The right marking laser for every plastic
Not all plastics are alike. Currently there are hundreds of different types, all of which react differently when processed by a laser - regardless of the wavelength. Depending on the type of plastic, a laser with infrared (1064 nm), green (532 nm) or ultraviolet (355 nm) light is selected for marking. Basically, users can mark plastics in four different ways: coloring, engraving, foaming and ablation.
Marking by engraving and ablation
Thermosetting plastics and elastomers are frequently engraved with a wavelength of 1064 nm. During the engraving process, material is ablated from the surface by means of melting and vaporizing. This results in sublimation of the material.
Multilayered plastics can also be marked by ablating a thin surface layer - or varnish, for instance. Here there should be a good contrast between the top layer and the substrate, as well as good absorption capacity for the laser wavelength, and the plastic should also have a very homogeneous layer thickness.
Marking by foaming and coloring
Dark thermoplastics are primarily marked by means of a color change, also with a wavelength of 1064 nm. Here a foaming of the material is obtained, i.e. an alteration in its surface. The matrix material of the plastic is made to melt briefly, and the resulting gas emissions are enclosed as gas bubbles during subsequent cooling.
Dark markings on light-colored materials are also created by means of a color change. This, however, occurs through carbonization with green or ultraviolet light at wavelengths of 532 nm and 355 nm. Since the thermal energy is only applied very locally here, the result is a clear, highly legible font or code with high contrast.
Marking with UV lasers
The use of UV lasers opens up new dimensions in the marking of plastics. With many materials, UV lasers achieve much higher-contrast marking as well as higher processing speeds. The energy of short-wavelength UV light causes a photochemical reaction enabling cold material processing. In this way, flameproof plastics - such as those used as housing materials in the electronics industry - can be marked especially well.