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Looking for fine focus with selectable beam quality?

Go with a fiber laser!

Laser Light

It travels at 299.792.458 meters per sec. Its visible spectrum ranges from 400 to 700 nanometers. Its smallest unit is a packet of energy, a photon. It is light, and its use is growing in tube and pipe production and fabrication facilities throughout the world.
In most of its natural and artificial forms, light has little power. However, a groundbreaking invention in the latter half of the 1950s increased its power and concentrated it in a small area. Thus was born a modern and revolutionary concept:  Light Amplification by Stimulated Emission of Radiation, or laser.

fiber laser is generated within a flexible doped glass fiber that is typically 10 to 30 feet long and between 10 and 50 microns diameter. Ytterbium is usually used as the doping element. You do not have to align the medium to cavity mirrors, nor maintain optics and alignment. In fact, it’s such an efficient lasing process that this laser can be small, air-cooled, and provide high wall plug efficiencies. Fiber lasers offer great “focusability” and a range of beam qualities, which can be tuned for each welding application.

Fiber Laser

Definition Fiber Laser 

A fiber laser is a special type of laser in which the beam delivery as well as the laser cavity is integrated into a single system inside an optical fiber with the beam generated within the fiber, unlike conventional lasers where the beam is generated outside and sent into the system. Considered as a special category of solid state laser, fiber lasers provide many benefits compared with other laser technologies, such as:

Maintenance-free operation

Ease of use

High reliability

High integration capability

Economical

Fiber Lasers: Exceptional attributes

The brightness, stability, and flexibility of modern fiber laser designs are revolutionary enabling new materials processing applications.

Fiber lasers are "the" recognized powerhouse in the manufacturing sector of numerous industries because of the throughput, reliability, and low cost of operation they make possible for machines that cut, weld, mark, and micromachine materials. Specific design elements distinguish fiber lasers among other industrial laser sources, and their unique attributes are enabling breakthrough manufacturing process capabilities. Specifically, high-power single-mode lasers for remote welding and widely flexible pulsed fiber lasers for cutting can address different process challenges by the full electronic control of all operating parameters.

The fiber laser is exceptional efficient at converting relatively low-brightness pump light from laser diodes into high-brightness output, where the output beam quality is often the only spatial mode allowed by the physics of the fiber design. Even though fiber lasers were capable of very high (100 W) output as early as the 1990s, it took the crash of the fiber communications market in 2001 to enable the commercial development of reliable fiber lasers. During the 1990s, companies spent billions of dollars solving the basic problems of coupling diodes to fibers with high reliability, splicing fibers with high power density, qualifying component technologies to meet the 25-year reliability required by undersea communications, and reducing the cost of these high-performance, high-reliability components.

Then, in the early 2000's, with the communications market all but gone, the technology investment was quickly redirected and tuned for use in the design of industrial fiber lasers.

Exceptional attributes

Fiber lasers are unique among all other industrial laser types because of two attributes: a sealed optical cavity and a single-mode, guided-wave medium. Modern fiber lasers, by design, have a fully sealed optical path that is immune to environmental contamination and remains optically aligned without need for adjustment. All internal components are either in-fiber or hermetically fiber-coupled, and the only free-space interfaces occur at the beam delivery optic, which includes a fused beam spreader to reduce the intensity at the first free-space interface. The active optical path is typically within a fiber waveguide that allows only one spatial mode of propagation (currently up to about 20 kW of optical power). Higher-power fiber lasers combine single-mode modules into high-brightness delivery fiber in fused fiber combiners.

The combination of the single-mode waveguiding and the fully sealed optical cavity provides a robust laser design that is fixed and measured at the time of manufacture and has minimal variation over time and temperature. Sealed pump diodes and nondarkening fiber technology result in lasers that can be used continuously in production for years without adjustment or degradation.

Which kind of fiber laser?

Continuous wave (CW)

With a CW laser, the laser output remains on until being turned off. For spot welding either a single weld or a seam, the laser output can be modulated – this means the laser is turned on and off rapidly. The CW laser’s peak power is the same as its maximum average power, so focused spot sizes are generally under 100 microns. CW fiber lasers are usually a good choice for general seam welding up to 1.5 mm depth for a 500W laser, high speed seam welding of same and dissimilar materials, and producing spot welds below 100 microns in diameter.

Quasi-continuous wave (QCW)

The QCW fiber laser’s peak power and pulse width characteristics are similar to those of the Nd:YAG laser. The QCW lasers offer single mode to multi-mode options with spot sizes from 0.02 to 1.0 mm. These lasers also shine in small spot size applications and penetration applications, although they really can handle many micro welding applications. 

Nanosecond Wave

The nanosecond fiber laser is a relatively new addition to the family. Often used for laser marking applications, nanosecond fiber lasers actually make a very cost effective welding solution. The nanosecond laser provides multi-kilowatt peak power, but with pulse widths around 60-250 nanoseconds that can be delivered between 20-500 kHz. This high peak power enables welding of almost any metal, including steels, copper, and aluminum. The nanosecond fiber laser’s very short pulse widths means you can get very fine control for welding small parts. This one is also a good choice if you need to weld dissimilar materials. 

