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# On-machine and in-process surface metrology for precision manufacturing

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## Abstract

On-machine and in-process surface metrology are important for quality control in manufacturing of precision surfaces. The definitions, requirements and tasks of on-machine and in-process surface metrology are addressed. The state-of-the-art on-machine and in-process measurement systems and sensor technologies are presented. Error separation algorithms for removing machine tool errors, which is specially required in on-machine and in-process surface metrology, are overviewed, followed by a discussion on calibration and traceability. Advanced techniques on sampling strategies, measurement systems-machine tools interface, data flow and analysis as well as feedbacks for compensation manufacturing are then demonstrated. Future challenges and developing trends are also discussed.

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... Surface roughness measuring systems on-machine and in-process for precise production is developed in order to increase surface quality of machined components [123]. Advanced surface metrology system in a manufacturing line is illustrated in the figure 9 [123]. ...
... Surface roughness measuring systems on-machine and in-process for precise production is developed in order to increase surface quality of machined components [123]. Advanced surface metrology system in a manufacturing line is illustrated in the figure 9 [123]. Fig. 9. Advanced surface metrology system in a manufacturing line [123]. ...
... Advanced surface metrology system in a manufacturing line is illustrated in the figure 9 [123]. Fig. 9. Advanced surface metrology system in a manufacturing line [123]. ...
Article
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Artificial Intelligence (AI) and Machine learning (ML) represents an important evolution in computer science and data processing systems which can be used in order to enhance almost every technology-enabled service, products, and industrial applications. A subfield of artificial intelligence and computer science is named machine learning which focuses on using data and algorithms to simulate learning process of machines and enhance the accuracy of the systems. Machine learning systems can be applied to the cutting forces and cutting tool wear prediction in CNC machine tools in order to increase cutting tool life during machining operations. Optimized machining parameters of CNC machining operations can be obtained by using the advanced machine learning systems in order to increase efficiency during part manufacturing processes. Moreover, surface quality of machined components can be predicted and improved using advanced machine learning systems to improve the quality of machined parts. In order to analyze and minimize power usage during CNC machining operations, machine learning is applied to prediction techniques of energy consumption of CNC machine tools. In this paper, applications of machine learning and artificial intelligence systems in CNC machine tools is reviewed and future research works are also recommended to present an overview of current research on machine learning and artificial intelligence approaches in CNC machining processes. As a result, the research filed can be moved forward by reviewing and analysing recent achievements in published papers to offer innovative concepts and approaches in applications of artificial Intelligence and machine learning in CNC machine tools.
... Since a workpiece is typically manufactured from the raw material to the final product by a manufacturing chain composed of a number of machines, people, and processes, several 'inline' sub-terms have been given through the years. Such conditions are clarified and classified in [32,33]; see Fig. 2. In addition, Gao et al. [32] highlighted the synonymous usage of 'in-situ' for 'on-machine' and 'in-process' in some manufacturing papers. By conducting this literature review, most articles that use such terms interchangeably are within Additive Manufacturing (AM). ...
... Since a workpiece is typically manufactured from the raw material to the final product by a manufacturing chain composed of a number of machines, people, and processes, several 'inline' sub-terms have been given through the years. Such conditions are clarified and classified in [32,33]; see Fig. 2. In addition, Gao et al. [32] highlighted the synonymous usage of 'in-situ' for 'on-machine' and 'in-process' in some manufacturing papers. By conducting this literature review, most articles that use such terms interchangeably are within Additive Manufacturing (AM). ...
... • In-process quality inspection: the measurement is carried out while the manufacturing process is taking place. Contrary to [32], Table 1 LoA scales for computerised and mechanised tasks within manufacturing (Frohm et al. 2008 where in-process quality inspection is a subcategory of on-machine, we believe certain applications allow to perform of in-process inspection without being mounted on a machine, as, for example, optical cameras allow long-distance measurement. Inprocess inspection should be a subcategory of on-and off-machine inspection. ...
Article
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Contemporary manufacturing must prioritise the sustainability of its manufacturing processes and systems. Zero Defect Manufacturing (ZDM) focusses on minimising waste of any kind using data-driven technology, hence enhancing the quality of all manufacturing aspects (product, process, service, etc.). Making things right on the first try is the central tenet of ZDM. In recent years, the application of automation for in-line quality inspection systems has begun to attract the interest of both practitioners and academics because of its capability to detect defects in real-time, and thus adapt the system to disturbances. In this work, we provide a systematic review of the literature on current trends in the application of automation for in-line quality inspection with the ultimate objective of achieving ZDM. Additionally, bibliometric and performance analyses have been performed to gain a complete picture of the field. In this work, we have collected bibliometric data from the most widely referred search engines for academic engineering papers, i.e. Scopus, Web of Science, and IEEE Explorer, involving a total of 145 academic publications from 2011 to 2021. Uniquely for this study, we used three research attributes for the analysis of the selected articles, that is, the level of automation, the condition for quality inspection, and the contribution to ZDM dimensions. The literature suggests that there is a lack of research on the use of in-line detection data for the prediction of defects or repair. Based on the results and our interpretation of the literature, an adapted framework of ZDM (Psarommatis et al., 2020a) and multi-layer quality inspection (Azamfirei et al., 2021a) is presented.
... Error compensation machining, during which the machining deviation of the workpiece from the designed nominal shape will be evaluated and then fed back to the NC controller, is considered a universally applicable and cost-effective approach in diminishing the machining error [6][7][8][9]. For compensation machining, precise measurement of surface machining error is imperative and critical. ...
... For compensation machining, precise measurement of surface machining error is imperative and critical. The strategies for measuring the surface form error can generally be categorized into two groups: (a) on-machine measurements that are carried out on the machining tools where the workpieces are manufactured and (b) off-machine measurements that are made by a stand-alone profilometer [8]. Compared with the off-machine measurements, the on-machine measurements can be performed soon after the manufacturing process (or even while the machining process is taking place), without the requirement to move the workpiece from the machining tool to the measuring instrument. ...
... However, during the on-machine measurement, the straightness/ roundness error of the manufactured workpiece is at the same level as the error motions of slide/rotary axes of the machine tools, which will be superposed into the measurement result and are major sources of the measurement error [8]. Therefore, the error motion of the machine tool axes cannot be ignored and error separation techniques, also termed self-calibrating techniques, should be employed to reduce their adverse effect. ...
Article
To compensate for the straightness error of the slide of a machine tool efficiently and precisely, on-machine self-calibrating measurement of the manufacturing error is critical. The Fourier 3-sensor (F3S) method proposed by Fung is promising in measuring the straightness profile of a workpiece accurately on a machine. However, it still suffers from two main challenges: the height difference between the second and the third probes and the stochastic uncertainty, both of which can significantly decrease the measurement precision. In this paper, we counter these two challenges, respectively, and propose the solutions accordingly. First of all, by resorting to the Laplace transform, an algorithm for the F3S method is proposed. Second, the adverse effect of the height difference between the second and the third probes is demonstrated. An approach is presented for estimating the height difference, and compensating for this. Third, to alleviate the stochastic uncertainty, a hybrid F3S method is developed: several F3S measurements are first performed under different probe spacings; then, the optimal Fourier coefficients of the straightness profile are individually selected from the candidate estimates in accordance to the determinant of the transfer matrix. Finally, practical straightness profile measurements were performed, respectively, on a grinding machine by adopting the hybrid F3S method and on a Taylor Hobson surface profiler. The results show that compared with the conventional F3S method, the hybrid F3S method reduced the measurement uncertainty significantly, and the straightness profiles estimated by the hybrid method and by the surface profiler were consistent with each other.
... This thesis addresses the need to explore the usage of advanced industrial robots for in-line quality inspection. Robotic in-line quality inspection is still facing challenges when it comes to replacing human operators in part inspection (Li et al., 2015;Babu, Franciosa, and Ceglarek, 2017;Kiraci et al., 2017;Liu et al., 2017;Babu, Franciosa, and Ceglarek, 2019;Gao et al., 2019;Phan, Quinsat, and Lartigue, 2019;Syam et al., 2019). Although previous studies have suggested the use of robotic in-line quality inspection, understanding the usage, enablers, and challenges in the changeable manufacturing context are still limited. ...
... The term 'in-line' is commonly used in the automotive industry to condition the place and time where the measurements are taken, i.e., in the production line. In Gao et al. (2019), different conditions for the measuring process are classified; see Figure 2.6. The maximum efficiency of quality control occurs when the measurement is carried out at the closest possible point to the manufacturing process; thus allowing for quick reaction on part deviations and potential operation process corrections (Gao et al., 2019). ...
... In Gao et al. (2019), different conditions for the measuring process are classified; see Figure 2.6. The maximum efficiency of quality control occurs when the measurement is carried out at the closest possible point to the manufacturing process; thus allowing for quick reaction on part deviations and potential operation process corrections (Gao et al., 2019). ...
Thesis
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The growing customer demands for product variety have put unprecedented pressure on the manufacturing companies. To maintain their competitiveness, manufacturing companies need to frequently and efficiently adapt their processes while providing high-quality products. Different advanced manufacturing technologies, such as industrial robotics, have seen a drastic usage increase. Nevertheless, traditional quality methods, such as quality inspection, suffer from significant limitations in highly customised small batch production. For quality inspection to remain fundamental for zero-defect manufacturing and Industry 4.0, an increase in flexibility, speed, availability and decision upon conformance reliability is needed. If robots could perform in-line quality inspection, defective components might be prevented from continuing to the next production stage. Recent developments in robot cognition and sensor systems have enabled the robot to carry out perception tasks they were previously unable to do. The purpose of this thesis is to explore the usage of robotic in-line quality inspection during changeable zero-defect manufacturing. To fulfil this aim, this thesis adopts a mixed-methods research approach to qualitative and quantitative studies, as well as theoretical and empirical ones. The foundation for this thesis is an extensive literature review and two case studies that have been performed in close collaboration with manufacturing companies to investigate how in-line quality inspection is perceived and utilised to enhance industrial robots. The empirical studies also aimed at identifying and describing what opportunities arise from having robotic in-line quality inspection systems. The result of this thesis is a synthesis of literature and empirical findings. From the literature study, the need for enhancing quality inspection was identified and a multi-layer quality inspection framework suitable for the digital transformation was proposed. The framework is built on the assumption that data (used and collected) needs to be validated, holistic, and online, i.e., when needed, for the system to effectively decide upon conformity to surpass the challenges of reliability, flexibility and autonomy. Empirical studies show that industrial robotic applications can be improved in precision and flexibility using the in-line quality inspection system as measurement-assisted. Nevertheless, this methodological changes and robot application face the hurdle of previous and current management decision when passing from one industrial paradigm to another (e.g., mass production to flexible production). A discussion on equipment design and manufacturing process harmony and how in-line quality inspection and management can harmonise such a system was provided.
