Optimal burn-in time to minimize the cost for general repairable products sold under warranty

Burn-in is used to improve product quality pre-sale. Particularly for products with an initially high failure rate sold under warranty, burn-in can be used to reduce the warranty cost. Since burn-in is usually costly and adds directly to the product manufacturing cost, optimizing the length of the procedure is a major problem. This investigation considers a general repairable product sold under warranty, and examines the optimal burn-in time for achieving a trade-off between reducing the warranty cost and increasing the manufacturing cost (since burn-in can be considered part of the manufacturing process). The expected total cost per unit sold is derived for various warranty policies (failure-free policies with and without renewing, rebate policy). The conditions required for burn-in to be beneficial are derived. Finally, a numerical example is presented.