Laser marking of plastics

Laser marking of plastic, or plastic engraving, is a process during which components are labelled or marked with the aid of a laser. The polymer that the plastic parts are made up of dictates the methods used and the energy input needed to laser mark the plastic. The result of the laser marking largely depends on the type of plastic being used, any additives in the plastic (such as dyes) and the type of laser being used to mark it. Laser marking is a non-contact optical process in which the plastic has to absorb the laser beam. This behavior is also utilized in the laser welding of plastics, during which one welding partner absorbs the laser beam and the other welding partner is transparent to the laser beam.

Many plastics and thermoplastics can be laser marked. Should a plastic’s properties dictate that it cannot be laser marked, it can usually be modified with a suitable additive or master-batch for plastic laser marking. Additives such as color pigments can also influence the plastics capability to be laser marked.

Laser marking is becoming more and more frequent in industrial applications since it is seen as particularly reliable, and provides numerous advantages. Laser marking is extremely robust and also forgery-proof. Its application can also be of a high quality.

Further advantages of plastic laser marking (versus conventional marking technologies) are:

• Creates permanent marking, as it is waterproof, wear- and heat-resistant, light-fast and resistant to chemicals
• Provides maximum flexibility in the marking design – can laser positions that would otherwise be difficult to mark
• Is a non-contact process 
  - and therefore no wear and tear of tools and no costs for consumables such as chemicals, inks etc. 
  - the material remains free from pressure, tensions and fixturing, so that consistently uniform results can be guaranteed
• Results in an unimpaired surface (color change)
• Requires only simple handling, no pre or post-treatment required

During the laser marking process, the plastics undergo optical surface changes. A variety of laser media are used here, and these will differ in how the laser is generated. A distinction is drawn between gas, dye and solid-state lasers. During the lasering of plastic, the result is influenced not only by the type of laser but also by the wavelength used. For most laser marking applications, solid-state lasers such as Nd:YAG, fibre lasers and CO2 lasers are the ideal beam sources.
At Ensinger, successful trials have been performed with the Nd:YAG solid-state laser, which is used very frequently in practice.

Nd:YAG stands for neodymium-doped yttrium aluminum garnet laser. It uses a neodymium-doped YAG crystal as an active medium. The best results were obtained at a wavelength of 1064nm and so this is the wavelength most frequently used.

Laser marking is increasingly replacing conventional printing methods. Particularly in the labeling of plastics, laser marking has developed into an established method. Above all, it has become more important in the context of quality assurance and traceability. As an example, plastics may be frequently given bar codes, articles or batch numbers for unique identification. Countless applications across all industries benefit from this. These include:

• Casing components made from plastic
• Electronic components
• Circuit boards for car parts
• Tools and tool handles

Not all high-performance plastics are capable of being laser marked. For example, unmodified POM (acetal) and polyamide PA do not usually display any color change upon marking with a Nd:YAG laser. Ensinger has managed to overcome this problem through the use of a laser additive, and resulted in TECAFORM AH LM white, laser-markable acetal.

We offer a wide range of plastic stock shapes which are suitable for laser marking including AH LM white, TECASON P MT and TECAPEEK natural. 

From our experience (based on a Nd:YAG laser with a wavelength of 1064 nm), the following plastic stock shapes have very good capability for laser marking:

Other plastic materials that are laser markable:

• PP biocompatible - TECAPRO MT black/white
• laser ABS - TECARAN ABS grey
• POM medical - TECAFORM AH black
• POM material - TECAFORM AH ID
• PET polymer - TECAPET white
• PET polymer - TECAPET black
• PBT GF30 - TECADUR PBT GF30 natural
• Polycarbonate - TECANAT natural
• PA66 GF30 - TECAMID 66 GF30 black
• PVDF - TECAFLON PVDF natural
• glass filled PEI - TECAPEI GF 30 natural
• PSU plastic - TECASON S natural
• PPS GF - TECATRON GF40 black
• PPS PVX  - TECATRON PVX black
• PEEK CF30  - TECAPEEK CF30 black
• PEEK PVX - TECAPEEK PVX black 
• PI Polyimid - TECASINT

The use of other lasers and changes to parameters may vary results.