There are different types of direct part marking. But the marking methods are selected depending on several factors associated with the item or the part.
The Department of Defense has allowed two types UID marking of the items- direct part marking and application of UID labels. Direct part marking involves marking the item with a globally unique identification on the item itself. It is the process of marking a part with barcode symbols to allow tracking of the part or item for their full life cycle. When it comes to permanent marking of the items, the DoD specifies that the UID marking of the item should be permanent for the functional life time of the item which may vary from several months to several years.
Basically, industries such as aerospace, automotive and electronic manufacturers prefer direct part marking for reliable identification of the parts and items. As the DoD requires physical mark of UID on the tangible assets, the DPM assures safety and warranty along with satisfying the regulatory requirements. The 2D data matrix code is the most preferred bar code type for the barcode symbols that are used for the direct part marking of the items. However, some companies prefer QR Code according to their requirement. The UID marking method enables management and tracking of the items ranging in their value and sizes.
The various marking methods of direct part marking are Abrasive blasting, adhesive dispensing, Cast, forge or mold, Dot peen, Electro-chemical etching, Embroidery, Engraving/milling, Laser marking, LaserShot peeing, Lique metal jet, Stencil. There are other marking methods such as embossing, vibro-etch and manual metal stamp, but they are not for applying machine readable micro-size symbols.
How the Direct Part Marking Methods are Selected for the Items
There are number of different factors basing on which it is decided whether direct part marking is suitable for the particular item.
Function of the Parts
For the parts that are used for safety critical applications such as high stress system, or aircraft engine, the non-intrusive marking methods are used.
Geometry of the Part or the Item
The direct part marking is difficult if the shape of the item or the part is not convenient for the marking. It is difficult to etch the data matrix code on a curved surface.
The direct part marking is difficult when the texture of the part surface is highly polished. The marking requires reducing the glare of the surface before marking.
Size of the Part
Though size of the parts is not a very important factor for using 2D data matrix code, the sizes of the texts are adjusted according to the available space.
Life Span of the Items and their Operating Environment
While selecting the method of direct part marking, it is essential to consider the functional life span of the items and the environment in which the items are used. It is important that the marking should be permanent.
Thickness of the Surface
It is essential to consider the thickness of the surface as there are chances of deformation of the part if the intrusive marking methods are used. The marking depth in most of the methods should not exceed 1/10 of the thickness of the part.