|Laser etch on glass epoxy
||Ink jet on ABS plastic
||Dot peen on metal
||Ink jet on plastic
|Laser etch on silk screen
||Chem etch on silicon
||Ink jet on glass
||Chem etch on metal
Codes, symbols, and text applied directly to a part’s surface (rather than affixed by a label or packaging) are known as Direct Part Marks (DPM). DPM are used widely in industrial part tracking from electronics manufacturing to automotive assembly. These marks are affixed directly to parts by abrading a part surface or marking in some other manner that cannot be discarded, torn, obscured, wiped off, or easily degraded. An example of an indirect mark is an inkjet code on a paper label or package, which can be removed from the part, damaged by physical contact, or distorted by moisture, temperature, and other elements.
An example of a direct mark is a code that is permanently etched directly onto the surface of a part, by a laser for example, which removes the surface layer of the substrate of a device to expose the code in a varying color or contrast. Other types of permanent marking include electrochemical etch and dot peen. These methods can also be used to abrade codes into identifier tags or plaques that can then be permanently affixed to a part.
Direct part marks are considered “permanent” because they are intended to last as long as the device itself, providing a means of device identification through the entire device lifecycle from manufacture to distribution to use and reuse. This is known as “cradle-to-grave traceability” and it ensures long-term product location in the supply chain (where was the part’s code scanned last?), product authenticity verification (who is the manufacturer indicated in the code data?), and responsiveness to adverse events like product recalls (which set of products were manufactured during the time that an adverse event took place, and where are the products now?).
It would require significant force to damage, remove, or otherwise render a direct mark illegible. For parts that must undergo excessive handling, reprocessing, or harsh industrial conditions, direct part marks ensure that the parts do not lose their identifying information throughout their life-cycles. Packaging and labels bearing identifying symbols or text may be separated from parts over time, but direct part marking ensures that a part will always be identifiable through manufacture and use.