Laser marking is a subcategory of laser engraving and it is a practice that uses lasers for etching and engraving different objects and surfaces. There many different laser marking processes. Some include color changes due to molecular or chemical alteration; others imply charring, melting, ablating, and foaming techniques. These are the main properties that set laser marking apart from conventional laser engraving. This technology can also be considered a general term for various surfacing techniques, such as laser bonding, printing and hot branding. The systems and machines used for laser marking and engraving are the same. Here’s a detailed guide with some of 2015’s most acclaimed and widely used laser marking processes.

Annealing

Annealing is a laser marking process created with an oxide layer on ferrous metals including high grade steel, iron, and steel, as well as on titanium through focused heating. In general, the oxide layer comes in a black nuance. It can have additional annealing colors too, like red, green and yellow. Usually the color depends on the level of heat applied to the layers. During the annealing process the surface of the material remains even. Nothing is removed, only the color is changed to mark a certain material through heating. The surface of the metal is penetrated at 20-30 µm thus making the engraving non abrasive. The mark can easily be removed through reheating at 700⁰C.

Frothing/color changing

Plastic has the capacity to absorb laser light. The carbon found in plastic and the color pigments are damaged and vaporized due to focused heating. The marking procedure involved a change in color; at the end of the process, the material’s frothing can be easily felt. The carbon compounds found in plastic goes through oxidization in order to structure CO2. CO2 then comes to the surface and forms a special froth layer. Based on the composition, the discoloration can be darker or lighter. In the specified marking area dark plastic becomes white whilst white goes gray or black. Frothing is a laser marking process that is applied exclusively to plastics.

Carbonizing

Carbonization is a laser marking procedure that uses a laser to darken the material being engraved. Basically, it consists in plastic bonds that are broken, and then follows the release of the bonds. A discoloration is produced that ranges from gray to blue/gray nuances, and finally to black. Plastic materials are used for this process, as well as organic materials including leather, wood, paper and packaging materials.

Engraving

As far as engraving that uses laser marking is concerned, the material is removed or taken out from a surface. The effect can be created in all kinds of materials. Ceramics, metals and plastic are engraved with laser markers; the beam of the laser goes into a surface and removes certain bits; the area marked is left with visible depressions of nearly 50 µm. Considering that the material is heated and at the same time predisposed to the ambient air, a mild discoloration will occur in the area being engraved. Because of the marking process it will become visibly more distinct than the rest of the material.

SSLE (sub-surface laser engraving)

This laser making process involves the engraving of an image placed in a translucent unyielding material. The procedure involves using a laser under the main surface to craft small fractures. The materials engraved are of extreme optical quality (appropriate for lenses that present low dispersion) to diminish beam distortion. Plastics can be used for this process, but also BK7 glass. Sub-surface laser engraving has become more cost efficient since 2009 when it started producing 3D images in promotional items and crystal souvenirs.

Nowadays, a varied number of enterprises offer customized souvenirs to investors, suppliers, and even employees. They take photos and 3D pictures and use SSLE to have them engraved into crystal materials. This idea can help companies appear more original and set themselves apart from competitors.

Ablation

Ablation is a laser marking technique that removes material from the surface being etched. A laser beam is used to irritate that area using low intensity laser flux. The absorbed laser energy heats the material, which sublimates or evaporates. At an increased laser flux, the material is modified into plasma. Generally, ablation involves using a pulsed laser to remove material. It is also possible to use laser ablation on a material with a continuous wave laser providing that the intensity of the laser is high enough.

Bonding

Bonding is another laser marking technique that makes use of lasers to etch a certain surface. The quality of the mark depends on various factors including marking speed, substrate used, laser spot size, material thickness, beam overlap, and laser parameters. Laser bonding involves various methods, including pad printing, spraying, roll coating, screen printing and others. The process involves three main steps:

• Marking material application
• Marking material irradiation with the laser in a desired mark
• Removal of extra material

Cutting

Cutting is a laser marking techniques that makes use of laser to trim certain types of materials. The process is commonly used in industrial manufacturing niches. Laser cutting involves the use of a high powered laser through optics. The optics of the laser works together with the computer numerical control (CNC) to guide the laser beam or material generated. A conventional laser employed for cutting materials would consist of a motion control system to pursue a G-code or CNC of the pattern following its cut onto the material. The laser beam is centered at the material; it is melted, vaporized, burnt or blown away using a jet of gas and thus leaving the surface looking flawless. Flat-sheet materials use industrial laser cutters, and also piping and other structural materials.

Laser marking has gained a lot of recognition over the past 10 years. Increasingly more companies are using these processes to have their products marked, etched or engraved thus ensuring their originality. The above mentioned processed are among the most widespread today; yet we have high expectations are other revolutionary techniques will soon penetrate the market.

By Michael Clark and Fimark.co.uk!