Lasers marking

Transparent and naturally coloured plastics can be marked from light to dark without loss of transparency light-coloured materials can be marked with sharp dark grey to black marking and contrasting colours from black to white can be applied to dark-coloured and black media. 

Pigments have been developed for both CO2 and Nd YAG laser systems. Low pigment concentrations (from about 0.1%) provide dark marking and higher concentrations (up to 1.5%) show a light-coloured marking. Items can be marked at up to 60()() a minute (pulse CO2) and up to 2000 mm s (Nd YAG). 

A new pigment system that reacts to the laser beam itself, independent of the polymer matrix, is being developed by Merck, in addition to its present range of conventional laser marking pigments, based on mica coated with metal oxides such as selenium and ferric. 

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Ti02/Mica (Sn, Sb)02/Mica laser sensitive laser marking of plastics, coatings [5.233]... 

From an application standpoint, high opacity, heat stability, IR reflectance, Hght-and weatherfastness as well as chemical resistance are the main reasons for using these pigments. Recent developments focus primarily on more economic higher strength versions, but there is also mention of new chemistries like Zn/Sn rutiles [3.85], new IR reflective chemistries [3.86, 3.87] as well as mixed metal oxides for new application fields Hke laser marking [3.88]. 

For laser marking to be effective, the energy of the laser beam must be retained in the material to cause local charring. Properly selected fillers are sufficiently opaque to absorb radiation and aid the process of marking. ... 

Figure 2.6 shows three standard diameter sizes (22, 28 and 32 mm) of zirconia femoral ball heads with laser markings to identify the individual part unequivocally. For example, the top ball carries the identification code 32-12/14M 96 Z 8179 that refers to a diameter of 32 mm, an inside taper of 12/14 mm, a medium neck length M, the year of manufacture (1996), the type of ceramics Z for zirconia, as well as the production number 8179. With this complete identification, it is possible to establish a quality test protocol and trace the history of this part that may... 

Laser technology is growing rapidly in the plastic coding area. A number of plastics are ideally suited for laser marking. However, most plastics require a higher concentration of the laser beam, resulting in a smaller mark area. The interaction of the laser beam with plastics varies. 

Figure 4. Contiuuous tone bitmap image printed on p er (left), and vector image laser marked on white polyethylene card (right).

Figure 5. Vector image YAG laser marked on black polyamide showing various line thicknesses and fill patterns.

Figure 6. Green laser marks both black and white on blue PBT.

Figure 7. Diode-pumped laser marks black and white on yellow acetal copolymer (POM).

G. Graff, Additives make possible laser marking of polyolefin components. Modern Plastics, April 1996,24-25. 

C. Herkt-Maetzky, W. Robers, Investigation of Color Change Reaction During Laser Marking of Plastics, Macromol. Symp., 100, 1995, 57-63. 

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