Design Of Assembly Systems Research Articles

Hybrid evolutionary multi-objective algorithms for integrating assembly sequence planning and assembly line balancing

Assembly sequence planning (ASP) and assembly line balancing (ALB) play critical roles in designing product assembly systems. In view of the trend of concurrent engineering, pondering simultaneously over these two problems in the development of assembly systems is significant for establishing a manufacturing system. This paper contemplates the assembly tool change and the assembly direction as measurements in ASP; and further, Equal Piles assembly line strategy is adopted and the imbalanced status of the system employed as criteria for the evaluation concerning ALB. Focus of the paper is principally on proposing hybrid evolutionary multiple-objective algorithms (HEMOAs) for solutions with regard to integrate the evolutionary multi-objective optimization and grouping genetic algorithms. The results provide a set of objectives and amend Pareto-optimal solutions to benefit decision makers in the assembly plan. In addition, an implemented decision analytic model supports the preference selection from the Pareto-optimal ones. Finally, the exemplifications demonstrate the effectiveness and performance of the proposed algorithm. The consequences definitely illustrate that HEMOAs search out Pareto-optimal solutions effectively and contribute to references for the flexible change of assembly system design.

Life cycle and unit-cost analysis for modular reconfigurable flexible light assembly systems

The article presents a decision support methodology for the selection of a modular reconfigurable assembly system using three-dimensional visualization, component-based simulation, efficiency, and economic analysis methodology. During the design and selection of an assembly system, measurement schemes should be established for determining and understanding design effectiveness. Measurements can be classed into two categories: cost and performance. Understanding assembly production costs is the first step towards increasing profits. The authors have developed an analysis method that integrates factory simulation, overall equipment efficiency (OEE), and economic analysis methods. Cost calculation includes life cycle cost (LCC), cost of ownership (COO), commonly used investment evaluation methods, discounted cash flow techniques, net present value (NPV), and internal rate of return (IRR). The idea is to use these integrated analysis methods in the selection and development of a light assembly system. The development is based on selected industrial standards and the authors’ own experience in assembly system design and simulation. The developed TCO (total cost of ownership) methodology is useful in system supplier and end-user communication; ideally, it is used in the assembly system sales process, it helps in trade-off analysis of the system concepts, and it improves system specification.

The role of the fuzzy cognitive map in hierarchical semantic net-based assembly design decision making

For today's highly industrialised and internet-centred business world, it has become essential for manufacturing companies to devise more intelligent assembly design (AsD) and decision support tools to promote customer satisfaction. In order to achieve high performance throughout a product's life-cycle, an AsD system should be able to assist designers' decision-making during assembly and joint design processes in order to avoid design specification violation. An assembly design decision (ADD) problem occurs when the current AsD violates assembly specifications. To obtain a robust design, appropriate joints should be determined by considering the mechanical and mathematical implications of assembly/joining. To tackle the ADD problem, we introduce a hierarchical semantic net (HSN) model to represent evaluation and AsD knowledge, which are of course present, both in the multi-criteria and in a knowledge-based ADD problem. However, the HSN model still requires a methodology for capturing manufacturing environment knowledge and utilising that knowledge for assembly design decision making (ADDM). In the present paper, to avoid the subjective criterion-weight determination of traditional multi-criteria evaluation techniques, we use a fuzzy cognitive map (FCM) in the ADDM framework. An Assembly Advisory (AsA) engine and FCM simulator are developed to implement the presented ADDM framework. We conduct experiments for a realistic welded structure using several scenarios to show the ADDM framework's feasibility. This paper shows that an FCM can be successfully utilised to determine weights of ADDM criteria while capturing manufacturing environment knowledge. An FCM also provides a rich environment for ‘what-if’ experiments to determine ADD criterion weights.

