The extended international development of the automotive industry has been supported in a part by crossdocking platforms set up between distant manufacturing plants and nearby first-tier suppliers. A ...cross-dock centre is an intermediate consolidation point in a supply chain linking a set of suppliers with a set of customers. Main advantages are a reduced lead time, a decrease of stock level and economies in transportation. At shop-floor, packages from inbound trucks are unloaded, moved across, sorted by destination and loaded onto outbound trucks. A case of study at Renault company is presented in this paper. Two important points are observed for this Renault crossdock center: (1) repackaging operations are performed for some products and (2) due to the high diversity of packages' dimensions and stacking rules, scheduling of inbound, repackaging and loading outbound trucks is a complex problem. We propose a mixed integer linear programming model to schedule inbound trucks' arrival times (considering given soft time windows), shop-floor repackaging operations and outbound trucks' departure times. Capacitated temporary storage zones and a capacitated repack workshop are considered at crossdock shop-floor. The model seeks to minimize penalty costs related to inbound trucks' arrival times and consequently unbalanced workload of the repack workshop. Implemented in CPLEX and tested on some instances provided by Renault, results of numerical experiments show the efficiency and pertinence of the model in the given industrial context.
•Mixed integer linear programming for inbound truck scheduling at crossdock centres.•Crossdocking industrial case of study from a major actor of automotive industry.•Industrial real-data numerical experiments.•Minimizing penalty costs related to unbalanced crossdock workload.
Companies are seeking more and more to offer customized goods and services to customers to be able to satisfy their needs. Several methods emerged to fulfill the needs of customization without ...affecting the performance of the company. Modularity has been considered as an effective method to address the challenges regarding variety management in the product and service domain. It has been addressed in the product domain but rarely in the service domain. This paper aims to provide a method to modularize a service-oriented system that consists of products and services. The method uses a set of modularization criteria and clustering techniques to form service-oriented system modules (product and/or service modules). The output of the clustering process is evaluated using indicators to provide decision-makers with insights into potentially preferred clustering alternatives. A test case is presented in order to show the applicability of the method.
To face market volatility, reconfigurable manufacturing systems (RMS) aim to efficiently and cost-effectively react to changes. We focus on one characteristic of RMS: the scalability (ability to ...adapt the volume of throughput). In the literature, the only few indicators for scalability are not always formally defined and usually only consider a partial view of scalability. Moreover, most of them are actually more suited for the configuration planning rather than for the design. However, the design of the RMS has a high impact on its scalability. We propose the first combinatorial definition of this problem and a new measure to fully assess the scalability of a system at the design phase. This measure, based on a multi-objective approach, can assess the scalability of single-product manufacturing systems, analysing all configurations that it can implement. We present numerical experiments to compare this indicator with a state-of-the-art scalability indicator and with some classical production line design indicators, and we show that future research should focus on scalability as a specific criterion to optimise during the design of an RMS. In addition, the results obtained allow us to infer some managerial insights on the best levers to use when performing a reconfiguration for scalability purpose.
Energy efficiency has become a major concern for manufacturing systems, due to industry being the largest user of scarce, finite energy sources, and also to recent events which have pushed energy ...prices to alarming levels. In the present Industry 4.0 context, Reconfigurable Manufacturing Systems (RMS) are therefore one of the most promising manufacturing paradigm. In this paper, we investigate the suitability of one of the most common types of RMS, the Parallel-Serial manufacturing line with Crossover, to help minimise the peak of the electric power consumption. More specifically, the balancing of such a production line is studied, so as to integrate power peak minimisation from the design stage. Thus, we define the Parallel-Serial-with-Crossover Assembly Line Balancing Problem with Power Peak Minimization, a new combinatorial NP-hard problem. We also propose a suitable time-indexed Integer Linear Program that integrates balancing and scheduling decisions and a matheuristic algorithm designed to tackle large-size instances. Both approaches are tested on a wide set of instances. The computational results show that relevant power peak reductions can be achieved (33% on average), opening up promising perspectives from both algorithmic and managerial viewpoints.
The design of a production system is a strategic level decision. One of the key problems to solve is the line balancing problem that determines the efficiency of a production or assembly line. This ...class of problem has been widely studied in the literature. It determines important features, such as the number of stations, the takt time or the working conditions. Most of the variants of this problem consider only one objective function, but nowadays companies have to take into account different criteria. In this study, we consider a bi-objective variant of the simple assembly line balancing problem. We present a generic branch-and-bound method to solve exactly this problem. The objective functions are to minimise the takt time and the number of stations. To do so, bounds and bound sets are developed. The resulting method is numerically tested and compared to an ϵ-constraint method. These experiments show that the bi-objective branch-and-bound algorithm outperforms an ϵ-constraint method using a state-of-the-art single objective algorithm for more than 80% of the instances. Finally, we propose an analysis of the cases where the branch-and-bound method is outperformed.
