Hot stamping is a technique that has been used to identify wires for decades. However, this technique has been banned by the US military aerospace platforms or significantly discouraged by the FAA for a number of years. There are many reasons to understand stamping techniques for aircraft wiring.
Two extreme examples of hot stamping gone wrong can be seen in the images below. A simple visual inspection of these wires shows that these wires are completely unusable. Obviously, a wire this damaged should not be placed on an aircraft, but what about hot stamping that has performed well?
Hot stamping is a technique that heats up stencils and then burns the top insulation layer with the impression of the letter. In the best case scenario, this only damages the first couple of mils of insulation thickness. The depth of damage to the wire insulation is not controlled and can significantly impact the wire insulation integrity and reliability.
Any other marking method is better than hot stamping. Printed labels, laser marking, printed shrink sleeves, or printing on the wire is better than hot stamping. When considering maintenance locations for you aircraft, ensure that the technology used to identify wires, if replacement is necessary, is not hot stamping.
If you are interested in aircraft wiring, you may want to read Lectromec’s article on Polyimide Wire Life Projection.