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Laser Marking Technology: Mechanism and Quality Characteristics

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If you attend trade shows or are regularly visited by traveling sales professionals, you have likely encountered your fair share of laser-engraved promotional items. Similarly, many of the everyday products and manufacturing components you encounter may have been marked with a laser. After all, lasers are commonly used to mark products and raw materials in industries of all kinds. According to Coherent, lasers are widely used in the automotive, electronics/semiconductor, aerospace, medical, consumer product and food/beverage industries to mark and engrave materials.

Modern laser marking systems are capable of precisely marking any number of materials including plastic, glass, metal, wood, leather, ceramics, and painted surfaces. Common forms of laser marking include alphanumeric codes that indicate lot numbers, expiration dates, and other product information.

Benefits of Laser Marking

Laser marking is far superior to other forms of marking, both in terms of quality and flexibility. Some of the benefits of laser marking include:

  • Precision
  • Automation
  • Permanent marks
  • Efficiency
  • Versatility
  • Non-contact marking
  • Computer controlled movement
  • Precise beam positioning
  • High speed laser marking
  • Consistency

Laser Marking Mechanism

Laser marking technologies use several mechanisms. In general, material is either vaporized, melted, or annealed. Laser marking processes include:

  • Vaporization - Vaporization produces a mark by vaporizing material, much like engraving. Thin layers of material can be removed using controlled vaporization.
  • Carbonization - Carbonization involves using photo-thermal or photo-chemical reactions to melt the material, thereby changing its color.
  • Material fusion / surface modification - This process involves destroying the material, which leaves a dark mark with minimal surface penetration.

Two main methods are used: mask marking and beam deflected marking. With mask marking, a stencil is projected onto the material. With beam deflected marking, the laser beam is deflected through a system of mirrors and lenses while computer software controls the mirrors.

These two different methods have their pros and cons. For example, while mask marking allows for high speed laser marking, it is time consuming to produce a mask. Mask marking is typically used for high volume production. On the other hand, changing patterns is easy with beam deflected marking because the patterns are produced using software. However, beam deflected laser marking systems tend to be more expensive.

Quality Characteristics of Laser Marking Technology

Laser marking technology produces high-quality laser marks. To assess the quality of laser marks, it's helpful to know what characteristics to look for. In general, the following laser marking characteristics are used to judge quality:

  • Contrast - Contrast refers to the brightness difference between the marked and unmarked surface of the material.
  • Width - Width refers to the width of the line segment that forms the basis of a character.
  • Depth - Depth refers to the depth of the marked surface. It depends on the material used, energy density, and beam and material interaction time.
  • Scattering - Scattering is an undesirable characteristic where droplets of surface material have scattered around the mark.
  • Microcracks - Microcracks are also undesirable as they could cause metals to corrode and could affect mechanical properties.

Laser marking technology is widely used to mark products in various industries, but there's not a one-size-fits-all solution. Start by determining which laser marking methods are appropriate for your application and then evaluate the quality characteristics of the systems you are considering.

Sources:

"Laser Applications" Coherent, http://www.coherent.com/Applications/

"Anaylsis of the Laser Marking Technologies", Revtn.ro, http://www.revtn.ro/pdf4-2008/4-Han_A.pdf

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