Laser technology is well suited for the marking of metals and non-metallic materials, such as paper, cardboard, wood, glass and polymers. The advantages of laser marking are: contact-free process, long lasting marking, speed, accuracy and flexibility. Marking techniques can be separated into three categories: vector marking, masked marking and dot matrix marking. In vector marking the beam is steered by mirrors and the figure is formed by drawing lines. In mask marking the laser beam goes through the slots in a mask and the shape is marked onto the work piece. In dot marking a pulsed beam is used to produce numerous dots, each representing a single pixel of the final marking.
Marking of materials can be achieved by scribing, material removal, color change or with a foaming technique. In scribing the material is vaporized, which leaves a colorless mark. Coated materials can be marked by selectively removing the coat. In this method the laser is only used to remove the surface material and does not react with the underlying base material. In the color change technique the color pigment in the material reacts with the beam, which results in a permanent color change. In foaming the work piece is melted locally, which produces small gas bubbles. The marking is seen as color change and material swelling.
Metals are usually marking with the Nd:YAG laser. The most often used laser for marking non-metallic materials is the CO2-laser, but the fiber and the Nd:YAG-lasers are also suitable. Existing marking applications can be found for example in grocery packages, product information labels, keyboards and ornaments.
Laser marking