These days, rising energy costs along with general concerns about major environmental issues (global warming, climate change), result in more and more strict production constraints for the industrial ...sector, which is known to be the first energy consumer and greenhouse gas emitter in the world. There is therefore a growing industrial need to address the problems of production systems related to energy aspects.
In this paper, a job-shop scheduling problem with energetic aspects is considered. The objective is to minimize production costs in terms of energy, while respecting a power peak limitation, along with more traditional production constraints. Two integer linear programming models are proposed for the addressed problem. In order to evaluate and compare the performance of these formulations, computational experiments are presented and numerical results are discussed and analysed.
Ergonomic aspects have a crucial role in manual assembly systems. They impact on the workers' health, final product quality and productivity. For these reasons, there is the necessity to integrate ...them into the assembly line balancing phase as, whereas, only time and cost variables are considered. In this study, human energy expenditures are considered as ergonomic aspects and we integrate them, for the first time, into the assembly line balancing problem type 2 through the rest allowance evaluation. We consider as an objective function the minimization of the smoothness index. Firstly, a new optimal method based on mixed integer linear programming and a new linearization methodology are proposed. Then, a heuristic approach is introduced. To complete the study, a computational experimentation is presented to validate the mathematical model and to compare the methodologies proposed in terms of computational time, complexity and solution. Additionally, we provide a detailed analysis of the impact that rest allowance evaluation can have on productivity comparing the results obtained, taking into account the rest allowance integration before, during and after the assembly balancing process.
Currently, the ageing population is getting higher attention in production systems due to the increasing percentage of the ageing workforce, which persists longer in the working environment. Older ...workers are more vulnerable because of a possible decrease in physical capacities but can have a higher experience level. It is important to evaluate these factors during production process decisions and adapt the working environment to such workers. In such a way, production systems performance and workers’ well-being are jointly achieved. In companies aiming to include these aspects, digitalisation and automation can provide tools that can be used at tactical, strategic or operational levels. For example, at the operational level, wearable sensors, smart devices or trackers can be used in analysing the working time, effort and physical fatigue of operators via human-energy expenditure. These measures can be used to assess the required recovery time. However, the most challenging step is to include these measures in the decision-making process to organise the working process for operators according to their profiles and health restrictions. In this paper, we show how fatigue can be incorporated into operational processes such as scheduling in the context of a Dual-Resource Constrained (DRC) job shop. We consider several models to integrate rest allowance into the scheduling process and present a heuristic approach to assign operations to workers and machines. The impact of rest allowance on system performance is measured and managerial insights are provided.
•We overview the impact of the presence of an ageing workforce in production with a focus on a DRC job shop. .•We study different models to integrate rest allowance in the scheduling process in DRC. .•We evaluate the impact of rest allowance on makespan.•We provide managerial insights for the fair inclusion of the ageing workforce in production.
In many assembly systems, ergonomics can have great impact on productivity and human safety. Traditional assembly systems optimisation approaches consider only time and cost variables, while few ...studies include also ergonomics aspects. In this study, a new multi-objective model for solving assembly line balancing problem is developed and discussed in order to include also the ergonomics aspect. First, based on main features of assembly workstations, the energy expenditure concept is used in order to estimate the ergonomics level, thanks to a new technique, called Predetermined Motion Energy System, which helps rapidly estimate the energy expenditure values. Then, a multi-objective approach, based on four different objective functions, is introduced in order to define the efficient frontiers of optimal solutions. To complete the study, a simple numerical example for a real case is presented to analyse the behaviour of Pareto frontiers varying several parameters linked to the energy and time value.
Reconfigurable manufacturing systems (RMS) intend to bridge the gap between dedicated and flexible manufacturing systems. If the literature is mainly focused on the design step and tactical planning ...of such systems, few research projects have addressed scheduling at the operational level. While setup times may occur in flexible manufacturing systems, reconfiguration times considered in RMS may affect several resources at once, and hence require specific modelling and solving approaches to be considered. This paper first formalises the problem at hand through integer linear programming. An iterative search method is then provided to obtain solutions to larger-scale instances. Results obtained on generated instances show that managing even few possible configurations can yield significant improvements in solutions' quality. Meanwhile, the extended search space implied by the increase in available configurations hinders the convergence to a good solution in a reasonable computation time, which suggests further investigations.
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