Tolerance Interface
Global standards for verifying the dimensions and geometrical specifications of manufactured parts establish clear rules for the relationship between measurement uncertainty and tolerances. Following iso 14253 ensures that the uncertainty of the measurement always works to the disadvantage of the party making the claim of conformity. This approach protects the buyer from receiving parts that are outside of the design limits.
Uncertainty Handling
Suppliers must prove that a part is within the specification by showing that the measurement result, including its expanded uncertainty, is entirely within the tolerance zone. In the iso 14253 framework, any result that falls near the limit such that the uncertainty crosses over the boundary is considered inconclusive. This rule forces the manufacturer to use more precise measurement equipment to prove compliance when parts are close to the edge of the allowed range.
Acceptance Criterion
Rejection of a part by a buyer requires the same level of proof as the acceptance by the supplier. A part is only proven non-conforming if the measurement result plus the uncertainty is entirely outside of the tolerance zone. This symmetry prevents disputes between the quality departments of different companies by providing a clear mathematical basis for the decision.
Metrological Traceability
Verification of the measurement process itself is required to ensure that the uncertainty calculations are valid. A lab must maintain its equipment according to a rigorous calibration schedule.
