SCHEDULING IN ROBOTIC CELLS - CLASSIFICATION, 2 AND 3 MACHINE CELLS

This paper considers the scheduling of operations in a manufacturing c ell that repetitively produces a family of similar parts on two or thr ee machines served by a robot. We provide a classification scheme for scheduling problems in robotic cells. We discuss finding the robot mov e cycle and the part sequence that jointly minimize the production cyc le time, or equivalently maximize the throughput rate. For multiple pa rt-type problems in a two-machine cell, we provide an efficient algori thm that simultaneously optimizes the robot move and part sequencing p roblems. This algorithm is tested computationally. For a three-machine cell with general data and identical parts, we address an important c onjecture about the optimality of repeating one-unit cycles, and show that such a procedure dominates more complicated cycles producing two units. For a three-machine cell producing multiple part-types, we prov e that four out of the six potentially optimal robot move cycles for p roducing one unit allow efficient identification of the optimal part s equence. Several efficiently solvable special cases with practical rel evance are identified, since the general problem of minimizing cycle t ime is intractable. Finally, we discuss ways in which a robotic cell c onverges to a steady state.