... The most straightforward task of on-machine surface metrology is to replace the conventional post-manufacturing inspection of the work piece surface carried out on an off-machine and stand-alone surface measuring instrument, so as to address data quality control in surface metrology. In this context, Gao et al. [63] described the state-of-the-art on-machine and in-process measurement systems and sensor technologies, overviewed the error separation algorithms for removing machine tool errors and discussed calibration and traceability. Additionally, they demonstrated some advanced techniques for sampling strategies, measurement systems-machine tools interface, data flow, analysis and feedback for compensation manufacturing. ...
... Gao et al. [63] discussed the metrological traceability forms when presenting inprocess measurement systems, namely: (i) machine metrology traceability; (ii) machining metrology traceability; and (iii) machined surface metrology traceability. The first concerns the machine that does the job, while the second talks about the element that shapes the surface and determines the surface state in terms of the form and texture. ...
... They are "Metrological analytical methods for data handling, storage, security and reliability" and "Use of cyber-physical systems, cloud computing, digital twins, artificial intelligence and machine learning". The first is captained by the dimensions of big data, with scientific publications mainly focused on real-time massive amounts of data processing, data batch and data veracity [52,54,56,63,69]. At the same time, CPS technologies, especially when integrated with IoT and cloud computing to generate CPM 3 [53,55,64,67], have stimulated a new generation of factories with ever-increasing intelligence, flexibility and self-adaptability. ...
Article
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Smart manufacturing comprises fully integrated manufacturing systems that respond in real time to meet the changing demands and conditions in industrial activities, supply networks and customer needs. A smart manufacturing environment will face new challenges, including those concerning metrological issues, i.e., analysis of large quantities of data; communication systems for digitalization; measurement standards for automated process control; digital transformation of metrological services; and simulations and virtual measurement processes for the automatic assessment of measured data. Based on the assumption that the interplay between smart manufacturing and digitalization of metrology is an emerging research field, this paper aims to present a systematic literature review (SLR) based on a bibliographic data collection of 160 scientific articles retrieved from the Web of Science and Scopus databases over the 2016–2022 time frame. The findings presented in this review and recommendations for building a research agenda can help policy makers, researchers and practitioners by providing directions for the evolution of digital metrology and its role in the digitalization of the economy and society.
... Лазер -уникальный, широко используемый инструмент, эффективность применения которого заключается в способности производить огромное количество высококонцентрированной энергии -до 10 12 Вт/см 2 . ...
... На рис. 7 показана система встроенной лазерной интерферометрии на горизонтальном плоскошлифовальном станке [12]. Для измерительной системы использовалась вертикальная конфигурация, в которой интерферометр устанавливался на не зависимой от станка метрологи-ческой раме для измерения асферической поверхности заготовки, расположенной примерно на 10 м ниже интерферометра. ...
Article
Full-text available
Прецизионное шлифование является наиболее эффективным методом изготовления точных и особо точных деталей с повышенными требованиями по качеству обработанных поверхностей. Применение лазерных измерительных технологий позволяет заметно повысить точность шлифовальных станков и оптимизировать процедуру комплексной оценки абразивного инструмента и точности шлифуемой детали непосредственно в зоне обработки.
... Syam et al. [18] developed a general methodology to develop in-line surface measurement instruments that focus on millimetre to micrometre feature size. Gao et al. [19] presented the classifications, tasks, and requirements of in-line surface metrology for precision manufacturing, as well as the associated measuring instruments and sensor technologies. ...
... As presented in [4] the quality inspection and control system must acquire the capacity not only to detect defects, but also to adapt to new standards and demands from the manufacturing control system while preventing historical defects from reoccurring. For in-line quality inspection to compete efficiently in accuracy and repeatability with traditional metrology room inspection, measurements must be holistic, thus requiring the exploitation of data and connectivity offered by Industry 4.0 [2,4,17,19]. Furthermore, precision manufacturing can be achieved by using in-line measurements [2,3,15,25]. ...
Conference Paper
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The Zero-Defect Manufacturing (ZDM) movement has received increasing interest from practitioners and academics. However, despite the academic development of the field, the adoption of ZDM enablers such as robotic in-line quality inspection applications has not increased as expected. This article explores the state of adoption of robotic in-line quality inspection at five global Swedish manufacturing companies. Results show that contrary to the case companies' beliefs, more people-and process-oriented challenges have been encountered compared with technological ones. Future work will focus on developing system design guidelines for robotic in-line quality inspection systems in the realm of ZDM.
... During recent decades, measurement processes have become more flexible, due to the integration of knowledge-driven algorithms in combination with multiple sensors and/or measurement technologies [1,2]. Exploiting the advantages offered by different measurement solutions, the design of advanced * Author to whom any correspondence should be addressed. ...
... • Focus variation microscopy (FVM): FVM is another wellestablished surface measurement technology that uses local contrast in narrow-depth-of-field 2D images to build up a 3D height map of a surface [61]. Current research in FVM technologies includes development of algorithms to improve measurement of, for example, smooth surfaces and vertical walls [62,63], as well as in measurement speed increases and measurement system size decreases to allow for in-process measurements [2]. A thorough review of recent advances in FVM technologies is available elsewhere [61]. ...
Article
Full-text available
Manufacturing has recently experienced increased adoption of optimised and fast solutions for checking product quality during fabrication, allowing for manufacturing times and costs to be significantly reduced. Due to the integration of machine learning algorithms, advanced sensors and faster processing systems, smart instruments can autonomously plan measurement pipelines, perform decisional tasks and trigger correctional actions as required. In this paper, we summarise the state of the art in smart optical metrology, covering the latest advances in integrated intelligent solutions in optical coordinate and surface metrology, respectively for the measurement of part geometry and surface texture. Within this field, we include the use of a priori knowledge and implementation of machine learning algorithms for measurement planning optimisation. We also cover the development of multi-sensor and multi-view instrument configurations to speed up the measurement process, as well as the design of novel feedback tools for measurement quality evaluation.
... Today, global manufacturing is evolving rapidly through the adoption of disruptive technologies towards a goal of autonomous 'Industrie 4.0' [8] featuring zero waste and carbon neutrality [9,10]. The realisation of smart manufacturing systems requires a step change in measurement capability to allow highly integrated precision metrology for in-situ, on-machine, and in-process measurements of manufactured components [11][12][13], which is not only non-contact, high speed, robust and low-cost, but that delivers a level of accuracy equivalent to or better than state-of-the-art laboratory-based instrumentation [14][15][16]. ...
... This propagation constant is the same for the light in the core and in the cladding, and can be used to define an effective index, n eff , which would be the refractive index of a homogeneous block of material which would give the same phase advancement in the direction of propagation when a plane wave is incident on it as is found along the optical axis of the fibre. Thus β = n eff k (11) The value of n eff lies between the index of the core and the cladding, and crucially is dependent on the diameter of the core. If the core diameter is changed, the value of β and hence n eff also changes. ...
Article
With increasing digitalisation of engineering and the development of smart manufacturing, precision metrology is gradually moving away from the laboratory into real-world environments and production platforms. Interferometry and focus detection are the most popular optical techniques for these types of application due to their non-destructive measurement, high resolution, and fast response. In this article, we discuss their basic principles, limitations and challenges, and new opportunities. Motivated by the rapid development of artificial materials, the application of metasurfaces to drive a new era for future miniaturisation of optical systems becomes suddenly viable. The article discusses advances in modern miniaturisation of optical techniques; and introduces an approach for evolving to a future using metasurface optics. Optical principles and feasibility studies are included in the discussion.
... Previous study shows the potential benefit of using DIC for workpiece deformation measurements during machining [8]. Contrary to common measurement devices such as strain gages or lasers, which provide point-wise measurements [9], DIC provides full-field measurements. Moreover, DIC has also proven its effectiveness in the manufacturing field [10] as well as in retrieving residual stress distributions [11,12]. ...
... DIC is based on the numerical processing of two pictures taken at two different load levels of a mechanical component undergoing deformations. Contrary to usual measurement techniques such as strain gages, position sensors or measuring probes [9], DIC offers full-field measurements and retrieves displacements at any point of the observed surface. The contrast of the surface of interest is generally enhanced by painting a speckle onto it. ...
Article
Raw parts with high mechanical performances used for aeronautical workpieces are generally obtained by mechanical processes such as molding and/or forging. They mostly undergo additional heat treatments. These processes may induce mechanical residual stress within the material. During the machining step, residual stress are released when material is removed, which leads to initial stress distribution disruption. Thus, the workpiece deforms to satisfy the internal equilibrium, therefore requiring additional operations to be performed to fulfill dimensional and geometrical restrictions. A method has been developed here in order to identify residual stress maps within metal workpieces during machining. This method relies on the residual stress measuring method called “Layer Removal Method” and on a non-contact full-field measuring technique called “Digital Image Correlation”. This development aims at improving traditional residual stress measuring techniques and to realize measurements under harsh conditions, namely during machining. Compared to classical measuring methods, the proposed one involves several improvements such as being a non-contact and optical measurement and being performed continuously during the machining process. This novel approach allows the determination of the initial residual stress distribution across the depth by measuring the through-thickness workpiece displacement fields induced by the residual stress release during machining. A residual stress map within a Al7010-T7451 aluminum alloy beam with a magnitude order lying between −35 MPa and 34 MPa has been retrieved. Obtained results have been compared with literature- and Finite Elements results. This novel approach would ensure measurement of residual stress distributions of a part being machined, allowing monitoring and predicting, in real-time, part deflection. Therefore, adapting machining sequences in real-time would be possible to prevent undesirable deformations.
... Surface measurements with nanometre or even sub-nanometre accuracy are required in some applications, as is the case for extreme-ultra violet lithography [193]. In other applications, it is also desirable to measure the surface of a part directly on or close to the production line in the shop floor, e.g., on-machine and in-process surface metrology, such as the precision manufacturing of micro lenses [265]. ...
... On-machine surface metrology for AM [280] and conventional manufacturing is an area of great interest since it allows immediate surface measurement after (or before) the manufacturing process without removing or repositioning the workpiece, replacing the traditional post-process inspection carried on a stand-alone surface measuring instrument. The term 'on-machine' refers to the measurement of the workpiece surface directly on the machine where the workpiece has been manufactured, whereas the term 'in-situ' refers to the measurement of the workpiece surface within the same work floor, without isolating the workpiece from the manufacturing environment [265]. In both cases, the measurement process can suffer from significant environmental disturbances, requiring the development of adequate methods to effectively mitigate the influence of such. ...
