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Assembly systems (ASs) have moved into the era of mass customisation and Industry 4.0 (I4.0). Mass customisation involves a shift from the production of high quantities of the same product to the production of low quantities of a high number of different products. This is changing the way in which companies assemble their products and has introduced a certain number of challenges. For example, there are increases in the numbers of parts to be moved, the quantities of data to be collected, and the skills of the human workers that companies must manage to meet their customers' demand. The adoption of I4.0 technologies can help companies to face these challenges. However, although companies and researchers have studied possible solutions based on I4.0 technologies for ASs and have introduced the concept of Assembly System 4.0 (AS4.0), no studies have tried to understand how these technologies impact on decision areas at the strategic, tactical, and operational levels. In this paper, we attempt to fill this gap through a systematic literature review that not only offers the opportunity to understand the current situation and the state of the art in this field but also gives an overview of possible future research challenges. [ABSTRACT FROM AUTHOR]

The World Robot Summit (WRS) is a robotic ‘challenge and exposition’ organized by the Japanese government to accelerate social implementation, research and development of robots working in realistic daily life, society, and industrial fields. In this paper, we introduce a robot competition of the Industrial Robotics Category of the WRS, called ‘Assembly Challenge’, which is organized by the WRS Industrial Robotics Competition Committee in order to promote the development of the next-generation production systems that can respond to new production demands in agile and lean manners. After the pre-competition held in Tokyo in October 2018, the main competition, the WRS 2020, was originally scheduled to be held in Aichi (partly in Fukushima) in 2020, which was also the Olympic year. However, due to the pandemic of COVID-19, the event was postponed, and the competition was actually held in Aichi in September 2021. In this paper, we introduce the contents and results of the WRS 2020 and analyze the results. We would also like to summarize the 5-year project since 2017 and discuss the outcomes of the WRS. [ABSTRACT FROM AUTHOR]

The World Robot Summit (WRS) Industrial Robotics Category tries to evaluate the performances of assembly robot systems using a task board. The task board comprises an assembly board (task board or board) and a set of parts assembled to the board. Utilizing an appropriate task board expects to facilitate the development of assembly robot systems. This paper examines the components necessary for the design of the task board through the results and analyzes of the task board competition in the WRS 2020 (held in September 2021). The task board will serve as a benchmark in developing an assembly robot system that can assemble the belt drive unit, an assembly model for the WRS 2020 assembly competitions. The success rate of each part of the competition and the correlation with assembly competitions reinforces the validity of the task board design. This paper describes that the WRS 2020 task board had a larger correlation with the belt drive unit used in the assembly competitions than that of the WRS 2018 (0.54 vs. 0.29). The design in the WRS 2020 is more appropriate than that in the WRS 2018 as a benchmark for assembling the belt drive unit. [ABSTRACT FROM AUTHOR]

This article reviews literature on the application of Discrete Event Simulation (DES) and optimisation methods for assembly systems. Data from papers is collated and classified based on application domain, optimisation objective functions, model formulations and optimisation methods. This classification enables the identification of key trends within the research. The most common objective functions applied within studies are time and throughput. In addition, what–if scenario analysis is identified as the most common optimisation method. An increase in the use of hybrid methods for simulation modelling and growing application of Artificial Intelligence methods for multi-objective optimisation of DES models has been noted. These growing trends provide a variety of interesting areas for progress in future research. [ABSTRACT FROM AUTHOR]

Two-stage assembly flow shop scheduling problem with D P m → 1 layout has been extensively considered in single factory; however, distributed two-stage assembly flow shop scheduling problem (DTAFSP) with D P m → 1 layout in each factory is not studied fully; moreover, teaching-learning-based optimisation is seldom used to solve DTAFSP. In this paper, a cooperated teaching-learning-based optimisation (CTLBO) is proposed to minimise makespan. Multiple classes are constructed. The whole search procedure consists of two stages and each stage possesses two teacher's phases and a learner phase. Class cooperation between the best class and the worst one is implemented by exchanging search times and search ability at the second stage and seldom adopted in the existing works. Extensive experiments are conducted and CTLBO is compared with the existing methods to test its performances. Computational results demonstrate that CTLBO has very competitive performances on solving the considered DTAFSP. [ABSTRACT FROM AUTHOR]

Due to the high cost pressure and the increasing variant diversity, the cooperation of humans and robots represents a promising technological solution to achieve higher flexibility and efficiency in assembly. It is therefore attracting significant interest from both researchers and practitioners. As a result, numerous reviews have been published addressing different aspects of human-robot collaboration, such as safety, interaction modalities, programming, and applications. However, in this paper, for the first time, the aspect of task allocation for collaborative assembly is methodologically examined through a systematic literature review. This paper presents the current state of the art in task allocation approaches, investigates the criteria for deciding on a suitable task assignment, and discusses challenges and future research needs. After filtering the 521 publications that resulted from the initial search process, 37 relevant publications were included in the analysis and grouped into a proposed classification consisting of two main categories, static and dynamic task allocation approaches. Based on the results of the literature review, this paper presents a reference model for human-robot collaborative assembly. [ABSTRACT FROM AUTHOR]

This paper suggests a new technique to facilitate consistent transition between planning and production stages of small lots of complex products (in quantities that do not justify full automation). Despite the usage of modern approaches such as design for assembly and design for manufacturing the typical product planning ends up before production planning begins, instead of having a unified seamless planning process. This paper presents a new three stage technique to fill the gap between product planning and production. The paper shows how to generate a rigorous production plan by: (1) extending the Bill-of-Materials to include additional required information, (2) constructing an assembly ‘method prototype’ and (3) using the ‘method prototype’ to calculate time standards for executing the assembly. A case study illustrates the proposed technique. [ABSTRACT FROM PUBLISHER]

