Walter Terkaj

Focused Flexibility in Production Systems

Manufacturing flexibility is seen as the main mechanism for surviving in the present market environment. Companies acquire systems with a high degree of flexibility to cope with frequent production volume changes and evolutions of the technological requirements of products. However, literature and industrial experience show that flexibility is not always a well-defined concept. Therefore it is really complex to understand and use flexibility during system design process. Indeed, the development of structured approaches to support the system design by considering basic flexibility forms is still an open issue. This work presents an Ontology on Flexibility aiming at providing a standard method to analyze flexibility. Firstly, it contributes in systemizing the large number of existing flexibility definitions and classifications. Secondly, it can be used to analyze real systems and to better understand their characteristics in terms of flexibility. Finally this ontology represents a key point of a general approach to design production system with the right level of flexibility.

Designing Manufacturing Flexibility in Dynamic Production Contexts

Manufacturing Flexibility is seen as the main answer for surviving in markets characterized by frequent volume changes and evolutions of the technological requirements of products. However, the competitiveness of a firm can be strongly affected by capital intensive investments in system flexibility. This chapter presents an approach to design new manufacturing system architectures endowed with the right level of flexibility required by the specific production problem. These systems are named Focused Flexibility Manufacturing Systems (FFMSs). The key idea consists in tuning system flexibility on the production problem to cope with uncertainty related to the evolution of product demand. The significance of this topic and its potential impact on the industrial sector in the medium-long run is testified by the interest shown by companies making initial efforts in this field.

Development of a Conceptual Reference Framework to Manage Manufacturing Knowledge Related to Products, Processes and Production Systems

The present work proposes a conceptual reference framework for the integrated modeling of product, production process and system data. The framework is flexible (easily adaptable to different production contexts), extendible and scalable (in terms of levels of details) and integrated (products, processes and systems are all considered and described). The framework has been developed as an object-oriented model by means of the UML (Unified Modeling Language) defacto standard. In particular, the class diagram of this UML model, representing the core portion of the framework, is described in detail. The conceptual reference framework was developed to support both researchers and industrialists – in different manufacturing domains – in the modeling activities behind their problem solving methodologies, also aiding them in exactly modeling the information they need. The basic idea behind the work is that a more effective use of the heterogeneous decision support methods, normally employed at the different enterprise levels, can be obtained if these methods are based a common conceptual model. The first two applications of the proposed reference framework are also described in the final sections.

A survey of RDF store solutions

This paper analyzes the potential of Semantic Web technologies to support innovation in industrial scenarios. The study focuses in particular on RDF stores, the software components dedicated to the storage, representation and retrieval of semantic information. Starting from a literature review, a qualitative analysis is carried out considering a set of these systems. RDF stores are evaluated to find the implementations that are best suited to play the role of backbone in a software architecture sharing information between the software tools adopted by the various stakeholders. This can be achieved if the architecture overcomes the problems deriving from the lack of integration between the involved software applications, providing in this way an integrated view on relevant engineering knowledge.

VFF: Virtual Factory Framework

The current complex market highlights the need of software tools supporting product engineering and manufacturing during the various stages of product and factory lifecycles. These are designed focusing on specific tasks, thus missing to satisfy the requirements of networked collaboration and concurrent engineering for the design and management of products, processes and production systems. A major challenge consists in the integration and harmonisation of the knowledge related to the factory of industrial companies by using a variety of multidisciplinary software tools. The topic is addressed by software providers and the scientific community, as demonstrated by the European project “Virtual Factory Framework” (VFF) that aims at developing an integrated framework to implement the next generation virtual factory. This paper describes the motivations behind the VFF concepts, together with the goals and the first results. Finally, it is presented how the Virtual Factory will be permanently synchronised with the Real Factory to validate its expected time and cost savings during the factory lifecycle phases.