Thesis
Full-text available
Additive manufacturing (AM) is increasingly being used to fabricate fully functional parts. In this scenario, tolerances for dimensions and surface finish become crucial, especially for applications with stringent requirements. Therefore, the measurement of AM parts is essential to ensure adequate performance and to inform the manufacturing process. Typical metal AM surfaces are highly irregular, exhibiting a large number of high aspect-ratio topographic features, deep recesses and loose particles, while polymer AM surfaces are often translucent or have low reflectivity. Because of these characteristics, it can be challenging for any surface measuring technique to accurately measure the topography of metal and polymer AM surfaces. Coherence scanning interferometry (CSI) is one of the most accurate methods for areal surface topography measurement. CSI uses an interferometric objective lens and spatially extended, spectrally broadband illumination. When scanning a surface along the optical axis through the focus of the interferometric objective lens, interference fringes will be visible only within a narrow surface height range, corresponding to the zero group-velocity optical path difference of the interferometer. This phenomenon is known as ‘low-coherence interference’ and provides a highly accurate non-contact sensing mechanism to determine the three-dimensional topography of a surface. CSI has the ability to measure a wide range of surface types, from optically smooth to rough, as well as discontinuous surfaces without the 2π ambiguity that can arise with single-wavelength, phase-shifting interferometry. However, due to the limited numerical aperture of the imaging system, CSI may suffer from poor signal-to-noise ratios when measuring high-slope angle topographic features and surfaces with significant texture, or more generally, surfaces with low reflectance, compromising the ability to reliably determine surface heights. Although previous CSI technologies have shown difficulties when measuring AM surfaces, recent progress in the development of CSI allows a significantly enhanced detection sensitivity through the use of advanced analysis techniques, such as filtering of the light source spectrum bandwidth, high dynamic range lighting levels, oversampling (i.e. adjusting the number of camera acquisitions over each interference fringe) and sophisticated topography reconstruction algorithms. In this thesis, the effects of the aforementioned advanced analysis techniques on the measurement of typical as-built metal AM surfaces covering various textures and slope distributions are empirically investigated and systematically analysed. Guidelines are provided for the optimisation of the measurement of metal AM surfaces by balancing the total data acquisition time, the size of the measurement area, and the percentage of measured data points (i.e. data coverage). The detailed surface topography information captured with CSI is essential for providing feedback to the manufacturing process and for quality control of AM products. To validate this, a challenging case study has been considered. The feasibility of ink-jet printing a transparent polymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (known as THV) to produce films of a few nanometres to several micrometres in thickness has been assessed using CSI. Solutions to minimise the ‘coffee ring’ effect and the formation of undesired wrinkle-like features on the surface when ink-jet printing THV are demonstrated. This work contributes to the field of polymer AM by providing insight into how to control and optimise the quality of ink-jet printed parts with the aid of surface metrology. Reducing measurement noise in CSI is an important consideration when measuring AM surfaces, in particular when the ability to capture data is compromised by poor signal-to-noise ratios. This thesis contributes to the understanding of the workings of measurement noise reduction methods and compares their effects when measuring surface topography in the presence of environmental vibration. The results provide guidance for the reduction of error in surface measurement for AM surfaces, and could be applied in a wider range of applications. The knowledge developed in this research is relevant to the manufacturing and scientific communities as CSI technologies are increasingly applied to the measurement of complex surfaces and in environments that resemble production areas more than metrology laboratories.
... The structural design of machine tool systems has always aimed for higher precision and efficiency, guaranteed by high static and dynamic performances [3]. Static and dynamic characteristics represent the ability to withstand elastic deformations between the tool and workpiece under steady and dynamic cutting loads, respectively [4]. Structural optimization design is a fundamental approach for improving static and dynamic performances and material utilization of machine tools [5]. ...
Article
Full-text available
This study addresses a dynamic modeling and design methodology for machine tools based on parallel artificial neural networks and genetic algorithms. Firstly, subjected to geometrical and static stiffness constraints, a machine tool optimization problem is proposed by minimizing the weighted functions of lower-order natural frequencies and frequency responses. Then, the dynamic analysis of the holistic machine tool is systematically investigated based on the proposed improved reduced dynamic model, leading to the formulation of the mathematical expression for multi-objective optimization. Utilizing genetic algorithms, the proposed optimization problem is solved after the functions between performance and design variables are approximated by employing feedforward backpropagation neural networks. Finally, an optimization example and experiments are implemented on a box-in-box type precision horizontal machine tool prototype. The designed machine tool offers expected dynamic behaviors over the task workspace. Experimental results demonstrate that the derived model is accurate and effective for the prediction of lower-order dynamics, as well as the effectiveness of the design methodology used in its development.
... Meter is one of the seven base units of the International System of Units (SI) 1 and the precise positioning measurement, including linear or rotary standard and displacement, plays an important role in in today's advanced manufacturing industry 2,3,4 In order to achieve accurate, reliable and worldwide comparable results for precise positioning, metrological traceability need to be established to guarantee the measurement results can be related to a reference through a documented unbroken chain of calibrations 5,6 . A metrological length traceability chain normally consists of realization of the definition of the Meter, value transfer between the test system and reference system for the measurands, and measurements of displacement and/or rotations 3 . ...
Preprint
Precise positioning measurement plays an important role in in today advanced manufacturing industry, and length traceability chain has been optimizing and enriching to fulfill the developing and various precise positioning requirement. In this paper, we propose a new length traceability chain based on chromium atom transition frequency, which is a combining utilization of fundamental physical constant accuracy and grating interferometer environmental robustness. The selftraceable grating pitch standard, the selftraceable angle standard and the selftraceable grating interferometer are promising to improve the measurement accuracy, consistency and selfcalibration ability in situ for precise positioning.
... Therefore, the feedback of the measured information is used for generating an accurate repair cutting path. By replacing the conventional post-manufacturing inspection made on an off-machine, on-machine surface metrology is utilized for the task of compensation machining, feedback process and machine tool diagnosis [98]. As one of the future trends, on-machine measurement and monitoring will be an essential part of the advanced machining process for automatic compensation tool path generation to realize the IoT-based activity in intelligent manufacturing. ...
Article
Full-text available
Additive manufacturing (AM), an enabler of Industry 4.0, recently opened limitless possibilities in various sectors covering personal, industrial, medical, aviation and even extra-terrestrial applications. Although significant research thrust is prevalent on this topic, a detailed review covering the impact, status, and prospects of artificial intelligence (AI) in the manufacturing sector has been ignored in the literature. Therefore, this review provides comprehensive information on smart mechanisms and systems emphasizing additive, subtractive and/or hybrid manufacturing processes in a collaborative, predictive, decisive, and intelligent environment. Relevant electronic databases were searched, and 248 articles were selected for qualitative synthesis. Our review suggests that significant improvements are required in connectivity, data sensing, and collection to enhance both subtractive and additive technologies, though the pervasive use of AI by machines and software helps to automate processes. An intelligent system is highly recommended in both conventional and non-conventional subtractive manufacturing (SM) methods to monitor and inspect the workpiece conditions for defect detection and to control the machining strategies in response to instantaneous output. Similarly, AM product quality can be improved through the online monitoring of melt pool and defect formation using suitable sensing devices followed by process control using machine learning (ML) algorithms. Challenges in implementing intelligent additive and subtractive manufacturing systems are also discussed in the article. The challenges comprise difficulty in self-optimizing CNC systems considering real-time material property and tool condition, defect detections by in-situ AM process monitoring, issues of overfitting and underfitting data in ML models and expensive and complicated set-ups in hybrid manufacturing processes.
... Therefore, the feedback of the measured information is used for generating an accurate repair cutting path. By replacing the conventional post-manufacturing inspection made on an off-machine, on-machine surface metrology is utilized for the task of compensation machining, feedback process and machine tool diagnosis [98]. As one of the future trends, on-machine measurement and monitoring will be an essential part of the advanced machining process for automatic compensation tool path generation to realize the IoT-based activity in intelligent manufacturing. ...
Article
Full-text available
Additive manufacturing (AM), an enabler of Industry 4.0, recently opened limitless possibilities in various sectors covering personal, industrial, medical, aviation and even extra-terrestrial applications. Although significant research thrust is prevalent on this topic, a detailed review covering the impact, status, and prospects of artificial intelligence (AI) in the manufacturing sector has been ignored in the literature. Therefore, this review provides comprehensive information on smart mechanisms and systems emphasizing additive, subtractive and/or hybrid manufacturing processes in a collaborative, predictive, decisive, and intelligent environment. Relevant electronic databases were searched, and 248 articles were selected for qualitative synthesis. Our review suggests that significant improvements are required in connectivity, data sensing, and collection to enhance both subtractive and additive technologies, though the pervasive use of AI by machines and software helps to automate processes. An intelligent system is highly recommended in both conventional and non-conventional subtractive manufacturing (SM) methods to monitor and inspect the workpiece conditions for defect detection and to control the machining strategies in response to instantaneous output. Similarly, AM product quality can be improved through the online monitoring of melt pool and defect formation using suitable sensing devices followed by process control using machine learning (ML) algorithms. Challenges in implementing intelligent additive and subtractive manufacturing systems are also discussed in the article. The challenges comprise difficulty in self-optimizing CNC systems considering real-time material property and tool condition, defect detections by in-situ AM process monitoring, issues of overfitting and underfitting data in ML models and expensive and complicated set-ups in hybrid manufacturing processes.
... Although there are many benefits to metal PBF technologies, the processes are poorly understood when compared to traditional subtractive manufacturing methods, resulting in a relative lack of confidence in the quality of parts being built [12,13]. A significant cause for the lack of confidence in additive components stems from the complex phenomena present during the build process [13][14][15][16], such as the meltpool mechanics, as well as cost concerns associated with wasted time and discarded raw materials when a build process fails [13,[17][18][19]. ...
Thesis
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Metal powder bed fusion systems have been rapidly gaining interest from high-value manufacturing sectors, such as aerospace and biomedical, due to the unique benefits the technology can offer in terms of part design flexibility and bespoke manufacturing. In-process monitoring techniques for metal powder bed fusion have become increasingly popular as the technology continues to mature. However, adequate methods of handling data collected from the manufacturing process have yet to be explored in depth. Due to the large quantities of potential data and the temporal constraints when monitoring the PBF process, automated data interpretation is essential to allow for real time defect detection to be achieved. In this thesis, a novel measurement method for PBF systems is proposed that uses multi-view fringe projection to acquire high-resolution surface topography information of the powder bed. Measurements were made using a mock-up of a commercial powder bed fusion system to assess the system’s accuracy and precision in comparison to conventional single-view fringe projection techniques for the same application. Featured based characterisation methods were applied to the measured topography to extract salient information about spatter and particles with the data being compared against a higher resolution reference measurement (focus variation). Results show that the multi-view system is more accurate, but less precise, than single view fringe projection on a point-by-point basis. The multi-view system also achieves a high degree of surface coverage by using alternate views to access areas not measured by a single camera. Measurements from the multi-view fringe projection system achieved similar reconstruction fidelity to the reference focus variation, in particular at the scales required for the largest targeted features (200 µm size and up). Topography partitioning and feature identification results achieved by feature based characterisation were comparable between fringe projection and focus variation.