The Industrial Assembly Challenge at the World Robot Summit 2020 was a competition showcasing the latest technologies in robot assembly tasks. Teams had two days to set up an autonomous assembly system and had to manipulate surprise parts on the competition day. The manufacturing industry has trended towards high-mix low-volume production, which often requires frequent tool changes and can be difficult to set up with industrial robots. Small- and medium-sized enterprises (SMEs) may struggle to use robots for a variety of products, particularly in assembly tasks requiring high accuracy and specialized tools. To improve assembly performance, we propose an assembly method using multiple types of sensors, including an RGB camera and six-axis force-torque sensor. This system allows for flexible assembly tasks without strict alignment, does not require jigs or dedicated hands for each object, and can be easily adapted to different production scenarios. In this paper, we present the motion strategy of our proposed assembly system that participated in the World Robot Summit 2020 and demonstrate how it was able to robustly accomplish tasks such as screw tightening and peg-in-hole by combining information from the camera with information from force-torque sensors. [ABSTRACT FROM AUTHOR]

As the complexity of spacecraft function has increased, the requirements for assembly quality and reliability have become more stringent. The current digital assembly simulation stays in the idealized structure and method verification, however, the spacecraft assembly process relies on manual and discrete operations, making it challenging for real time assembly quality tracing and process clarification. This paper takes the spacecraft assembly process as the research object, studies the real-time data acquisition method that fuses the acquisition node and the assembly process, and establishes the virtual-real mapping process around the central data space. A Digital twin system corresponding to the actual spacecraft assembly process was constructed based on the spacecraft assembly cell unit. The states of the manufacturing process in the physical world are fed back to the virtual space. The problems faced during assembly are reflected in real-time, and the corresponding behaviour is simulated. Based on the real-time data acquisition, real-time monitoring and numerical analysis for comparison are realized, providing a feasible solution for the application of Digital twin in the spacecraft assembly scenario. [ABSTRACT FROM AUTHOR]

As a result of the advantages of the steel fiber reinforced concrete pavement structure, which includes high strength, high stiffness, and high stability, a large number of steel fiber concrete pavements will be used for highway construction in China. As a result, numerous cracks develop, which significantly reduces the life of the road; therefore, the study of the jointing problem is vital. As concrete research on the influence of the load transfer capacity and service life of prefabricated steel fiber reinforced concrete joints on the structural design and use function of the whole and pavement panels, the paper proposes two joint forms, tongue-and-groove and overlap. Using experiments and software, the stress and reflection of prefabricated road panels of the two joint forms are analyzed for different axial loads. The analysis reveals that the maximum tensile stress, shear stress, and deflection of the precast panels of both joint forms increase linearly as the axle load of the vehicle increases, while the service life decreases relatively. The load transfer capacity is independent of the axle load magnitude, and the load transfer capacity difference between the two types of joints is minimal and excellent. [ABSTRACT FROM AUTHOR]

This paper considers a two-stage assembly flowshop scheduling problem with distinct due windows to minimise the sum of weighted earliness and tardiness. There are several identical parallel machines which produce parts in the first stage. When the required parts are available, a single assembly machine can group these parts into products in the second stage. It is assumed that a part can be split into sub-parts which can be processed independently on the parallel machines in the first stage. Setup is also considered. A mathematical model is established to describe and define the proposed problem. A new decoding method is developed by extending an existing decoding method. Two novel operators, named part splitting (PS) and optimal idle time insertion (ITI), are incorporated into the decoding procedure for improving the quality of the solution. A rule named Priority of Earliness and Tardiness (PET) and a Complete Immunoglobulin-based Artificial Immune System (C-IAIS) algorithm are proposed for solving the problem. To evaluate PET and C-IAIS algorithm, several existing algorithms are used in the experiments. Computational results show that C-IAIS algorithm performs better than other algorithms for solving the proposed problem. [ABSTRACT FROM AUTHOR]

This paper describes two metrics to measure the complexity involved in assembly and disassembly tasks for open architecture products during its use phase. The approach proposed is based on the summary of all tasks required to assemble and disassemble a predefined set of modules to generate several product variants, which comprise different working levels or functionalities. The aim of the method is to provide a useful tool to designers in the analysis of product complexity regarding use and further phases in which the assembly and disassembly of modules are required. The benefits and usefulness of the metrics are oriented to enhance the sustainability performance of products through the measurement of complexity in modular systems for the decision-making during the design stage. The reduction of complexity involves significant benefits in all lifecycle phases of product, especially when the user or customer is responsible for many related tasks (maintenance, upgrading, reconfiguration and final disposal of modules). The metrics and their calculation process are illustrated using two case study products. [ABSTRACT FROM AUTHOR]

The success of wind power development in Northern Friesland (Germany) is mainly due to its ‘citizen wind parks’. However, their historical emergence, as well as their astonishing scale-up from small to large wind farms, is little understood from the inside. Following the critical approach of assemblage thinking, this paper’s proposal is to revise the notion of ‘assembly’ to investigate collective processes of ‘attunement’. The paper stresses the practical work of valuating ‘things’ and making them commensurable in the light of the relations (inherited practices, place attachments, project perspectives) grounded in a place. This approach makes it possible to identify the ways in which assemblies from Northern Friesland have negotiated and transformed an inherited landscape into a shared wind power landscape. We call this activity in which local assemblies engage ‘a polity’. Finally, we illustrate the term’s conceptual potential by discussing its scope and links to techniques of power that follow from environmental ‘governmentality’. [ABSTRACT FROM AUTHOR]