A Petri net model for the design and performance evaluation of a flexible assembly system

PurposeThe purpose of this paper is to present a Petri net (PN) model based on assembly plan is presented for modeling a flexible assembly system (FAS) configuration, determining an optimal work‐in‐process (WIP), lead time, throughput, and utilization of each station.Design/methodology/approachPN model is developed for design, analysis, and performance evaluation of a FAS, keeping in view the assembly line balancing. PN is optimized using weighted WIP. The throughput is bounded by the utilization of the bottleneck machines.FindingsThe PN optimization gives minimum WIP corresponding to the maximum production rate. Minimum WIP leads to minimum lead time. The weighted arcs make the model simple and reduce the optimized number of kanbans. Moreover, the PN model pushes more inventory to the initial assembly phase. This reduces the total cost of the WIP.Research limitations/implicationsIn the proposed PN model, the transportation times are included in the transitions times. In the future research, the proposed model can be extended for inclusion of transportation times for AGVs.Practical implicationsUsing the PN model, the assembly manager may design, analyze, evaluate, and even optimize the layout of the assembly system for minimum WIP, maximum throughput, and reduced lead time. The determination of the total WIP, total number of stations in the assembly system, and the number of servers at each station may be helpful in factory floor management. The same cycle time is managed at each assembly station for the purpose of line balancing. It may result in the highest efficiency and the shortest idling time along with ease of management and supervision.Originality/valueThis paper presents a new PN model for the design and performance evaluation of a dual kanban FAS.

Precise manipulation approach to facilitate interactive modular fixture assembly design in a virtual environment

PurposeThe virtual design environment offers users an opportunity to interact with a virtual prototyping rather than physical models and to build a fixture configuration in a realistic way. But the virtual reality (VR) environment tends to be inaccurate because humans have difficulty in performing precise positioning tasks. Therefore, it is necessary to implement precise object manipulation methods for assembly and disassembly activities, so that users can perform modular fixture configuration design efficiently in VE. The purpose of this paper is to develop a VR‐based modular fixture assembly design system, which supports the design and assembly of modular fixture configuration in a virtual environment.Design/methodology/approachGeometric constraint‐based method is utilized to represent and treat the assembly relationship between modular fixture elements. The paper presents a hybrid method of rule‐based reasoning and fuzzy comprehensive judgment to capture the user's operation intent and recognize geometric constraint. Through degrees of freedom based analysis, a mathematical matrix is presented for representing and reducing allowable motion of fixture elements, and a constraint‐based motion navigation approach is proposed to ensure that the manipulation of a fixture component not violate that the existing constraints.FindingsThe paper finds that the proposed techniques are applicable to the convenient manipulation and accurate positioning of fixture elements in a virtual environment.Practical implicationsComponent manipulation plays a key role in interactive virtual assembly design. The proposed approach in this paper enables interactive assembly design of modular fixture in virtual environment.Originality/valueThis paper presents a geometric constraint‐based approach that realizes automatic assembly relationship recognition, constraint solving and motion navigation for interactive modular fixture assembly design in a virtual environment.

Knowledge-based vehicle body conceptual assembly design

The paper discusses the architecture of a knowledge-based vehicle body conceptual assembly design system. The proposed system addresses problems when applying knowledge-based techniques to vehicle body design at the conceptual design stage and later stages. The paper mainly gives a proposed framework and organization of the conceptual assembly design system with the help of knowledge-based engineering, where it takes into integrated consideration the assembly sequence, joint configuration, and tolerance allocation in the autobody assembly design process planning. Heuristic knowledge and empirical knowledge play active roles in the generation of the assembly sequence and dimension chain, the configuration of joint types, and the allocation of tolerance limits, and qualitative simulation is knowledge reasoning or rule reasoning with all kinds of rule, criterion, and principle, so that the knowledge-based vehicle assembly design system can improve assembly concept quality by means of qualitative simulation to fulfil the concurrent integration between conceptual design and detail design stages.

Virtual Manufacturing in Research & Industry

The paper focuses on the research & development of the Digital Factory solutions for industry. The developed methodology and solution of Factory Mock Up (FMU) is presented. The results of research and development cover design of assembly system, its processes, simulation model, ergonomic analysis etc. In the paper are presented the solutions developed in the framework of co-operation with industrial partners like Volkswagen Slovakia, Thyssen Krupp – PSL, Whirlpool. The advantages, restrictions and way of utilization of Digital Factory solutions are also shown in the paper.

