Jesús Racero

Machine cell formation in generalized group technology

In this paper, we study the configuration of machine cells in the presence of alternative routings for part types. The objective function is the minimization of transportation costs. Limits on cell sizes as well as separation constraints (i.e. machines that are not allowed to be placed in the same cell) and co-location constraints (i.e. machines that must be placed in the same cell) may be imposed. An efficient Tabu Search (TS) algorithm is proposed to solve this problem. Extensive computational experiences with large-size problems show that this method outperforms some existing Simulated Annealing (SA) approaches.

Cell design and multi-period machine loading in cellular reconfigurable manufacturing systems with alternative routing

This paper deals with the design and loading of Cellular Reconfigurable Manufacturing Systems in the presence of alternative routing and multiple time periods. These systems consist of multiple reconfigurable machining cells, each of which has Reconfigurable Machine Tools and Computer Numerical Control (CNC) machines. Each reconfigurable machine has a library of feasible auxiliary machine modules for achieving particular operational capabilities, while each CNC machine has an automatic tool changer and a tool magazine of a limited capacity. The proposed approach consists of two phases: the machine cell design phase which involves the grouping of machines into machine cells, and the cell loading phase that determines the routing mix and the tool and module allocation. In this paper, the cell design problem is modelled as an Integer Linear Programming formulation, considering the multiple process plans of each part type as if they were separate part types. Once the manufacturing cells are formed, a Mixed Integer Linear Programming model is developed for the cell loading problem, considering multi-period demands for the part types, and minimising transportation and holding costs while keeping the machine and cell utilisations in each period, and the system utilisation across periods, approximately balanced. An illustrative problem and experimental results are presented.

Cell formation and scheduling of part families for reconfigurable cellular manufacturing systems using Tabu search

A reconfigurable cellular manufacturing system (RCMS) consists of multiple reconfigurable machining cells, each of which has one or more reconfigurable machine tools (RMTs), a setup station, and an automatic material handling and storage system. As part of the RCMS design process, similar parts must be grouped into part families and the RMTs must be arranged to form parallel cell configurations. A RCMS is designed at the outset for rapid changes in its components, allowing the production of multiple part families in each parallel cell. This paper proposes a new approach to simultaneously solve the cell formation and the scheduling of part families for an effective working of a RCMS. A new mixed integer linear programming model is used to represent both problems at the same time with the objective of minimizing production costs. Two types of production costs are considered: reconfiguration (i.e. setup) costs for changing from one family to the next one, and under-utilization costs for not using the RMT resources. A small size example is used to illustrate this integrated methodology. Computational experiments have been carried out adapting some larger instances from the literature on cellular manufacturing systems. Solving large instances optimally becomes prohibitive in terms of computational effort. That is why an approximate method, based on a Tabu search (TS) algorithm, has also been developed. Results show the ability of this algorithm to find good-quality production schedules of part families in a RCMS without requiring long computing times. It can be concluded that a RCMS can attain manufacturing flexibility without losing cost-effectiveness and that the approach proposed in this paper can efficiently solve real-world problems.

Environmental Issues in Vehicle Routing Problems

In the last decade interest in environment preservation is increasing and environmental aspects play an important role in strategic and operational policies. Therefore, environmental targets are to be added to economic targets, to find the right balance between these two dimensions. Green logistics extend the traditional definition of logistics by explicitly considering external factors associated mainly with climate change, air pollution, noise, vibration and accidents. Among the logistical activities, the vehicle routing problem (VRP) is one of the most widely researched and has mainly focused on economic objectives, not considering explicitly environmental issues. In this chapter, a realistic variant of the VRP with heterogeneous vehicle fleets in which vehicles are characterized by different capacities and costs, has been considered and external costs have been estimated using international research projects, and have been included as part of a mixed-integer linear programming model to solve a realistic variant of the VRP. To solve medium to large-size VRP instances, heuristic approaches are necessary. An impressive number of heuristic have been proposed for the VRP in the literature. In this chapter, one heuristic is developed to find good solutions to the proposed eco-efficiency model: a savings heuristic when time windows are not considered. Since there are no instances for this problem variant, the algorithm is validated with benchmarking problems adapted from the literature, offering good solutions and quickness. The selection of eco-efficiency routes can help to reduce the emissions of air pollutants, noises and greenhouse gases, without losing competitiveness in transport companies.

