Laser marking, also known as laser coloring, charring or laser dark marking, is achieved when a laser beam alters the surface of a material. A low-power beam is required to accomplish this slight alteration of the surface. High contrast marks can be created by laser marking without damaging the material. When laser marking plastic surfaces, it can be called "charring", while annealing is often used for laser marking metal. There are four main types of laser marking.
Laser foaming is when a laser heats a polymer, causing it to melt and form foam-like bubbles. This process is commonly used in packaging materials and the automotive industry.
Laser annealing is commonly performed on metals such as steel, titanium, and stainless steel. First, the metal surface is heated by the laser beam, causing the oxygen below the surface to diffuse. As a result, the metal begins to oxidize internally, and once it cools, the oxidation causes a color change.
Laser Carbon Migration
Carbon migration is used for metals and metal alloys. The laser beam forces the carbon to migrate to the surface of the material, creating dark marks.
Laser coloring is used on plastics and metals. Heat specific parts according to expected results. Change the pulse frequency and width of the laser to produce different colors and tones. This means that lasers used in color laser marking processes must have a wide range of power levels, frequencies and speeds.
What is the laser engraving process?
Laser engraving involves physically removing material from the surface of a workpiece using a laser beam. This process exposes a cavity that shows the image to the eye. The engraved image can also be felt by hand.
The laser beam generates intense heat, which causes the material to evaporate. This is usually done quickly, as the material is vaporized with each pulse. Deeper markings can be achieved by repeated passes. Laser engraving is considered a subset of laser marking. Still, it's ideal for creating some personalized or custom projects for emotional or commercial purposes. It's also the fastest way to make marks with a laser engraver.
Laser engraving is not ideal for marking safety-critical components. The maximum engraving depth for laser engraving is also typically 0.020 inches, although depths of 0.125 inches are possible in some materials such as graphite. The laser engraving process offers a variety of options as engraving can be done on a wide variety of materials, including but not limited to plastic, wood, leather, metal, glass, and more. Laser engraving is more legible and offers more font options than traditional engraving on small items like jewelry. Laser engraving also has less chance of product damage or deformation.
What is the laser etching process?
During laser etching, the laser beam is pulsed, releasing sudden bursts of energy at specific time intervals. A 100-watt pulsed laser can deliver 100,000 pulses in one second. Each pulse contains one millijoule of energy and can reach a peak power of 10,000W.
Because lasers require less energy to etch a unit area of metal than to engrave, the pulses are farther apart. When the beam hits the surface, the material absorbs its energy and converts it into heat. Although the metal reflects most of the energy of the beam, it also absorbs some of the energy and converts it into heat. With laser etching, the material absorbs just enough energy to melt its microsurface and expand.
When the energy of the beam is converted into heat, the temperature of the material increases. At such high temperatures, the surface becomes malleable, so the shape changes. The surface changes locally as the material melts and cools in milliseconds. Surface roughness changes, creating permanent marks. The surface roughness is then permanently altered. Color changes occur due to different patterns on the surface of the material. For high-quality markers, black and white provide the best contrast. Of course, the laser etching process is tuned for each application, so it is slightly different.