Modular Assembly System Research Articles

Planning of Workstations in a Modular Automotive Assembly System

In a turbulent market environment an assembly system with a high level of flexibility and changeability is necessary. Especially in the automotive industry the developments towards product differentiation and shorter product lifecycles require highly flexible and changeable assembly systems. One basic enabler to reach this goal is modularization. In a modular assembly system having uncoupled workstations and a flexible transportation of products, however, the methods of production planning need to be adapted as well.In this paper, the well-established methodology of assembly line balancing for the planning of workstations in an assembly line production is analyzed. However, it is shown that this methodology as well as other methods to plan workstations in an assembly system are not applicable for a modular assembly system due to its different characteristics. For this reason, a new planning method to assign assembly tasks to workstations is developed, based on the different targets and restrictions of a modular assembly system.In this method, the assignment of assembly tasks to workstations is primarily based on their position in the assembly priority chart of the products being assembled. The application of the described method is shown in an example of a product-based modular automotive assembly system developed by the authors. In this context, the method is one main aspect of planning and operating a modular assembly system, which is supposed to handle the further increasing diversity and dynamics of the automotive industry by its high level of flexibility and changeability.

Smart Adaptable Assembly Systems

In today's manufacturing environment, change has become a constant. Modern assembly systems must adapt to products, markets, technologies and regulatory requirements. The assembly industry is undergoing vast changes with the rapid development of production automation, process control, information technologies and networking. Variant-oriented assembly systems have been developed to achieve more flexibility and adaptability to enable adding product variants and scaling production. Smart assembly systems where intelligence is embedded in the products, work stations and system are emerging to achieve more autonomy in communication between entities in the system and more adaptable control of assembly flow and system performance. This paper highlights some advances in assembly technologies and systems and new trends of modularity and reconfigurable using a modular and reconfigurable assembly system. Future directions and challenges are outlined.

Simulation-based Production Planning and Execution Control for Reconfigurable Assembly Cells

In order to meet the continuously changing market conditions and achieve economy of scale, a current trend in the automotive industry is the application of modular reconfigurable assembly systems. Although they offer efficient solution to meet the customers needs, the management of these systems is often a challenging issue, as the continuous advance in the assembly technology introduces new requirements in production planning and control activities. In the paper, a novel approach is introduced that enables the faster introduction of modular assembly cells in the daily production by offering a flexible platform for evaluating the system performance considering dynamic logistics and production environment. The method is aimed at evaluating different modular cell configurations with discrete-event simulation, applying automated model building and centralized simulation model control. Besides, the simulation is linked with the production and capacity planning model of the system in order to implement a cyclic workflow to plan the production and evaluate the system performance in a proactive way, before releasing the plan to the production. The method and the implemented workflow are evaluated within a real case study from the automotive industry.

Linear Constraint Programming for Cost-optimized Configuration of Modular Assembly Systems

In this paper, we develop an optimization model for providing a logical layout for reconfigurable assembly systems from a library of available equipment modules. The design problem addresses the challenges in equipment selection to build workstations and subsequently the entire assembly system. All the available equipment modules are assumed to be modular and each of them retains a subset of skills (capabilities). The set of all available equipment modules, their skills, mode of physical connectivity (ports) and costs are known. The objective is to minimize the overall equipment cost without violating their physical connectivity (ports) constraints and the precedence constraints of the assembly process requirements. The analysis of the problem and the state-of-art review steered us to the following: (1) the design problem is very closely related to the assembly line balancing problems; (2) a few Genetic Algorithm (GA) based approaches are already available for the capital cost optimization of multi-part flow-line (MPFL) configurations that includes the operational precedence constraints; (3) to our knowledge, this is the first work to combine the equipment physical connectivity constraints with task precedence in order to provide a valid and optimal configuration solution. A formalized mathematical model is developed to select suitable subsets of equipment modules and group them into workstations to construct an optimal logical layout. A number of scenarios based on an industrial case study are simulated and the results are analysed to evaluate the performance of the proposed models.

Design and management of reconfigurable assembly lines in the automotive industry

Automotive suppliers are facing the challenge of continuously adapting their production targets to variable demand requirements due to the frequent introduction of new model variants, materials and assembly technologies. In this context, the profitable management of the product, process and system co-evolution is of paramount importance for the company competitiveness. In this paper, a methodology for the design and reconfiguration management of modular assembly systems is proposed. It addresses the selection of the technological modules, their integration in the assembly cell, and the reconfiguration policies to handle volume and lot size variability. The results are demonstrated in a real automotive case study.

