Pure cycles in dual gripper robotic cells

In this study, we discuss pure cycles in $m$-machine dual gripper robotic cells. A material handling robot loads/unloads the machines and transports the parts between the machines. The robot is assumed to have dual grippers so that it can carry two parts simultaneously. Identical parts are to processed on machines which have the ability to perform all the operations that a part requires. Manufacturing systems in which there are flexible machines like CNC machines have this kind of ability. We consider pure cycles where each part is processed by only one of the machines and each machine processes exactly one part in a cycle. We first determine the feasibility conditions for the pure cycles and an algorithm that generates all feasible pure cycles for a given number of machines. We analyse 2-machine robotic cells in detail and prove that one of the particular five pure cycles among a huge number of feasible pure cycles always provides the optimal solution. We determine the parameter values in which each of the five cycles is optimal. In 2-machine robotic cells, we show that pure cycles in dual gripper robotic cells always dominate pure cycles in single gripper robotic cells. By using problem parameters, an experimental study is performed and the average and maximum benefits of using a dual gripper robot instead of a single gripper robot are determined. The effects of problem parameters are also examined.