... is a photogrammetric-based 3D reconstruction approach offering low-cost data acquisition, automated image processing, and high accuracy in the 3D reconstruction of well-textured objects (Remondino et al., 2014;Ahmadabadian et al., 2017). The MVS method has been used in various areas such as reverse engineering (Menna et al., 2010;Geng and Bidanda, 2017), medicine (De Benedictis et al., 2018;Kim et al., 2018), quality control (Gao et al., 2019), industrial inspection (Rodríguez-Gonzálvez et al., 2017;Karami et al., 2022a) or 3D micromeasurement (Atsushi et al., 2011;Lu and Cai, 2020). However, photogrammetric methods failed or produce noisy results in areas with textureless or repetitive textures, or significant illumination variations across camera stations. ...
Article
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Image-based 3D reconstruction has been successfully employed for micro-measurements and industrial quality control purposes. However, obtaining a highly-detailed and reliable 3D reconstruction and inspection of non-collaborative surfaces is still an open issue. Photometric stereo (PS) offers the high spatial frequencies of the surface, but the low frequency is erroneous due to the mathematical model's assumptions and simplifications on how light interacts with the object surface. Photogrammetry, on the other hand, gives precise low-frequency information but fails to utilize high frequencies. As a result, in this research, we present a fusion strategy in Fourier domain to replace the low spatial frequencies of PS with the corresponding photogrammetric frequencies in order to have correct low frequencies while maintaining high frequencies from PS. The proposed method was tested on three different objects. Different cloud-to-cloud comparisons were provided between reference data and the 3D points derived from the proposed method to evaluate high and low frequency information. The obtained 3D findings demonstrated how the proposed methodology generates a high-detail 3D reconstruction of the surface topography (below 20 µm) while maintaining low-frequency information (0.09 µm on average for three different testing objects) by fusing photogrammetric and PS depth data with the proposed FFT-based method.
... With the rapid improvement of the functionalities of major equipment and cutting-edge instruments, the requirements on the surface quality of key opto-electronics components are increasing continuously [1][2][3]. Functional components are developing towards large sizes, complex shapes, high precision, and multi-scale integrity. The microscaled defects have significant impact on the functionalities of key functional components, such as the telescopic mirrors, photovoltaic wafer, opto-electronics films etc. Henceforth the full-area measurement of large specular components has become a great challenge in the field of precision engineering [4]. ...
Article
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The microscopic characterization of the surface defects on large opto-electronics components is essential to ensure the performance of major equipment. However, existing technology cannot achieve efficient and reliable fast cross-scale measurement due to the requirement on vertical scanning or polarization modulation for multi-frame capturing at each position. An effective approach is proposed to solve this problem, which needs to record only one interferometric hologram at each location and achieves full-area measurement by traversing over the surface. The overlapped area between adjacent regions is specified by wavefront registration and the topography in this area is obtained by two-step phase shifting and holographic reconstruction. Experimental results demonstrate that the proposed method can achieve fast and fast measurement of large specular components with high accuracy and high efficiency.
... Precision positioning is a fundamental operation in manufacturing, such as tool positioning with respect to a workpiece in a machine tool or the positioning of a probe with respect to a measurement target in a profile measuring instrument [1][2][3][4]. As the basis for precision positioning, displacement sensors for single-axis measurement, including laser interferometers [5,6] and linear encoders [7,8] have been developed over the past several decades. ...
Article
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A modified two-axis surface encoder is proposed to separately measure both the in-plane displacement and the Z-directional out-of-plane displacement with minor crosstalk errors. The surface encoder is composed of a scale grating and a small-sized sensor head. In the modified surface encoder, the measurement laser beam from the sensor head is designed to be projected onto the scale grating at a right angle. For measurement of the X- and Y-directional in-plane scale displacement, the positive and negative first-order diffracted beams from the scale grating are superimposed on each other in the sensor head, producing interference signals. On the other hand, the Z-directional out-of-plane scale displacement is measured based on the principle of a Michelson-type interferometer. To avoid the influence of reflection from the middle area of the transparent grating, which causes periodic crosstalk errors in the previous research, a specially fabricated transparent grating with a hole in the middle is employed in the newly designed optical system. A prototype sensor head is constructed, and basic performances of the modified surface encoder are tested by experiments.
... This factor is always important, especially when the measurements are taken on a machine that is not calibrated. In their study, Gao et al. present several algorithms to separate these errors [23]. Hrehova et al. describe the application of non-contact sensors using a neural network to detect points on the surface of the workpiece [24]. ...
Article
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Laser scanning technology has been used for several years. Nevertheless, no comprehensive study has been conducted to prove that the application of confocal chromatic sensor (CCHS) laser technology is effective and suitable to verify the integrity parameters of machined surfaces in terms of cutting tool damage. In this paper, the optimization and effects of five factors (cutting speed, feed, depth of cut, attachment length of the workpiece, and tip radius) on the roundness deviation measured by CCHS and, at the same time, on the amount of wear on the back side of the cutting part of the tool were studied according to ISO 3685, which was measured with a microscope. The results obtained were evaluated using the gray relational analysis method (GRA), in conjunction with the Taguchi method, and the significance of the factors was demonstrated using the analysis of variance (ANOVA) method.
... However, as smart manufacturing puts more emphasis on in-process decision-making and closed-loop control, conventional static 3D optical sensing may no longer satisfy the requirement, given that real-time data acquisition and processing are needed. Taking the advanced additive manufacturing technology as an example where in-process diagnosis plays a significant role, a real-time 3D optical sensing system can be extremely valuable if incorporated into the envelope of an additive printing machine to acquire the layer-by-layer surface topographies of the printed constructs [7,8]. Achieving this, however, poses significant challenges for current 3D optical sensing techniques, given the combined requirements of high speeds and high accuracies for the measured 3D surface topographies. ...
Article
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This paper presents examples of high-speed 3D optical sensing for research and applications in the manufacturing community. Specifically, this paper will focus on the fringe projection technique as a special technology that can be extremely beneficial to manufacturing applications, given its merits of simultaneous high-speed and high-accuracy 3D surface measurements. This paper will introduce the basic principles of 3D optical sensing based on the fringe projection technique as well as the enabled manufacturing research applications, including both in-situ/in-process monitoring and post-process quality assurance.
... DHM does not have sufficient resolution for in-line measurement for microstructured surfaces for the following reason. For measurements in production line, i.e., in-line measurements [8], it is necessary to keep a sufficient distance between the tip of a measuring instrument J o u r n a l P r e -p r o o f and an object to be observed. This is to avoid possible collisions between the tip of a measuring device and components with different heights in a product, and to open up the possibility of using jigs and tools near the observation object. ...
Article
In case of in-line inspection of optical functional micro-structured surfaces with phase response as well as amplitude response, higher resolution than the diffraction limit and phase measurability are needed. We proposed a novel coherent super-resolution method named complex-amplitude-response SIM (structured illumination microscopy). An equation is derived that enables extraction of frequencies higher than the diffraction limit of the complex-amplitude response distribution of a sample from multiple acquired images, which had not been obtained previously. This equation was validated through theoretical analysis by using images calculated by numerical optical simulation that were assumed to be acquired. Numerical analyses using the derived equation and simulations of image acquisition revealed that the proposed method is able to measure phase- and amplitude-response distributions of samples with a resolution higher than the diffraction limit. It was demonstrated that the proposed method is able to separate two points at a submicron distance of 500 nm under conditions of visible light and long W.D. (NA 0.2) and measure the phase difference with a maximum error of approximately 0.03 rad (∼π/100). When the amplitude response distribution of a sample is uniform and consists only of phase responses, the structure of the sample cannot be observed by standard optical microscopy. Numerical simulations revealed that the proposed method is able to visualise such samples with fine periodic phase responses on the submicron scale (∼500 nm) beyond the diffraction limit. Furthermore, we have shown that the proposed method is able to detect phase defects in ultra-fine optical functional structures with periods of less than 100 nm, which is expected to characterize the next generation metasurfaces.
... Although this issue can be addressed by conducting an experiment with a large Fizeau form interferometer capable of capturing the diffracted wavefront from the whole area of a large-scale VLS grating [27], it costs too much to prepare such an interferometer in ordinary research laboratories and machine shops. Another solution for this issue is to perform stitching measurements [28][29][30]. The authors' group has carried out stitching calibration of a long-range linear scale [31], and a linear scale in size of 105 mm over the aperture of a Fizeau interferometer (100 mm) has successfully been evaluated. ...
Article
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A new method based on the interferometric pseudo-lateral-shearing method is proposed to evaluate the pitch variation of a large-scale planar variable-line-spacing (VLS) grating. In the method, wavefronts of the first-order diffracted beams from a planar VLS grating are measured by a commercial Fizeau form interferometer. By utilizing the differential wavefront of the first-order diffracted beam before and after the small lateral shift of the VLS grating, the pitch variation of the VLS grating can be evaluated. Meanwhile, additional positioning errors of the grating in the lateral shifting process could degrade the measurement accuracy of the pitch variation. To address the issue, the technique referred to as the reference plane technique is also introduced, where the least squares planes in the wavefronts of the first-order diffracted beams are employed to reduce the influences of the additional positioning errors of the VLS grating. The proposed method can also reduce the influence of the out-of-flatness of the reference flat in the Fizeau interferometer by taking the difference between the measured positive and negative diffracted wavefronts; namely, self-calibration can be accomplished. After the theoretical analysis and simulations, experiments are carried out with a large-scale VLS grating to verify the feasibility of the proposed methods. Furthermore, the evaluated VLS parameters are verified by comparing them with the readout signal of an absolute surface encoder employing the evaluated VLS grating as the scale for measurement.
... With the development of computer-aided design (CAD) modeling technology, free-form surfaces with superior geometric properties [1,2] have become complex and commonly used features in engineering, such as automobile coverings, aircraft wings, turbine blades, and injection mold surfaces. Through the on-machine measurement (OMM) technology [3,4], the quality of these complex surfaces can be directly inspected on computer numerical control (CNC) machine tools after machining. However, due to the influence of geometric characteristics, tolerance requirements, inspection instruments, and other factors in the inspection process of the surface, the relationship between the surface itself and the OMM performance (number of measured points, measurement efficiency, measurement results, etc.) is complicated. ...
Article
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With the on-machine measurement (OMM) technology, the quality of curved workpieces can be measured directly on the machine after computer numerical control machining. Aiming at the problem that the complexity of surface measurement in traditional methods is only judged by subjective experience and is difficult to calculate, an image-based surface measurement complexity (SMC) quantitative model is proposed. First, according to the curved surfaces’ characteristics during the OMM process, the concept of SMC is introduced by analyzing several key factors. Then, the curvature and smoothness information of three-dimensional surfaces is converted into two-dimensional images’ information by using the conformal mapping with dimensionality reduction. Next, based on the image color and texture complexity calculation, a mathematical model combined with the area and profile correction coefficients is established. Finally, the SMC model’s validity is verified by a set of design-machining-inspection experiments on curved surfaces, and the relevant laws between the SMC and measurement efficiency and measurement accuracy are presented.
