Product Manufacturing Information (PMI) is increasingly embedded in CAD files and standards continue to evolve, widening chances for error among design, production and metrology. Metrologic DCS outlines four practices to make GD&T workflows more reliable, from reading design intent to reports delivered to the shop floor.
Start with PMI, not re-keyed tolerances
To use PMI, teams must decode the design intent: which feature is targeted, which references apply and which tolerance is specified. Manual decoding is error-prone: a value copied incorrectly or a reference misunderstood can lead to inspection against a requirement other than the one defined. Software that starts from PMI and creates features and evaluations from the digital part definition avoids re-keying, reduces interpretation gaps and saves time at the first stage of program preparation, according to Metrologic DCS.
Automate datum reference frames
The datum reference frame (DRF) sets the measurement origin and is built from reference features such as A, B and C. It also determines which degrees of freedom are constrained for evaluation. Building it in the wrong order or choosing degrees of freedom poorly can make the same part appear conforming or non-conforming depending on the operator, Metrologic DCS says, describing this as a major source of GD&T misinterpretation. Automating the step so that the DRF and constrained degrees of freedom follow the drawing definition, rather than an operator’s choice, supports repeatable results across operators, machines and sites. In Metrolog, the DRF is created automatically when a GD&T is evaluated, and the degrees of freedom are selected accordingly.
Reuse imported DRFs
References are already defined in the CAD model, with labels placed by the design office. Recreating them during program preparation wastes time, can introduce discrepancies and forces rework whenever the definition changes. On a part with many annotations, it is also difficult to track which ones have been handled and which still need measurement. Starting from PMI-derived DRFs and predefining GD&T from them helps preserve the design office’s references and maintain visibility of progress. Metrologic DCS says its Scan GDT function reads decoded PMI and assigns a status, allowing users to validate both the decoding and the measurement.
Reports should explain what to correct
A report limited to pass or fail does not tell the shop floor what to do. If an operator does not know which kind of defect is present, adjustments may become trial and error, producing scrap and correction loops. Metrologic DCS recommends tailoring reports to their readers: a table of numerical values for quality control, a go/no-go report for a quick decision and a decomposition analysis for the operator. Metrolog separates the defect of an evaluated feature into four types—form, size, position and orientation—alongside the global defect, so the dominant type and the first correction are easier to identify. The company says a good report reduces scrap and speeds corrective action.