Laser marking uses a low-power laser beam to leave lasting marks on materials. This is achieved by changing the appearance of the material using material oxidation. During this process, the material surface remains intact and the final mark is clean and defect-free.
Engraving, on the other hand, removes material by evaporation. Using a high-power laser beam to remove the outer surface of the material, it can be engraved to a depth of 0.020 inches in metal (but 0.125 inches in materials such as graphite).
Laser marking is commonly used for logos, barcodes, QR codes and other text markings on plastics and metals, while laser engraving is used on metal, thermoplastic, glass, leather and wood surfaces. Some machines can both mark and engrave, while others are dedicated to one or the other.
Types of laser marking and engraving machines
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There are four types of laser marking and engraving machines. Some are suitable for marking and engraving, while others focus on one of the two:
Designed as a practical solution for marking plastics and glass, UV lasers can engrave a wide range of materials, from metal to paper.
These lasers are designed for high-density and low-density polyethylene and synthetic fibers, making them suitable for laser engraving applications where product surface protection is required.
The most popular type of laser for marking and engraving. A fiber laser is a solid-state laser with a very small focal diameter and much greater intensity than a CO2 system.
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These are ideal for permanent marking, including serial numbers and barcodes. Additionally, because they can produce strong laser marks with extremely small focal lengths, they are ideal for metal engraving (including coated metals) and high-contrast plastic markings.
Although one of the first gas lasers to be developed, CO2 lasers remain one of the most useful types and are the highest power continuous wave lasers currently available.
Modern CO2 lasers generate a laser beam in a sealed glass tube filled with gas (usually carbon dioxide). The high pressure then passes through the tube and reacts with the gas particles, increasing their energy and producing light.
CO2 lasers are commonly used for cutting and welding. Low power CO2 laser marking machines are more suitable for non-metallic materials and plastics.
YAG lasers, often referred to as flash lamps or lamp-pumped lasers, utilize a lamp (bulb) as the pumping mechanism and a crystal as the gain medium. Both are located in optical resonators that reflect light and help generate laser light.
Although widely used throughout the manufacturing industry, bulbs are becoming obsolete due to their short lifespan and frequent replacement
Advantages and disadvantages
Compared to other laser wavelengths, UV lasers require much lower power to produce clear marks and absorb better by almost all materials. Also, unlike other marking and engraving techniques, there is no long downtime, which means the process is - often - very quick and easy.
Marks produced by UV lasers are essentially tamper-proof because they sit below the surface of the material and the material does not come into direct contact with the laser marking equipment. This allows for clean operation and minimal contamination. It is because of these capabilities that UV lasers are frequently used in the medical and pharmaceutical industries.
Fiber lasers are ideal for marking difficult materials such as gold and nickel plating, plastics, PCBs and other sensitive materials and layers. They can also be used for deep engraving and annealing smoothing of medical devices.
Fiber lasers are suitable for deep engraving when combined with a high power master oscillator power amplifier (MOPA). MOPA will increase the peak power output of the laser and optimize beam quality for precise marking and deep engraving.
Overall, fiber lasers are high-performance, reliable and often compact compared to other laser marking and engraving machines.