Geometric Dimensioning and Tolerancing (GD&T) links design, production and metrology. Metrologic DCS says that when the language is misinterpreted, teams can end up with conflicting measurements, scrap and costly back-and-forth. The company attributes growing risk to Product Manufacturing Information (PMI) being embedded in CAD files and to evolving standards, and offers four practices for making inspection workflows more reliable.
The first recommendation is to treat PMI as the starting point. The vendor says manual decoding of design intent—identifying the targeted feature, references and tolerance—is error-prone; a copied value or misunderstood reference can lead to inspection against the wrong requirement. Using software that reads PMI avoids re-keying tolerances and creates features and evaluations from the part’s digital definition. Metrologic DCS claims this reduces interpretation gaps and saves time in program preparation.
The second is to avoid rebuilding datum reference frames (DRFs) by hand. A DRF is made up of reference features A, B and C and determines which degrees of freedom are constrained. The company warns that an incorrect build order or poorly selected degrees of freedom can make the same part appear conforming or non-conforming depending on the operator. It recommends automating the step so the DRF and degrees of freedom follow the drawing definition; in Metrolog, it says, the DRF is created automatically when a GD&T is evaluated.
The third is to reuse DRFs imported from the CAD model. References A, B and C already carry labels from the design office, and recreating them wastes time and can introduce discrepancies, according to the company. It also notes that parts with many annotations can make it hard to track which have been handled. Starting from PMI-derived DRFs, and using Scan GDT to assign status to decoded annotations, is presented as a way to validate both decoding and measurement.
The fourth is to tailor reports to the reader. A pass/fail result does not tell a machine operator what to correct, the vendor says, while trial-and-error adjustment can create scrap and correction loops. It suggests numerical tables for quality control, Go/No-Go reports for quick decisions and decomposition analysis for operators. Metrolog separates an evaluated feature’s defect into form, size, position and orientation alongside the global defect, so the dominant type can be addressed first.