Production Systems Flexibility: Theory and Practice George Chryssolouris*. Konstantinos Georgoulias*. George Michalos* * Laboratory for Manufacturing Systems & Automation Department of Mechanical Engineering and Aeronautics, University of Patras, Rio, Patras 26500, Greece (Tel.: +30 2610 997262, email: xrisol@lms.mech.upatras.gr ) Abstract: The current, unstable market environment promotes flexibility as a valuable attribute of manufacturing systems. This paper discusses the concept of production system flexibility and its evolution over the years in the academic literature as well as in the industrial practice. The main flexibility types and the respective quantification approaches are introduced. The development of IOH[LELOLW\ PHWULFV DOORZV WKH FRQVLGHUDWLRQ RI IOH[LELOLW\ LQ WKH VWDNHKROGHUV¶ GD\-to-day decisions for the efficient design and operation of manufacturing systems. Selected paradigms, regarding the introduction of the flexibility concept to industrial practice, are also provided and their results are discussed. An outlook of the future requirements in terms of flexibility, based on the current market environment and the latest trends in manufacturing, has been also provided. Keywords: Production systems; Flexible manufacturing systems; Flexibility measurement. 1. INTRODUCTION For many decades, cost and production rates have been the most important performance criteria in manufacturing, and companies relied on dedicated mass production systems in order to achieve economies of scale. However, as the living standards improve, it is increasingly evident that the era of mass production is being replaced by the era of market niches (Chryssolouris, 2006). Especially nowadays, manufacturing firms noW RQO\ WKH\ KDYH WR VDWLVI\ WKH FXVWRPHUV¶ requirements but also to operate profitably in an often turbulent market. Shorter product lifecycles, increased numbers of new models as well as variants, uncertainties and fluctuations in the market demand, are some of the reasons that have forced engineers to consider flexibility as an important aspect of the manufacturing systems (Georgoulias et al., 2009). In some cases, flexibility may also be considered as an attribute that can indirectly support a manufacturing firm to reduce costs, retain quality levels and ensure delivery reliability. Even if flexibility remains a key issue for modern manufacturing systems, the complexity of the industrial practice often leads to empirical assessments, tailored for specific situations. Additionally, since flexibility is a subject with special properties, it is usually perceived in many different ways. The next chapters aim to describe the basic aspects of flexibility, to indicate solutions to quantitatively measure flexibility and to explore how flexibility should be considered within a holistic change management framework. 2. MANUFACTURING SYSTEM FLEXIBILITY A number of definitions have been provided for the term flexibility. Additionally, similar, close terms such as re- configurability, changeability, versatility and several others have been discussed in literature. This has provided a rather complicated academic and industrial environment for examining flexibility. In this work, in accordance to what was initially introduced in the work of Chryssolouris and Lee (1992), the flexibility of a manufacturing system is determined by its sensitivity to a change and it is evaluated by calculating the expected cost of accommodating possible changes in the operating environment. The lower the expected change cost is, the less sensitive the system is to changes in its operating environment and thus, the system is considered being more flexible. When starting to examine flexibility in more detail, we may identify different types of flexibility which, more or less, relate to the problem they intend to respond to. Thus, we may frequently come against terms such as machine flexibility, process flexibility, product flexibility, routing flexibility, volume flexibility, expansion flexibility, operation flexibility, production flexibility and others. However, in general, we may observe that high flexibility or low sensitivity to a change provides a manufacturing system with three principal advantages. It is convenient to think of these advantages as arising from the various types of flexibility that can be summarized in three main categories (Chryssolouris, 2006): x Product flexibility enables a manufacturing system to make a variety of part types using the same equipment. In the short term, this means that the system has the Proceedings of the 14th IFAC Symposium on Information Control Problems in Manufacturing Bucharest, Romania, May 23-25, 2012 978-3-902661-98-2/12/$20.00 © 2012 IFAC 15 10.3182/20120523-3-RO-2023.00442