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Laser marking is a type of non-contact marking

Apr 30 , 2021

Marking is split into two main categories: "contact marking" and "non-contact marking”. Laser marking is a type of non-contact marking. This section introduces the basic principles and features of laser marking as well as marking examples.

 

Laser marking principles

Laser marking advantages

Laser marking subcategories

Laser marking processing examples

Laser marking principles

Laser marking is used for marking logos, product names, serial numbers, model numbers, and other information onto a product by irradiating the target with a laser light to melt, scorch, peel, oxidise, cut, or discolour the surface. Laser markers can be roughly divided into two types: masking laser markers and scanning laser markers.

uv laser

Masking

Masking

Laser light is applied to a mask surface, and only those parts that pass through the mask are marked. Masking enables high-speed, high-resolution marking, but masks that match the content being marked must be prepared. This results in increased labour and costs when marking various patterns.

 

Scanning

Scanning

Scanning irradiates a target with a single laser light, and marking is performed in a stroke-like motion. More specifically, a laser light emitted from an oscillator is captured (scanned) by the scanning mirror and applied to the surface of the target for marking. Conventional scanning methods only allow control from the X and Y axes, meaning the light could only be scanned on a flat surface. Today’s laser markers, however, can control the Z-axis height using a scanning mirror, making it possible to mark a wide variety of targets with various shapes.

 

These scanning mirrors are called galvano mirrors, and a system that uses one or more of these mirrors is called a “galvano scanner” or “galvano mirror scanning system”. 

 

Recently, marking applications with various types have become common, and the high-speed capabilities of scanning lasers help cover weaker aspects of production. This has resulted in an increase in scanning systems that allow for a higher degree of freedom.

 

Laser marking advantages

This section explains the advantages of laser marking compared with stamping, labeling, engraving, and printing marking methods.

 

High-accuracy marking

Laser markers use laser light irradiated to a specific point, making high-accuracy marking possible. Even small characters can be easily identified, ensuring reliable quality control.

 

Non-fading marking

With labeling and printing methods, labels or printed surfaces may peel off or fade, making it impossible to identify the printed content. With laser marking, however, there is no need to worry that marked content will disappear over time.

 

Various marking methods

Lasers can be used for a variety of marking methods including surface melting and scorching, plating and paint peeling, oxidisation, and discolouration. Selecting the best marking method ensures damage-free marking regardless of the target material.

 

High-speed marking

Utilising high-output laser light, laser markers are capable of high-speed marking for efficient production.

 

Laser marking subcategories

Laser markers can be used to perform various marking tasks, including the following.

 

Paint peeling

This method provides contrast against the base material colour by peeling the paint, printed surface, or plating layers of a target for marking.

Cartons

Cartons

Paint peeling

Paint peeling

Peel the paint or printing on the target surface to bring out the contrast with the colour of the base material.

Surface peeling

The surface of a target is removed, marked, or engraved in some way. This method is generally referred to as engraving.

Air filters

Air filters

Surface peeling

Surface peeling

The surface of a target is cut or engraved.

Colour development

The surface of a target is scorched, oxidised, or discoloured by the laser light.

Wiring instrument

Wiring instrument

Colour development

Colour development

The surface of the target itself is coloured, resulting in high-contrast areas.

Laser-based colouration can be divided into four main principles.

 

Foaming

Condensing

Carbonisation

Chemical change

1. Foaming

Foaming

When the base material is irradiated with a laser, gas bubbles are generated inside the material due to the thermal effect of the radiation. Gasified, evaporated bubbles are contained in the surface layer of the base material and create a whitish swelling. These bubbles are particularly visible with darker base materials and result in “thin” colouration.

 

(Example) Base material colour: 

Black→ Changes to Grey

Red→ Changes to Pink

2. Condensing

Condensing

When the base material absorbs the laser energy, the thermal effect increases the molecular density. The molecules are condensed and the colour changes to a darker colour.

 

3. Carbonisation

Carbonisation

When an area continuously receives high energy, macromolecules of the element around the base material are carbonised and turn black.

 

4. Chemical change

Chemical change

The “pigment” elements in the base material always contain metallic ions. The laser radiation changes the crystal structure of the ions and the hydration level in the crystal. Consequently, the composition of the element itself changes chemically, resulting in colour development due to the increased intensity of the pigment.

 

Laser marking processing examples

Laser-based marking is performed as follows. The available types of lasers—such as CO2 lasers, YVO4 lasers, and YAG lasers—depends on the target material and the desired marking method.

 

Processing Task Main Target Material

Surface melting Plastic

Surface scorching Paper, plastic

Surface peeling Plated metal, printed paper

Surface oxidisation Metal

Surface peeling Glass, metal, plastic

Surface colouration Plastic

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