Tolerance analysis of an assembly is an important issue for mechanical design. Among various tolerance analysis methods, statistical analysis is the most commonly employed method. However, the conventional statistical tolerance method is often based on the normal distribution. It fails to predict the resultant tolerance of an assembly of parts with non-normal distributions. In this paper, a novel method based on statistical moments is proposed. Tolerance distributions of parts are first transferred into statistical moments that are then used for computing tolerance stack-up. The computed moments, particularly the variance, the skewness and the kurtosis, are then mapped back to probability distributions in order to calculate the resultant tolerance of the assembly. The proposed method can be used to analyse the resultant tolerance specification for non-normal distributions with different skewness and kurtosis. Simulated results showed that tail coefficients of different distributions with the same kurtosis are close to each other for normalised probabilities between −3 and 3. That is, the tail coefficients of a statistical distribution can be predicted by the coefficients of skewness and kurtosis. Two examples are illustrated in the paper to demonstrate the proposed method. The predicted resultant tolerances of the two examples are only 0.5% and 1.5% differences compared with that by the Monte Carlo simulation for 1,000,000 samples. The proposed method is much faster in computation with higher accuracy than conventional statistical tolerance methods. The merit of the proposed method is that the computation is fast and comparatively accurate for both symmetrical and unsymmetrical distributions, particularly when the required probability is between ±2σ and ±3σ. [ABSTRACT FROM PUBLISHER]

Process capability indices are useful tools for evaluating the ability of a process to produce products that meet certain specifications. The assembly quality is dependent on the distribution of variations of assembly dimensions, which is in turn dependent on mating conditions in the mechanical assembly. Since it is often difficult to measure the assembly dimensions in the production stages, they are not considered as a direct inspection objective. Rather, the inspection and evaluation of quality is carried out by specifying whether the assembly requirements satisfy the specified limits. Therefore, we can basethe process capability indices on the assembly dimensions. In most real life cases, the observations are fuzzy. In this paper, a novel method based on fuzzy concepts for process capability analysis of assembly dimensions in mechanical assemblies is presented. According to this scheme, sample observations of manufactured variables are described as fuzzy numbers. The proposed method is able to estimate the ability of the manufacturing process in satisfying the assembly quality in the mechanical assemblies with asymmetric tolerances which have non-normal distributions. In this paper, a proper criterion based on the probability of fuzzy set to interpret the computed fuzzy results is proposed, so these results are converted to the interpretable results for making a decision to evaluate the assembly quality. Furthermore, a new fuzzy-based quantity factor for expressing the percent contributions of effective manufacturing variables on the assembly quality is presented. The application of the presented method is demonstrated through an example and its results are discussed. [ABSTRACT FROM PUBLISHER]

This paper examines how the choice of materials exposure impacts workstation performance, in terms of non-value-adding work, space requirements and ergonomics. In a typical Swedish automotive setting, components are exposed in wooden pallets with frames beside the assembly line and supplied by forklift truck. In a case study, three workstations on an assembly line were studied and redesigned following the principles of lean production, using smaller plastic containers for the materials exposure. After the redesign, the space required for materials was reduced by 67%, non-value-adding work decreased by 20%, and walking distance was reduced by 52%. Furthermore, the ergonomics for the assembly operator improved greatly, with a 92% reduction of potentially harmful picking activities, thereby almost eliminating potentially harmful body movements. The theoretical contribution of this paper is firstly the development of an analysis model describing the impact of material exposure on workstation performance and secondly development of the existing categorisation of work operations to include different materials handling activities. The most important managerial implication is an increased understanding of the relationship between space, ergonomics, non-value-adding work and materials exposure. These findings have direct implications on workstation design in industry. [ABSTRACT FROM AUTHOR]

Stochasticity in assembly processes is often associated with the processing time and availability of machinery, tools and manpower, however in this paper it is determined by probability of an assembly task successful completion which here is referred to as task reliability. We present a mathematical model for optimising the expected assembly cost, and consider two scenarios: the first a situation where a failure of one assembly task requires rework of that task alone; second a situation in which a failure in the midst of the process requires resumption of previously completed tasks. In the worst case scenario the assembly process must restart from the beginning. We show that the first scenario is insensitive to sequencing unless there are set-up costs. In the second scenario the process is sensitive to tasks' sequence. We present a heuristic that argues for accomplishing more uncertain tasks (with less reliability) earlier in the process to decrease the expected cost of assembly, and show that in a mutually dependent assembly process, when tasks' reliabilities are similar, the cheaper tasks should be executed earlier in the process. [ABSTRACT FROM AUTHOR]

This paper introduces a novel modelling method for variation propagation calculation of 3-D assemblies taking into account geometric variation and part deformation, which are neglected in most models in tolerance analysis. Initially, numerical studies are carried out in order to illustrate the characteristics of strain distribution in components and contact forces on the mating surfaces of a 3-D assembly. According to these characteristics, a linear equivalent model using springs to represent the elastic mating surfaces with geometric variation was presented. Then, the equilibrium criterions corresponding to actual contact situations and iterative searching algorithm of the equilibrium status of contacting were developed. The proposed modelling and calculation method were finally applied to the assembly of two machined parts, on which finite-element analyses and experimental tests were conducted to validate the effectiveness and accuracy. This linear contact model also shows an important advantage on modelling and calculating efficiency, which enable the practical application to variation propagation calculation in both tolerance design and assembly process. [ABSTRACT FROM PUBLISHER]

