Grading Permanent Marks: Understanding Quality Scores and What They Mean for Manufacturing
What Does It Mean to "Grade" a Mark?
Grading a permanent mark is the process of assigning a quality score to a mark based on a detailed analysis of its physical and data characteristics. It is the output of the verification process: giving manufacturers an objective assessment of how well a mark was applied.
Under the two primary international standards, ISO/IEC 15415 for 2D barcodes and ISO/IEC TR 29158 (AIM DPM) for direct part marks, marks are graded from A (4.0, highest quality) to F (0, fail). The grading process evaluates multiple parameters simultaneously:
- Symbol Contrast – the difference in reflectance between dark and light elements.
- Modulation – the uniformity of dark and light cells across the mark.
- Fixed Pattern Damage – integrity of the finder and timing patterns.
- Axial Non-Uniformity – consistency of cell size in both axes.
- Grid Non-Uniformity – how well cell centers align to an ideal grid.
- Unused Error Correction – how much of the built-in error recovery capacity remains available.
A critical rule of grading: the lowest individual parameter grade becomes the overall grade for the mark. A mark that scores an A on seven parameters but an F on one is graded F overall. This stringent approach ensures that every quality dimension must meet the required threshold.
Why Is Mark Grading Important?
Grading transforms the abstract concept of "mark quality" into an actionable, documented metric. For manufacturers, a verified grade provides proof that a mark meets contractual and regulatory requirements and gives them the diagnostic information needed to improve their marking process when quality falls short.
Without consistent grading, manufacturers operate blind. A mark might pass a basic read test today but have insufficient error correction capacity to survive years of service in a harsh environment. A subtle uniformity issue might also cause intermittent scan failures downstream, creating supply chain disruptions that are difficult to trace back to their source.
Grades also support continuous process improvement. By monitoring grade trends over time, engineers can detect process drift, such as a laser misaligned or a pin marking stylus wearing down, before it causes outright failures.
Common Applications for Mark Grading
Aerospace and defense: Turbine engine components must achieve minimum grade thresholds (often B or better) under AS9132 or AIM DPM standards. Manufacturers provide grade certificates to OEM customers as documented proof of compliance.
Automotive tier suppliers: Major automakers require suppliers to demonstrate that direct part marks on safety-critical components achieve a specified minimum grade under AIM DPM standards.
Medical device manufacturers: Grading is part of the quality management documentation required by FDA 21 CFR Part 830 and EU MDR for UDI marks on implantable and reusable devices.
Process control and optimization: Manufacturers use in-line grading data to monitor marking system performance, schedule maintenance, and adjust marking parameters like laser power, speed, and focus to maintain consistent output quality.
Looking for a part-marking solution that includes vision systems for grading your marks?
Grading is not just a compliance checkbox: it is an essential quality management tool that helps manufacturers produce marks that will perform reliably for the life of the part. Schmidt Marking Systems can design and buld the right marking technology to produce, verify, and grade permanent marks to your industry's standards. Contact us today to learn about your options.