A team-oriented design methodology for mixed model assembly systems

Team-oriented approaches are widely being used in modern real life assembly systems, as are other modern systems. In this paper, first the literature of single and mixed model assembly line balancing, which plays an important role for the design of assembly systems, is reviewed. The associated literature matrixes reveal that team-oriented approaches do not have an intensive research area. Second, a team-oriented mathematical programming model for creating assembly teams (physical stations) in mixed model assembly lines is devised. Owing to the fact that this model is NP hard, a scheduling based heuristic algorithm is developed. The mixed model assembly line design methodology, which includes a team-oriented algorithm as a step, is proposed. Both model sequencing and worker transfer systems are included in the methodology. The algorithms for each step of the methodology are also coded by using MATLAB and MS Excel is used as the user interface. Furthermore, the presented methodology was applied in a chosen segment of a real life mixed model tractor assembly system.

Co-Evolution of Product Families and Assembly Systems

To cope with the intense global competition that is characterized by high product variety and short life cycles, manufacturers need to share manufacturing systems across products and product generations. Co-evolution of product families and assembly systems is proposed as a novel methodology for the joint design and reconfiguration of product families and assembly systems over several product generations. The co-evolution methodology capitalizes on the opportunities for design and assembly system reuse that are offered by modular product architectures and reconfigurable assembly systems. As a result, co-evolution can lead to reduced product development costs and increased responsiveness to market changes.

Transition of interarrival time patterns between automated and manual configurations of assembly systems

The paradigm of hybrid automatic/manual assembly systems has recently been extended by reconfigurable systems that allow exchanging manual and automated production modules with minimum interruption of the system control and operation. However, both types of assembly systems exhibit different interarrival time patterns for layouts that employ asynchronous workpiece transport on tracks with multiple routes and loops. In this work, it has been shown analytically that for Gaussian processing time distributions the queue length follows heavy-tailed unimodal and bimodal distributions. Based on the resulting outlier probability, an analytical model for predicting the limits of allowable processing time variance for deterministic interarrival time models is proposed. This model is positively validated with simulation analysis by comparing different levels of processing time variance. It is concluded that established design practices such as cycle-time balancing and synchronization should be avoided in reconfigurable hybrid assembly system design because they introduce interarrival-time turbulence in the automated system.

Concurrent product portfolio planning and mixed product assembly line balancing

Reconfigurable products and manufacturing systems have enabled manufacturers to provide “cost effective” variety to the market. In spite of these new technologies, the expense of manufacturing makes it infeasible to supply all the possible variants to the market for some industries. Therefore, the determination of the right number of product variants to offer in the product portfolios becomes an important consideration. The product portfolio planning problem had been independently well studied from marketing and engineering perspectives. However, advantages can be gained from using a concurrent marketing and engineering approach. Concurrent product development strategies specifically for reconfigurable products and manufacturing systems can allow manufacturers to select best product portfolios from marketing, product design and manufacturing perspectives. A methodology for the concurrent design of a product portfolio and assembly system is presented. The objective of the concurrent product portfolio planning and assembly system design problem is to obtain the product variants that will make up the product portfolio such that oversupply of optional modules is minimized and the assembly line efficiency is maximized. Explicit design of the assembly system is obtained during the solution of the problem. It is assumed that the demand for optional modules and the assembly times for these modules are known a priori. A genetic algorithm is used in the solution of the problem. The basic premise of this methodology is that the selected product portfolio has a significant impact on the solution of the assembly line balancing problem. An example is used to validate this hypothesis. The example is then further developed to demonstrate how the methodology can be used to obtain the optimal product portfolio. This approach is intended for use by manufacturers during the early design stages of product family design.

