Manufacturing flexibility: Measures and relationships

Abstract

The study and formulation of manufacturing flexibility measures has been inhibited by the lack of a conceptual structure to encourage model development. In this paper, we introduce a framework to facilitate the development of flexibility measures. It also proves to be useful in validating measures of flexibility types. Measures of various flexibility types are drawn from the literature and compared with the purposes and criteria for the flexibility types and the `best' measures are presented. For volume and expansion flexibility, the framework is used to develop new measures. This is followed by a discussion of the relationships among flexibility types and some sample relationships are highlighted.

Introduction

Flexible manufacturing systems (FMSs) are technologies combining the benefits of both computers and numerical control machine tools. They have been hailed as the solution to challenges facing manufacturing industries world-wide. However, soon after the rapid growth in FMS installations, operations managers realized that the simple investment in flexible manufacturing systems would not readily answer the market's desire for more rapid delivery, more product variety, more customized product designs, and higher product design turnover as evidenced by reduced product life cycle lengths. Several companies have illustrated how successful use of FMS has resulted in the above mentioned benefits to customers (e.g. Motorola, Toyota). These companies have realized that a successful technical implementation alone is not enough and that FMS investment must correlate with the corporate and manufacturing strategy the firm is following. When both business and technical success is achieved, the celebrated flexibility benefits may ensue, as recognized by Voss (1988). However, there is ample evidence (see Jaikumar, 1986) to suggest that the management of these technical systems is no easy task.

Bolwijn and Kumpe (1990) and De Meyer et al. (1989) have identified `flexibility' as the focus of the next competitive battle. De Meyer et al. state that this battle “will be waged over manufacturers' competence to overcome the age old trade-off between efficiency and flexibility”. However, confusion over what constitutes flexibility still occurs. Gerwin (1993) suggests that the lack of full understanding of manufacturing flexibility is inhibiting progress towards the utilization of flexibility concepts in industry and impeding manufacturing managers from evaluating and changing the flexibility of their operations. Gunasekaran et al. (1993) and Gerwin (1993) identify the measurement of flexibility and performance as an important hurdle to achieving a full comprehension of FMS behavior, and a stepping stone to establishing full economic-based measures. Gunasekaran et al. (1993) also state that the complex inter-relationships among various aspects of flexibility will be further advanced by the development of flexibility measures and that understanding these flexibility trade-offs “can help the management to support the manufacturing strategy of the firm”. Empirically measuring flexibility in manufacturing has begun recently (see Dixon, 1992; Upton, 1994Upton, 1997) in specific industries. Such studies promise much but sound measures of flexibility need to be developed first. In this paper we introduce a framework to facilitate flexibility measure development, introduce two new measures, and analyse the relations among some flexibility types.