Design of Flexible Production Systems

Tullio Tolio is Full Professor of "Manufacturing and Production Systems". He teaches "Manufacturing", "Integrated Production Systems" and "Reconfigurable Manufacturing Systems" at Politecnico di Milano, 2nd Faculty of Engineering (Faculty of System Engineering). He is the head of the course on "Management of Research" offered to all Ph.D. students of the Politecnico di Milano.

He has carried out research activities at the Laboratory for Manufacturing and Productivity (LMP) of the Massachusetts Institute of Technology (MIT). He has been scientific responsible for the Politecnico di Milano of the Brite Euram project MOD-FLEX-PROD (EU - 4th framework Programme of the EU)and of the IST project DRIVE (EU - 5th framework Programme) funded by the European Community, and of the project SPI7 funded by MURST (former Italian Ministry of University and Research). He is national coordinator of the project "Methodologies and tools to design production systems with focused flexibility" funded by MIUR (Italian Ministry of University and Research), scientific responsible for the Politecnico di Milano of the project FIRB01 "Software frameworks and technologies for the development and maintenance of open-source distributed simulation code, oriented to the manufacturing field" and of the Network of Excellence VRLKCiP "Virtual Research Lab for a Knowledge Community in Production" (EU - 6th framework Programme). He has published more than 100 papers in international journals and international conferences. He is Fellow of the CIRP (the International Academy for Production Engineering) and member of AITEM (Associazione Italiana di Tecnologia Meccanica -Italian association for manufacturing. Regarding management activities, he is the Delegate of the Rector of Politecnico di Milano on "Quality assurance in education" and Head of the Division "Tecnologie Meccaniche e Produzione (Manufacturing)" of the Department of Mechanical Engineering of Politecnico di Milano; in the years 2000-2003 he was Head of the Ph.D. program in "Manufacturing and Production Systems" of Politecnico di Milano.

In the last decade, the production of mechanical components to be assembled in final products produced in high volumes (e.g. cars, mopeds, industrial vehicles, etc.) has undergone deep changes due to the overall modifications in the way companies compete. Companies must consider competitive factors such as short lead times, tight product tolerances, frequent market changes and cost reduction. Anyway, companies often have to define production objectives as trade-offs among these critical factors since it can be difficult to improve all of them.

Even if system flexibility is often considered a fundamental requirement for firms, it is not always a desirable characteristic of a system because it requires relevant investment cost which can jeopardize the profitability of the firm. Dedicated systems are not able to adapt to changes of the product characteristics while flexible systems offer more flexibility than what is needed, thus increasing investment and operative costs. Production contexts characterized by mid to high demand volume of well identified families of products in continuous evolution do not require the highest level of flexibility; therefore, manufacturing system flexibility must be rationalized and it is necessary to find out the best trade-off between productivity and flexibility by designing manufacturing systems endowed with the right level of flexibility required by the production problem. This new class of production systems can be named Focused Flexibility Manufacturing Systems-FFMSs.

The flexibility degree in FFMSs is related to their ability to cope with volume, mix and technological changes, and it must take into account both present and future changes. The required level of system flexibility impacts on the architecture of the system and the explicit design of flexibility often leads to hybrid systems, i.e. automated integrated systems in which parts can be processed by both general purpose and dedicated machines. This is a key issue of FFMSs and results from the matching of flexibility and productivity that respectively characterize FMSs and Dedicated Manufacturing Systems (DMSs).

The market share of the EU in the machine tool sector is 44%; the introduction of focused flexibility would be particularly important for machine tool builders whose competitive advantage is based on the ability of customizing their systems on the basis of needs of their customers. In fact, even if current production contexts frequently present situations which would fit well with the FFMS approach, tradition and know-how of machine tool builders play a crucial role. Firms often agree with the focused flexibility vision, nevertheless they decide not to pay the risk and efforts related to the design of this new system architecture. This is due also to the lack of well-structured design approaches which can help machine tool builders to configure innovative systems. Therefore, the FFMS topic is studied through the book chapters following a shared mission: "To define methodologies and tools to design production systems with a minimum level of flexibility needed to face, during their lifecycle, the product and process evolution both in the technological and demand aspects. The goal is to find out the optimal trade-off between flexibility and productivity".

The book framework follows the architecture which has been developed to address the FFMS Design problem. This architecture is both broad and detailed, since it pays attention to all the relevant levels in a firm hierarchy which are involved in the system design. Moreover, the architecture is innovative because it models both the point of view of the machine tool builder and the point of view of the system user.

The architecture starts analyzing Manufacturing Strategy issues and generating the possible demand scenario to be faced. Technological aspects play a key role while solving process plan problems for the products in the part family. St