Cycle time analysis in reentrant robotic cells with swap ability

In this paper, reentrant robotic cells composed of a robot with swap ability for a single part type is studied. In this regard, we restrict our attention to the two-machine reentrant cell scheduling problem. In the cell, a part visits the machines at least once. To minimise the cycle time, the sequence of robot moves must be optimised. Based on our previous study on the optimality of robotic cells, we restrict our investigation to only one-unit cycles. Therefore, all one-unit cycles are generated and their cycle time formulae are developed. Initially, we determine both essential and sufficient conditions for different cycles to be optimal and present the regions of optimality when each part reenters the first machine two times. We determine optimality conditions for different cycles when each part reenters both machines two times. Finally, sensitivity analysis is performed for both cases and the influence of the parameter values in the regions of optimality for each cycle is shown.