U-SHAPED ASSEMBLY LINE BALANCING WITH TEMPORARY WORKERS

U-shaped assembly lines are useful in an efficient allocation of workers to stations. In assembly lines, temporary workers are placed to correspond to the fluctuation of demand. Sets of feasible tasks for temporary workers are different from those of permanent workers. The tasks which are familiar to permanent workers also vary. For the U-shaped assembly balancing problem under these situations the optimal cycle times for a given number of temporary workers and the optimal number of workers for given cycle time are derived and compared between U-shaped line balancing and straight line balancing. We also discuss the optimal allocation for a single U-shaped line and two U-shaped lines. In several cases, in particular when high throughputs are required, it is shown numerically that the number of temporary workers in optimal allocation for two lines is less than that of optimal allocation for a single line.