Down fiber assembly is a heterogeneous and hierarchical system whose structure can be hardly characterized. At the meantime, its thermal property is valuable for usage, it would guide design if the correlation between thermal performance and structure can be understood. In this paper, fractal approach was introduced to characterize the microstructure of down fiber assembly. Fractal dimensions of fiber assemblies are calculated by box-counting method and are found to be positively correlated with basic structural parameters such as fiber mass and volume fraction. Meanwhile, the results indicate that increasing fractal dimension will lead to an enhancement of thermal insulation performance. [ABSTRACT FROM AUTHOR]

This paper demonstrates that a distributed control and planning system can fulfil an idealised mixed-model assembly problem and compete with traditional systems. The anarchic manufacturing system is a distributed planning and control system, based on a free market structure, where system elements have decision-making authority and autonomy. Mixed-model assembly is typically managed centrally for production planning and control, using simplification and hierarchical structures to manage complexity. In developing anarchy, inter-job cooperation is implemented to synergise jobs together and fulfil global objectives efficiently. The anarchic system maximises available flexibility, through embracing complexity, and reduces myopic decision making by maximising an agent's lifetime profitability. Through agent-based simulation experiments, the anarchic system is compared to fixed and flexible centralised systems. The proposed system outperforms traditional systems when the scenario's structural flexibility allows agile and delayed dynamic decision making. Additionally, the anarchic system managed dynamic bottleneck disruptions as effectively as flexible centralised systems. [ABSTRACT FROM AUTHOR]

This paper studies the performance of constant work-in-process (CONWIP) assembly system with multi-loop in mass production, multi-products and low volume and one-of-a-kind production (OKP) environments using simulation. We propose five basic design patterns of CONWIP loop and develop eight control policies of CONWIP loop based on the design pattern for standard assembly system. The performance of developed loop policies is evaluated in three production environments. In particular, control policies of CONWIP loop in OKP environment provide a valuable reference for OKP shop floor controlling. A heuristic algorithm of searching work-in-process (WIP) upper bound, the deadlock phenomenon in CONWIP assembly system and suggestion are introduced specifically. The summary of CONWIP installation guidelines in the mixed assembly system can apply CONWIP theory to practise. [ABSTRACT FROM AUTHOR]

Packaging is typically the last task in a production process, especially in an assembly system. If an assembled product is sold as a single unit, its packaging is normally performed by the last workstation, in order to obtain a ready-for-sale product. Moreover, assembled product often comes with its accessories, packaged all together and supplied to the customer as a single unit: a sales kit. Due to the variety of products and accessories, the variety of kits is continuously increasing, requiring a complex definition of the best packaging strategy to adopt. The present paper aims to analyse the packaging problem in a production system, identifying and comparing the packaging strategies. These strategies provide, through a comparison model of total cost functions, a decision-making procedure for operations managers. Through a simulative study, a set of convenience areas for each analysed packaging strategy is derived. The findings from an industrial case study are also reported to validate the proposed methodology. [ABSTRACT FROM AUTHOR]

This paper considers the socio-political implications of a series of closely spatially and temporally related early medieval cemeteries from England and how they might be read as charting the emergence of both individual communities and of collective supra-local society. The case study is from early post-Roman Britain in a region that during the sixth century AD became the historically documented Anglo-Saxon kingdom of Kent. Four distinct communities appropriated an earlier burial landscape, arguably by a process of negotiation, reflecting the formation of a small-scale, supra-local society based around a site of occasional gathering. A key notion is that periodic gathering and local stability could be core features of large-scale polity formation. Overall, a case is made for the long-term cohesion of a local territory, reliant on an ancient mode of social organization. [ABSTRACT FROM AUTHOR]

In this paper the archaeological evidence for pre-eminent elite assemblies in medieval Scotland is explored. The paper presents the first accurate reconstructed layout of an important medieval royal complex at Scone in Scotland. A chronological framework for the royal assembly mound is discussed in relation to new dating evidence. Evidence for augmentation and enclosure of the mound is highlighted to illustrate how managed adaptations of space may have been used to organize and change the performative and political functions of temporary elite gatherings. These new results are compared with examples of royal space from western Europe, citing similarities with imperial Carolingian models that were rooted in late antique architectures of governance. Abbreviations: PoMS: Beam, A., J. Bradley, D. Broun, J. R. Davies, M. Hammond, M. Pasin (with others). 2012. The People of Medieval Scotland, 1093 - 1314. Glasgow and London. www.poms.ac.uk [accessed 30 May 2018]. RPS: Brown, K. M. et al. (eds). 2007-2017. The Records of the Parliaments of Scotland to 1707. University of St Andrews, http://www.rps.ac.uk [accessed November 2017]. [ABSTRACT FROM AUTHOR]

The paper presents the design to construction process of an ultra-lightweight hybrid temporary structure consisting of a combination of bending-active glass fiber-reinforced polymers arches, a restraining system made of stainless steel cables, and a translucent membrane envelope. After a brief introduction to the basic design concepts and versatility of the modular system to create different shapes, the paper focuses on the fast-track erection procedure that enables to build the pavilion in a very short time. A multi-disciplinary team had collaborated at the design development of the temporary pavilion, built with the aim of deepening a wide range of aspects that are peculiar to temporary architecture. The aim of the second design-to-construction loop, following the first loop which resulted in the construction of the first full-scale prototype, is two-fold: firstly to optimize the innovative mix of lightweight structural components with the aim of reducing the total weight of the building (and thus facilitate transport and installation), and secondly to test the technical details designed to favor reversibility and to ensure the re-usability of the structure for multiple cycles of use. The paper concludes by showing the results achieved and the lesson learned from the first construction of the temporary pavilion in occasion of a one-week event and anticipating the further studies regarding the interface between structure and membrane envelope, also in relation to the building expected life-span and requirements. [ABSTRACT FROM AUTHOR]

