The convergence of subtractive and additive manufacturing opens new possibilities in prototype development. Our hybrid approach machines critical interfaces on 3D-printed substrates, enabling functional prototypes with embedded sensors or conformal cooling channels. For medical device innovators, this means producing MRI-compatible titanium housings with internally polished lumens in 5 working days. Consumer electronics clients leverage this technology to validate magnesium alloy chassis prototypes featuring CNC-milled antenna cutouts alongside printed thermal dissipation structures. Performance benchmarking shows 60% faster assembly validation compared to traditional welded prototypes.