Laser Engraving
This is the most common term and simply defined, means that in the process of creating the mark, material is removed or vaporized during the process. An example in our business is CO2 laser engraving plastic for signage. This is often a two-ply plastic with one color called the "cap" laminated to a contrasting color called the "core". The engraving process removes the cap and exposes the core to create a sign that has an attractive look. There is also engraving in the processing of metals. Typically used to guarantee permanence, material is removed to create depth. Usually this is a process reserved for 1,064nm wavelength lasers (YAG for example) as those types of lasers couple well with metals. When engraving metals this way the laser is breaking the machined surface of the object, so oxidation or rusting can occur as a result. This would be a question at the time of feasibility testing. "Do you want depth? If so do you realize that the base material could oxidize? Depending on the answer the next option might be Laser Marking.
Laser Marking
Annealing or precipitation marking is commonly used when processing metal items where the surface of the part must stay intact. Often items like surgical implants, surgical instruments or high precision bearings require this type of marking. With laser marking, the heat of the laser actually redistributes the carbon in the material to create a jet black mark with only micron level surface disruption. If done correctly there will be no oxidation or rusting even under salt spray tests or autoclaving. If you processed the same material with a CO2 laser you would get an engraved marked with no contrast. This is all a matter of wavelength and how it reacts to the material OR the pigment in the material.
