The Drift Nobody Measures: How Accumulated Specification Variance Dismantles Multi-Tier Supply Chains
Across distributed manufacturing networks, individual suppliers routinely operate within their stated tolerances—yet final assemblies still fail. The mechanism behind this paradox is tolerance drift: the compounding of minor specification deviations across supplier tiers until the cumulative effect exceeds what any single inspection point is designed to detect. Understanding how this propagation occurs, and how to interrupt it, is one of the most consequential engineering challenges facing US ma