Cell design and loading with alternative routing in cellular reconfigurable manufacturing systems

Abstract This paper deals with the design and loading of a Cellular Reconfigurable Manufacturing System (CRMS) in the presence of alternative routing. A CRMS consists of multiple reconfigurable machining cells, each of which has Reconfigurable Machine Tools (RMT) and Computer Numerical Control (CNC) machines, a setup station and an automatic material handling and storage system. Each RMT has a library of feasible auxiliary machine modules for achieving a particular operational capability of the RMT. Each CNC machine has an automatic tool changer and a tool magazine of a limited capacity. The machine cell design problem involves the grouping of machines into machine cells. This problem is performed once, prior to the cell loading, using two cell formation methods from the literature. Once the resulting cells are physically implemented, a mixed-integer linear programming problem is developed for determining the routing mix (i.e. which proportion of each part type to be assigned to each alternative route) and the tool and module allocation (i.e. how many auxiliary modules and tools of each available type to be assigned to each RMT and CNC machine within each formed cell) in order to minimize total intercellular movements of parts. An illustrative problem and experimental results are presented.

Development based on reverse engineering to manufacture aircraft custom-made parts

The need for custom-made parts is increasing constantly due to its application in different industrial sectors: medical prosthesis, car parts, aircraft parts, etc. In the aerospace sector, reverse engineering (RE) techniques are used to machine parts whose geometry requires to be customised for each produced aircraft. Due to discrepancies between the aircraft digital mock-up (DMU) and actual as-built components, the interface parts manufactured using only the aircraft DMU will not fit properly within the available physical space of each specific aircraft. Since they have to fit in with large components subject to variable deformation states in the assembly process. The MISTRAL project addresses such issue. Taking a file with 3D point cloud data as main input, it proposes an alternative approach to the one currently in use to manufacture custom-made parts. The result is a prototype development carried out mainly in CATIA v5. The developed solution was tested with a typical family of parts.

Parking Search Modelling In Freight Transport And Private Traffic Simulation

The work performed in order to achieve better approximation to relity in traffic simulation is presented. A microscopic traffic simulator was developed to use as a tool for urban planning issues related to freight transport and private traffic. The paper describes the general operating principles of the parking search model for both private traffic and freight transport and discusses test runs carried out after the simulator was implemented.

Design and Implementation of a Prototype for Information Exchange in Digital Manufacturing Processes in Aerospace Industry

Aerospace companies have a wide range of information systems with different functionalities that are used along the aircraft lifecycle; this causes problems in terms of integration, information exchange and long term archiving of data. Ongoing standardization efforts, mainly under the standard ISO 10303 and the LOTAR initiative are addressing such problems. This communication shows a starting work dealing with the exchange of aircraft industrialization information. It proposes a simplified data structure to illustrate and validate an exchange approach based on combining ISO 10303 EXPRESS-G, UML class diagram and ISO 10303 EXPRESS-I. The PLM software Aras Innovator was used to make the implementation and validate the approach.

Design Methodology and an Integrated Decisions Support System for Sustainable Transportation Plans

The transport is one of a major source (15%) of greenhouse gases contributors’ and the road transport accounts for 80% of emissions divided equally between urban and interurban. The Sustainable Urban Mobility Plans arise as a shock measure, with the aim of increasing energy efficiency, environmental quality and externalities reduction from the road transport. This chapter proposes a standardized methodology to develop Sustainable Transportation Plan that includes an information system and decision support system (based on indicators) that helps to manages sustainable mobility plans and aid in the evaluation and strategies selections. The system is based on free tools, as geographic information system libraries (GEOEXT), Java programming environment and MySQL database manager in an open distributed system, which are used to support data collection and mobility analysis.

An Integrated Decisions Support System and a GIS Tool for Sustainable Transportation Plans

The Kyoto Protocol agreement sets to Spain a 15% of increment in the emissions from 1990, on the other hand, they fixed the reduction of 8% in the European Union. Today, Spain is at 52% over the base year, the transport is one of a major source (15%). Likewise, the road transport accounts for 80% of emissions divided equally between urban and interurban.The Sustainable Urban Mobility Plans arise as a shock measure, with the aim of increasing energy efficiency, environmental quality and externalities reduction from the road transport. This chapter describes the design and development system that manages sustainable mobility plans. The system is based on free tools, as geographic information system libraries (OpenLayer), Java programming environment and MySQL database manager in an open distributed system, which are used to support data collection and mobility analysis.Also, a decision support system based on socio-economic indicators, mobility, energy and environmental indicators has been integrated to aid in the evaluation and strategies selections.