Setting the Mark

Laser marking systems have become smaller and more compact. Photo courtesy of LNA Laser Technology.

Laser marking and engraving is one of the largest laser application segments in terms of units sold to manufacturing industries worldwide. Almost all items manufactured today need to be marked for traceability or branding, and the process is used across a range of industries: medical device, automotive, aerospace, defense, electronics, semiconductor, industrial tools, firearms, secure ID such as drivers’ licenses and passports, and jewelry.

Lasers used for marking can vary in the wavelength spectrum from UV (355 nm) to far infrared (10,600 nm), depending on the material and application requirements. The majority of lasers used for marking in manufacturing fall in the infrared 1-micron (1,064-nm) wavelength, commonly referred to as YAG-type lasers, or the far infrared CO2 lasers. The choice is mainly material-driven. One-micron infrared lasers, called diode-pumped solid-state (DPSS) or more commonly fiber lasers, are used to mark mainly metals and many plastics. Far infrared CO2 lasers are used to process mainly organic materials such as wood, leather, glass, foam, and stone and for some plastic engraving with no contrast.

Shorter-wavelength lasers such as green (532 nm) and UV (355 nm) are reserved for applications requiring high material absorption and low impact on the material to avoid surface alterations such as heat-affected zones, material removal, and recast. Short-wavelength marking and processing applications include solar panels, computer hard disk components, semiconductor components, PCB/flex circuits, and medical devices, particularly implants. In addition, short-wavelength lasers have a smaller focused spot size, allowing for very small marking in certain microapplications.

CO2 lasers are the most mature of the marking laser technologies, and the architecture has remained relatively similar over the past few decades. The applications fields are well-established and include awards and gifts and high-speed packaging across many industries. The biggest changes in technology in this area have come in the 1 μm and under spectrum. Technology trends over the last 20 years have allowed the lasers to become increasingly compact, efficient, and maintenance-free, all at a significantly lower cost.

Fiber laser technology in particular has had the most impact in industrial applications. Fiber laser technology uses an ytterbium-doped fiber-optic cable coupled with single emitter laser diodes. The result is a highly reliable, compact, cost-efficient laser source that eliminates costly components and maintenance needed in previous industrial laser marking technologies.

In a manufacturing plant, a laser marker can be integrated in several ways, including as a turnkey standalone workstation or inline on an existing production line. A turnkey stand-alone system can be a simple manual load/unload system or semior fully automated. Inline system integration can be done in almost any workflow scenario. In either case, it is important to implement recommended safety measures such as enclosures, interlocks, filtered viewing windows, and fume extraction based on the type of laser.

When choosing a laser marker, there are several important factors to consider. They are:

• The material to be marked— metal, plastic, other.

• Desired type of mark—surface, engraved, high-contrast, elaborate.

• Size of parts and marking area.

The choice of laser for laser marking is mainly material-driven. Fiber laser technology is used to mark metals and many plastics. Photo courtesy of LNA Laser Technology.

• Marking cycle speed and time to match production throughput.

Once you have identified these requirements, the laser marking system supplier should be able to determine the appropriate laser features to meet the application needs. The laser characteristics will be critical to the success of the application.

First, the type of laser to be used will be determined based on the material being processed. Next, laser power, in watts, will be chosen. The power level is important in achieving the desired production speed and, in some cases, the engraving depth within a certain time. The size of the area that needs to be marked determines if standard focal lenses can be used or if motion control on the X and Y axes will be needed.

Laser Marking Software

All laser marking systems include software that translates what needs to be marked—logos, alphanumeric text, bar codes, etc.—to the laser beam delivery via an embedded control hardware much like the tool path for CNC machining. The laser software allows importing of vector and raster graphics, generates alphanumeric text like a word processor, and generates 1-D (linear), and 2-D (data matrix, QR) bar codes and serialization of part numbers or other data such as date and lot numbers.

The control hardware allows for communication with external devices such as host networks and PLCs, as well as motion control through the laser marking software.

Why Laser Marking?

The most common competing marking technologies are inkjet and mechanical dot peen marking products, although others are pad printing and electro or chemical etching. Inkjet offers high-contrast marking, high speed particularly for on-the-fly applications such as in the packaging industry, flexibility in integration, and a lower initial investment; however, the mark quality is low, impermanent, and the cost of consumables and maintenance downtime may offset the lower initial cost.

Dot peen systems are also highspeed, flexible to integrate, provide permanent marking depth, and have a lower initial cost, but the mark is low-contrast. The high impact exerts mechanical stress on the material, which can be noisy, and they require frequent maintenance to change tools.

For a higher upfront investment, laser marking technology offers high speed, high contrast, permanent markings, flexible integration, flexibility for part variations such as curved or nonuniform surfaces, noncontact, high quality, and little maintenance.

www.lnalaser.com