Geometric Dimensioning and Tolerancing (GD&T) links design, production and metrology. Applied well, it helps a part assemble and function as intended; misinterpreted, it brings conflicting measurements, scrap and costly back-and-forth. Metrologic DCS says Product Manufacturing Information (PMI) is increasingly embedded in CAD files as standards evolve, and offers four ways to close the gap to shop-floor reporting.
Start from the PMI
Using PMI means decoding design intent: which feature is targeted, which references apply, which tolerance is specified. Done manually, the step is error-prone, since a mis-copied value or a misunderstood reference sends a part to inspection against a requirement nobody specified. Metrologic DCS recommends software that starts from the PMI instead of asking users to re-enter tolerances, so features and evaluations are built from the part's digital definition — no re-keying, fewer interpretation gaps and time saved at the start of program preparation.
Automate the datum reference frame
The Datum Reference Frame (DRF) defines where measurement starts. Built from reference features A, B and C, it determines which degrees of freedom are constrained. Made in the wrong order or with poorly chosen degrees of freedom, it can let the same part be declared conforming or non-conforming depending on the operator — a major source of GD&T misinterpretation, the company says. It advises automating the step so the DRF and degrees of freedom follow the drawing, making results repeatable across operators, machines and sites; in Metrolog, it says, the DRF is created automatically when a GD&T is evaluated.
Reuse imported datum reference frames
References A, B and C already carry labels placed by the design office in the CAD model. Recreating them wastes time, invites discrepancies and forces rework whenever the definition changes; on a heavily annotated part it is also hard to see what has already been handled. Metrologic DCS advises starting from the DRFs carried by the PMI and predefining GD&T from them. Its Scan GDT function is said to read decoded PMI and assign a status, so decoding and measurement can both be validated.
Tailor reports to the reader
A report limited to pass or fail does not tell the shop floor what to do; an operator who cannot identify the defect type adjusts by trial and error, producing scrap and correction loops. The company suggests 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 is said to split a feature's defect into four independent types — form, size, position and orientation — beside the global defect, so the dominant type is immediately visible.