How Does Laser Marking Work?

Why use lasers for marking/engraving?

Lasers are preferred in many areas because of the need for a permanent marking that is informative, cost effective and aesthetically pleasing. Laser engraving is used in a number of industries to provide products, components and articles with lifetime traceability in the form of plain text, 1-, 2- or 3-dimensional codes and graphics like matrix codes.

What does laser marking mean?

When laser marking, the laser light is used to alter the materials properties locally, which produces text and/or shapes.  

Definitions

There are several ways to describe material processing using laser light. Laser marking and laser engraving are two concepts that are sometimes used synonymously and sometimes with distinction in its meaning. Laser etching is also used to describe the process of marking a material. Below are a few definitions.

Engraving involves vaporizing the materials surface locally, in a small and focused spot. By moving the laser beam around on the surface, patterns can be formed from the vaporized parts of the material surface.

Thermochemical reaction occurs when plastics react to exposure from laser radiation. The resulting mark will have different properties based on what reaction takes place. Common reactions are melting, foaming and bleaching, all of which are a function of the material composition and color of the material. Additives may sometimes be used to achieve color change or induce coloured markings. Also called contrast marking.

Annealing by laser causes a color change on most polished steel types. By carefully heating the steel with the laser, you get dark contrast markings with good readability without any material removed.

Ablation by laser is made ​​on anodized, plated and painted materials by removing the top layer and expose the base material which is in a contrasting color.

Laser wavelengths

The wavelengths of laser light used in industrial application of the laser is commonly around 1060 nm and 10600 nm (10.6 microns), solid-state lasers and CO2 respectively,

1060 nm is a wavelength in the frequency range called near infrared. Laser sources in this frequency range are usually used to process and label non-organic materials such as metals and plastics. Examples of laser sources are Nd: YAG and fiber Ytterbium lasers. Typical applications are marking metals and plastics by color change or engraving.

10600 nm or 10.6 microns is a wavelength in a range of frequencies called the mid infrared. 10600 nm is preferably used for labeling organic materials such as textiles, paper, glass and wood, but also plastics (normally only engraving). 10600 mn affect the material solely thermally. Carbon dioxide lasers (CO2) produces a laser light with 10600 nm.

Laser Light uses in labeling

Materials

10600 nm (CO2)

1060 nm (Nd: YAG / Fiber Laser)

Plastics without addition

Engraving only

Both engraving and color change

Metals

No

Yes

Anodized metal

Yes

Yes

Glass

Yes

No (yes with 355 nm)

Silicon wafers

No

Yes

Ceramics

Yes

Yes

Paper, cardboard

Yes

No (inks can be removed)

Wood

Yes

No

 

Two principles for guiding a laser beam:

Control of the laser beam can be achieved in a number of ways and falls into two categories. These are Cartesian control and mirror Galvanometers.

Cartesian control means that the laser beam is fixed and the object to be marked moves in the x and y coordinates with a so-called XY table. Switching the beam and controling the movement of the material with the XY table is made ​​by means of laser software and electronics.

In some cases, laser machines that are Cartesian based are, in fact, hybrid machines. This means that the material moves in for example the y direction and the laser beam in the x-direction. When controlling the laser in one single axis like this, it is commonly referred to as a "flying optic" system. Laser cutting machines are often hybrid machines with "flying optic" in one or two stages.

Galvanometer mirror control utilizes a pair of strategically placed live mirrors just before the focusing lens. These mirrors are attached to small, yet extremely quick analog or digital electric motors, also referred to as "galvos". By altering the angle of the mirrors using the galvos, the beam can be guided within a limited area, through an F-theta lens and onto the surface of the material.  

Controlling the laser beam with the Galvanometer principle means that the marked object doesn't have to be moving unless it is outside of the lens range. Another advantage of Galvanometer control is how quick it can execute marks. 

Commonly marked materials

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Here are examples of materials commonly used in laser marking. Among plastics, we mark ABS plastic, LEXAN, Noryl, HDPE and PET. Metals that work well for marking are Kovar, anodized metal, aluminum, stainless steel and copper. Ceramic is also an acceptable marking material.

Depth marking or laser engraving

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The picture shows depth marking or laser engraving as it is most commonly referred to. The metal has been eroded by vaporising the material. Marking Method: Galvanometer scanner and 1060 nm laser light.

 

Laser marking in the automotive industry

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Laser marking is common in the automotive industry. These are some examples of how laser marking can be applied to form precise and aesthetically pleasing icons on buttons, covers, rims etc. Marking Method: Galvanometer scanner and 1060 nm laser light.

 

Laser marking / engraving of codes

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Data matrixes and barcodes can be advantageously marked by laser. Codes provide large amounts of information per unit of surface space, compared to plain text. Marking Method: Galvanometer scanner and 1060 nm laser light.

 

Laser Marking / Engraving in packaging applications

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Marking packaging with lasers have several advantages. Resulting marks are clear and easy to read, permanent, and does not require the package to be physically touched. Marking Method: Galvanometer scanner and 1060 nm laser light.

 

Laser Marking / Engraving in medical metal applications

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Here we see some examples of laser markings in metal medical equipment. For example surgical tools, instruments and implants. Pacemaker bodies can be made traceable by both datamatrix codes and plain text. Marking Method: Galvanometer scanner and 1060 nm laser light.

Laser Marking / Engraving in plastic medical applications

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Medical applicaton of laser marking in plastics. Marking Method: Galvanometer scanner and 1060 nm laser light.

Laser Marking / Engraving in cutting tools

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A very common application is laser marking of cutting tools. Marking Method: Galvanometer scanner and 1060 nm laser light.

Laser marking / engraving of raceways and gears

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Laser marking / engraving of keyboards

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Laser marking / engraving of electrical and electronic equipment

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Laser marking / engraving of promotional gifts and accessories

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Laser marking / engraving on wood, glass and other non-metals

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Laser marking / engraving for traceability

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