Laser Engraving and Marking on Plastic: operation, advantages and applications

Laser marking on plastic or laser engraving on plastic is a process by which components are labeled or marked with the aid of a laser.

The polymer of which the plastic parts are made determines the method used and also the amount of energy needed to carry out the laser engraving of the plastic. The result of laser marking depends on both the type of plastic and the additives used such as dyes and the type of laser used.

How does laser marking on plastic work?

Laser marking is an optical process in which plastic absorbs the laser beam without having any contact with it. This typical behavior is also exploited in the laser welding of plastics, a process during which one welding joint absorbs the beam while the other welding joint is transparent to the laser.

Many different types of plastics and thermoplastics can be laser marked. If a plastic cannot be laser marked, it can usually be processed with an additive or masterbatch suitable for laser marking plastic.

By masterbatch we mean a concentrated mixture of pigments and / or additives encapsulated during a thermal process in a support resin which is then cooled and cut into a granular form. Additives such as color pigments can also affect laser marking ability.

The key in the plastic laser engraving process is to achieve sufficient absorption of the laser beam into the material. Metals tend to reflect most of the ray, while in plastic the reflection is widespread and absorption is very high.

The low thermal conductivity of the plastic means that the energy loss during laser marking is low, so processing is very fast. The absorption by the macromolecular structure of the plastic is usually in the ultraviolet and infrared range.

For further information read -> Why UV Lasers are used: applications, characteristics and types

The advantages of Laser Marking on Plastic

Procedures such as laser marking and engraving are used more and more frequently in the industrial field as they are considered particularly reliable and also offer numerous advantages over conventional marking technologies:

The marking is permanent, as it is waterproof, resistant to wear and heat, light and chemicals;
Laser marking is an extremely effective, high quality and forgery-proof process;
Maximum flexibility in the design of the marking, so it is also suitable for areas usually difficult to access;
The whole process takes place without any contact with the material;
There is no tool wear and no additional cost for extra materials such as chemicals, inks, etc;
The processed plastic is always free from pressures, tensions and fixings, in order to guarantee consistently uniform results;
Processing is simple and no pre-treatment or post-processing is required;
Thanks to the short set-up times of the laser machine and the flexibility offered, even small batches can be marked economically.

Types of lasers used

During laser marking, plastics undergo optical surface changes through exposure to the aforementioned beam. For this purpose, a variety of laser supports are used, which differ in the way the beam is generated. During plastic processing, the result is influenced not only by the type of laser but also by the wavelength used.

The wavelength of the laser plays an important role in marking plastic. If solid state lasers with doubled (532 nm) or tripled (355 nm) frequency are used, the range of plastic materials on which a good laser marking result can be obtained becomes very wide.

Also considering the economic factor, most laser marking applications are made with infrared sources (Fiber, Nd: YAG).

Laser marking on plastic with infrared laser

For further information read -> From the C02 Laser to the Fiber Laser, let's discover the most popular types of lasers

Methods of Laser Marking on Plastic

Foaming leaves a tangible mark on the surface of all polymers, but also on some metals. The heat induced by the laser melts the surface and later, due to the rapid cooling, the bubbles remain encapsulated in the material, thus forming a positive sign, which can be touched by hand. Depending on the material this sign is light or dark in color. In this case the laser operates at a low power level and with longer pulses.
Plastic carbonization. This technique allows to obtain strong color contrasts on bright surfaces and can be used for both polymers and biopolymers. During the carbonization process, the laser heats the surface of the material which releases oxygen and hydrogen. The surface of the plastic is thus carbonized due to the concentration of carbon. This technique has slightly longer marking times than other processes.
Color change. Color change laser marking is an electrical process that reorders or destroys pigmented macromolecules and ensures maximum readability. No material is removed, the surface is smooth and unaltered, but a little foaming is possible. The color variation can be both light and dark although for the most part it is a dark toning.
Laser removal or ablation. Laser removal is used with multilayer plastics (laminates). During the removal process, the laser beam removes the thin covering top layers that are applied to the base material, such as paints. This creates an effect of color contrasts due to the differences between the various layers.

Laser engraving on plastic medical devices

Fields of application

Laser marking is increasingly replacing conventional printing methods, particularly in the labeling of plastics, where it has now become the preferred method.

Above all, the laser is privileged in the context of traceability. Plastics are often assigned barcodes or lot numbers to identify their origin. Countless applications in all industrial sectors benefit from the use of lasers, such as:

Plastic housings
Plastic casings
Electrical outlets
Keyboards
Buttons and switches
Identification labels for animals
Films
Sensors
Electronic components
Printed circuits
Tools

Laser Marking on Plastic for Traceability

Plastic suitable for Laser Marking

Not all high performance plastics are inherently capable of being laser marked. For example, polyoxymethylene acetal resin POM and thermoplastic polyamide PA if not modified with additives usually do not show any color change when marking with an infrared laser (Fiber, Nd: YAG).

In this case, the use of certain additives is therefore proposed. With a fiber laser it is possible to mark many commercial plastics, such as polycarbonate, ABS, and many others with a permanent, fast and high quality finish.

Some plastics suitable for laser marking are:

PEEK - natural TECAPEEK
Medical PEEK
PEEK 30 filled with glass fibers
PBTP
Medical PPSU
ABS
PETP
TECAFORM AH LMTECASON P MT

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