What is Fiber Laser Marking?

Lasers have made a lasting mark on modern manufacturing- literally. 

Technological advances in solid-state laser technology allow manufacturers to set permanent marks into parts with extreme precision. Processes such as laser cutting, laser engraving, color marking, and others are possible thanks to the advent of the fiber laser and the fiber laser marking machine. These processes are popular in both amateur workshops and dedicated manufacturing facilities, and marking is only possible thanks to laser marking systems--but what are fiber laser systems, and how do they work? This article will explore what a fiber laser marking machine is, how it functions, its advantages and disadvantages as a manufacturing process, and finally its industrial applications in modern industry. 

In general, laser engraving is the most subtractive manufacturing process, followed by laser etching, and then laser marking. Fiber laser engravers produce deep-set grooves that maintain their fidelity through extreme conditions and can be fine-tuned to the user’s desired depth. Laser etchings are shallow marks and include so-called laser ablations in which a top coating is lasered off, exposing the underlying material.

Laser marking is a category of its own, as it removes no material but changes its surface properties. The four most common reasons for marking a material are for:

• Annealing: changing the mechanical properties of the material in the laser’s path (this is typically performed with metals)
• Carbon migration: carbon at the material/laser interface chemically bonds to its surface, creating permanent black markings.
• Coloring: specific-colored marks made by heating the underlying material (ex. Titanium can become any desired color given a specific temperature is reached)
• Foaming: creating marks lighter than the underlying workpiece (only possible with plastics)

Most laser marking systems have the capacity to perform engraving, etching, and marking, so this article will not differentiate when speaking about specific models/specifications. However, understand that each term is not synonymous.

Regardless of the type of laser marking system, the chosen laser machine will employ uv lasers, CO2 lasers, and/or fiber lasers. This article will focus on the fiber laser, as it is a good balance between power, speed, and affordability, but know that other types are available. 

Fiber lasers emit high-intensity light at wavelengths that are hundreds to thousands of nanometers in length, placing them somewhere between ultraviolet and infrared wavelengths (typically invisible to the human eye). For fiber lasers specifically, wavelengths of 1030-1090 nm are often chosen as those wavelengths correspond to ytterbium-based fiber lasers and provide the best results on metals. This contrasts with CO2 lasers, which generate high-intensity light at thousands to tens of thousands of nanometers that is more suited for organic materials.

To explain the basic operating procedure of a fiber laser marking machine, the next section will detail how fiber lasers work and how they can produce extremely high-quality marks.

Laser is an acronym that stands for Light Amplification by the Stimulated Emission of Radiation. To briefly summarize without going too far into the particle-physics-weeds, lasers are set up so that the following steps occur in succession to produce superheated beams of light:

1. Photons from a light source (or laser diodes) stimulate a material (in our case, ytterbium), heightening the energy state of its electrons.
2. As the electrons change energy states, they absorb the incoming photons. 
3. More photons from the original light source come along and knock the electrons back down to their ground state.
4. When the electrons return to their ground state, they emit more photons.
5. These photons are “corralled” back towards the electrons and cause an exponential generation of photons via steps 1-4.
6. These photons are directed so that their wavelengths fall in sync, forming a coherent, focused beam of light which is then amplified further and directed to the output of the laser. 

Note this list is highly simplified, but it hints at the most important aspect of this process- the fiber optics.

The optical fiber is built with an outside cladding with a low refractive index and an inside core with a high refractive index. The difference in refractive indices causes the light beam to concentrate in the core, where the desired photon cascade occurs. Rare earth elements are used to dope the inner core, as these elements emit discrete wavelengths not found in more common elements. In our case, Ytterbium is doped in the core material because its electrons emit a specific and discrete wavelength that produces high peak power. Additional parts of typical fiber lasers are combiners, amplifiers, master oscillator, gain fibers, etc. but know that all these components work to increase, isolate, and coalesce the signal into a coherent laser at the output.

Fiber Laser System 

Laser marking machines program a fiber laser beam to emit onto a workpiece in a specific path, allowing for all kinds of desired markings. It is difficult to generalize the setup of every fiber laser marking machine.

The X and Y galvanometers accept precise electromechanical movements from a programmable microcontroller. The lens focuses the incident laser beam onto the workpiece, while the galvanometers move the laser in X-Y coordinates based on the user’s design. This setup allows the user to create a design, load it into the microcontroller of the marking machine, and execute the command autonomously and at high speeds. 

Advantages of Fiber Laser Technology

Below is a short list of some of the benefits of fiber laser systems:

• Fiber laser technology provides high contrast marks that can survive sterilization, chemically corrosive, and/or other extreme environments
• Fiber laser marking is a no-contact solution, and requires little to no maintenance over long periods of time
• Fiber laser markers provide high speed marking, are compact, can be easily deployable, require no recalibration, and offer low error
• Production is cheap, reaches  faster speeds, waste-free, energy-efficient, and requires no additional resources apart from the workpiece

Disadvantages of Fiber Laser Technology

Below is a brief summary of some of the considerations and limitations of fiber laser systems:

• Laser marking only works in 2D applications
• Fiber laser marking machines have a high initial investment cost
• Materials with high hardness, low ignition points, and other unsuitable characteristics cannot be used, limiting election
• Fiber laser marking machines come in a variety of sizes and arrangements, with some suited towards use with an exclusive process

Automotive industry

• Parts traceability (country of origin, serial numbers, barcodes)
• Dashboard markings/buttons

Integrated Circuitry

• Tiny graphics and texts on ports, connection points, etc.
• Non-contact ablations to reveal underlying IC layers

Electronics industry

• Thin metals manufacturing/marking
• Exceptionally clean and aesthetically pleasing markings, logos, text, etc.

Medical industry

• Acid, corrosion, high temperatures, and sterilization resistant printed labels
• Traceability for LIS, hospital databases, biofluid storage, medical devices, etc.

Jewelry industry

• Text/graphics inscriptions into rings and necklaces
• Gem cutting/engraving

Food industry

• Packaging labels, text, graphics, etc,
• Cans, bottles, container labeling

General Manufacturing

• Burr removal
• Non-industry specific custom metal marking finishes