to be published ASME International Design Engineering Conferences & Computers and Information in Engineering Conference, Washington DC, 2011


Varun J. Prabhakar and Peter Sandborn
CALCE Center for Advanced Life Cycle Engineering
Department of Mechanical Engineering
University of Maryland
College Park, MD 20742


Long life cycle products, commonly found in aviation, medical and critical infrastructure applications, are often fielded and supported for long periods of time (20 years or more). The manufacture and support of long life cycle products rely on the availability of suitable parts, which over long periods of time, leaves the parts susceptible to a number of possible supply chain disruptions such as suppliers exiting the market, counterfeit part risks, and part obsolescence. One solution to mitigating the supply chain risk is the strategic formulation of suitable part sourcing strategies (optimally selecting one or more suppliers from which to purchase parts over the life of the part's use within a product or within an organization). Strategic sourcing offers one way of avoiding the risk of part unavailability (and its associated penalties), but at the possible expense of qualification and support costs for multiple suppliers. Existing methods used to study part sourcing decisions are procurement-centric where cost tradeoffs focus on part pricing, negotiation practices and purchase volumes. These studies are commonplace in strategic parts management for short life cycle products; however, conventional procurement-centric approaches offer only a limited view when assessing parts used in long life cycle products. Procurement-driven decision-making provides little to no insight into the accumulation of life cycle cost (attributed to the adoption and use of the part), which can be significantly larger than procurement costs in long life cycle products. This paper presents a new life cycle modeling approach to quantify risk that enables cost effective part sourcing strategies. The method quantifies obsolescence risk as "annual expected total cost of ownership (TCO) per part site" modeled by estimating the likelihood of obsolescence and using that likelihood to determine the TCO allowing sourcing strategies to be compared on a life cycle cost basis. The method is demonstrated for electronic parts in an example case study of linear regulators and shows that when procurement and inventory costs are small contributions to the part's TCO, the cost of qualifying and supporting a second source outweighs the benefits of extending the part's effective procurement life.

Keywords: Total cost of ownership, part sourcing, supply chain, obsolescence, electronic parts

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