Development of Polymer Concrete with Non-Standardised Fillers for Innovative Building Materials

The use of polymer concrete in building construction is a relatively new application. A building block system (Modular Assembly System: MAS-System) and the mobile fabrication technology for the reversible construction of buildings with regionally available aggregates, were developed in a project of applied research. The aspects of the successful material development are described, especially with regard to the characterisation of both the binders and the polymer concretes, considering strength and durability. The polymer concrete consists approximately of 90 % fillers, 10 % polymer binder and additives. The investigation of the binder-system included the determination of gel time and temperature development, shrinkage, wetting of formwork materials and immersion tests with marine water. The aim was an adaptation and optimisation of the binder system. The characterisation of mechanical properties of the polymer concrete was realised by determining its strength in a temperature range between - 40 °C and 60 °C. Compression tests on wall segments were also realised. Ageing is an important aspect of the durability of polymer bonded materials. Special tests were used for an accelerated ageing, including impacts of temperature change, cold rain water and natural radiation.

An Approximation Approach for Solving a Continuous Review Inventory System Considering Service Cost

【The modular assembly system can make it possible for the variety of products to be assembled in a short lead time. In this system, necessary components are assembled to optional components tailor to customers' orders. Budget for inventory investments composed of inventory and purchasing costs are practically limited and the purchasing cost is often paid when an order is arrived. Service cost is assumed to be proportional to service level and it is included in budget constraint. We develop a heuristic procedure to find a good solution for a continuous review inventory system of the modular assembly system with a budget constraint. A regression analysis using a quadratic function based on the exponential function is applied to the cumulative density function of a normal distribution. With the regression result, an efficient heuristics is proposed by using an approximation for some complex functions that are composed of exponential functions only. A simple problem is introduced to illustrate the proposed heuristics.】

Filtration-based synthesis of micelle-derived composite membranes for high-flux ultrafiltration.

Ideal membrane configurations for efficient separation at high flux rates consist of thin size-selective layers connected to macroporous supports for mechanical stabilization. We show that micelle-derived (MD) composite membranes combine efficient separation of similarly sized proteins and water flux 5-10 times higher than that of commercial membranes with similar retentions. MD composite membranes were obtained by filtration of solutions of amphiphilic block copolymer (BCP) micelles through commercially available macroporous supports covered by sacrificial nanostrand fabrics followed by annealing and removal of the nanostrand fabrics. Swelling-induced pore generation in the BCP films thus covering the macroporous supports yielded ∼210 nm thin nanoporous size-selective BCP layers with porosities in the 40% range tightly connected to the macroporous supports. Permselectivity and flux rates of the size-selective BCP layers were adjusted by the BCP mass deposited per membrane area and by proper selection of swelling times. The preparation methodology described here may pave the way for a modular assembly system allowing the design of tailored separation membranes.

The Impact of Modular Assembly on Supply Chain Efficiency

This article studies the impact of modular assembly on supply chain efficiency. In the modular assembly approach, a manufacturer acquires pre‐assembled modules from its suppliers, rather than the individual components, as in the traditional assembly approach. We analyze the competitive behavior of a two‐stage modular assembly system consisting of a manufacturer, and a supplier who pre‐assembles two components into a module. The firms can choose their own inventory policies and we show the existence of Nash equilibrium in the inventory game. Moving from the traditional to the modular approach has a twofold effect on the supply chain. First, we investigate the effect of centralizing the component suppliers. It can be shown that when there is no production time shift, the module supplier always holds more component inventories than suppliers do in the traditional approach, which yields a lower cost for the manufacturer. However, the suppliers, and therefore the supply chain may incur a higher cost in the modular approach. Second, we study the effect of a shift in production time from the manufacturing stage to the supplier stage. From numerical studies, it has been found that such a lead time shift always benefits a centralized supply chain, but not necessarily so for a decentralized system. Combining the two effects, we find that the modular approach generally reduces the cost to the manufacturer and the supply chain, which explains the prevalence of modular assembly from the perspective of inventory management. These results also provide some insight into how firms can improve supply chain efficiency by choosing the right decision structure and lead time configuration.

A system for multilocus chromosomal integration and transformation-free selection marker rescue.

Yeast integrating plasmids (YIPs) are a versatile tool for stable integration in Saccharomyces cerevisiae. However, current YIP systems necessitate time- and labor-intensive methods for cloning and selection marker rescue. Here, we describe the design, construction, and validation of a new YIP system capable of accelerating the stable integration of multiple expression constructs into different loci in the yeast S.cerevisiae. These 'directed pop-out' plasmids enable a simple, two-step integration protocol that results in a scarless integration alongside a complete rescue of the selection marker. These plasmids combine three key features: a dedicated 'YIPout' fragment directs a recombination event that rescues the selection marker while avoiding undesired excision of the target DNA sequence, a multifragment modular DNA assembly system simplifies cloning, and a new set of counterselectable markers enables serial integration followed by a transformation-free marker rescue event. We constructed and tested directed pop-out YIPs for integration of fluorescent reporter genes into four yeast loci. We validated our new YIP design by integrating three reporter genes into three different loci with transformation-free rescue of selection markers. These new YIP designs will facilitate the construction of yeast strains that express complex heterologous metabolic pathways.

