Performance Evaluation of Flexible Manufacturing Systems with Starving

Abstract

Real-life flexible manufacturing systems (FMS) often suffer to a considerable extent under utilization losses which are due to limited local and/or central buffer space and the limited velocity of the material handling system (MHS). In particular two forms of performance deterioration are distinguished: blocking and starving. A workstation is blocked if it cannot dispose of a finished piece because there is no buffer space — neither local nor in the central buffer. Blocking has been studied by several researchers (Akyildiz 1988a, 1988b, Altiok and Perros 1986, Suri and Diehl 1986, Gershwin and Schick 1983, Perros 1984, Yao and Buzacott 1985, 1986). In an earlier paper, the authors have made a proposal to estimate the influence of blocking on the performance of an FMS (Tempelmeier, Kuhn and Tetzlaff 1989) using standard closed queueing network algorithms. According to our experience, in industrial practice blocking often does not seem to be a severe problem during the configuration phase of an FMS, because in many cases it is possible to allow for enough central buffer space at moderate costs to prevent blocking. However even if the central buffer space is large enough, the limited velocity of the material handling system (MHS) in combination with limited local buffer space may lead to a form of reduction of machine utilization that is known as starving.