... The linear interpolation isometric compensation eliminates most of the linear movement error and achieves a high positioning accuracy of less than one micrometer in one-meter length. The compensation procedures for straightness, squareness, and kinematic errors have been examined a lot [9][10][11], including constructing a kinematics error model, such as the multi-body theory [12] or a linear motion error model [13], selecting a consistent approach, such as the reversal method [14], and spherical test approach [15] to draw the error map, generate compensation data according to the machining path, and modify the compensation data according to the machining results. From the view of the control theory and mechanical dynamics, the basis for implementing the above procedure is the axis that moves the compensation data and can quickly respond during the total machining process. ...
Article
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This paper describes a method for measuring and compensating the roundness error of a larger mandrel manufactured by an ultra-precision diamond-turning lathe aimed to obtain a calibration cylinder with a roundness of less than 0.1 μm. The diamond-turning machine has a cross-stacked hydrostatic guideway, produces a cutting depth and feed movement direction, and a dual-spindle system that is firmly connected to the bed. Due to the good repeatability of aerostatic spindles, only in situ rather than online real-time measurements are required. To this end, three high-precision capacitance displacement sensors were utilized to detect the cross-section of the workpiece and the time domain via the three-point error separation technique to separate the roundness error from the rotation motion error. The slow tool servo (STS) cutting technique was employed to compensate for the roundness error, which did not require extra axes, only the excellent dynamic response of the feed axis; hence, the servo control parameters could be suitably adjusted. The experimental results reveal that the low-order harmonic error, often caused by aerostatic spindles, is almost removed completely. For this particular lathe, the experiments indicate that about 60% of the rotational error motion is compensated, and the roundness error is reduced to less than 0.1 μm, which is evaluated by the least-squares circle method.
... To compensate workpiece setting errors, a scanning type on-machine measurement device Nanochecker (FANUC corp.) is adopted in this study by expecting the merits of integration and simple-to-understand probe-surface interaction (Gao et al., 2019). Since the device is controlled by the same NC system, the actual workpiece position and orientation can be detected in the machine coordinate system. ...
Article
Ultraprecision cutting used for creating highly precise components and particularly micro-shapes requires ultraprecision machine tools. However, these machine tools are operated under restricted cutting conditions such as feed rate and depth of cut, resulting in low productivity. Therefore, this study deals with this problem by devising a novel ultraprecision cutting system with automation of the workpiece setting operation. In the devised system, the workpiece is roughly machined by an ordinary machine tool. After that, an industrial robot transfers the workpiece to an ultraprecision machine tool to complete the rest of the machining process. The proposed machining system overcomes two types of errors. The first is the shape error due to rough machining on the ordinary machine tool. It is practically difficult to create the expected shape exactly in rough machining, and therefore the shape error of the roughly machined workpiece is affecting the finish machining directly. The other is the setting errors due to the transfer of the workpiece to the ultraprecision machine tool from the ordinary machine tool. The differences from the ideal workpiece position and orientation are detected to identify the setting errors. Thus, the roughly machined workpiece is scanned to derive an error map by on-machine measurement. Additional tool paths are generated for semi-finish machining, and the error map helps to eliminate the form errors induced by rough machining. The NC program for finish machining is modified to compensate the identified workpiece setting errors. Finally, finish machining can be conducted on the roughly machined workpiece. Hence, the removal volume in finish machining on an ultraprecision machine tool is reduced, and the time required for the whole machining process is expected to be shorter. The experimental results confirm that the developed ultraprecision cutting system contributes to the automated workpiece setting operation to create micro-shapes with high accuracy.
... Hence, machine vision could provide a contactless and automated method of measuring surface roughness, which replaces conventional methods [2]. In conventional systems, the surface quality is measured by the use of mechanical stylus profilers and determined by offline operation [123]. For examining the quality of the machined surfaces, e.g., the roughness of the surface, the technical descriptions are hard to be assured using a simple one-step process. ...
Article
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Computer vision provides image-based solutions to inspect and investigate the quality of the surface to be measured. For any components to execute their intended functions and operations, surface quality is considered equally significant to dimensional quality. Surface Roughness (Ra) is a widely recognized measure to evaluate and investigate the surface quality of machined parts. Various conventional methods and approaches to measure the surface roughness are not feasible and appropriate in industries claiming 100% inspection and examination because of the time and efforts involved in performing the measurement. However, Machine vision has emerged as the innovative approach to executing the surface roughness measurement. It can provide economic, automated, quick, and reliable solutions. This paper discusses the characterization of the surface texture of surfaces of traditional or non-traditional manufactured parts through a computer/machine vision approach and assessment of the surface characteristics, i.e., surface roughness, waviness, flatness, surface texture, etc., machine vision parameters. This paper will also discuss multiple machine vision techniques for different manufacturing processes to perform the surface characterization measurement.
... These methods are commonly used in various applications [4][5][6]. In particular, in the field of industrial metrology, they can be used for quality control [7][8][9][10], inspection [11][12][13][14], reverse engineering [10,[15][16][17] or 3D micro-measurement [18][19][20]. ...
Article
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Image-based 3D reconstruction has been employed in industrial metrology for micro-measurements and quality control purposes. However, generating a highly-detailed and reliable 3D reconstruction of non-collaborative surfaces is still an open issue. In this paper, a method for generating an accurate 3D reconstruction of non-collaborative surfaces through a combination of photogrammetry and photometric stereo is presented. On one side, the geometric information derived with photogrammetry is used in areas where its 3D measurements are reliable. On the other hand, the high spatial resolution capability of photometric stereo is exploited to acquire a finely detailed topography of the surface. Finally, three different approaches are proposed to fuse both geometric information and high frequency details. The proposed method is tested on six different non-collaborative objects with different surface characteristics. To evaluate the accuracy of the proposed method, a comprehensive cloud-to-cloud comparison between reference data and 3D points derived from the proposed fusion methods is provided. The experiments demonstrated that, despite correcting global deformation up to an average RMSE of less than 0.1 mm, the proposed method recovers the surface topography at the same high resolution as the photometric stereo.
... Several physical parameters such as angle, position, and length are of the utmost importance for greater precision and accuracy for these optical devices. Till to date, various methods have been employed to measure the angle using protractors, calipers, and fixed angle gauges since ancient times [2,3]. These days, optical fiber sensors have received much attention because of their compactness, low-cost, lightweight, small size, electrically passive operation, implementation of multiplexing schemes, and immunity to electromagnetic interference [4]. ...
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The developed angle sensors are usually used for either clockwise or an anti-clockwise direction. Here, we present a relatively new setup of two angle sensors (1-D and 2-D) for independent and simultaneous clock and anti-clockwise rotation measurements. The proposed sensor is based on the twisted macro-bend coupling method (TMBC), in which two fibers are twisted and bent. The two-angle sensors are presented in which sensor-1 consists of a single twisted bend and sensor-2 contain two twisted bends on a single transmitting fiber. The angle measurement relies on the coupling of macro-bend loss. The stepper motor is used to drag the twisted fiber, resulting in a change in the bending radius that increases or decreases the macro-bend loss. A novel cascading method is introduced in the TMBC method for the sensor-2 and, two stepper motors are used in the second experiment. To prove the practicality, several test scenarios are conducted for both sensor configurations. The experimental results show that sensor-1 can measure angle ±180º, whereas the full clock and anti-clockwise cycle are achieved through sensor-2, having a measurement range is ±360º. Therefore, the proposed sensor can be a potential means for accurate angle measurement in industrial applications.
... Therefore, optical instruments prove to be more suitable for dimensional evaluation and perform quality characterization. Recent developments in metrology area concern the attempt to include quality characterization by means of optical techniques in the IM process, in order to obtain better precision and more reliable results [24]. In the present work, optical measurements of molded part length and surface measurements are performed via confocal microscope CSM 700 (ZEISS, Milan, Italy) by using a Z-scan acquisitions technique and following the ISO 25178-2 standard, which regulates roughness evaluation from optical topographic measurements. ...
Article
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Quality evaluation of micro injection molded products is a complex task, in particular when instruments basing on contact methods are used and issues in measurements could arise due to the contact tool dimension not fitting well with extremely narrow features. Therefore, in these cases, optical methods may be preferred for the evaluation of molded products’ dimensions and surface quality, especially for parts devoted to applications requiring functional purposes. In this context, the present paper proposes the use of surface parameters as a quality index for the evaluation of both the micro injection molding process and the resulting products. To this aim, two experimental procedures were implemented to allow for: (i) the evaluation of the most suitable surface parameters identified in relation to the process parameters; (ii) comparisons of the surface parameters findings with those obtained by classic dimensional quantity via a designed experimental plan (DoE). The results show that the surface parameters, evaluated in critical areas of the components, can ensure reliable estimates for the surface quality of the molded parts and can be preferred in comparison to linear measurements
Article
A measurement method based on a confocal probe on the second harmonic generation that can measure linear and angular displacements in the focusing point is proposed. In the proposed method, a pinhole or an optical fiber placed in front of the detector in conventional confocal probes is replaced by a nonlinear optical crystal, which is utilized as a medium generating second harmonic wave whose light intensity changes by the linear and angular displacements of a target under measurement. The feasibility of the proposed method is verified by theoretical calculations and experiments with the newly designed optical setup. Experimental results have demonstrated that the developed confocal probe has a resolution of 20 nm and 5 arc-seconds for measurement of linear and angular displacements, respectively.
Chapter
Due to increasing efforts to shorten the time to market of new vehicle models, press tooling is under increasing competitive pressure. The manufacturing of press tools for high-quality body components depends on a large extent on the quality of the tools active surfaces as free-form surfaces. The use of non-contact optical measurement methods to digitize the tool surfaces creates high-density point clouds that have great potential to improve the manufacturing process through their analysis. In this paper, a method for the analysis of these point clouds is presented, which combines the qualitative and quantitative analysis of active surfaces, to enable conclusions about the process strategy and allow further optimizations to achieve cost and time savings. It is demonstrated on the example of a test specimen with characteristic elements of a press tool for vehicle body components. A parameter SQ is defined, which describes the area percentage inside of tolerance limits, acting as a quality parameter for the manufacturing result. The used test specimen achieves a SQ value of 93.9%. The robustness of SQ is investigated by a variation of the tolerance limits and a possible applicability to other components outside of vehicle body components is considered. Furthermore the distribution of the shape deviation is evaluated to determine whether too much or too little material removal causes the deviations, as well as in which angles it mainly occurs. It can be shown that the qualitative analysis of the false color image can be confirmed by the quantitative results of the proposed method. Based on this, optimization measures for the machining process are derived.Keywords3D-metrologyData analysisPress tool manufacturingMilling precision
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In this paper, a practical issue of the application of cubic boron nitride (CBN) cutting tools for the machining of steel 100Cr6 thin-walled bearing rings is addressed. Three geometries of the commercially available CBN cutting inserts were tested at different machining parameters. The effect of geometry was assessed in terms of surface integrity, considering 2D profile parameters, 3D topography of the surface, and residual stresses in the surface layer. The results were sometimes contradictory, since the same cutting inserts provided the largest and the lowest values of the topography parameters, dependent on different cutting conditions. In general, CBN cutting inserts with XCEL geometry ensured the smallest profile parameters Ra and Rz, and the spatial parameters of Smr1 exhibited the largest values among all tested tools, suggesting reduced wear resistance. Residual stresses analysis did not reveal any inacceptable or potentially dangerous surface layer state after machining.
