Direct part marking (DPM) is the permanent marking of an item with a machine-readable barcode for tracking purposes. It is used in the aerospace industry, as well as in automobile and electronics manufacturing. DPM is useful for product management because it allows the same part to be tracked over its entire life cycle. Many methods of applying direct part marking exist, including dot peen systems, laser marking, electrochemical etching, and ink jet. Various direct part marking codes are also used.
Dot peen marking uses a pin, known as a stylus, to create indented dots on a metal surface. The pin is driven either pneumatically or electromechanically into the metal by the marking machine. The pattern of dots created by dot peen marking is a two-dimensional square of indentations that can be read by a machine to identify the part. In creating the code, factors such as dot size and depth are carefully controlled by calibration of the marking machine to achieve consistency. Dot peen marking is widely used across industries because of its flexibility, ease of application, and cost-effectiveness.
Other methods of direct part marking are used where appropriate. Electrochemical etching employs chemicals to etch the surface of a metal through a stencil. Ink jet marking uses quick-drying ink to mark painted surfaces on which other types of identification may be difficult to read. Laser marking, less widely applied due to its higher cost, uses a laser beam to melt or change a surface and produce marks.
Companies and government agencies who use direct part marking have found that two-dimensional codes are most effective for their purposes, rather than the alphanumeric engravings that can also be produced through DPM. The most commonly used codes are Data Matrix™ and Quick Response Code, or QR Code®. While Data Matrix™ tends to be used in the telecommunication and aerospace industries, QR Code® is often used in the automobile industry.
The Data Matrix™ code consists of a square of black and white dots or cells. Dot peen technology will produce a set of indentations in a square, appearing as positive and negative space. Data Matrix™ codes can be as small as 300 micrometres in width while still being readable, allowing them to be used on very small electronics.
QR Code®, like Data Matrix™, is a two-dimensional square code consisting of black and white areas. QR Codes® have the advantage of being able to contain more alphanumeric characters than Data Matrix™, but they are also thought to be the less secure of the two. For this reason, government agencies and industries that require high security prefer to use Data Matrix™.