J Intell Manuf (2012) 23:1885–1891 DOI 10.1007/s10845-011-0505-9 Cyclic scheduling of a robotic flexible cell with load lock and swap Fariborz Jolai · Mehdi Foumani · Reza Tavakoli-Moghadam · Parviz Fattahi Received: 26 July 2008 / Accepted: 17 January 2011 / Published online: 2 February 2011 © Springer Science+Business Media, LLC 2011 Abstract In this paper, we study the problem of robotic cell scheduling with m machines with flexibility, load lock and swap assumptions. The robotic cell repetitively produces parts of identical types. We determine the cycle time of all 1-unit cycles in this type of robotic cell and present two new lower bounds for robot move cycles with load lock and swap, either there is flexibility or inflexibility. We also provide a new robot move cycle and prove that it dominates all classi- cal robot move cycles considered in the existing literature of m-machine robotic cells. Keywords Robotic cell · Cyclic scheduling · Automated manufacturing · Flexibility · Load lock · Swap Introduction Flexible Manufacturing Systems (FMS) integrate machine tools, material handling, storage systems, computers and robots, i.e. Shukla and Chen (1996). One important char- acteristic of FMS is that different machines work together within a common workspace, Chan and Chan (2004). We use the term “cell” for this workspace. Wei and Mejabi (2008) indicated that minimizing intercell trips in a cellular manufacturing system may maximize the benefits that the system can provide. F. Jolai (B ) · M. Foumani · R. Tavakoli-Moghadam Department of Industrial Engineering, College of Engineering, University of Tehran, Tehran, Iran e-mail: fjolai@ut.ac.ir P. Fattahi Department of Industrial Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan, Iran Robotic cells are one of general types of cells and have a key role in reconfigurable manufacturing systems, i.e. Mehrabi et al. (2000). A classical robotic cell is a flow shop consisting of a robot, an input buffer ( M 0 ), an output buffer ( M m+1 ) and m machines namely M 1 , M 2 ,..., M m , in the cell. The robot transports a part from input buffer to M 1 and then transfers it from M 1 to M 2 . This pattern repeats for machines M 3 , M 4 ,..., M m as well. When M m completes its processing on the part, the robot transfers the part to the output buffer. If input and output buffers are created in the same location, they are presented by I/O or virtual machine M 0 and called load lock in this paper, see Fig. 1. One robot performs all transfers of each part between these machines. Most of classical robotic cells have three important assumptions as follows: • A machine only can perform one operation type on a part and order of the operations is assumed to be fixed for producing each part type. • Input and output buffers are arranged in different loca- tions. • A machine (or a robot) should be free, and a robot (or a machine) should be busy for loading (or unloading) a part onto machine. In this paper we relax these assumptions as below: • A machine is capable to perform all of operations required for producing one part and the order of opera- tions for producing each part type can be interchanged. If we can perform a mixture of operations by one machine, it is called process flexibility (Browne et al. 1996) and if we can interchange the order of operations for each part type on a machine; it is called operational flexibility (Akturk et al. 2005). 123