Direct Part Marking Basics for Industrial Traceability Systems
Matching direct part marking physics to substrate hardness and surface roughness secures ISO 29158 compliance and reduces total unit traceability costs.
Rockwell Hardness
Meaning
Material testing standards provide a numerical value for the resistance of a metal to permanent indentation. Measuring rockwell hardness involves applying a preliminary minor load followed by a major load to a diamond or ball indenter. The resulting value is based on the net increase in the depth of the indentation, rather than the diameter of the mark.
Indentation Depth
Sensors calculate the hardness by comparing the position of the indenter before and after the major load is applied. This method is faster than other hardness tests because it does not require optical measurement of the indentation.
Scale Selection
Different combinations of loads and indenters are used to test a wide range of materials from hardened steel, soft plastics, copper or aluminum. The C scale is the most common for high-strength alloys used in aerospace and automotive components. Choosing the wrong scale can lead to inaccurate data that compromises the safety of the final assembly.
Technicians must calibrate the testing machine regularly to ensure that the depth measurements remain within the tolerances defined by ASTM E18.
Procurement Requirement
Purchase orders for industrial raw materials specify a range of rockwell hardness to ensure the metal can withstand the stresses of the intended application. If a batch of steel arrives with a hardness value outside the contracted limits, the buyer has the right to reject the shipment. Manufacturers rely on these tests to verify the success of heat treatment processes and to maintain the quality of their supply chain.
Hardness data acts as a proxy for other mechanical properties like tensile strength and wear resistance.