Beyond the working curve: industrial perspectives on cross-platform process equivalence in vat photopolymerization

Context. The working curve introduced by Jacobs remains a widely used reference for characterising cure depth as a function of radiant exposure in vat photopolymerization. Recent interlaboratory studies have shown that conventionally measured working-curve parameters can vary markedly between laboratories and that improved spectral control and procedural standardisation substantially improve reproducibility. Position. Working-curve agreement is necessary for meaningful comparison, but it is not sufficient to establish cross-platform process equivalence. Part-level outcomes can also depend on the spectral distribution and spatial delivery of light, oxygen-related interfacial effects and thermal conditions, and the state and handling history of the resin. Approach. This Perspective surveys peer-reviewed literature and public standards relevant to working-curve measurement, optical delivery, oxygen inhibition, process-parameter sensitivity and additive-manufacturing qualification. Three observation domains are used to organise the discussion: spectral, atmospheric and material-history. They are presented as categories for observation rather than as a causal model or ranked hierarchy. Implications. Cross-platform qualification should therefore retain the working curve as a metrological anchor while confirming performance at part level under the operational conditions of intended use. Scope. No new experimental data, universal equivalence criterion or quantitative causal hierarchy is proposed.