Analysis and design of split and merge unpaced assembly systems by metamodelling and stochastic search

The study presents a new approach in optimal interstage buffer allocation problem of split-and-merge unpaced open assembly systems, which are increasingly being used in modern manufacturing systems, particularly in automotive industries. Allocations of interstage buffers to accommodate the work-in-process inventories are optimized in an attempt to maximize the overall system production rate. A simulation model developed is used in conjunction with genetic algorithms (GA) to find optimal interstage buffer configurations yielding a maximum production rate. However, simulation is extremely time-consuming due to lengthy computational requirements, especially when used in a stochastic search algorithm. In an attempt to overcome this problem, an alternative approach in simulation metamodelling based on artificial neural networks (ANN) is developed. The optimization problem previously conducted through simulation and GA is reconsidered by integrating the metamodelling approach into the GA, replacing the simulation model. The new ANN-GA approach not only gives solutions with no statistically significant difference in comparison with the original simulation GA approach, but also demands significantly less computational time. The proposed methodology intends to help practising system design engineers to take quicker decisions regarding the assembly system design parameters. The potential of metamodelling to solve manufacturing systems problems are also discussed.

Total cost of ownership analysis for modular final assembly systems

The objective of modern assembly processes is to produce high-quality and low-cost products. Understanding manufacturing costs in the system design phase is the first step to increasing profits. Throughput, utilization, and cycle time continue to be emphasized as key performance indicators for the planning of new assembly systems, but the cost issues need to be analysed as well. The authors are developing a novel analysis methodology that integrates component-based simulation, Overall Equipment Efficiency with Cost of Ownership, and other analysis methods to improve the design of flexible, modular reconfigurable assembly systems. The development of the Total Cost of Ownership (TCO) analysis tool is based on selected industrial standards and the authors’ own experience of assembly system design and simulation. The TCO method is useful in system-supplier and end-user communication, and helps in trade-off analyses of system concepts. A fictitious case study illustrates the use of the TCO method.

Buffer allocation and performance modeling in asynchronous assembly system operations: An artificial neural network metamodeling approach

This article investigates metamodeling opportunities in buffer allocation and performance modeling in asynchronous assembly systems (AAS). Practical challenges to properly design these complex systems are emphasized. A critical review of various approaches in modeling and evaluation of assembly systems reported in the recently published literature, with a special emphasis on the buffer allocation problems, is given. Various applications of artificial intelligence techniques on manufacturing systems problems, particularly those related to artificial neural networks, are also reviewed. Advantages and the drawbacks of the metamodeling approach are discussed. In this context, a metamodeling application on AAS buffer design/performance modeling problems in an attempt to extend the application domain of metamodeling approach to manufacturing/assembly systems is presented. An artificial neural network (ANN) metamodel is developed for a simulation model of an AAS. The ANN and regression metamodels for each AAS are compared with respect to their deviations from the simulation results. The analysis shows that the ANN metamodels can successfully be used to model of AASs. Consequently, one concludes that practising engineers involved in assembly system design can potentially benefit from the advantages of the metamodeling approach.

Knowledge-intensive collaborative design modeling and support: Part II: System implementation and application

Contemporary design problems embody significant levels of complexity, which make it unlikely that a single designer can work alone on a complex design problem. Knowledge-intensive collaboration has emerged as a promising discipline for dealing with the modeling and decision-making processes in distributed design systems. In this paper, we present the implementation and application of a web-based knowledge-intensive collaborative design support system called WebKIDSS. With the modularization of design, a modules networked system could be developed and deployed according to CORBA standard to facilitate the rapid construction of the concurrent integrated distributed models for the design process and the coordination among designers within the range of enterprises and even virtual enterprises. The prototype web-based collaborative design platform, is implemented for proof-of-concept through the distributed knowledge server based framework (KS-DMME) with concurrent integration of multiple cooperative knowledge sources and software using Java/Java Bean and CORBA technologies. The unified user interface of the WebKIDSS provides a cross-platform for distributed users to access to module servers throughout the network. By use of the developed the prototype system, collaborative design can be carried out in an integrated and distributed open environment on the internet/intranet. Based on the preliminary application to the collaborative design of a micro robotic assembly system on the Internet, the developed system indicates some advantages to increase the efficiency of the design coordination and decision-making in the design process.