Mechanical performance of bolted modular GFRP composite sandwich structures using standard and blind bolts

This paper presents a mechanically bolted modular assembly system of GFRP web–flange sandwich structures used for beam and slab applications. Built-up modular sections consisting of standard GFRP pultruded I or box profiles are incorporated between two GFRP plates to form a sandwich structure, which can then be assembled in the transverse direction to form a one-way spanning slab system. Modular sandwich specimens were prepared via mechanically bolting the component profiles, and were then tested under four-point bending. The load-carrying capacity was evaluated, and the degree of composite action and the detail of the bolted connections, such as the spacing and type of bolts, were investigated. It was found that the composite action offered by the bolted connections decreased with the increase of load, and only partial composite action was achieved at ultimate loads. In addition, the degree of composite action was also dependent upon the bolt spacing. Finally, a finite element modeling approach was established to predict structural stiffness and the degree of composite action of bolted GFRP sandwich specimens. The models showed good comparisons with the experimental results.

Symbiotic Assembly Systems – A New Paradigm

Assembly systems have been pressed in recent years to provide highly adaptable and quickly deployable solutions in order to deal with unpredictable changes following market trends. This has led to the development of multiple paradigms, namely Flexible Assembly System, Holonic Assembly Systems, Evolvable Assembly Systems, Modular Assembly systems, etc. Mostly these focus on increasing availability of automation, however this focus has overshadowed the human element in assembly systems. The lack of a clear human element in these approaches resulted in non-necessary automation and increase complexity. This paper proposes a new paradigm of Symbiotic Assembly Systems (SAS) in order to integrate the human aspects into these developments. The motivation is human actors should be treated as an intrinsic component of assembly systems. This would result in a system that can take advantage of its component's individual strengths (human or machines), and create a symbiotic environment. Beyond machine automation, human interventions in the system need not only to be modelled as processes but also integrated into the whole system operation. The idea builds on biological systems and their ability to establish symbiotic environments resulting in optimal collaborations. This paper proposes the conceptual vision of Symbiotic Assembly Systems and identifies the necessary developments required to achieve such paradigm. Furthermore it reports on how the developments from other paradigms can be integrated into SAS. An illustrative example is presented to demonstrate the potential of this approach.

Automation Concepts and Gripping Solutions for Bonding with Reactive Multilayer Systems

Reactive multilayer systems (RMS) represent an innovative heat source for the establishment of solder joints. They offer fast bonding processes that introduce very little thermal input and internal stress on the bonded parts. The current application process of RMS is predominantly manual labor. There are a couple of challenges to be overcome to automate this process, a requirement for its introduction into industrial production.In this paper we evaluate the requirements for an automated joining process with RMS and devise a concept of a modular assembly system for different product structures. Furthermore we show our results in gently and reliably gripping and handling of RMS.

Learning and reuse of engineering ramp-up strategies for modular assembly systems

We present a decision-support framework for speeding up the ramp-up of modular assembly systems by learning from past experience. Bringing an assembly system to the expected level of productivity requires engineers performing mechanical adjustments and changes to the assembly process to improve the performance. This activity is time-consuming, knowledge-intensive and highly dependent on the skills of the engineers. Learning the ramp-up process has shown to be effective for making progress faster. Our approach consists of automatically capturing information about the changes made by an operator dealing with disturbances, relating them to the modular structure of the machine and evaluating the resulting system state by analysing sensor data. The feedback thus obtained on applied adaptations is used to derive recommendations in similar contexts. Recommendations are generated with a variant of the k-nearest neighbour algorithm through searching in a multidimensional space containing previous system states. Applications of the framework include knowledge transfer among operators and machines with overlapping structure and functionality. The application of our method in a case study is discussed.

