Metrologic DCS has published four recommendations for reducing Geometric Dimensioning and Tolerancing (GD&T) interpretation gaps as Product Manufacturing Information (PMI) becomes more common in CAD files and standards evolve. The advice spans from design intent to shop-floor reports.
Start with PMI
The first step is to decode the design intent carried by PMI: the feature being targeted, the references and the tolerance. Metrologic DCS notes that manual handling is error-prone; an incorrectly copied value or misunderstood reference can lead to inspection against a requirement that was not specified. Its advice is to use software that starts from PMI rather than requiring tolerances to be re-entered, so features and evaluations come from the part’s digital definition. The claimed result is less re-keying, fewer interpretation gaps and time saved at the beginning of program preparation.
Automate the DRF
The datum reference frame (DRF) defines where measurement starts. It consists of reference features A, B and C and determines which degrees of freedom are constrained for evaluation. Metrologic DCS warns that an incorrect build order or poor selection of degrees of freedom can make the same part appear conforming or non-conforming depending on the operator. It recommends automating this step so the DRF and degrees of freedom follow the drawing definition. In Metrolog, the DRF is created automatically when a GD&T is evaluated.
Reuse CAD references
CAD models already carry reference labels A, B and C from the design office. Recreating them during program preparation wastes time, can introduce discrepancies and forces rework when definitions change, according to the company. Parts with many annotations also make it difficult to track which items have been handled. Metrologic DCS advises starting from PMI-derived DRFs and predefining GD&T from them while keeping a clear view of annotation location and measurement status. In Metrolog, Scan GDT reads the decoded PMI and assigns a status so users can validate decoding and measurement.
Make reports actionable
A report limited to “pass” or “fail” does not tell the shop floor what to correct, Metrologic DCS says. Operators who do not know the defect may adjust by trial and error, creating scrap and correction loops. The company recommends reports tailored to the reader: a numerical table for quality control, a Go/No-Go report for quick decisions and a decomposition analysis for the operator. Metrolog separates a feature’s defect into form, size, position and orientation alongside the global defect, making the dominant type visible. Metrologic DCS says this reduces scrap and speeds corrective action.