Laser Marking Fundamentals and How to Use a Laser Marking Machine
Laser marking can be used for marking or processing various types of materials. There are also several different marking and processing methods. However, the appropriate laser marking system and peripheral equipment vary depending on the material and desired marking or processing method. The laser light being used can also vary. This section introduces basic knowledge required for performing laser marking.
- What is laser marking?
- Laser marking on metal
- Laser marking on plastic
- Laser marking on other materials
- Processing with a laser marking machine
- How to use a laser marking machine
- Laser marking machine types and features
- Laser marking videos
What is laser marking?
Laser marking is a marking method that uses a focused laser beam to alter the surface of a target.
The laser beam is emitted by an oscillator and scanned using a mirror (known as a scanning mirror), and a focusing lens is then used to focus the beam on the target and mark it by altering the surface.
Because laser marking involves using light to change the target surface, this method is more resistant to abrasion than ink-based marking, and the marking does not fade over time.
Laser marking on metal
Laser marking can be performed on metal through black-annealed marking, where the laser causes oxidation; white marking, where the laser is used to scrape away the target surface; and engraving, where the laser is used to carve deep into the target surface. Each method is used for a specific purpose. This section explains the characteristics of each method.
Black-annealed (oxidation) marking
When the laser beam is applied to the marking target, the focus is shifted so that only the heat will be conducted. Applying heat without engraving the target forms an oxide film on the surface. This film appears black and represents black marking.
White etching marking
The laser beam is applied to the marking target at the focal point. The metal surface is slightly removed to expose an uneven surface. This cause irregular reflection of light to create marking that appears white.
Laser light irradiates the focal point and etches the surface of the target for marking. A deeply engraved impression can be made by increasing the amount of engraving by increasing the laser irradiation count.
Laser marking on plastic
There are three patterns for marking on plastic using a laser: Foaming, where the laser causes bubbling; chemical change, where the laser reacts with the pigments in the plastic; and carbonization, in which a high-energy laser is applied to the target surface.
When the base material is irradiated with a laser, bubbles are generated inside the material. These bubbles are sealed under the surface layer of the base material, causing them to appear white. Foaming is more visible on darker base materials.
As the laser light reacts with the metal ions in the base material pigment, a chemical change occurs, resulting in color development. The appearance varies depending on the color and material of the target.
When high energy is continuously applied to an area, macromolecules of the element around the base material are carbonized and turn black. The polycarbonate material shown on the right is transparent but produces a beautiful black color when carbonized.
Laser marking on other materials
Laser marking can also be used for marking materials other than metal and plastic. For example, in addition to ceramic, paper, and wood, laser marking can be used on various transparent and translucent targets. Laser marking can also be used on targets with a surface coating that can be peeled off to reveal the underlying base material or painted surface.
Processing with a laser marking machine
Laser marking can be used for various processing applications such as cutting, drilling, and surface reformation in addition to marking. High-accuracy processing of target areas is possible by scanning the light to the desired shape.
During cutting, the laser light is scanned to the specified location to cut the desired shape. In addition to easily cutting complicated shapes, this process can also be used for removing gates and burrs or other purposes.
In this process, the laser light is used to remove a target’s surface material, such as paint, film, or plating. Surface reformation also changes the wettability of the surface material to increase the bonding strength and prevent any paste from flowing out.
Laser-based drilling uses laser light to irradiate a single point of a target to drill a hole through melting and evaporation. Controlling such factors as the size and power of the laser light makes it possible to drill holes as necessary for the application.
How to use a laser marking machine
Laser marking requires not only a laser marking machine but also a device for setting the marking target in the correct position.
Laser marking machines are available as stand-alone systems, where targets are set and marked one at a time; indexing systems, where several targets are positioned separately for marking; and inline systems, where targets are marked during transportation. This section introduces the features and applications of each system type.
With a stand-alone laser marking system, targets are placed one at a time on the stage for marking. This type of system is best for use with targets of various sizes and shapes requiring frequent tooling changes such as height adjustment.
System specifications can be customized to include automatic stage lifting/lowering and foot switches for starting marking.
Indexing systems include a positioning device that moves targets placed on a turntable to the marking position.
With this type of system, marking can be performed toward the back while targets are being placed toward the front, allowing for shorter cycle times than stand-alone systems.
Inline systems are suited for marking while a target is being transported along a production line.
In certain situations, marking is possible without stopping the target, but other situations require the target to be stopped.
The ability for inline systems to mark targets on a production line makes them indispensable for mass production.
Laser marking machine types and features
There are various types of laser marking machines available, each with different laser wavelengths, and each best suited for different materials and applications. This section introduces the features and applications of the typical types of laser marking machines: fiber laser marking machine, UV laser marking machines, and CO2 laser marking machines.
Fiber Laser Marking
Fiber laser marking machines have a 1090 nm wavelength, making them IR (infrared) lasers. Fiber lasers can mark a wide range of materials, though they are optimized for metal marking applications. Their high power makes them perfect for annealing and engraving applications, but they cannot mark transparent objects since IR light passes straight through.
UV Laser Marking
UV lasers use a highly absorptive wavelength (355 nm) to mark parts. This high absorption rate allows UV lasers to perform "cold marking," ensuring that no extra heat stress is applied to materials, including those with high reflectance such as gold, silver, and copper. This minimizes soot and burrs caused from typical marking and processing.
CO2 Laser Marking
CO2 laser marking machines have 10x the wavelength of standard wavelength systems. They're great at marking paper, resins, wood, rubber and transparent materials (like glass and PET). However, it's nearly impossible to mark metal with a CO2 laser marking machine because the laser light is not absorbed.
Laser marking videos
These videos show laser marking on various materials and products.
Learn about the different finishes created with each application and the takt time required for marking.
- MD-F Rotational Marking
- Watch a KEYENCE MD-F laser precisely mark a rotating dial around a 360 degree circumference.
- MD-F Z-Map Demo
- Watch how a KEYENCE MD-F laser utilizes an STL file to precisely mark a 3D profile.
- ML-Z Radiator
- Watch a KEYENCE ML-Z laser mark a radiator.