Article
Accurate recovery of complex surfaces of manufactured artefacts frequently requires intensive sampling, resulting in inefficient measurements for some point-by-point probe instruments. To tackle this problem, we fully exploit Gaussian Process (GP) to guide the super resolution (SR) model to perform efficient and accurate sampling. The model makes use of a kernel-based GP method to model these low-frequency geometric features, while a pretrained SR method with multiple residual attention blocks is used to focus on the high-frequency features and further improve the details of the surface. In addition to geometric errors and distance information, global uncertainty from the statistical properties of the GP and an additional feature error from the SR are combined as critical criteria to select the most informative points of the surface. The effectiveness of the proposed method was demonstrated through several experiments on synthetic and real-world data, showing that the proposed method achieves state-of-the-art performance for pointwise measurements.
Article
Large measurement ranges and curvature changes are characteristics of curved surfaces, making it difficult to measure their topography. In this study, a four-axis measurement system is developed, and a tilt scanning measurement method using a chromatic confocal sensor is proposed to measure curved surfaces. The measurement area is divided into different parts, in which the tilt scanning measurement is performed with different angles of the chromatic confocal sensor. After the scanning, the complete measurement data are restored by data processing and stitching. Compared with conventional scanning methods, the proposed method expands the range of measurement. Finally, the effectiveness of the developed measurement system and the tilt scanning measurement method is clearly verified by measuring a spherical specimen with a radius of 50 mm.
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Small and Medium Enterprises (SMEs) and Micro, Small, and Medium Enterprises (MSMEs) contemplate integrating machine vision with high throughput manufacturing lines to ensure a consistent quality of standardized components. The inspection productivity can improve considerably by substituting machine vision with manual inspection activities. The pre-trained Convolutional Neural Networks (CNNs) can facilitate enhanced machine vision capabilities compared to the rule-based classical image processing algorithms. However, the non-availability of labeled datasets and lack of expertise in model development restricts their utilities for SMEs and MSMEs. The present work examines the practicality of utilizing publicly available labeled datasets while developing surface defect detection algorithms using pre-trained CNNs considering case studies of typical machined components - flat washers and tapered rollers. It is shown that the publicly available surface defect datasets are ineffective for specific-case such as machined surfaces of flat washers and tapered rollers. The explicitly labeled image datasets can offer better prediction abilities in such cases. A comparative assessment of common pre-trained CNNs is conducted to identify an appropriate network while developing a surface defect detection framework for machined components. The common pre-trained CNNs VGG-19, GoogLeNet, ResNet-50, EfficientNet-b0, and DenseNet-201 showing prediction abilities for similar classification tasks have been examined. The pre-trained CNNs developed using explicit image datasets were implemented to segregate defective flat washers and tapered rollers as sample components manufactured by SMEs and MSMEs. The performance assessment was accomplished using parameters estimated from the confusion matrix. It is observed that EfficientNet-b0 outperforms other networks on most parameters, and it can be preferred while developing a surface defect detection algorithm. The outcomes of the present study form the basis for developing an integrated vision-based expert system for surface defect detection tasks.
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Laser triangulation sensors are one of the most commonly used optical sensors in dimensional metrology and quality control. This article presents a method for simulating the laser speckle-induced measurement uncertainty, representing a major performance limitation of these sensors, as well as the effects of speckle reduction mechanisms based on spatio-temporal averaging. To investigate the relation between triangulation angle and the resulting speckle-induced uncertainty, simulations are performed for three sensor geometries, revealing that a larger angle results not only in a smaller measurement range but also in a reduced influence of laser speckle and a smaller uncertainty. A parameter study on a speckle-reducing moving diffuser mechanism, integrated into the optical sensor path, investigates the achievable improvement for various combinations of motion frequency and amplitude. The accuracy of the simulation results is validated by measurements conducted with an experimental setup, demonstrating good agreement between the measured and simulated uncertainty values with and without the speckle reduction mechanism. It is shown that the diffuser is capable of reducing the resulting speckle-induced measurement uncertainty by up to 63%.
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The implementation of the concepts of a smart home - smart city implies a high level of automation using control and measuring devices and equipment, as well as computer and informational technologies. One of the effective trends of automation is the widespread use of computer measuring systems Article presents the model of operation of a computer measuring system with digital data processing is proposed. The presented model is based on the semi-Markov model of operation of an analog-to-digital converter, on the semi-Markov model of an embedded personal computer, on the analytical formula for calculating the availability factor of computer measuring system. The analytical expression for the availability factor of a computer measuring system includes both the technical and operational characteristics of the computer, as well as the metrological and technical characteristics of the analog-to-digital converter. The specified expression allows to find the optimal value of calibration and verification interval. Determination of the optimal calibration interval required to control the metrological characteristics during long-term operation of the computer measuring system. The developed model can be used to set requirements for the metrological support of instruments and de-vices used in the framework of the automation trend in the sphere of housing and communal services.
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An angle sensor based on multiple beam interference of a Fabry-Pérot etalon employing a mode-locked femtosecond laser as the measurement beam is proposed. Output angles are evaluated by using estimated local maxima within a measurement bandwidth of an output fringe spectrum detected by an optical spectrum analyzer. In the proposed method, fringe spectra produced by beams from transmittance and a reflectance side of the Fabry-Pérot etalon are detected individually, and intensities of two spectra are divided to increase the visibility by narrowing a spectrum width. Confirmation of an increase in the visibility is conducted by comparing full width half maximum values of spectra obtained by a constructed optical setup, and evaluation accuracies were compared by repeating measurements for 100 times. The output angle using estimated local maxima of the divided spectra is then evaluated to verify the feasibility of the proposed method. As a result, it is confirmed that the proposed method improves the accuracy of angle determination by one order of magnitude.
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Advances in industrial manufacturing and an increasing trend towards direct integration of measurement systems in the production line require flexible, fast, precise and robust systems. This paper presents the development and evaluation of a fully automated robot-based in-line measurement system, suitable for applications incorporating process variability and uncertainty, however, requiring single micrometer resolution and low instrumentation effort. The system utilizes laser triangulation in combination with mechanical 2D-scanning for fast and precise measurements. Lissajous trajectories and a computer vision algorithm based on edge detection are used to locate relevant features within the scan area. This allows alignment of the measurement tool, by using plane fits, to optimally utilize the measurement range of the sensor system for a high resolution scan, applied to a refined area, providing robustness and flexibility. For a scan area of 25×25mm the measurement uncertainty equals 6.4μm at 2σ. The system accuracy is evaluated to 2.2μm. The combined standard uncertainty of reference sample measurements equals 1.2μm.
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Based on the Talbot effect of optical gratings, we propose a novel out-of-plane optical displacement sensor with an ultracompact structure, to the best of our knowledge. Using two optical gratings with a slight angle between them, two angular-modulated signals with a phase difference of 90° are obtained associated with a two-quadrant photodetector, which are in sinusoidal relationship with the displacement in the direction perpendicular to the grating plane. Using an interpolation subdivision circuit with a subdivision factor of 1000, out-of-plane displacement measurement with a resolution of 11.23 nm within a range of 1 mm is obtained.
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Ultraprecision mold machining combined with precision glass molding is the most promising technology for the mass production of glass microlens arrays (MLAs). However, fabricating an MLA with a high aspect-ratio (AR) (ratio of height to aperture), submicron scale profile accuracy, nanoscale surface finish, and good consistency remains a considerable challenge. A local spiral diamond milling (LSDM) method is proposed to generate a high AR MLA on a nickel-phosphorous (Ni-P) plated mold. A spiral toolpath generation algorithm that considers the tool edge radius and performs profile error (PV) compensation is developed. Each lenslet at any local position can be precisely machined by controlling the servo motions of the three translational axes. Then, the entire MLA can be generated by shifting the toolpath to go through the centers of all lenslets according to the MLA layout. The tool parameters are optimized to avoid local and global tool interference during machining. The generated toolpath provides steady slide axis movements to avoid dramatic changes in cutting speed and acceleration. An MLA with an AR of 0.166 is fabricated. The results show that the fabricated mold and the molded lenses have a profile accuracy (PV) of less than 1 μm and a surface roughness (Ra) of less than 14 nm. The cross-sectional profiles indicate that the fabricated MLA has high machining consistency.
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The design and testing of different optical heads were performed to evaluate the pitch deviation of a diffraction scale grating with a small diffraction angle. Based on the proposed pitch deviation evaluation method employing optical angle sensors based on laser autocollimation, a modified optical head with position-sensitive detectors (PSDs) is first designed and constructed by following the conventional optical configuration. Owing to the small angle of diffraction of the first-order diffracted beams, the modified optical head has a large working distance, resulting in poor sensor stability. Therefore, a novel and compact optical head employing a pair of small prisms is designed and developed to shorten the working distance of the optical head. An additional modification was also made to the developed compact optical head in such a way that collimator objectives (COs) in the laser autocollimation units are removed to improve the sensor sensitivity. Experimental comparisons were conducted using the three types of optical heads to verify the feasibility of the developed optical angle sensor with PSDs.
Article
This keynote paper mainly focuses on advancements of machining technology and systems for enhanced performance, increased system integration and augmented machine intelligence, critically hinging on new sensors, sensor systems and sensing methodologies being robust, reconfigurable and intelligent, while providing direct adoption and plug-and-play use in industrial practice. One chief novelty is given by the key enabling technologies of Industry 4.0 where integration of sensing systems in manufacturing plants is a cornerstone for transforming conventional manufacturing concepts into digital manufacturing paradigms. Application examples to industrial processes, future challenges and coming trends in machining monitoring are shown.
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In contrast to measurements of the dimensions of machined parts realized by machine tools and characterized by CMMs, software results are not fully traceable and certified. Indeed, a computer is not a perfect machine and binary encoding of real numbers leads to rounding of successive intermediate calculations that may lead to globally false results. This is the case for poor implementations and poorly conditioned algorithms. Therefore, accurate geometric modelling and implementations will be detailed. Based on the works of National Metrology Institutes, the problem of software traceability will also be discussed. Some prospects for this complex task will finally be suggested.
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In order to enhance the measurement availability for manufacturing applications, on-machine surface measurement (OMSM) is integrated onto the machine tools, which avoids the errors caused by re-positioning workpieces and utilizes the machine axes to extend the measuring range as well. However, due to the fact that measurement probe actuation is performed using the machine tool axes, the inherent kinematics error will inevitably induce additional deviations onto the OMSM results. This paper presents a systematic methodology of kinematics error modelling, measurement, and compensation for OMSM on an ultra-precision turning lathe. According to the measurement task, a selective kinematics error model is established with four primary error components in the sensitive measurement direction, based on multi-body theory and a homogeneous transformation matrix (HTM). In order to separate the artefact error from the measurement results, the selected error components are measured using the reversal method. The measured error value agrees well with the machine tool’s specification and a kinematics error map is generated for further compensation. To verify the effectiveness of the proposed kinematics error modelling, measurement, and compensation, an OMSM experiment of an optically flat mirror is carried out. The result indicates the OMSM is the superposition of the sample surface form error and the machine tool kinematics error. With the implementation of compensation, the accuracy of the characterized flatness error from the OMSM improves by 67%.
