Beam-steered Nd:YAG (Neodymium:Yttrium Aluminum Garnet) laser marking provides a unique combination of speed, permanence, and imaging versatility in a noncontact marking process. Laser marking can generate considerable savings in reduced manufacturing and tooling costs; elimination of secondary processes and consumable disposal; and reduced inventory expense, quality-control costs, and maintenance downtime. Laser marking frequently improves the aesthetic appearance of the marking image, thereby increasing the product’s perceived value.Of all materials, plastics are the most challenging in terms of the laser’s interaction with the material and the required https://www.nahls.co.jp/ image quality. The wide variety of material chemistries and colors and the aesthetic requirements of most plastics applications require special consideration in both material chemistry and imaging techniques. The successful implementation of laser marking technology requires a working knowledge of the laser marker’s function and capabilities and a committed, team approach by the user.

Marking Fundamentals

Laser marking is a thermal process that employs a high-intensity beam of focused laser light to create a contrasting mark on the material surface. As the target material absorbs the laser light, the surface temperature increases to induce a color change in the material and/or vaporization of material to engrave the surface.Beam-steered laser marking employs mirrors mounted on high-speed, computer-controlled galvanometers to direct the laser beam across the target surface. Each galvanometer provides one axis of beam motion in the marking field. A multi-element, flat-field lens assembly subsequently focuses the laser light to achieve high power density on the work surface while maintaining the focused-spot travel on a flat plane. The laser output is gated to blank the beam between marking strokes.Marking can be accomplished at speeds of up to 5000 mm/sec with positioning speeds between marking strokes of 50,000 mm/sec. Because the process relies on heat conduction into the plastic, marking speeds are usually slower than the system’s maximum capability to allow sufficient conduction to achieve the desired results.The beam-steered marker can duplicate virtually any black-and-white image, including variable line widths and images as small as 0.0001 inch. Present computer-imaging technology produces highly intricate graphics with line widths, resolution, and accuracy well below 0.001 inch. Because the image is created by “drawing” with the laser beam, the marking time is dependent on the amount and complexity of the text and graphics. With computer-generated imaging, any graphic element or the entire marking program can be instantly changed before a new part is positioned for marking.Nd:YAG lasers amplify light of 1.06mm wavelength in the near-infrared. They are unique among the different types of lasers in that they operate much like an “optical capacitor.” In pulsed operation, the Nd:YAG laser stores energy between pulses, resulting in peak powers of kilowatts of light energy. A Nd:YAG laser emitting 75 watts of continuous light, pulsed at 1 kHz, emits a train of pulses with peak powers of 110,000 watts. The “optical capacitor” effect provides the peak power necessary to vaporize material. For plastics applications, the laser must also be run in a “top hat” mode, where the power distribution is fairly even across the cross section of the laser beam in order to eliminate “hot spots” in the marking path.The beam-steered Nd:YAG marker frequently replaces acid and electro-etch systems, stamping and punching systems, and those other marking systems that permanently mark products by imprinting or engraving. It also replaces other, less permanent printing systems, including ink jet.