LASER MARKING: Choosing the best laser for your application

Thinking- Laser marking: Choosing the best laser for your application

Today there are many different types of marking lasers that can mark all materials. Up until a few years ago, there were limits in terms of quality and range of markable materials, but this is no longer the case.
You can find the right laser marker based on the type of material and the expected result.

Given this wide range of possibilities, picking a suitable laser is not an easy task and can be a challenge for many operators in the industry. In this article, we will try to clarify what to keep in mind when choosing the right laser marker for our needs.

First of all, we need to understand the laser characteristics and the material properties of our components.

The main parameters to consider when choosing are: the type of material, themarking quality, the aesthetic to be achieved and the speed. In the case of stand-alone laser markers, speed is identified with cycle time. Cycle time is the time it takes for a component to complete its entire marking path, from its introduction into the system to the (if any) reading of the 2D code.

Among those lasers you have most often heard of are Fiber, Wave, UV and, of course, CO2 lasers. Each of these adapts to one material more than another. In general, we know the Fiber laser for its total effectiveness on metals. The Green Wave laser is more suitable for plastics, like the more famous UV laser. The CO2 laser is the most widely used for marking organic materials. Within the Fiber category, there are also technological alternatives suitable for particular applications. We are talking about the MOPA laser and the Picosecond laser. We will discuss them in more detail at the end of this article.

It is important to understand how the material to be marked absorbs laser light at the wavelength of the laser itself. Ferrous and non-ferrous materials have excellent absorption at 1064 nm, while precious metals do so at 355 and 532 nm. Plastics also absorb the higher wavelength laser output.

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Laser technologies

The Nd: YAG laser was introduced to the market almost 30 years ago and is perhaps the most famous and well-known in the industry. This is because of the large number of applications it covers. Originally, these lasers were lamp-pumped. They later evolved, replacing lamps with diodes. Diode-based systems are robust with an excellent expected service life. An advantage of Nd: YAG lasers is their laser beam quality. This is due to the smaller spot size. This, along with short pulses, produces high peak power that can be useful in deep engraving with sharp, clear marks and small characters.

mARCATURA-iNCISIONEVS Laser marking: Choosing the best laser for your application
start-stop1 Laser marking: Choosing the best laser for your application

The vanadate laser can emit at three different wavelengths: 1064, 532 (green) and 355 nm (blue). Vanadate lasers are also diode-pumped and are particularly suitable for ablation marking and heat-affected zone applications. One of the biggest areas of vanadate laser application is Day&Night Marking. In this case, the laser removes the top coating of the component (usually buttons inside automotives), exposing the surface underneath with the functional indicator. As these buttons are backlit, their effect is the same as we all know from the buttons on stereos, windows, or air conditioning.

The advent of the Fiber laser signified a real revolution in the world of lasers and marking. The fiber laser has become the focus of every application and has been tested and refined to suit almost every market requirement. It is especially effective in metal laser marking.

One thing to keep in mind is that the output power of all solid-state lasers degrades over time, but it is possible to calibrate the system to maintain the same power in the laser as the day it left the factory.  This will allow the laser to maintain the same mark quality and speed as the day it arrived and was put into production.

The Fiber laser wavelength is 1064 µm, with an extremely small focal diameter. This leads to increased intensity, which is 100 times greater than that of CO2 lasers, with the same average output power.

lab-laser Laser marking: Choosing the best laser for your application

Beam properties

A Gaussian beam has an M² of 1 and allows for the smallest spot size in relation to the wavelength and the optics used. The best beam quality possible in Nd: YAG and vanadate laser marking systems has an M² of 1.2. Fiber-based systems generally have an M² value of 1.7. This means a larger spot size and less power density. Better beam quality means smaller linewidths, sharper contours, higher marking speed (because of high power density), and deeper engraving.

Pulse repetition rate

The YAG and vanadate lasers are very different from the fiber laser with respect to peak power and the pulse repetition frequency range. The pulse duration can be adjusted in the case of special Fiber systems such as the MOPA laser.

Typical reference values ​​of a marking system
Typical values YAG VANADATe ytterbium
Pulse Duration (ns)
10-150
5-30
10-200
Beam Quality (M² )
<1.2
<1.2
<2
Peak Power (kW)
High 100 kW
Medium 80 kW
Low 10 kW
Average Power(W)
5-30
5-40
10-50
Pulse repetition frequency range
5-80 kHz
20-120 kHz
20 kHz - 1 MHz
Applications

The most common terms used in laser marking include: engraving, annealing, selective ablation, and surface removal. One type of laser is more suitable than another depending on the application and material. If we look for example at the Day&Night components, a vanadate laser performs well. The surface removal process is adapted to the characteristics of this laser, which are short pulse and repetition speed. Speed is crucial to avoid burning plastic components.

Ablation also is a common practice in laser marking anodized aluminum.

DayNight_large1 Laser marking: Choosing the best laser for your application
UDI-Code-Lsit-Laser-Marking Laser marking: Choosing the best laser for your application

Another very common application for which a special Fiber laser is effective is annealing on medical components. These are usually made of stainless steel and titanium. We are of course talking about all components such as prostheses, surgical instruments, and dental components. The high peak power of the Picosecond laser is ideal here for achieving black and impalpable markings.

The resistance of this laser marking to passivation cycles and corrosion due to aggressive agents is more significant than in other cases. This is because laser marking can be used to indicate to the surgeon some important dimensional information about the component in question. The low reflective effect of the Picosecond laser is another element that favors this product over others in the medical field.

Choosing a laser marker

The world of lasers and marking will continue to grow and evolve for years to come. The technology will have to meet the changing demands of the manufacturing environment and the competitive market.  Choosing a laser marking supplier is important because there is such a wide range offered and it can be easy to make mistakes. Relying on someone who knows their job also means benefiting from the advice of an expert who knows how to tailor their offer to our needs and not the other way around.

LASIT has been an expert in customizing its laser systems for 30 years. From mechanics to software, no request is too great, and we protect our customers’ interests across the board. Here you can find an article on 10 guidelines that we have identified for making the best choice of laser marker.

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