A Review on Manufacturing Flexibility

The topic of manufacturing flexibility has been addressed by many scientific contributions in the past years, thus highlighting the relevance of the problem both at industrial and academic level. Internal and external issues need to be faced at the same time when designing a manufacturing system and its flexibility; indeed, products and processes are easily and frequently changed by market and manufacturing strategies, while production systems must cope with relevant inertia which slow down their changes. Therefore, a fundamental issue consists of filling the modeling gap between a production problem and the manufacturing system best suited to face it. Current literature provides a huge research on the analysis of flexibility, as a solution to cope with uncertainty in the market and to support the manufacturing strategy. However, the link between the need of flexibility and the design of manufacturing systems is still weak. This need includes a deeper understanding of the nature of flexibility and, in turn, a clear definition of the dimensions of flexibility. This chapter reviews the state of the art of the literature on manufacturing flexibility by proposing also a conceptual framework for its formalization.

Design of Focused Flexibility Manufacturing Systems (FFMSs)

Manufacturing systems design must provide effective solutions to cope with the demand during the whole system life-cycle. The problem consists of selecting the appropriate set of resources which best fits the requirements of the addressed production problem. When the demand is characterized by a family of products undergoing technological and volume modifications, the system design process becomes quite complicated. Starting from present and forecasted information, machine tool builders have to design systems endowed with the flexibility and reconfigurability levels that enable the system to face the production problem variability during its life. In spite of the relevance of this topic, there is a lack of tools to explicitly design system flexibility and reconfigurability considering the uncertainty affecting the problem. By addressing two main types of uncertainty, i.e. demand variability and resource availability, this chapter presents a solution method based on multi-stage stochastic programming, to support the design of new manufacturing system architectures whose level of flexibility is focused on the specific production requirements. The problem variability is modeled through scenario trees and the solution is a capacity plan with an initial system configuration and possible reconfigurations. Testing experiments have been carried out considering an industrial case to study the benefits that this approach can offer to machine tool builders.

Ontology-based modeling of production systems for design and performance evaluation

This paper presents the extension to an ontology-based data model supporting the design and performance evaluation of production systems. This extension aims to link the modeling of the spatial representation of physical objects with the characterization of their states and behavior. Furthermore, the formalization of the performance history of a production system and its components is addressed to capture both the spatial and state evolution of the objects. Such history can be provided by simulation runs or gathered from a monitoring system. A test case is described and then used to show how different software tools can be integrated to support the integrated design and evaluation of a production system.

Virtual factory manager

The current challenges in manufacturing engineering are the integration of the product/process/factory worlds (data and tools) and the synchronization of their lifecycles. Major ICT players already offer all-comprehensive Product Lifecycle Management suites supporting most of the processes. However, they do not offer all the required functionalities and they lack of interoperability. An answer will be given by the development of a Virtual Factory Framework (VFF): an integrated virtual environment that supports factory processes along all the phases of its lifecycle. This paper will focus on the Virtual Factory Manager (VFM) that acts as a server supporting the I/O communications within the framework for the software tools needing to access its data repository. The VFM will ensure data consistency and avoid data loss or corruption while different modules access/modify partial areas of the data repository at different times. Finally, an industrial case study will show the potentiality of the VFM.

A stochastic programming approach to support the machine tool builder in designing Focused Flexibility Manufacturing Systems (FFMSs)

Manufacturing system design is a critical phase for machine tool builders as it is necessary to provide profitable system solutions which cope with the requirements of the potential customers, while finding the best trade-off between the maximising profit and the probability to win orders. These objectives are often in conflict and the scarce presence of methodologies and tools which support the design process leads the machine tool builder to base the solution on qualitative criteria mainly learnt from past experience. This paper presents a system design approach which aims at selecting the optimal set of resources characterising the system with the appropriate degree of flexibility to address the present production problem and its forecasted changes. Production systems that embed these features are defined by the authors as Focused Flexibility Manufacturing Systems (FFMSs). The presented design approach has been tested on an industrial case study. The results suggest to machine tool builders the opportunity of developing new machine types that can increase the profitability of the designed manufacturing systems.