Ultraviolet DPSS lasers offer several benefits for plastics marking over near-infrared lasers, including the ability to produce a photo-chemical color change, unaccompanied by any material damage or toxic fumes, without the need for solvents or material additives. Furthermore, UV wavelengths can be focused to small spot sizes, enabling a marking resolution as high as 2,500 dpi. In addition, because this cold marking occurs at laser intensities well below those that would damage the plastic, there is a wide process window that is tolerant of variations in material or ambient conditions. This also makes the marking operation less sensitive to initial set-up and simplifies marking of contoured components. AVIA Family of DPSS Lasers The 3.5-mm diameter output beam from the AVIA-X laser was directed through a galvonometer scan head and a 100-mm focal length post-scanner telecentric lens to deliver a focused spot with a calculated diameter of 14 microns at the work surface. Scanner software package was used to control the scanner movement and laser triggering. A comparison of various marking techniques is highlighted in Figure 1. Easily readable marks were produced on plastics at a scan rate of 2000 mm/sec (Figure 2).

Comparison of Marking Techniques
	UV Laser Cold Marking	IR Laser Marking	Pad Printing	Inkjet Printing	Engraving After Moulding	Injection Mould Engraving
Flexible / programmable
Durable, permanent mark
No ecologically unfriendly additives or solvents
No degradation of material properties
No thermal damage
No toxic fumes
Low consumables cost
Low maintenenace cost
Speed	High	High	Medium	High	Low	High
Aesthetic quality	High	Medium	Medium	Low	Low	Medium
Resolution / detail	High	Low	Medium	Low	Low	Medium
Note:   UV = Ultra-violet   IR = Infra-red

Fig. 1 - Comparison of Marking Techniques..

Fig. 2 - UV Cold-Marked Kitchen Utensil.

Cold marking with UV lasers enables materials to be chosen based on their functional properties, with the assurance that high-contrast marks can be produced with a flexible, reliable, non-contact process. Reject rates are reduced, material costs are minimized, and the marking process is made more robust and reliable than for techniques based on longer wavelength lasers. The ability to produce high-resolution marks even contributes to the perceived value of the component by permitting high-resolution graphics or micro-text to be included.

Material	Plastic
Process	Marking and Engraving Ablation-Material Removal