Current industry regulations require parts to have clear, legible markings, thus increasing the popularity of laser marking. Previous industrial trends required manufacturers to use traditional engraving or screen printing processes to mark surfaces. These processes were non-permanent, costly, and often resulted in part defects.
However, the introduction of laser marking now allows engineers and manufacturers to create numbers, images, or characters without compromising part quality. Instead of using physical tools to etch surfaces, this technology uses a focused laser beam to create easily readable, non-damaging marks.
Laser marking is a versatile process that includes various techniques such as engraving, etching, foaming, and carbon migration. The correct marking method depends on your materials and quality requirements. Read on as we discuss the details of this innovative technology.
What is laser marking and how does it work?
Laser marking is a process that uses a focused beam of light to create permanent marks on the surface of a target component. This process is typically performed using a laser machine that employs an oscillator, scanning mirror, and focusing lens.
This machine also allows for automated and high-speed processing, leaving permanent, traceable marks on a variety of materials. Laser marking allows for the marking of parts and products with:
Text, including part numbers and serial numbers;
Machine-readable data, such as unique ID codes, 2D data matrix codes, barcodes, etc.;
Images.
Innovation Center Laser Marking Method
Laser marking technology creates durable marks on the surface of a part by generating a focused beam containing a high energy level. A mirror is used to release the accumulated energy into a coherent beam directed at the material surface.
As the beam interacts with the part surface, heat energy is transferred from the beam to the surface. Therefore, the appearance and properties of the material change. Depending on the energy level, the laser can engrave, etch, anneal, or discolor the surface with great precision.
The focused beam is aimed only at specific areas on the material, ensuring precise, high-contrast, and high-quality markings. These marks are permanent, and you can easily read or scan them on any surface. Therefore, this marking process is ideal for operations where durability and accuracy are critical.
Evolution and History of Laser Marking
Laser technology originated with Albert Einstein in the early 1900s and further developed with the invention of the first CO2 laser in 1964. Peter Houldcroft of the Cambridge Welding Institute (TWI) pioneered the first commercial application of laser materials processing. The earliest applications of "laser processing" were driven by manufacturers of automotive and aircraft parts.
To improve computer engraving, Electrox developed the first commercially available axial-flow CO2 laser machine as the primary source for laser marking systems. Technological advancements in the 1980s and 1990s led to the integration of computer systems into laser marking. More efficient and modern fiber lasers were introduced in 2001 and have continued to improve since.
Today, laser marking machines are more advanced, accurate, fast, and environmentally friendly. More versatile and cost-effective laser marking technologies are now available to create high-quality, durable marks directly on the surface of parts. These technologies are faster, more compact, and can create marks on a wider range of substrates.
Because of the more powerful and flexible systems, users can create consistent markings on a large number of products. Therefore, they can achieve their business goals in a short time and at a lower cost.
Types of Laser Marking Technologies
There are various laser marking technologies suitable for different applications. Each technology has its advantages and disadvantages, and your choice will depend on your budget, quality requirements, and application. Let's examine some of these technologies.
Laser Engraving
This process involves using a laser beam to remove some material from the surface of a component. During this process, the material absorbs the heat of the laser, melts, and evaporates, creating a recessed mark. The material also reacts with the air, causing a color change that makes the mark more unique.
Laser engraving does not involve consumables. Therefore, it has lower operating costs compared to other engraving methods that use special inks or drills. Lasers are suitable for a variety of materials, including metals, plastics, and ceramics. Therefore, engineers use it in many different applications.
laser etching
This highly versatile process creates markings on a workpiece by melting its surface. A laser beam produces raised marks by directing a large amount of energy to a small, localized area. As a result, the surface melts and expands, changing color to black, gray, or white.
Etching is commonly used to create permanent markings such as serial numbers, data matrix codes, logos, and barcodes. It is also a versatile process applicable to a wide variety of metals, including aluminum, lead, steel, magnesium, and stainless steel.
Laser Annealing
In laser annealing, a laser beam locally heats the surface of a material to create a mark. The beam penetrates only 20 to 30 µm into the material surface, resulting in very little surface change. This localized heating causes the material to discolor. Depending on the temperature of the heated layer, the mark can be black, red, yellow, or green.
The result of laser annealing is a permanent, wear-resistant mark. Laser annealing works best on ferrous metals and titanium. Therefore, it is used in a wide range of industries, from healthcare to automotive, food and beverage, and aerospace.
Carbon Migration
In this method, thermal energy from the laser breaks down the bonds in the plastic, releasing oxygen and hydrogen. This reaction causes the target area to darken, resulting in a gray to bluish-gray mark. Carbonization, or carbon migration, has always been ideal for marking synthetic polymers and organic materials.
It is suitable for paper, wood, leather, packaging materials, etc. However, carbon migration is less suitable for dark-colored objects. The resulting gray mark has low contrast with the rest of the workpiece, making the mark difficult to read.
Foaming
When you need to create light-colored markings, carbon migration may not be very helpful, but foaming is better suited for such applications. The process involves heating the surface of the material with a laser, melting it and creating bubbles. As the bubbles oxidize, they form a foam that reflects light.
This method is one of the best marking options for dark-colored components. This is because the markings are raised above the component's surface, providing a higher contrast with the rest of the surface. It is also ideal for marking polymers.
Discoloration
In this technology, a laser removes a layer from the workpiece, exposing the underlying layer. The removable material absorbs heat from the laser and evaporates, creating contrast. Therefore, it is crucial to ensure that the color of the topcoat differs from the substrate color.
This method is more effective for coated materials such as anodized aluminum because it displays excellent and clear markings. Other materials suitable for color-changing are laminates, films, and foils. It is an excellent technique for marking labels, accessories, and packaged items.
