Designing of an Assembly Line based on Reliability Approach

The problem of Assembly Line Balancing is to assign a set of tasks to anordered sequence of workstations without violating the precedence constraints. Theefficiency of the line will increase when tasks are more evenly distributed. In general, theefficiency measure(s) should be optimized subject to cycle time restriction andprecedence constraints. Under the deterministic setup, efficiency of the system can bemeasured in various ways. Research works, reported so far, mainly deal with balancingloss as an inverse measure of efficiency. As a result, in earlier works balancing loss hasbeen minimized subject to precedence constraints.In case the work elements are bestdescribed in terms of stochastic time, the entire problem has to be addressed with adifferent measure of efficiency. Expected variance of the idle times of workstations canbe viewed as an inverse measure of stability of the system. A more appropriate and directmeasure could be the reliability of the system such that each workstation adheres toassigned cycle time with high chance.The present work defines the reliability of the assembly line in terms of cycle time anddistribution of the tasks times and offers an optimization formulation for the problemunder precedence constraints. For demonstration purpose, one well known example inthe literature has been addressed under stochastic setup.