Task assignment methods usually rely on the fixed mean processing times of operations with the intent of balancing the workload assigned to operators or workstations in the production line. This assignment usually neglects the variability of operator processing times. In this work, a methodology in which the time in which an operator executes a task is variable, accordingly to a learning model, is proposed. It is exploited in order to assess the real-time task assignment adopted in the actual factory. The results show that, by including a learning model, it is possible to predict more accurately the long-term cycle time of the process. Standard scheduling strategies (first operator available, the operator closest to the machine) were compared with learning-oriented strategies (the most skilled, the least skilled). Through the case study, the paper addresses the problem of using a dynamic task assignment.an illustration. [ABSTRACT FROM AUTHOR]

Tolerance analysis aims to evaluate the functional requirement of mechanical assemblies in the design stage. As one of the typical tolerance analysis methods, the polytope model has shown great potential in Computer-Aided Tolerancing (CAT) field based on a series of constraints. However, existing research outcomes on this topic rarely consider form defects and the combined effects of form defects and surface deformations. This limitation may cause inaccuracy of tolerance analysis results. Hence, this paper integrates form defects and surface deformations in polytope-based tolerance analysis. Specifically, form defects are considered based on the concept of Skin Model Shapes and surface deformations are calculated based on a Conjugate Gradient-Fast Fourier Transform (CG-FFT) method. Then, the modeling method of the new polytope model is elaborated based on surface types and different types of constraints. Moreover, a case study is conducted to explain the procedure of polytope-based tolerance analysis. Through operations of the polytopes, tolerance analysis results are obtained, and the comparison with conventional polytope analysis results shows the considerable effects of form defects and surface deformations. It is expected that the proposed method can have a more realistic and accurate analysis result because of its consideration of real surface contact status. [ABSTRACT FROM AUTHOR]

Dielectrophoresis (DEP) is an electrode-medium process used to control the movement of Carbon nanotubes (CNTs) within a solution under nonuniform electric fields. CNTs are typically dispersed into a solvent to form a homogeneous suspension in order to prevent their aggregation and to improve solubility. This paper starts with a short review of the techniques used to improve the compatibility of CNTs with a target medium. Then, direct and indirect variations in CNTs' velocities as a function of DEP force were investigated, under different dispersion mediums, for a rectangular electrode pair with a 10 μm gap subjected to a 500 kHz AC signal with an amplitude of 10 V. The effects of changes in permittivity, conductivity, viscosity, and density of the medium were presented and discussed. Simulation results from this study were used to further clarify the role of the medium on the motion of CNTs during alignment using a DEP process prior to an actual alignment. [ABSTRACT FROM AUTHOR]

In order to increase flexibility and reduce costs, assembly systems are changing from simple mixed-model assembly lines, to multi-lines systems, where some components are assembled in secondary lines, called feeder lines, connected to the main line by a ‘pull philosophy’. The production of different models in such a complex multi-lines assembly system, where the tasks to perform could be very different from model to model, impacts the production with very high workload time variations, with the consequence of lack of productivity. If operators can perform tasks on different stations on both the feeder and the main lines these time variations can generally be absorbed. But if working across the stations is not possible (closed stations), the balancing of these workload time variations becomes critical. In such contexts the consolidated approach, that allows to configure mixed-model-multi lines assembly system with a single average model representative of the whole mix, can be very limited and is unable to bring substantial results. This paper aims to introduce an innovative sequencing model for mixed-model-multi-lines system, in the case of closed stations, in which it is possible to obtain, after a first long term configuration, a short term balancing, using an appropriate sequencing, for a given production mix and characteristics of the assembly system. The proposed procedure is applied to un-paced assembly lines and validated through simulation and industrial applications. [ABSTRACT FROM PUBLISHER]

The constant research for efficiency and flexibility has forced assembly systems to change from simple/single assembly lines to mixed model assembly lines, while the necessity to reduce inventory has led the transition from single to multi-line systems, where some components are assembled in secondary lines, called feeder lines, connected to the main one by a ‘pull philosophy’. A possible approach to configure such an assembly system is to balance the main line first and use the retrieved cycle time to balance each feeder line separately, which is a questionable solution, especially if operators can perform tasks on both the feeder and the main line. Moreover for its complexity the mixed model balancing problem is usually solved transforming it into a single model by creating a single ‘virtual average model’, representative of the whole production mix. The use of a virtual average model assumes that the processing times of some models are higher or lower than the cycle time, which creates overload/idle time at the stations. This approach, especially in complex multi line production systems, largely reduces the assembly line productivity and increases the buffers dimensions. This paper faces the mixed model assembly line balancing problem in the presence of multiple feeder lines, introducing an innovative integrated main-feeder lines balancing procedure in case of unpaced assembly systems. The proposed approach is compared with the classical one and validated through simulation and industrial applications. [ABSTRACT FROM PUBLISHER]

In this paper we consider the mixed model assembly line reconfiguration problem in the context of auto production which is characterised by a make-to-order production process and a huge product variety. Starting from a given line balancing solution the goal is to minimise production costs in the short term for a largely known production program by reassigning and shifting tasks between workstations. We present a mathematical optimisation model that aims at minimising the costs incurred by overload situations, regular workers and reconfiguration measures. Due to the model's complexity, lack of data and acceptance issues it is hardly possible to fully automate the solution process in an industrial environment. Therefore, we present a decision support approach that consists of visualisation components, new numerical indicators and an integrated heuristic optimisation procedure to semi-automate the reconfiguration process. In particular, reconfiguration costs can be taken into account and no complete precedence graph is required. Finally, we show on the basis of two industrial case studies that our approach can be successfully applied in a practical environment where it was capable of drastically reducing the occurrence of overload situations. [ABSTRACT FROM AUTHOR]

