Metrologic DCS has set out four recommendations for reducing geometric dimensioning and tolerancing (GD&T) interpretation gaps, from reading design intent in product manufacturing information (PMI) through to the reports handed to the shop floor. The company notes that PMI is increasingly embedded in CAD files and that standards keep evolving, widening the scope for error; misinterpreted tolerances, it says, produce conflicting measurements, scrap and costly back-and-forth between design, production and metrology teams.
Start from the PMI. Decoding design intent means identifying the targeted feature, its references and its tolerance. Done manually, the step is error-prone: a value copied incorrectly or a reference misunderstood sends inspection against a requirement that was not the one specified. Metrologic DCS recommends software that takes PMI as its starting point instead of requiring tolerances to be re-entered, so that features and their evaluations are created from the part's digital definition.
Do not rebuild datum reference frames by hand. The datum reference frame (DRF) is built from reference features A, B and C and fixes which of the part's degrees of freedom are constrained for the evaluation. Built in the wrong order, or with poorly selected degrees of freedom, the same part can be declared conforming or non-conforming depending on the operator. The company advises automating the step so that the frame follows the drawing definition; in its Metrolog software, the DRF is created automatically when a GD&T is evaluated.
Reuse imported DRFs. References A, B and C already carry labels placed by the design office in the CAD model. Recreating them wastes program-preparation time, invites discrepancies and forces rework whenever the definition changes, and on heavily annotated parts it is hard to track which annotations have been handled and which remain to be measured. Starting from PMI-derived DRFs addresses the first problem; Metrolog's Scan GDT reads decoded PMI and assigns a status so that both decoding and measurement can be validated.
Tailor reports to the reader. A report limited to pass or fail does not tell an operator what to correct, which the company links to trial-and-error adjustment, scrap and correction loops. Metrologic DCS suggests numerical tables for quality control, go/no-go reports for quick decisions and decomposition analysis for operators. Metrolog separates the defect of an evaluated feature into form, size, position and orientation alongside the global defect, showing which type dominates and therefore what to correct first.