Article
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A multilateration technique using three laser trackers to assess the geometrical errors of machine tools, not from a volumetric approach, but from a geometrical one is presented. It has been applied to a medium-size milling machine together with other more conventional systems, including laser interferometer, reference ball artifacts, and self-centering probes. A comparison among all these different techniques and the errors obtained has been carried out in order to determine their respective limitations and the sources of uncertainty affecting each of them. This has been used as a first step to establish the advantages and limitations of this multilateration technique, especially when verifying large machine tools. The options for using only one laser tracker have also been studied and their limitations established.
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Micro- and nano-machining technology has been applied in industry to generate high-precision parts with micro/nano-metric accuracy or feature size in the recent decades. Cutting is one of the most powerful manufacturing processes, and the material removal mechanism is urgently demanded by the industry to understand and improve the micro/nano-machining process efficiently at a low cost. This paper presents the recent advances in cutting mechanism and its applicability for predicting the surface generation and chip formation, especially when material is removed in micro- and nanoscale. In addition to the industry-concerned performance parameters, fundamental physical parameters such as stresses, strains, temperatures, phase transformation, minimum uncut chip thickness and size effects are discussed in this paper for the in-depth understanding of the micro/nano-cutting process.
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Surface measurement is fundamental to further enhance accuracy and efficiency in ultra-precision machining. Advanced on-machine measurement (OMM) is evolving as the key enabling technology for autonomous and intelligent manufacturing. The present work integrates an interferometric probing system on an ultra-precision turning machine. However, due to relatively harsh environment in the machine tools, metrology characteristics of surface measuring instrument would deviate from those tested in laboratories. In order to improve the performance of on-machine measurement system, it is necessary to calibrate the OMM system and compensate the systematic errors. Three major error sources, including on-machine vibration, machine tool kinematic errors, and linearity errors are investigated according to the characteristics of interferometric single point OMM. For on-machine vibration, a theoretical study of the relationship between sampling frequency, scanning parameters, vibration frequency and topography frequencies of interest is first presented. Static and scanning vibration tests are performed in order to select the proper sampling frequency. Machine scanning error is mapped for OMM correction with the proposed kinematic error modelling measurement and compensation method. Calibration of the response curve and linearity error correction is conducted by measuring a radially distributed step height sample on the machine. Experimental investigation is conducted which proves the validity of proposed calibration methodology and the effectiveness of OMM. After the calibration process, OMM results agree well with calibrated offline measurements.
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It has been a challenge to position optical freeform surfaces precisely owing to their complex shapes and lack of references. High accuracy in their machining is therefore found to be extremely difficult to achieve. This situation constrains their effective application to a certain degree. An easy-operation method based on fringe deflectometry is proposed to ensure a high-accuracy position of freeform surfaces during machining. A measuring model is established, and we use experimental results to confirm its validity and accuracy. The effectiveness of the proposed method is also validated by case studies such as remounting, measurement data matching, and optical alignment.
Article
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Background Absolute test is one of the most important and efficient techniques to saperate the reference surface which usually limits the accuracy of test results. Method For the position error correction in absolute interferometry tests based on rotational and translational shears, the estimation algorithm adopts least-squares technique to eliminate azimuthal errors caused by rotation inaccuracy and the errors of angular orders are compensated with the help of Zernike polynomials fitting by an additional rotation measurement with a suitable selection of rotation angles. Results Experimental results show that the corrected results with azimuthal errors are very close to those with no errors, compared to the results before correction. Conclusions It can be seen clearly that the testing errors caused by rotation inaccuracy and alignment errors of the measurements can be consequently eliminated from the differences in measurement results by the proposed method. Keywords Absolute test Shear rotation Error correction Zernike polynomials
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In streamlined manufacturing systems, the added value of inspection activities is often questioned, and metrology in particular is sometimes considered only as an avoidable expense. Documented quantification of economic benefits of metrology is generally not available. This work presents concrete examples from industrial production, in which the added value of metrology in manufacturing is discussed and quantified. Case studies include: general manufacturing, forging, machining, and related metrology. The focus of the paper is on the improved effectiveness of metrology when used at product and process design stages, as well as on the improved accuracy and efficiency of manufacturing through better measuring equipment and process chains with integrated metrology for process control.
Conference Paper
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Inspection of parts is traditionally carried, out once a manufacturing procedure has been completed, in an environmentally controlled metrology laboratory. Financial pressures, increases in production speed and automation have led to inspection moving out of the metrology laboratory to the production floor and traditional tactile sensing tools such as CMMs are being replaced by 3D optical scanners. The use of this novel technology allows for inspection to take place during manufacture rather than waiting for the part to be completed. Unlike metrology laboratories, workshops tend to be particularly harsh environments where there is little control over important factors such as: temperature, humidity and lighting. With this in mind, NPL has designed and manufactured dimensional transfer artefacts to provide dimensional traceability from the metrology laboratory to the workshop. These artefacts include features that can be easily modelled mathematically, machined accurately and are representative of those typically produced on production lines.
Book
Precision Nanometrology describes the new field of precision nanometrology, which plays an important part in nanoscale manufacturing of semiconductors, optical elements, precision parts and similar items. It pays particular attention to the measurement of surface forms of precision workpieces and to stage motions of precision machines. The first half of the book is dedicated to the description of optical sensors for the measurement of angle and displacement, which are fundamental quantities for precision nanometrology. The second half presents a number of scanning-type measuring systems for surface forms and stage motions. The systems discussed include: • error separation algorithms and systems for measurement of straightness and roundness, • the measurement of micro-aspherics, • systems based on scanning probe microscopy, and • scanning image-sensor systems. Precision Nanometrology presents the fundamental and practical technologies of precision nanometrology with a helpful selection of algorithms, instruments and experimental data. It will be beneficial for researchers, engineers and postgraduate students involved in precision engineering, nanotechnology and manufacturing.
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Next-generation astronomical telescopes will offer unprecedented observational and scientific capabilities to look deeper into the heavens, observe closer in time to the epoch of the Big Bang, and resolve finer details of phenomena throughout the universe. The science case for this next generation of observatories is clear, with science goals such as the discovery and exploration of extrasolar planets, exploration of dark matter and dark energy, the formation and evolution of planets, stars, galaxies, and detailed studies of the Sun. Enabling breakthrough astronomical goals requires novel and cutting-edge design choices at all stages of telescope manufacturing. In this paper, we discuss the integrated design and manufacturing of the next-generation large telescopes, from the optical design to enclosures required for optimal performance.
Book
The Handbook of Surface and Nanometrology explains and challenges current concepts in nanotechnology. It covers in great detail surface metrology and nanometrology and more importantly the areas where they overlap, thereby providing a quantitative means of controlling and predicting processes and performance. Trends and mechanisms are explained with numerous practical examples. Bringing engineering and physics together at the nanoscale reveals some astonishing effects: geometric features such as shape change meaning; roughness can disappear altogether; signals from instruments have to be dealt with differently depending on scale. These and other aspects are dealt with for the first time in this book. It is relevant not only for today's technology but also for future advances. Many aspects of nanotechnology and precision engineering are considered in chapters on manufacture, characterization, standardization, performance and instrumentation. There is a special chapter on nanometrology and this subject permeates the whole book. The Handbook of Surface and Nanometrology is the only book that covers these subject areas and is the definitive work in this field. This book is indispensable for firms making, trading, and researching semiconductor devices, MEMS, and micro-optics, as well as tradition precision engineering products. It will also be useful in quality control as well as for research scientists, development engineers, and production managers.
Article
As high-precision measuring instruments have developed, interferometers have been widely applied in the measurement of lengths and of the shape of surfaces, with nanometer precision. The emergence of the laser is one of the revolutions that has led to a well-defined traceability route to the definition of the meter via interferometry. Another change is the ever-increasing adoption of detector arrays substituting for conventional methods of recording and analyzing interferograms. New applications have also arisen from the adoption of microscopes, optical fibers, chip-level components and diffractive optical elements, developing enhanced analogues of conventional interferometers, which have the advantages of high integration, low noise levels, and complete sets of measuring instruments with a high level of automation. Since the requirements for measurement parameters and the environment are becoming more complex, we expect that the related instruments will play a progressively significant role in the progress of advanced manufacturing processes and quality control. Multi-sensor integrated flexible measurement methods have been proposed to perform measurements with holistic, more accurate and reliable information. However, most of the proposed methods are not intelligent and are highly integrated, providing only specific solutions for given measuring tasks. In this paper, the principles, progress, prospects and development trends of interferometry are reviewed.
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This work studies multiscale analyses and characterizations of surface topographies from the engineering and scientific literature with an emphasis on production engineering research and design. It highlights methods that provide strong correlations between topographies and performance or topographies and processes, and methods that can confidently discriminate topographies that were processed or that perform differently. These methods have commonalities in geometric characterizations at certain scales, which are observable with statistics and measurements. It also develops a semantic and theoretical framework and proposes a new system for organizing and designating multiscale analyses. Finally, future possibilities for multiscale analyses are discussed.
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This study proposes an identification and compensation method for the geometric errors of the rotary axes in five-axis machining centers, based on the on-machine measurement results of the machined workpiece. Geometric errors can be identified from the shape geometry of the workpiece machined by five-axis motions because the influence of the errors appears on the shape geometry. An observation equation can be obtained based on the geometric error model and machined shape. The actual geometric errors can be identified by the least square matching of the measured and simulated machined shapes. In order to confirm the effectiveness of the proposed method, an actual cutting test and a simulation are performed. Based on their results, it is confirmed that the proposed method can successfully identify the geometric errors in the simulation. However, these errors cannot be identified in the experiments because a few of them do not have sufficient influences onto the machined shape. On the other hand, although the geometric errors cannot be correctly identified, it is confirmed that the they can be adequately compensated for based on the identified errors in both the simulation and experiment.
Article
The in situ geometry measurement of microstructures in the laser chemical machining (LCM) manufacturing process places high demands on measurement systems because the specimen is submerged in a closed fluid circuit. The steep slopes of the manufactured micro-components and the general lack of accessibility hinder the use of standard techniques such as tactile measurement or conventional confocal microscopy. A technique based on confocal fluorescence microscopy shows promise for increasing the measurability on metallic surfaces with large curvatures. By applying an intensely scattering fluorescent coating to the specimen, the surface position can be determined by the change in fluorescence signal at the boundary between specimen and coating. In contrast to the currently tested thin coatings ($$< 100\, \upmu \hbox {m}$$) the measurements in layers thicker than $$1\, \hbox {mm}$$, as required for in situ application at the LCM process, show distinct dependencies on the fluorescent medium in terms of concentration and index of refraction. Hence, a fundamentally different signal evaluation approach based on a physical model of the fluorescence signal is needed to extract the surface position information from the detected fluorescence intensity signal. For the purpose of validation, the measurement of a step geometry is performed under the condition of a thick fluid layer and referenced with a tactile measurement. As a result, the model-based approach is shown to be suitable to detect the geometry parameter step height with an uncertainty of $$8.8\, \upmu \hbox {m}$$ for a step submerged in a fluid layer with a thickness of $$2.3\, \hbox {mm}$$.