Mixed-model assembly lines are widely used in a range of production settings, such as the final assembly of the automotive and electronics industries, where they are applied to mass-produce standardised commodities. One of the greatest challenges when installing and reconfiguring these lines is the vast product variety modern mixed-model assembly lines have to cope with. Traditionally, product variety is bypassed during mid-term assembly line balancing by applying a joint precedence graph, which represents an (artificial) average model and serves as the input data for a single model assembly line balancing procedure. However, this procedure might lead to considerable variations in the station times, so that serious sequencing problems emerge and work overload threatens. To avoid these difficulties, different extensions of assembly line balancing for workload smoothing, i.e. horizontal balancing, have been introduced in the literature. This paper presents a multitude of known and yet unknown objectives for workload smoothing and systematically tests these measures in a comprehensive computational study. The results suggest that workload smoothing is an essential task in mixed-model assembly lines and that some (of the newly introduced) objectives are superior to others. [ABSTRACT FROM AUTHOR]

Assembly sequence planning (ASP) is the foundation of the assembly process planning which plays a key role in the whole product life cycle. In this paper, a unique ASP reasoning method supported by the artificial intelligent technique of case-based reasoning (CBR) is proposed and developed. First, based on the previous ASP literatures review and the CBR characteristics analysis, the systematic architecture of the CBR based ASP is presented. Then, some key techniques including assembly case modelling, similar case retrieving, case based reasoning, and case base maintenance, etc., are explored thoroughly. To enhance the efficiency and quality of the reasoning process, genetic algorithm (GA) is designed and applied to automatically inferring of the reference assembly sequence. Finally, the corresponding software system with an engineering example is given to demonstrate the effectiveness of the CBR based ASP. [ABSTRACT FROM AUTHOR]

A key characteristic for industrial production in the Industry 4.0 paradigm is the connection of physical items like sensors, devices and enterprise assets, connected both to each other and to the Internet. In this Internet of Things environment, things will sense more data, become context-aware and provide added-value information to assist people take more relevant and valuable decisions. Context-aware information distribution may offer substantial value to manufacturing. It provides taskrelevant information or services to users in a manufacturing shop-floor improving decision making through context-driven recommendations. This paper presents a context-aware information distribution system to support users in an industrial environment. The system aims at utilising data collected from sensors located at a shop-floor in order to increase the visibility of shop-floor processes by providing the right information, to the right people, at the right time. The system's architecture and key elements have been developed for a pilot implementation in the white goods industry and are presented in this study. [ABSTRACT FROM AUTHOR]

This paper is to the assembly and fabrication for typical nano device-SWCNT FET for example, facing the large-scale assembly and fabrication for nano devices, and carrying out the experimenal research. Assembly method of SWCNTs FET is by floating potential and dielectrophoresis principle. Six hundred devices are assembled less than per square centimeter. The experimental results show th at large-scale assembly is realized, and the success rate of ideal assembly for SWCNTs FET is achieved. [ABSTRACT FROM AUTHOR]

The demand for flexible production systems in which the flexibility at assembly processes is increased by new forms of human-robot collaboration rises. Besides occupational safety the transparency of the robot's actions and the mental effort are of special importance. Based on the fact that anthropomorphic features of a robotic system can improve its acceptance, anthropomorphic movements of a gantry robot in an assembly cell are compared to conventional point-to-point movements. Results of a study with 20 male participants, in which the influence of these movements of the gantry robot on mental effort, prediction time and prediction accuracy was investigated, are presented in this paper. Results show that the participants could predict the target position of the presented movement significantly faster and more accurately when the gantry robot was controlled by the anthropomorphic motion primitives (α = 0.05). The mental effort ratings show in general reduced values for the anthropomorphic movement, but this effect is statistically not significant. [ABSTRACT FROM AUTHOR]

Distributed hybrid flow shop scheduling (DHFS) problem has attracted much attention in recent years; however, DHFS with actual processing constraints like assembly is seldom considered and reinforcement learning is hardly embedded into meta-heuristic for DHFS. In this study, a distributed assembly hybrid flow shop scheduling (DAHFS) problem with fabrication, transportation and assembly is considered and a mathematic model is constructed. A new shuffled frog-learning algorithm with Q-learning (QSFLA) is proposed to minimise makespan. A three-string representation is used. A newly defined Q-learning process is embedded into QSFLA to select a search strategy dynamically for memeplex search. It is composed of four actions based on the combination of global search, neighbourhood search and solution acceptance rule, six states depicted by population evaluation on elite solution and diversity, and a newly defined reward function. A number of experiments are conducted. The computational results demonstrate that QSFLA can provide promising results on the considered DAHFS. [ABSTRACT FROM AUTHOR]

