What is Laser Engraving?

Laser engravers have been used in manufacturing to produce permanently mark for decades. Since the pulsed fiber laser was developed and gained traction as a marking source in the mid to late 2000’s there has been significant demand for this technology. These pulsed fiber lasers combined with CO₂, Nd:YVO₄, picosecond and femtosecond lasers offer a solution for almost every material. Today, laser engraving provides a cost-effective, high-speed, high-quality solution for many markets and countless applications, driven by the need for tracking and traceability.

How does a Laser Engrave

A laser can create a permanent engraved mark on a wide variety of materials including metals and plastics. As the name suggest laser engraving removes a small amount of material. If the process requires no material removal, laser marking can be used.

There are two types of laser engravers;

Laser Plotters – use gantry style motion where the focus head is mounted on xy axes. The fixed focus head moves from side to side across the entire width of the engrave while incrementing in the other axis to create the engrave. The advantage of the system is that a large area can be processed, typically 2ft x 2 ft or more. However, the system only uses CO₂ and “continuous wave” fiber lasers that limits the range of materials that can be engraved. Also, the plotter is very slow, as it must traverse the entire width turning the laser off and on, so there can be a lot of “wasted” motion over sections that are not engraved. Also, the gantry style motion has a large footprint. These laser plotters are not used on production lines, rather in standalone operation as engravers of organics, while offering the dual purpose operation of cutting thin materials.

Laser Scan Head – motion is provided by compact scan head that contains two mirrors mounted orthogonally to each other to enable xy motion. The mirrors are mounted to small rotary motors where rotary motion over a distance translates to linear motion. See figure x. As the motors move very small distances, marking speeds are very high. The two mirrors direct the laser through a focus optic known as an F theta lens. The F theta lens provides focus over an area, not just a single point. The engrave area known as the “field size”, is typically 6” x 6”, and can be adjusted by changing the focal length of the F theta lens. While the laser scan head does not have the working area of a plotter it can mark extremely quickly, use any laser source, and is extremely compact. These systems are ideally suited to either production lines or standalone operation.

Laser engravers are extremely flexible capable of creating any mark; alphanumerics, machine readable codes (e.g. DataMatrix codes), graphics and logos with high resolution and quality. The process is non-contact process, does not require any consumables, and is used across every manufacturing industry.

Lasers for Engraving

Pulsed Fiber	Pulsed fiber lasers operating around 1 micron are well-matched to the absorption characteristics of most metals, generally making them the first choice for engraving of these materials. These lasers offer a cost-effective engraving solution with low cost of ownership, high reliability, long lifetime, excellent beam quality, and ease of implementation. Two main variants of the pulsed fiber laser markers exist; Q switched and MOPA (master oscillator power amplifier). The Q switched version provides nanosecond pulses with a pulse shape, pulse width and peak power as a function of the frequency. The MOPA offers more flexibility, able to customize and select pulse shape, duration and peak somewhat independent of frequency.
CO₂	CO₂ lasers output in the far infrared, around 10 microns, that aligns well with organic materials and plastics. This makes them ideal for engraving wood, and plastics. For plastics, the typically non-contrasting engraved mark is read using ambient or additional lighting that interacts with the engrave depth “creating” contrast to the base material.
Nd:YVO₄	Nd:YVO₄ or vanadate lasers are diode-pumped solid-state lasers (DPSS) provide the best mark engrave due to excellent beam quality, and very short pulses (<20ns) with high peak power (>20kW).
Picosecond and Femtosecond lasers	When absolute precision for both the depth and quality are needed these lasers provide the ultimate control and resolution. Using very short pulse durations, microns of material can be removed at a time, enabling precise mark depths.

What Materials Can Be Engraved with Lasers?

Lasers can engrave many materials, with the selection of laser depending on mark resolution, quality, contrast, and budget.

Plastics: Almost every plastic can be engraved using either a CO₂ laser, nanosecond fiber laser or Nd:YVO₄ laser. Common materials include nylons, PET, polycarbonates, polyethylene, polypropylene, ABS, and the list goes on! In many cases the mark needs to have contrast and depth, this can usually be achieved using a pulsed fiber or Nd:YVO₄ laser.

Metals: A wide variety of metals can be engraved including stainless steels, carbon steels, aluminum, nickel, and titanium. These types of applications can be in automotive, aerospace, firearms, and consumer goods markets. The laser can quickly and efficiently remove material to a precise depth. The flexibility of the laser is such that material removal can be controlled and optimized similarly to a machining operation. For example, at the start of the engraving process the laser uses high power to remove larger amounts of material, then when getting near to the required depth can remove less material to provide a high resolution, quality engrave. In some applications a finishing pass can be made to provide a contrasting mark at the bottom surface of the engrave. For metal engraving high power laser markers are recommended, typically 50-100W, have sufficient power to deliver engrave depths with fast cycle times.

What are the benefits of Laser Engraver with scan head

There are many benefits of laser engraving -

Non-contact process – there is no mechanical force on the part
Permanent – for additional wear resistance the engrave depth can be tailored to last as long as the lifetime of the part
Easy to use, simply line integration – simple software makes use and integration plug and play
No consumables – a green process with no inks, stylus or other to replace
Extremely reliable – laser engravers have been around for decades and are extremely robust
Long lifetime – typically ten of thousands of operation hours, for example pulsed fiber lasers can last well beyond 50,000 hours of operation
Engrave alphanumerics, machine codes, graphics and logos
Flexibility – dynamically size the mark, single or multiple parts, stationary or on the fly, custom serialization, database incremented codes, you name it, it can do it!