Machine-Capability Studies for Additive Manufacturing: Repeatability, Reproducibility, Nested Variation and Acceptance

Additive production contains nested sources of variation: feature within part, part within build, position within build, build within machine, machine within site and site within organisation. Repeatability examines variation under nominally unchanged conditions; reproducibility introduces declared sources such as operator, machine, day or site. Orientation and position can create deterministic dimensional or cure differences. Cp/Cpk-type summaries can be useful only when the measured distribution, specification basis and stability assumptions are defensible. A reference geometry improves comparability across machines, while production parts test the specific requirement set. Qualification therefore depends on preserving the measured state, configuration and exception history needed to distinguish these mechanisms in production rather than relying on nominal recipe identity alone.

ER-344.