Metrologic DCS has published guidance for manufacturers seeking to reduce disagreements over Geometric Dimensioning and Tolerancing (GD&T) as product manufacturing information (PMI) becomes more common in CAD files and standards continue to evolve. The company says GD&T connects design, production and metrology, but misinterpretation can lead to conflicting measurements, scrap and repeated exchanges between teams.
The first recommendation is to start inspection programming from PMI. According to Metrologic DCS, using PMI requires decoding design intent: the targeted feature, the references and the tolerance. Manual entry is prone to copying errors or misunderstood references, which can cause a part to be inspected against the wrong requirement. The company recommends software that uses PMI as its starting point, so features and evaluations are created from the part’s digital definition without re-keying tolerances.
Second, the company advises against rebuilding datum reference frames (DRFs) by hand. A DRF defines where measurement starts, is made up of reference features A, B and C, and determines which degrees of freedom are constrained. Metrologic DCS says the wrong build order or poorly selected degrees of freedom can lead the same part to be declared 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 its Metrolog software, the company says the DRF is created automatically when a GD&T is evaluated.
Third, Metrologic DCS recommends reusing DRFs imported from PMI to limit rework. Reference labels A, B and C are already defined in the CAD model by the design office, the company notes, and recreating them can waste time and introduce discrepancies. It also recommends tracking which annotations have been handled and where their measurement stands. In Metrolog, Scan GDT is said to read decoded PMI and assign a status for validating decoding and measurement.
Finally, the guidance calls for reports tailored to their readers. A pass/fail result does not tell a machine operator what kind of defect is present, which the company says can lead to trial-and-error adjustments and correction loops. It suggests numerical tables for quality control, Go/No-Go reports for quick decisions and decomposition analysis for operators. Metrolog is said to split an evaluated feature’s defect into form, size, position and orientation, alongside the global defect, so users can see which type dominates.