors and identify industrial robots’ positioning errors. A procedure for the quasi-static compliance calibration of serial articulated industrial manipulators is proposed by Theissen et al. A review of the kinematic modeling theory and a derived algorithm to identify error sources for a six-axis industrial robot are presented by Alam et al. Nagao et al. derive a forward kinematics model and identify the kinematics parameters for the calibration of a robot-type machine tool. A novel trajectory generation algorithm, including a corner smoothing method for high-speed and high-accuracy machining by industrial robots, is proposed by Tajima et al. Sato et al. study the vibration characteristics of an industrial robot and derive a mathematical model that represents the dynamic behavior of the system. In the context of smart manufacturing, a multilayer quality inspection framework including a measurement ...<more>

In recent years, manufacturing technologies have been progressing with the high demands of industry. In the automobile and aircraft industries, for example, the manufacturing processes have been requiring for technologies that allow for high machining rates of lightweight and/or difficult-to-cut materials. Medical device production includes the machining of biocompatible materials that have high mechanical strength. Information devices require high quality in ultra-precision manufacturing processes. Measurement and characterization technologies in manufacturing have also been essential in the progress. Along with evolution of manufacturing technologies, scientific studies have been done on manufacturing phenomena and the control of processes, based on physical and/or mathematical aspects.

This special issue is promoted by the International Conference on Leading Edge Manufacturing/Materials & Processing (LEM&P2020), which was canceled to protect the health and wellness of our community from COVID-19, and by the Research Committee of Cutting Technologies in the Japan Society for Precision Engineering.

This special issue includes 17 papers that detail progress and innovations in the following areas:

- Characterization of materials

- Fundamental study and modeling of material removal process

- Manufacturing control and optimization

- Manufacturing processes for new/hard materials

- Micro-/Nano-scale manufacturing

- Tool manufacturing and performance

- Metrology and evaluation

- Surface characterization

This special issue also includes not only technical but also scientific discussions, suggesting new key technologies for future manufacturing. We hope this will help the readers to understand the manufacturing processes and improve their operations.

We thank the authors and the reviewers for their generous cooperation and the editing staffs for their many contributions.

The application of digital geometry processing is undergoing an extension from small industrial products to large-scale structures and environments, including plants, factories, ships, bridges, buildings, forests, and indoor/outdoor/urban environments. This extension is being supported by recent advances in long-range 3D laser scanning technology. Laser scanners are mounted on various platforms, such as tripods, wheeled vehicles, airplanes, and UAVs, and the laser scanning systems are used to efficiently acquire dense and accurate digitized 3D data of the geometry, called point clouds, of large-scale structures and environments. As another technology for the acquisition of digital 3D data of structures and environments, 3D reconstruction methods from digital images are also attracting a great deal of attention because of their flexibility.

The utilization of digital 3D data for various purposes still has many challenges, however, in terms of data processing. The extraction of accurate and meaningful information from the data is an especially important and difficult problem, and many studies on object and scene recognition are being conducted in many fields. How to acquire useful and high-quality digital 3D data of large-scale structures and environments is another problem to be solved for digital geometry processing to be widely used.

This special issue addresses the latest research advances in digital geometry processing for large-scale structures and environments. It covers a broad range of topics in geometry processing, including new technologies, systems, and reviews for 3D data acquisition, recognition, and modeling of ships, factories, plants, forests, river dikes, and urban environments.

The papers will help the readers explore and share their knowledge and experience in technologies and development techniques in this area. All papers were refereed through careful peer reviews. We would like to express our sincere appreciation to the authors for their excellent submissions and to the reviewers for their invaluable efforts in producing this special issue.

Due to changes in the global industrial structure, the number of employees in the manufacturing industry has decreased in developed countries. One of solutions to this situation offered in Industry 4.0 is “the utilization of robots and AI as alternatives to skilled workers.” This solution has been applied to various operations conventionally performed by skilled workers and has yielded consistent results. A skilled worker has two skills, namely, “physical operation skill” and “decision making skill,” which correspond to the utilization of robots and AI, respectively.

Conventionally, robots have simply played back programs they were taught. However, owing to feedback technologies using force, position, or various other sensors, robots have come to be able to perform smart operations. In some of these, the capabilities of robots exceed those of human workers. For example, while humans are highly adaptive to various operations, it is difficult for them to maintain a constant force or position for long periods of time.

Generally, humans make decisions about operations according to their experience, and this experience is gained from many instances of trial and error. Now, the trial-and-error learning of AI has become significantly superior to that of humans in terms of both number and speed. As a result, many systems can find operational strategies or answers much faster than humans can.

This special issue features papers on robot hands, path planning, kinematics, and AI. Papers related to robot hands present an actuator using new principles, new movements, and the realization of the precise sense of the human hand. Papers related to path planning present path generation on the basis of CAD data, path generation using image processing, automatic path generation on the basis of environmental information, and the prediction of error and correction. Path generation using VR technology and error compensation using an AI technique are also presented. A paper related to kinematics presents the analysis and evaluation of a new mechanism with the aim of new applications in th...<more>

As abrasive technologies are currently indispensable for production processes in the automotive, aerospace, optics, telecommunications, and healthcare industries, among others, it is essential that the application of abrasive processing to production be optimized and improved. To those ends, it is necessary to understand how to approach the task, as there are many processing factors to consider. However, priority is given to understanding the abrasive processing mechanism that determine finishing results, as well as the relationship between the processing factors and individual conditions. Measurement, analysis, and evaluation technologies are also important. Furthermore, the development of new abrasive tools or machining fluids and the active use of physicochemical phenomena are key to the development of advanced abrasive technologies.

