Design of a fully automated robotic spot-welding line

The mixed model assembly line design problem includes allocating operations to the stations in the robotic cell and satisfying the demand and cycle time within a desired interval for each model to be produced. We also ensure that assignability, precedence and tool life constraints are met. Each pair of spot welding tools can process a certain number of welds and must be replaced at the end of tool life. Tool replacement decisions not only affect the tooling cost, but also the production rate. Therefore, we determine the number of stations and allocate the operations into the stations in such a way that tool change periods coincide with the unavailability periods to eliminate tool change related line stoppages in a mixed model fully automated robotic assembly line. We provide a mathematical formulation of the problem, and propose a heuristic algorithm.