Optimization Design of Modular Desktop Micro-Assembly System Based on Genetic Algorithm

For solving the problem of non-silicon MEMS assembly, the framework of Modular Desktop Micro Assembly System (MDMAS) is proposed, the fundamental principles and functional modular partition method of which is described in this paper. Based on it, the structure-capability correlation matrix and structure autocorrelation matrix are established, and the multi-objective optimization design model is constructed. In addition, GA (genetic algorithm) is introduced for best solution searching, and the proposed design method is validated

The Impact of Modular Assembly on Supply Chain Efficiency

This paper studies the impact of modular assembly on supply chain efficiency. In the modular assembly approach, a manufacturer acquires pre-assembled modules from its suppliers, rather than the individual components, as in the traditional assembly approach. We analyze the competitive behavior of a two-stage modular assembly system consisting of a manufacturer, and a supplier who pre-assembles two components into a module. The firms can choose their own inventory policies and we show the existence of Nash equilibrium in the inventory game. Moving from the traditional to the modular approach has a two-fold effect on the supply chain. First, we investigate the effect of centralizing the component suppliers. It can be shown that when there is no production time shift, the module supplier always holds more component inventories than suppliers do in the traditional approach, which yields a lower cost for the manufacturer. However, the suppliers, and therefore the supply chain may incur a higher cost in the modular approach. Second, we study the effect of a shift in production time from the manufacturing stage to the supplier stage. From numerical studies, it has been found that such a lead time shift always benefits a centralized supply chain, but not necessarily so for a decentralized system. Combining the two effects, we find that the modular approach generally reduces the cost to the manufacturer and the supply chain, which explains the prevalence of modular assembly from the perspective of inventory management. These results also provide some insight into how firms can improve supply chain efficiency by choosing the right decision structure and lead time configuration.

Distributed Bayesian diagnosis for modular assembly systems—A case study

The growing interest in modular and distributed approaches for the design and control of intelligent manufacturing systems gives rise to new challenges. One of the major challenges that have not yet been well addressed is monitoring and diagnosis in distributed manufacturing systems. In this paper we propose the use of a multi-agent Bayesian framework known as Multiply Sectioned Bayesian Networks (MSBNs) as the basis for multi-agent distributed diagnosis in modular assembly systems. We use a close-to-industry case study to demonstrate how MSBNs can be used to build component-based Bayesian sub-models, how to verify the resultant models, and how to compile the multi-agent models into runtime structures to allow consistent multi-agent belief update and inference.

Assembly of custom TALE-type DNA binding domains by modular cloning

Transcription activator-like effector (TALE) DNA binding proteins show tremendous potential as molecular tools for targeted binding to any desired DNA sequence. Their DNA binding domain consists of tandem arranged repeats, and due to this repetitive structure it is challenging to generate designer TALEs (dTALEs) with user-defined specificity. We present a cloning approach that facilitates the assembly of multiple repeat-encoding DNA fragments that translate into dTALEs with pre-defined DNA binding specificity. This method makes use of type IIS restriction enzymes in two sequential cut-ligase reactions to build dTALE repeat arrays. We employed this modular approach for generation of a dTALE that differentiates between two highly similar DNA sequences that are both targeted by the Xanthomonas TALE, AvrBs3. These data show that this modular assembly system allows rapid generation of highly specific TALE-type DNA binding domains that target binding sites of predefined length and sequence. This approach enables the rapid and flexible production of dTALEs for gene regulation and genome editing in routine and high-throughput applications.

Computability and Complexity in Self-assembly

This paper explores the impact of geometry on computability and complexity in Winfree’s model of nanoscale self-assembly. We work in the two-dimensional tile assembly model, i.e., in the discrete Euclidean plane ℤ×ℤ. Our first main theorem says that there is a roughly quadratic function f such that a set A⊆ℤ+ is computably enumerable if and only if the set X A ={(f(n),0)∣n∈A}—a simple representation of A as a set of points on the x-axis—self-assembles in Winfree’s sense. In contrast, our second main theorem says that there are decidable sets D⊆ℤ×ℤ that do not self-assemble in Winfree’s sense. Our first main theorem is established by an explicit translation of an arbitrary Turing machine M to a modular tile assembly system $\mathcal{T}_{M}$, together with a proof that $\mathcal{T}_{M}$ carries out concurrent simulations of M on all positive integer inputs.

Multi-Agent Architecture for Self-Configuring Modular Assembly Systems

Abstract Assembly systems today require an increasingly higher level of physical and logical adaptability. Methods and tools are needed to adapt assembly systems to market changes in a timely and cost effective manner. The requirement for increased responsiveness has led to the development of new modular concepts which provide the bases for achieving higher system adaptability through increased component/module interchangeability and reusability. The modularization of physical and control infrastructure does, however, only address one aspect of the issue and there is still a lack of appropriate tools and methods to support the rapid configuration and re-configuration of such systems for changing sets of requirements. This paper proposes an agent architecture for the self-configuration and re-configuration of equipment modules into systems based on a given set of requirements. A new agent model has been developed which addresses the specific needs of modular assembly systems catering both for physical and logical constraints of the modules as well as their joint emergent behaviour.