Cutting-edge studies focusing on advanced abrasive technologies were collected for this special issue, which includes 12 papers covering the following topics:

- Quantitative evaluation of surface profile of grinding wheel

- Elucidation of grinding mechanism, based on grinding force

- Novel grinding wheel

- High-efficiency and high-accuracy grinding of difficult-to-cut materials

- Polishing technology using magnetic fluid slurry

- Application of ultrasonic waves or ultra-fine bubbles to coolants, and their effects on them

- Planarization technology for single-crystal silicon carbide

This issue is expected to help its readers to understand recent developments in abrasive technologies and to lead to further research.

We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.

This is the fifth Special Issue on Design and Manufacturing for Environmental Sustainability. The first Special Issue on this topic was issued in 2009, and the previous one was in 2018. The acceptance of sustainability has been increasing, as evidenced by the United Nations’ Sustainable Development Goals (SDGs), various carbon neutral movements, and, among others, the gradual recognition of potential impacts of the EU’s “Circular Economy,” which promotes circulation-based businesses to increase the employment and market competitiveness of the EU. This increase in acceptance has brought with it increased activity in the research area of design and manufacturing for environmental sustainability, with the result that this fifth Special Issue includes seventeen well-written papers, a significant increase over the six that appeared in the fourth.

The first paper “Potential Impacts of the European Union’s Circular Economy Policy on Japanese Manufacturers” overviews the EU’s Circular Economy and points out key enabling technologies. To approach environmental sustainability, we should promote various technologies related to ecodesign, process technologies, business strategy, and digital technology. At the same time, we must focus on life cycle design and management, an indispensable technology which synthesizes a sustainable circulation system by integrating the technologies mentioned above. Accordingly, this Special Issue covers both aspects, with the seventeen manuscripts in it organized as follows. The first three papers, authored by Y. Umeda et al., K. Halada, and M. Kojima, give overviews and discuss requirements for technological development. The next two manuscripts by K. Fujimoto et al. and Y. Kikuchi et al. discuss modeling, simulation, and assessment of circulation systems. Papers six to eight, written by W.-H. Chung et al., S. Yamada et al., and K. Yoda et al. develop life cycle design methods. The remaining manuscripts advance fundamental technologies. Manuscripts nine to eleven, by R. Yonemoto et al., T. Samukawa et al., and Y. Yaguchi et al., deal with sustain...<more>

With the recent development of new technologies such as the Internet of Things (IoT), Cyber-Physical Systems (CPS), and cloud-based systems, the smart manufacturing concept based on ICT or AI is expected to have tremendous potential to realize a digital transformation with customer involvement in production. The role of production will need to change accordingly, as it is obvious that the traditional business model based on process chains for production functionality has limitations for further growth. In production, it is necessary to consider value chains with service factors for adding innovative value to products. Value creation is an important concept to the realization of a sustainable ecosystem in production.

This special issue addresses the latest research on value creation in production and service systems. Including ten advanced research papers and one development report, it covers a wide range of topics, including smart factories, logistics, distribution with value chains; product service systems; sustainable ecosystems with value in production and service industries; the sharing economy in production systems with cloud computing; the application of digital transformations in production and service systems.

All papers and reports were refereed through careful peer reviews with experts. The editors deeply appreciate the authors for their careful work and the reviewers for their invaluable efforts, without which this special issue would not have been possible. Finally, we hope this special issue provides valuable information to our interested readers and encourages further research on value creation in production.

The “process chain” concept for the integration of multiple manufacturing processes has been attracting attention in the field of manufacturing in recent years. In a number of specialized fields, laser-based processes in particular are actively being studied, as their high flexibility allows them to be used not only as individual manufacturing processes but also in combination to develop new ones.

Most of the practical laser technologies involve heat, which can be used for thermal processing to change surface properties or for removal processing. In recent years, lasers have also been used as a heat source for additive manufacturing, as well as ultra-short-pulsed lasers being applied to non-thermal processes.

This special issue features various studies and reports that present the latest advances as well as current challenges in laser-based/assisted manufacturing. It includes nine related papers that indicate the possibilities and future of new laser processing technologies.

We deeply appreciate all the authors and reviewers for their efforts and contributions, and we also hope this special issue will encourage further research on laser-based/assisted manufacturing.

The accuracy of a three-dimensional (3D) positioning system can ultimately be evaluated via measurement of a 3D vector between command and actual end-effector positions at arbitrary points over the entire workspace. This is a simple, yet challenging, metrological problem. The motion accuracy of a machine tool is traditionally evaluated on an axis-to-axis basis, with every error motion of every axis being independently measured as part of a one-dimensional measurement process in a different setup. Toward the ultimate goal of 3D position measurement over the entire workspace, research efforts have offered several new, practical measurement technologies.

This special issue covers the technical and academic efforts regarding the evaluation of machine tool accuracy. The papers in this special issue clarify the latest research frontiers regarding machine tool accuracy from a metrological viewpoint. In the first paper, by Montavon et al., error calibration technologies and their management are reviewed within the Internet of production concept. Long-term accuracy monitoring and management are clearly among the most crucial technical challenges faced regarding machine tools, and the work by Xing et al. is related to them. Ibaraki et al. presented machining tests to evaluate the thermal distortion of a machine tool. Peukert et al. studied the dynamic interaction between machine tools and their foundations. Various 3D measurement schemes for determining machine error motions have been investigated by many researchers, and some have been implemented in industrial applications. Kenno et al. and Florussen et al. investigated 3D measurement using the R-test for five-axis machines. Miller et al. studied simultaneous measurement of six-degree-of-freedom error motions of a linear axis. Nagao et al. presented an error calibration method for a parallel kinematic machine tool.

The editors appreciate the contributions of all the authors, as well as the work of the reviewers. We are confident that this special issue will further encourage research and engineering work for improving the accuracy and performance of machine tools.