Lead-time variability in a homogeneous queueing model of batching

In the last decade a growing interest can be perceived in manufacturing lead time as a performance measure for batching decisions. Especially in complex job shops the more traditional models are less adequate because they do not take into account the queueing phenomena in front of a bottleneck in the production process. A number of authors study the relationship between batch sizes and the average queueing delay or average time in system. However, in production planning also the lead-time variability will be important, for instance with respect to safety stock or safety time determination and due date setting. For that reason in this paper the relationship between batch sizes and lead-time variability is investigated. In general, a minimization of the average queueing delay or average time in system will not result in a minimum lead-time variability.