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TRUMPF annealing application

Annealing: using the laser to apply long-lasting markings to metal

Annealing is an established method for applying long-lasting markings to steel and metals. This is due to the fact that these materials show annealing colors when heated with a laser. These colors are highly dependent on the temperature at which the metal is heated. This is caused by an oxide film being generated on the surface during annealing; the oxide properties determine the color impression.

The main advantage of annealing: the surface remains completely intact; the marking is easily legible, long-lasting and resistant to abrasion. Annealing is ideal wherever a precision fit must be maintained or material bulging is prohibited. This is why this procedure is ideal for consumer goods such as cooking utensils, or medical products, for example.

How annealing works: the procedure for laser marking of metals

TRUMPF laser marking annealing application

In order to generate annealing, the laser heats the metal locally until just before its melting point. During this process, the structure of the lattice changes; oxide is generated on the workpiece surface which is shown by the appearance of different annealing colors. These colors are temperature-stable up to approximately 200 °C. If temperatures are higher, the lattice reverts to its normal state – the mark disappears. The surface finish remains completely preserved.

In general, annealing is only possible with metals which change color under the influence of heat and oxygen, i.e. steels and titanium, but not with aluminum or non-ferrous metals. It is also not possible to mark hard metals with a dark contrast using the annealing procedure.

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What are the advantages of annealing with a laser?

Gentle on the material

The material surface is hardly affected by the marking process and remains smooth even after the mark has been applied.

Simply clean

Due to the smooth surface, hardly any organic residue can stick to the annealing. It is therefore particularly suitable for objects that are cleaned often.

Long-lasting legibility

With the right selection of parameters, annealing markings remain intact and legible - even after numerous cleaning cycles, as is common with many medical products.

Established and suitable for product marking

Annealing has become established in medical technology in recent years and, along with the innovative black marking procedure using ultrashort pulse lasers, is ideal for product identification for unambiguous traceability, also in line with UDI guidelines.

Examples of annealing applications

Annealing markings on cast iron

Laser annealing is often used to apply QR codes or data matrix codes to metallic surfaces. The laser creates a very high-quality black mark. Contrast and visibility can be further increased by creating a white background behind the marked area. In addition to the increased contrast, the viewing angle at which the marking can be read also increases.

TRUMPF laser marking application

Marking consumer goods

The surface remains intact during annealing; the marking is easily legible, long-lasting and resistant to abrasion. This makes annealing perfect for marking cooking utensils.

TRUMPF laser marking annealing application

Decorative purposes

Annealing on basic utility items can be used for purely decorative purposes, such as with this cheese slicer. The mark is easy to detect even after numerous cleaning cycles.

TRUMPF laser marking annealing application - bronchoscope

Annealing for the application of lines, dots and scales

On objects like this bronchoscope, the marking lines, dots and scales must be easily legible, high-contrast and well-protected from wear.

TRUMPF laser annealing application - medical products

Product marking, product logos

Lasers create easily legible and high-contrast annealing which is ideal for applying product identifications and logos.

Design by laser marking on titanium

Creating annealing colors

By selectively setting the laser power, precise annealing colors, and therefore also colored graphics, can be created on many steels.

Clean surfaces

Clean surfaces are fundamental, especially in the medical field. Thanks to annealing, the smooth surfaces remain free of organic material even at the marked areas.

Manual: Laser marking in brief

Discover the comprehensive manual "Laser marking in brief" and find out about the technical background of the processes and laser systems as well as a guideline on practical marking. Download it here!

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