Fiber laser : The breakthrough

Fiber Laser : revolutionary Tool!

The base for a new industrial Revolution

Fiber laser cutting drives a production revolution

Fiber lasers boost the production output at a much lower cost

As fiber lasers grew to what they are today, the industry was learning the benefits and the reality this technology offered.

For over 30 years, carbon-dioxide (CO2) lasers have reached what seems like a threshold of power and capability, with the majority of CO2 laser machines being purchased in the 4–5kW range (with occasional 6kW versions purchased). It took approximately 15 years before 3kW CO2 laser sales became common, and another five years or so before 4kW became the main power choice of end users. Higher-power CO2 lasers (6kW and higher) have been available for many years, going back into the 1990s. And while sales of high-power CO2 lasers increased slightly in the 2000s, they never approached the volume of sales in the 4–5kW range. There are good reasons for that—and when one looks at benefit vs. cost, it becomes a little clearer as to why.

First of all, there have been great improvements in CO2 laser technology, with the advent of beam choppers, electronically controlled shutters, polarization, beam collimation, better controls, and so on. And as these developments improved CO2 lasers, they became more user-friendly. The industry demand was not for the high-mix, low volume of today—we really did not see this strategy until the crash in 2000. But the industry was changing and efficiency in manufacturing was still improving. As CO2 lasers improved, so did their demand and sales. With that said, CO2 lasers still were relatively expensive, and required a lot of incoming power and maintenance.

The mid-1990s saw a stronger movement towards laser technology and by the time the market crashed in 2000, lasers were already mainstream, rivalling punching as the primary weapon of choice in the manufacturing sector. So, the strategy for manufacturing went into a streamlined overhaul overnight, as the term "high-mix, low-volume" became the new mantra for efficient manufacturing. This demanded just-in-time production and the laser was the tool because they reduce or eliminate setup when switching from job to job. It makes no difference if it is a 10-piece job in 1.2mm steel or a 1000-piece job in 8mm steel—the beam of a laser is the ultimate tool.

The sweet spot of 4000–5000W of power was ideal for 99% of anything that had to be cut. So, why didn't 6000W or higher CO2 lasers dominate the market? There is not one definitive answer, but it certainly could be any combination of things. We know that these higher-wattage machines could clean-cut with nitrogen (N2) faster than lower-wattage 4 and 5kW lasers. The higher-power spot density allowed for faster vaporization of material, which in turn allowed for faster head movement and cutting process. The direct result would be faster overall production of parts cut with N2, and no secondary processes to remove oxidation for painting or welding operations downstream.

Oxidation is a common by-product of using oxygen (O2) as an assist gas. To help give an idea of the benefit to a 6kW CO2 laser vs. a 4kW version in 6mm mild steel with N2 as the assist gas, the 4kW will cut this material around 1500-2000mm per minute . The 6kW version will be approximately 2800–3200 mm/min. In addition to significantly faster speeds, the higher-power CO2 laser also increased capacity thickness, expanding a shop's capability to process thicker mild and stainless steels, as well as aluminium. So, it would seem like this technology would be a logical step in the evolutionary process to become more productive and efficient. However, that is where CO2 lasers seemed to have found the proverbial ceiling. Higher power in the CO2 laser world comes at a price and for every increase in wattage, there are also increases in the cost of operation, number of components, electrical consumption, and overall maintenance of the system. There is a distinct trade-off for capital investment and increased cost of operation vs. productivity and increased capability. The justification is often a stretch, guiding the buyer back into that 4–5kW range once again.

The breakthrough

After 2000, lasers dominated the blanking market for fabricating, outselling punching on a regular basis—a title it still holds today. In 2005, fiber technology became a buzzword for laser cutting, and while there were areas of sales within the metal working market, most of the early sales were seen in the European manufacturing market. In fact, most of the primary laser original equipment manufacturers (OEMs) did not even have fiber laser technology in their line-up yet. From around 2005 to 2010, fiber sales were very small in volume in the US, with maximum available wattages around 2kW. It was at the 2010 EuroBLECH tradeshow in Germany when several of the larger OEMs unveiled their versions of the technology, and at the Fabtech 2011 tradeshow, it seemed like fiber lasers in the US had their coming-out party. Even so, fiber accounted for only about 5–10% of all laser sales for cutting applications in 2011. However, several manufacturers already had pushed the power envelope to 4kW right out of the gate. By Fabtech an deuroblech 2014, fiber lasers were about the only kind of laser cutting machine at the show, with power levels of 2–12kW on the floor! In this same timeframe, the percentage of fiber vs. CO2 laser sales has risen dramatically, with 2015 showing fiber lasers outselling CO2 lasers for the first time.