This article deals with the relationship between a sonic entanglement and its ruling in a weekly assembly. In doing so, material participation is foregrounded through focus on this specific entanglement and the ways in which it is enacted within the context of a weekly assembly of a citizen-led project. Based on ethnographic work developed in el Campo de Cebada - a temporary use open-air urban site - I describe the case of a noise complaint, and how relationships around it are deployed in multiple directions. Different heterogeneous actors play specific roles in the development of a controversy, and the assembly of the project in question deals with them in order to govern them. The paper is organised around three moments: (1) the emergence and formation of a sonic entanglement; (2) the bestowing of legitimacy on the weekly assembly to deal with a controversy lacking legal standing; and (3) the process of ruling that sonic entanglement by the legitimised assembly. In studying this case, I explore how activist projects are complex heterogeneous assemblages that are developed, governed, and ultimately benefit from the enactment of what I call the ‘politics of welcoming’. I argue that those politics of welcoming - against politics of confrontation - are based on the management of timing through several governance mechanisms that allow stretching, lengthening, delaying, shortening or slowing time. Among those mechanisms, but not limited to them, we find radical openness, under-definition, re-definition, subjective perception, interpretation, exception and postponement. [ABSTRACT FROM AUTHOR]

The paper describes an application based on Virtual and Augmented Reality technologies specifically developed to support maintenance operations of industrial products. Two scenarios have been proposed. In the first an operator learns how to perform a maintenance operation in a multimodal Virtual Reality environment that mixes a traditional instruction manual with the simulation, based on visual and haptic technologies, of the maintenance training task. In the second scenario, a skilled user operating in a multimodal Virtual Reality environment can remotely train another operator who sees the instructions about how the operations should be correctly performed, which are superimposed onto the real product. The paper presents the development of the application as well as its testing with users. Furthermore limits and potentialities of the use of Virtual and Augmented Reality technologies for training operators for product maintenance are discussed. [ABSTRACT FROM AUTHOR]

A Carbon Emission Signature (CES) and a Carbon Emission Label have been proposed for manufactured products in previous CIRP (College International pour la Recherche en Productique) annals. This paper considers two things: (1) an example of a CES calculation for assembly with CO2 emissions and (2) the need for a transparent method of calculation. In comparing carbon footprint calculations for 17 websites, the results are found to vary more than threefold depending upon the site used and even more between different methods illustrating the need for standardisation in emission calculations for carbon accounting. [ABSTRACT FROM AUTHOR]

A fundamental demand of construction design is human safety from structural failure. As a consequence, buildings generally tend to be structurally optimized with cost as the main target parameter. However, a cost-suboptimized structural design often leads to poor constructability decisions with subsequent waste. This paper presents initial research in the development of a design structural matrix (DSM) method able to identify constructability obstacles between structural design and assembly and thus eliminate waste. Empirical data based on a case study of long-span timber structures is used in the development and analysis of the method. The DSM was found to be a holistic tool for systematic consideration of structural design and constructability requirements by providing a standardized system view, a detailed element view, and physical and functional interactions among elements and modules. The DSM was also shown to aid in detailed design and production management through the use of simple matrix tools. [ABSTRACT FROM AUTHOR]

A two-sided assembly line balancing problem is typically found in plants producing large-sized high-volume products, e.g. buses and trucks. The features specific to the assembly line are described in this paper, which are associated with those of: (i) two-sided assembly lines; (ii) positional constraints; and (iii) balancing at the operational time. There exists a large amount of literature in the area of line balancing, whereby it has mostly dealt with one-sided assembly lines. A new genetic algorithm is developed to solve the problem, and its applicability and extensibility are discussed. A genetic encoding and decoding scheme, and genetic operators suitable for the problem are devised. This is particularly emphasized using problem-specific information to enhance the performance of the genetic algorithm (GA). The proposed GA has a strength that it is flexible in solving various types of assembly line balancing problems. An experiment is carried out to verify the performance of the GA, and the results are reported. [ABSTRACT FROM AUTHOR]

The aim of this paper is to describe an assembly line paradigm that exploits the latest trends in handling and assembly technologies. Mobile robotic units, flexible and exchangeable end effectors, equipped with automated integration capabilities are used to achieve a highly reconfigurable and autonomous line as opposed to the existing fixed assembly lines, which are difficult to be reconfigured. In a study for the automotive assembly case, the benefits of the new paradigm over the traditional assembly schemes are quantified with the help of different simulated operational conditions. [ABSTRACT FROM PUBLISHER]

In this paper, we use molecular dynamics simulations to study the assembly of DNA-grafted nanoparticles to demonstrate specifically the effect of bidispersity in grafted DNA strand length on the thermodynamics and structure of nanoparticle assembly at varying number of grafted single-stranded DNA (ssDNA) strands and number of guanine/cytosine (G/C) bases per strand. At constant number of grafted ssDNA strands and G/C nucleotides per strand, as bidispersity in strand lengths increases, the number of nanoparticles that assemble as well as the number of neighbours per particle in the assembled cluster increases. When the number of G/C nucleotides per strand in short and long strands is equal, the long strands hybridise with the other long strands with higher frequency than the short strands hybridise with short/long strands. This dominance of the long strands leads to bidisperse systems having similar thermodynamics to that in corresponding systems with monodisperse long strands. Structurally, however, as a result of long–long, long–short and short–short strand hybridisation, bidispersity in DNA strand length leads to a broader inter-particle distance distribution within the assembled cluster than seen in systems with monodisperse short or monodisperse long strands. The effect of increasing the number of G/C bases per strand or increasing the number of grafted DNA strands on the thermodynamics of assembly is similar for bidisperse and monodisperse systems. The effect of increasing the number of grafted ssDNA strands on the structure of the assembled cluster is dependent on the extent of strand bidispersity because the presence of significantly shorter ssDNA strands among long ssDNA strands reduces the crowding among the strands at high grafting density. This relief in crowding leads to larger number of strands hybridised and as a result larger coordination number in the assembled cluster in systems with high bidispersity in strands than in corresponding monodisperse or low bidispersity systems. [ABSTRACT FROM AUTHOR]