Article
The traditional three-dimensional measurement system based on linear-structured light usually involves mechanical scanning platforms to perform the linear scanning, which make the structure of the system huge and complicated. The emergence of the galvanometric laser scanner solves the problem by using a galvanometer to replace the mechanical scanning platform. The employment of the galvanometer can improve the speed of scanning and simplify the structure of the system. However, there are few approaches available to calibrate this kind of system. In this paper, a high-precision calibration method is proposed to calibrate the galvanometric laser scanning three-dimensional measurement system. A precision motorized linear stage and a planar target are applied in this method. The planar target is used for the camera calibration based on Zhang’s method and the precision motorized linear stage for the laser plane calibration. The validity and accuracy of this method are evaluated by scanning the standard component. The experiments conducted suggest that the proposed method is valid and accurate for the calibration of the galvanometric laser scanning system.
Chapter
In precision engineering, the demands for close tolerances and accurate dimensions on workpieces are challenging to manufacture but critical for reliable function when assembled into a mechanical system. These dimensions have to be confirmed by measurement, and such measurements always include disturbances that cause the measurement results to deviate. Typically, the resulting deviations are small, but they can be large enough to prevent a proper decision about a workpiece being taken. Therefore, an appropriately rigorous estimation of measurement uncertainty is essential in the production process. This chapter is about measurement uncertainty and follows the most recent Guide to the Expression of Uncertainty in Measurement, commonly called the GUM. From elementary single variable statistics through uncertainty propagation, the chapter shows the reader how to estimate uncertainty in the result of a measurement process. The concept of propagation of uncertainty distributions and Monte Carlo methods of uncertainty estimation are also presented.
Book
Advances in engineering precision have tracked with technological progress for hundreds of years. Over the last few decades, precision engineering has been the specific focus of research on an international scale. The outcome of this effort has been the establishment of a broad range of engineering principles and techniques that form the foundation of precision design. Today's precision manufacturing machines and measuring instruments represent highly specialised processes that combine deterministic engineering with metrology. Spanning a broad range of technology applications, precision engineering principles frequently bring together scientific ideas drawn from mechanics, materials, optics, electronics, control, thermo-mechanics, dynamics, and software engineering. This book provides a collection of these principles in a single source. Each topic is presented at a level suitable for both undergraduate students and precision engineers in the field. Also included is a wealth of references and example problems to consolidate ideas, and help guide the interested reader to more advanced literature on specific implementations. Features " Written as a textbook, this work is a modern examination of precision engineering in all its aspects " Provides extensive coverage of kinematic principles and design procedures " Surveys dimensional metrology concepts and analysis " Brings in coverage of uncertainty including Monte Carlo methods " Examines the micro- and nanotechnology aspects of precision instruments and machines
Book
The measurement and characterisation of surface topography is crucial to modern manufacturing industry. The control of areal surface structure allows a manufacturer to radically alter the functionality of a part. Examples include structuring to effect fluidics, optics, tribology, aerodynamics and biology. To control such manu­facturing methods requires measurement strategies. There is now a large range of new optical techniques on the market, or being developed in academia, that can measure areal surface topography. Each method has its strong points and limitations. The book starts with introductory chapters on optical instruments, their common language, generic features and limitations, and their calibration. Each type of modern optical instrument is described (in a common format) by an expert in the field. The book is intended for both industrial and academic scientists and engineers, and will be useful for undergraduate and postgraduate studies.
Article
Hole straightness deviation is the critical performance indicator in deep hole gun drilling process, particularly in manufacturing of corrosion resistant alloys like Inconel 718 with high yield strength. Poor understanding on the root causes of straightness deviation and difficulty to reduce it has dramatically increased the complexity and the manufacturing cost of this manufacturing process. Due to the fast tool wear in machining of Inconel, gun drills have to be changed frequently after a very short drilling distance. However, it has been found that the gun drill tool geometry cannot be precisely controlled, as there is a lack of appropriate gun drill regrinding and measurement system. In this study, a customized gun drill regrinding system integrated with an in-situ gun drill measurement system is designed and developed to obtain high-quality gun drills with precisely controlled tool geometry. The effect of apex offset variation on the hole straightness deviation is studied through 12 unsupported gun drilling experiments at thin-wall positions of an Inconel 718 workpiece with 160 ksi yield strength. 4 types of apex offset variation conditions (consistent, reciprocating, decreasing and increasing) with 3 times of repetition tests are conducted, and the measurement results have shown that consistent apex offset leads to the smallest hole straightness deviation among all the conditions. Through a series of FEM analysis and further measurement of internal cylindricity of machined holes, it has been concluded that unbalanced cutting force components applied on the previous gun drilled hole due to the inconsistent apex offset will cause the new formed hole to be deviated toward thin wall, due to the relatively larger material deformation at the thin-wall side than at the thick-wall side.
Article
On-machine measuring (OMM) systems are being more and more applied in machine tools in order to measure workpieces on the machine itself. Many of these systems are directly mounted in the machine spindle, so the measuring uncertainty is affected by clamping positioning and orientation variations, especially when integrating optical systems based on machine vision. This paper presents a self-calibration technique for vision systems by using redundant information of on machine measurements, avoiding extra mechanical anchoring or calibration means. It has been applied to a vision system with the angular placement uncertainty of a tool holder coupling being the main uncertainty contributor. A milling machine pilot case has been selected for demonstration, showing an effective self-calibration capability both in laboratory and industrial conditions.
Article
A new method, in which the wavefronts of the zero-order and the positive and negative first-order diffracted beams from a planar scale grating in Littrow setup are analyzed by a Fizeau interferometer, is proposed to evaluate the Z-directional out-of-flatness as well as the X- and Y-directional pitch deviations of the planar scale grating over a large area. Meanwhile, the surface profile of the reference optical flat in the Fizeau interferometer can also be determined in a much simpler and more efficient approach than the commonly used liquid-flat reference and three-flat test calibration methods. Simulations are presented to verify the feasibility of the proposed method.
Article
Laser microprocessing is a very attractive option for a growing number of industrial applications due to its intrinsic characteristics, such as high flexibility and process control and also capabilities for noncontact processing of a wide range of materials. However, there are some constrains that limit the applications of this technology, i.e., taper angles on sidewalls, edge quality, geometrical accuracy, and achievable aspect ratios of produced structures. To address these process limitations, a new method for two-side laser processing is proposed in this research. The method is described with a special focus on key enabling technologies for achieving high accuracy and repeatability in twoside laser drilling. The pilot implementation of the proposed processing configuration and technologies is discussed together with an in situ, on-machine inspection procedure to verify the achievable positional and geometrical accuracy. It is demonstrated that alignment accuracy better than 10 lm is achievable using this pilot two-side laser processing platform. In addition, the morphology of holes with circular and square cross sections produced with one-side laser drilling and the proposed method was compared in regard to achievable aspect ratios and holes' dimensional and geometrical accuracy and thus to make conclusions about its capabilities.
Article
This paper presents a simultaneous multi-segmented mirror orientation test system (SMOTS) using localized sheared images. A CMOS camera captures images of reflected 2D sinusoidal patterns from the test mirrors as their orientation changes. Surface orientation is measured to within 0.8 µrad (0.16 arcseconds) for a flat mirror. In addition, we measure the variation of seven mirror segments simultaneously. Furthermore, SMOTS is applied to measure the orientation of two concave mirrors with an accuracy of 2.7 µrad (0.56 arcseconds). The measurement time for seven segments is 0.07 s. This technique can monitor the mirror segment orientation in an open/closed-loop for various optical setups.
Article
In this paper, a four-probe measurement system is implemented and verified for the carriage slide motion error measurement of a large-scale roll lathe used in hybrid manufacturing where a laser machining probe and a diamond cutting tool are placed on two sides of a roll workpiece for manufacturing. The motion error of the carriage slide of the roll lathe is composed of two straightness motion error components and two parallelism motion error components in the vertical and horizontal planes. Four displacement measurement probes, which are mounted on the carriage slide with respect to four opposing sides of the roll workpiece, are employed for the measurement. Firstly, based on the reversal technique, the four probes are moved by the carriage slide to scan the roll workpiece before and after a 180-degree rotation of the roll workpiece. Taking into consideration the fact that the machining accuracy of the lathe is influenced by not only the carriage slide motion error but also the gravity deformation of the large-scale roll workpiece due to its heavy weight, the vertical motion error is thus characterized relating to the deformed axis of the roll workpiece. The horizontal straightness motion error can also be synchronously obtained based on the reversal technique. In addition, based on an error separation algorithm, the vertical and horizontal parallelism motion error components are identified by scanning the rotating roll workpiece at the start and the end positions of the carriage slide, respectively. The feasibility and reliability of the proposed motion error measurement system are demonstrated by the experimental results and the measurement uncertainty analysis.
Article
Additive manufacturing (AM) is pushing towards industrial applications. But despite good sales of AM machines, there are still several challenges hindering a broad economic use of AM. This keynote paper starts with an overview over laser based additive manufacturing with comments on the main steps necessary to build parts to introduce the complexity of the whole process chain. Then from a manufacturing process oriented viewpoint it identifies these barriers for Laser Beam Melting (LBM) using results of a round robin test inside CIRP and the work of other research groups. It shows how those barriers may be overcome and points out research topics necessary to be addressed in the near future.
Article
This paper presents a novel technique for more easily measuring cutting tool wear using knife-edge interferometry (KEI). Unlike an amplitude splitting interferometry, such as Michelson interferometry, the proposed KEI utilizes interference of a transmitted wave and a diffracted wave at the cutting tool edge. In this study, a laser beam was incident on the cutting tool edge, and the photodetector was used to determine the interference fringes by scanning a cutting tool edge along the cutting direction. The relationship between the cutting tool wear and interferometric fringes generated by edge diffraction phenomena was established by using the cross-correlation of KEI fringes of two different cutting tool-edge conditions. The cutting tool wear produced the phase shift (attrition wear) and the decay of oscillation (abrasive wear) in the interferometric fringe. The wear characteristics of the cutting tool with a radius of curvature of 6 mm were investigated by measuring the interferometric fringes of the tool while cutting an aluminum work piece in a lathe. As a result, the attrition and abrasive wear of cutting tool showed a linear relationship of 5.62 lag/wear (μm) and 1.14E-3/wear (μm), respectively. This measurement technique can be used for directly inspecting the cutting tool wear in on-machine process at low-cost.