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Laser-marked plastic part used in medical technology

Laser marking plastic

Lasers mark plastic components not only permanently and flexibly, but also very environmentally and material friendly. This is due to the fact that - compared to conventional marking procedures - no templates or consumables such as ink are required. Laser markings on plastic surfaces are always smudge and abrasion resistant. The laser marking of plastics basically involves three separate processes: changes in colour, alterations to surfaces and the ablation of layers.

Procedures in the laser marking of plastic parts

The key to laser marking of plastics is achieving sufficient absorption of the laser beam into the material. In metals, most of the beam is reflected, while in plastics, transmission, diffuse reflection and absorption are more important. The low heat conductivity in plastics means low energy losses during marking. Plastics can therefore be marked much faster than metals. Absorption by the macromolecular structure of plastics is usually in the ultraviolet and far infrared range. In additives such as carbon black or dyes, absorption occurs at varying wavelength spectrums. Since lasers with different wavelengths are available, the wavelength can be optimised for the respective material.

Which plastics can be laser marked?

TRUMPF marking lasers: overview of markable plastics

Short-pulse lasers achieve good results with a range of marking types depending on the plastic, the laser wavelength and additives used. To achieve high legibility and marking quality, it is recommended to mix laser-sensitive additives into some industrial plastics. The properties of the plastics remain largely unaffected.

Depending on the application, laser wavelength plays an important role in the marking of plastics. Using frequency-doubled (532 nm, green) or tripled (355 nm, UV) solid-state lasers extends the range of plastics that are easy to mark. These lasers often achieve better results than standard systems with wavelengths of 1,064 or 1,030 nm.

What is important when marking plastics?

Plastics are materials that pose several challenges to many marking systems. The main objective of marking systems is the long-term legibility of markings, but ink, for example, has inherent limitations. Moreover, not all plastics are the same. The varying properties and additives in plastics often require individualised marking solutions. Lasers are much more flexible in coping with these challenges, tolerating even minor surface soiling, and able to begin marking immediately without having to first create templates, which are required, for example, by screen and pad printing processes.

Types of laser marking for plastics

Colour change

Colour change in the laser marking of plastics includes discolouration, bleaching and carbonisation. Colour molecules can be selectively bleached out or their colour changed. Laser beam energy is used to break down or change the structure of individual molecules, such as colour pigments. Surfaces remain largely unaffected and smooth. In carbonisation, carbon-containing plastics burn or carbonise on the surface. The process is typically used for light-coloured plastics.

Ablation

Multi-layer or coated plastics can be laser-marked by ablating a thin top layer. Contrast is created by the colour of the base material or base coating. This removes coatings or special layers in laser marking film. Buttons in vehicle interiors are an example of markings achieved by layer ablation. In daylight, the symbols are white and at night they are backlit. For day and night designs, lasers with high pulse-to-pulse stability are available to ensure precise and homogeneous layer ablation.

Foaming

Foaming or melting are surface-altering processes. For laser marking plastics, the laser selectively melts the matrix material, creating gas bubbles which become trapped during cooling. The resulting raised markings are about 20 to 40 μm high and relatively wide. The light is diffusely reflected, and the marking on dark plastic appears bright. Foaming is therefore usually used for black and dark colours.

Colour change: process diagram

TRUMPF application marking laser annealing

The laser dose alters selected molecules and thus brings about a change in colour.

How can flame-retardant or flame-resistant plastics be laser marked?

TRUMPF marking laser application in flame-retardant plastics

Especially when processing flame-retardant plastics, it is important that the material and wavelength are optimally matched to each other. Here, the use of a UV laser is recommended. Dark grey markings can then be made on light materials. Discolouration is caused by the break-up of chemical compounds. As the material does not burn or carbonise, it is referred to as "cold marking" with high surface qualities.

Foaming: process diagram

TRUMPF marking laser application foaming scheme

In foaming, markings appear raised

Marking plastic with lasers: your benefits

Flexible

Lasers can be precisely adjusted to the respective plastic using a range of optional wavelengths, powers and parameters.

Gentle

Cold and non-contact laser marking means that the component surface remains virtually unaffected.

High quality

The laser achieves even the most intricate markings which are high-contrast, clean, and without any smudges.

Durable

Laser inscriptions on plastics neither fade nor rub off and therefore remain perfectly legible even after years.

Application examples of plastic marking

Speech processor

Speech processor with antenna laser-marked with the TruMark Series 3000 (MED-EL Elektromedizinische Geräte Gesellschaft m.b.H.):

Screwdriver handle

Plastic screwdriver handle marked with the TruMicro Mark 2030 ultrashort pulse laser (KLS Martin):

Laser-marked test joint for a hip implant

Test joint for hip implant

3D plastic marking of a test joint for hip implants with the TruMark 6030 (SAMAPLAST AG)

ID labelling

Colour changing and foaming enable the flexible creation of highly legible, durable and high-contrast labels and images, e.g. ID cards.

TRUMPF laser marking on plastic automotive components

Product identification

The flexible laser tool applies high-contrast and permanently legible, high-resolution product markings even in difficult to access areas.

To the overview

Success story of our customer Samaplast AG

Stefan Schar, Head of Finishing and Logistics at Samaplast AG

The laser system helps us to process a vast array of materials. All relevant parameters are stored, so we can seamlessly import new part geometries as STEP files and generate programs effortlessly

Read story

Find out now about the solution that meets your needs for the laser marking of plastics

UV marking lasers, fibre lasers and solid-state lasers in the infrared wavelength range are ideally suited as beam sources for laser marking of plastics.

White paper: 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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Manual: Laser marking in brief

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Contact

TRUMPF Ltd.

Telephone +44 1582 725335

Fax +44 1582 399260

Downloads

Marking lasers brochure

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Plastics marking in medical technology

pdf - 421 KB

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