DNA functionalisation is a proven route to program an assembly of nanoparticles into a vast array of nanostructures. In this paper, we used coarse-grained molecular dynamics simulations to study DNA-functionalised nanoparticles and demonstrate the effect of grafted DNA strand composition, specifically the placement and number of contiguous G/C bases in the grafted DNA single strands, on the thermodynamics and structure of nanoparticle assembly at varying grafting densities and particle sizes. At a constant G/C content, nanoparticles assemble more readily when the G/C bases are placed on the outer or middle portions of the strands than on the inner portion. In addition, the number of neighbours within the assembled cluster decreases as the placement of the G/C bases goes from the outer to middle to inner sections of the strand. As the G/C content decreases, the cluster dissociation temperature,Td, decreases, as the enthalpic drive to assemble decreases. At a high G/C content (number of grafts and G/C placement are held constant), as particle size decreases,Tdincreases. This is because the smaller particles experience a lower entropic loss than do larger particles upon assembly. On the other hand, at a low G/C content, small changes in particle size lead to negligible changes inTd. [ABSTRACT FROM AUTHOR]

In this paper, tubular structure has been obtained by self-assembly of cholesterol derivative via sol–gel process. The tube structure and the formation mechanism have been studied and certified by scanning electron microscopy, infrared, ultraviolet-visible spectroscopy (UV–vis) and x-ray diffraction (XRD) data. It is predicated that the tube has been formed by the curl of sheet structure, and the aggregates are composed of two molecules of 1 with H aggregate in laminar structure at micro level. [ABSTRACT FROM PUBLISHER]

This paper investigates the conditions of the manufacture of low-cost technology in China with the examples of 'pirated' VCD players, 'no-name' DVD players, and Shenzhen's development as a techno-urban city. It emphasizes the significance of the cultural logic of original equipment manufacturers (OEMs) and argues that the various transformations and deflections that are derived from ubiquitous OEM experiences have gone beyond the original model of an authorized OEM, experiences that are to some extent embodied in the transgression of brand name and patent hegemonies, which are mainly controlled by high technology companies. OEMs have been associated with China's current imperative and uninhibited development of low-cost technology capitalism. 'Made in China' signifies the production of any product, legal or illegal, for transnational high technology giants or domestic technology manufacturers. Learning to 'become an OEM' in China has partly resulted in excessive technological mimesis that may be part of an unauthorized, underground economy that is based on low-cost technology. Based on the Shenzhen experience, part of this study will show industrial production-oriented OEM cultures in which illegal operations and counterfeit trade are incorporated, even in city projects that are shared by municipal governments and Chinese technological companies, and undergo spatial restructuring in the development of the economy, consumerism, and urbanism. [ABSTRACT FROM AUTHOR]

Finite element (FE) modelling techniques have become a popular tool for exploring welding and clamping sequence dependence in sheet metal assemblies. In the current paper, the dimensional variability associated with different assembly clamping sequences is investigated with a FE contact modelling approach implemented in the commercial code Abaqus. A simplified channel section assembly consisting of a top hat and bottom plate is the case study investigated. Expected variation modes of bow and twist were used to simulate key variability sources in the main structural component under investigation; the top hat of the channel section. It was found that final assembly variability can change considerably depending on clamp sequence selection. It was also found that different clamp sequences can control particular modes of variation better than others, and that there is not one particular clamping sequence that is the best for containing all variation modes. An adaptable assembly process is therefore suggested, where given the shape of input components the best available clamping sequence is selected. Comparison of the performance of the proposed adaptable clamping sequence to traditional fixed clamping sequences shows improvements for the dimensional control of variability in non-rigid components. While introducing such a method in production would require inspection of each component being assembled and investigation of the alternative clamping sequences, given access to fast and detailed dimensional inspection technology such as optical coordinate measuring machines (OCMM's), the approach shows promise for future application. [ABSTRACT FROM AUTHOR]

In complex manufacturing environments, meeting the due dates of the jobs and minimizing in process inventories are important performance metrics. One of the common characteristics of complex production systems is production-assembly network of operations. This paper presents an auction-based algorithm for simultaneous scheduling of all manufactured and assembled jobs in a dynamic environment, where the objective function is to minimize both the due date penalties associated with the final products and the inventory cost of the work in process. An auction-based approach using a Mixed-Integer Linear Programming (MILP) model to construct and evaluate the bids so that the auction mechanism mimics a Lagrangian relaxation-based subgradient optimization to ensure global optimality is proposed. The inner structure of the problem enables very efficient calculation of bids for each job or assembly. Using a full factorial experimental design the properties of the proposed algorithm are analyzed. Results show that the proposed auction based algorithm performs better than the popular dispatching rules and is more scalable than the MILP model or direct implementations of the subgradient algorithm. Furthermore, the proposed algorithm is designed to work in a dynamic environment. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) has the potential to substantially alter the manner in which products of the future are engineered. Currently there are many applications of VR during the product engineering process from design and analysis through to process planning, assembly, machining and shop floor layout. VR takes a multitude of forms, including immersive, desktop, augmented, and is rapidly developing as a tool that can be used in the engineering of products. This paper looks at the use of immersive VR as a tool for analysing both design and manufacturing product engineering activities in a series of research projects involving assembly planning and cable harness design. It focuses particularly on the use of the non-intrusive logging of users in such environments as a means to obtaining a rich data source for activity analysis and its potential within computer integrated manufacturing environments as a means of providing downstream engineering data. [ABSTRACT FROM AUTHOR]