Interlaboratory Round-Robin Design for Vat-Photopolymer Materials

An interlaboratory study can estimate how a material or method behaves when transferred beyond one laboratory, but it can also confound resin state, machine, operator, post-processing and measurement. Vat-photopolymer systems are unusually sensitive to this problem because the test article is created through a coupled chain of liquid-material handling, optical exposure, layerwise manufacture, washing, drying, secondary cure, conditioning and measurement. A nominally shared resin and CAD file do not establish a common measurand. This review develops a round-robin architecture for vat-photopolymer materials. It separates method-precision studies from manufacturing-capability comparisons, defines specimen-state controls, compares centralised and distributed operations, and connects protocol transfer to repeatability and reproducibility statistics. The design uses a pilot phase, locked data definitions, process-control records, blind duplicates and hierarchical analysis. Direct evidence from an interlaboratory working-curve study demonstrates how large dispersion can arise when procedure, light engine and measurement are insufficiently harmonised. The central conclusion is that a useful round robin must be designed around a declared decision and variance structure. More laboratories, specimens or measurements do not repair an ambiguous protocol, and a reproducibility standard deviation is not a universal material property.