Equipment ontology for modular reconfigurable assembly systems

Evolvable and Reconfigurable Assembly Systems (RAS) enable enterprises to rapidly respond to changes in today’s increasingly volatile and dynamic global markets. One of the key success factors for the effective use of RAS is methods and tools that can rapidly configure and reconfigure assembly systems driven by changing requirements. The focus of this paper is the development of a suitable equipment model to support the effective design of reconfigurable assembly systems. The work has been motivated by the need to provide solutions for increasing product customisation and volume changes over the product life-cycle that directly impact on the final product assembly. The paper proposes a comprehensive equipment ontology to enable effective decision-making during the design and evaluation of new RAS configurations. The proposed ontology is based on the function-behaviour-structure paradigm, and is formalised to facilitate its application in distributed web-enabled decision-making environments. The equipment configuration and reconfiguration approach and prototype decision-making environment are illustrated using system design examples.

Design of international assembly systems and their supply chains under NAFTA

The purpose of this paper is to provide a decision support aid for the strategic design of an assembly system in the international business environment created by NAFTA. The strategic design problem is to prescribe a set of facilities, including their locations, technologies, and capacities, as well as strategic aspects of the supply chain, selecting suppliers; locating distribution centers; planning transportation modes; and allocating target levels (i.e., amounts) for production, assembly, and distribution. The objective is to maximize after-tax profits. This paper presents a mixed integer programming model that represents the complexities of the international design problem as well as relevant enterprise-wide decisions in the US–Mexico business environment under NAFTA. It deals with a broad set of design issues (e.g., bill-of-material restrictions, international financial considerations, and material flow through the entire supply chain) using effective modeling devices (e.g., linearizing non-linearities that arise in modeling transfer prices and allocating transportation charges). Examples demonstrate how managers might use the model as a decision support aid.

Environmental protection and quick assembly feature at autumn shows

PurposeThis paper highlights new automated assembly system components introduced in late 2004. Products meet new levels of environmental protection and offer features for quicker assembly system design and commissioning.Design/methodology/approachAttended various trade shows and contacted key vendors for information on product introductions.FindingsVendors are addressing more and more application needs with features like more compact components, more features, innovative materials and new answers to system design and application problems.Research limitations/implicationsNot all the new products which may have been introduced have been covered.Practical implicationsUsers and systems integrators can find new component answers to previously troubling requirements of automated assembly system design and commissioning.Originality/valueHighlights new assembly system component offerings that may be real problem solutions for system designs and integrators who previously considered products to not fully address their requirements.

Performance analysis of assembly systems with unreliable machines and finite buffers

An unreliable assembly system is studied in which different types of components are processed by two separate work centers before merging to an assembly station with random breakdown. Blocking at the work centers and starvation at the assembly station may occur because of finite buffer sizes and uncertainties in job arriving times and processing/assembly times. We derive the system stability condition, and obtain formulas for the system state probabilities, blocking probabilities, starvation probability, stockout probability, system availability in the steady state. We also obtain the distributions of blocking times and first failure times, respectively. Through numerical examples, we elaborate on the monotonous properties of the performance measures, and draw the insights into the impacts of the system parameters on its various performance indices, which provide important guidance for design of assembly systems.

Automated Generation of Assembly System-Design Solutions

Any assembly system-design problem which consists of generating system configurations and assignment of tasks to the stations has a set of solutions. The number of feasible solutions may be staggering, even for products consisting of a relatively small number of parts assembled on a small number of stations. As the size of the product and the assembly system grow, it may become difficult to develop a complete set of design solutions for in-depth analysis. Here an automated method is described by which the complete sets of system configurations and assembly sequences may be generated, and feasible solutions, consisting of a matched element from each set, can be rapidly derived. These solutions may then be tested for various performance metrics, some of which may not be expressed mathematically. In designing assembly systems, the layout of stations and the assignment of assembly tasks to these stations are important design problems. This paper proposes a set of algorithms to quickly generate the configurations of the assembly system and assign tasks to the configurations. Once the matching of tasks to the configurations is complete, the performance of these various design alternatives, such as productivity, can be evaluated to allow selection of configurations with the best performance.