Guarantee Direct Part Mark Code Quality

DPM code quality blog banner

Direct part marking (DPM) is the process of permanently marking a part via laser or chemical etching, dot peening, or inkjet printing. DPM codes are common in industries like automotive, aerospace, electronics, and medical device because a part may need to:

  • Pass through harsh chemicals or oils that would damage a label-based barcode, like the engine of a car 
  • Be tracked for its entire lifecycle due to regulatory or safety reasons, like a knee replacement for a patient 
  • Be very small, making it difficult to label, like a smartphone component

The ability to track and trace parts with DPM codes helps minimize counterfeiting, ensure quality, and comply with a variety of regulatory requirements like The United States Food and Drug Administration (FDA) Unique Device Identifier (UDI) mandate and the European Commission Medical Device and In Vitro Diagnostic Regulations (MDR/IVDR) for medical devices.

DPM code on medical device
DPM codes cannot just be reprinted like a label

Direct part marking methods are prone to producing codes with low contrast, poor cell position, or inconsistent cell size. In addition, the surface being marked can be matted, cast, or highly reflective, and is seldom as clean and uniform as a label. Surfaces can be smooth and shiny, streaked, coarse, or granular. Therefore, the verification method for DPM codes must provide reliable and consistent results under all conditions. An unreadable DPM code can be a significant problem, which can lead to having to discard the part entirely or can cause safety recall issues down the line. 

Ensure DPM code quality with barcode verification

Barcode verification is used to reliably determine the quality of the DPM code. Verification is an essential part of any barcode tracking system, requiring a calibrated barcode verifier, that can produce a quality grade based on specific, predefined criteria. It verifies whether the barcode itself is compliant and has the right data structure as well as determining the mark quality. The grade is a prediction of how well a code can be read throughout its entire lifecycle, not just early scan points.

The manufacturer of the part has no control over the equipment customers and subsequent users will use for DPM code reading, and the conditions under which this reading will occur. Marks should thus be of the highest possible quality, with maximum contrast and consistency. 

According to the ISO/IEC TR 29158 (AIM DPM)  international standard, the barcode verifier has to identify various relevant variables and then analyze them to determine how much influence they have on causing a barcode to fail to read. This is used to predict scanning success with various scanners under various conditions.

A verifier has to check for proper size and location of each cell, overall geometry, any damage, and contrast. The type and quality of the lighting has a significant effect on DPM code verification. The standard allows 30- and 90- degree lighting angles in addition to 45-degree and dome lighting. 30- and 90-degree lighting make it possible to illuminate symbols on challenging surfaces such as curved or reflective substrates. The image of the code must be captured to be analyzed and a verification grade assigned. 

DPM code verification lighting types
Once the verification process is complete and a formal grade has been generated, the next step is to see what parameter(s) are causing the grade to be lowered. To read the ISO 29158 quality parameters and common solutions, download the Understanding Barcode Verification Results Whitepaper.

Alison Guzman

More Posts on


Join MyCognex


Cognex representatives are available worldwide to support your vision and industrial barcode reading needs.

Contact Us