When modular prototypes demand interchangeable parts with micron-level fit, conventional CNC milling often falls short—here’s how wire and sinker EDM machining became my secret weapon for achieving ±0.0002″ tolerances across multi-component assemblies. Drawing from a real medical device project that cut assembly failures by 94%, this deep-dive reveals the specific EDM strategies, parameter tables, and hard-won lessons that separate prototype success from expensive rework.