From 2005 to 2010, fiber laser sales remained modest. This could be for several reasons, but most likely it had to do with familiarity and a comfort level. In that timeframe, few of the larger OEMs offered this option, and end users were uncertain if this technology was here to stay or just a passing fancy. As more OEMs began to offer their machines and more machines began to get into the field, legitimacy came to the technology. Once this hurdle was overcome, the fiber laser revolution turned into a power revolution, with wattages increasing seemingly every 6 months or so.

The New Age

As fiber lasers grew to what they are today, the industry was learning the benefits and the reality this technology offered. When first introduced, one of the primary selling points was the low operating cost vs. CO2 lasers. The operating cost of a fiber laser is a fraction of CO2 lasers and even lower compared to alternative cutting methods, as a fiber laser requires no maintenance to the source. But more importantly, the simplicity of the design means increasing power does not mean significantly increasing consumables, electrical consumption, or maintenance. In fact, the limiting factor for increasing power revolves around the ability to scale diodes and modules while maintaining a high-quality beam. By doing this, the power is increased, allowing for faster and thicker processing. Today's 6kW fiber laser can process that same 6mm mild steel with N2, as we mentioned before, at 5000mm/min. If you recall, the 6kW CO2 laser was in the 2800-3200mm/min range.

So, one can assume that the dramatic increase in power is driven by demand in the marketplace, and the fact that the marketplace is accepting this power revolution because there is not yet a significant downside. The justification of fiber laser productivity vs. cost is much easier to make than with the CO2 laser in these higher power ranges—along with this comes the increase in capacity. Fiber lasers are also a strong alternative to blanking methods such as plasma and water jet, as fiber lasers can effectively cut thick plate and the wavelength is now conducive to cutting unique materials such as copper. Today's fiber lasers have only a few optics in their cutting head plus one cutting nozzle, both of which are relatively inexpensive over the life of the machine. Operating costs on fiber lasers will generally range between €1–3 per hour, depending upon what is included in those costs and how they are calculated. This, combined with the overall capability of the new generation of fiber lasers, makes the fiber laser an attractive alternative to almost any current blanking process.

Considerations

Of course, there are Limitations that must be addressed, and high-wattage fiber lasers are proving to offer their own manufacturing balancing acts. Some might consider these "good" issues, but they do require additional planning. A 6kW fiber laser is significantly faster than the 4 and 2kW fiber laser machines, as well as any CO2 laser alternative. Add plasma and water jet in the mix, and the productivity of this one machine will double or even triple throughput from the same or less floor space compared to previous operations. Some manufacturers have even reported that their machine is so fast that the Green Light On is actually lower than their slower predecessors, mainly because of the fact that these lasers are piling up downstream processes. This ability to overload production has forced manufacturers to rethink downstream processes like material handling and bending operations. A balanced shop flow can be easily altered by just one high-powered machine and can often mean that the next capital investment may need to be focused on the bending process, such as auto-tool-change press brakes and robotic technology. And what about material handling? These are serious considerations that may not have been considered before—but make no mistake, high-power fiber lasers will improve overall throughput.

In summary, high-power fiber lasers have evolved and quickly found their place in the fabricating industry for many reasons. They are as easy to operate as their lower-powered counterparts. Any additional capital investment can be offset by significantly higher production and lower operating costs than CO2 laser machines in that power range. The ability of fiber lasers to process thick plate has also opened the door to alternative processes, such as plasma and water jet. The industry has lifted the veil of obscurity and shown fiber lasers to be a viable solution for today's blanking needs, such that it suddenly has become the blanking solution to address that ever-shrinking wiggle room between low-volume orders and profitable production output. High power, more production, less cost, more flexibility, and more profit—today's fiber laser offers all of this to manufacturers.

In metal working applications, medium power Fiber Lasers in the range 50W to 2000W offer new degrees of operational freedom and process control. The ability to operate with pulse lengths continuously tunable from a few microseconds to full CW operation and with pulse repetition rates up to tens of kilohertz offers the applications engineer the ability to optimise the process conditions over a wide range of applications. 

Due to their monolithic single mode fiber construction Fiber Lasers do not suffer from changes in focus position due to thermal lensing as the average power is changed, and don’t require periodic adjustment or tuning of the Laser cavity or component maintenance to ensure output stability.

Traditional laser welding technologies, such as continuous-wave CO2 welding lasers are limited in terms of accuracy and undesired, high heat input into the weld. On the other hand, the limitations of traditional pulsed Nd:YAG or the newly developped pulsed QCW are the maximum welding speed, the minimal spot size that can be achieved and the electrical to optical energy conversion efficiency that can be obtained. Ever more applications are demanding a higher precision control, lower heat input and lower electrical energy consumption. Continuous Wave Fiber Laser Welding is a technology that offers those features.

In a fiber laser, the laser light is generated in an active fiber and guided to the work piece by means of a flexible delivery fiber, which acts as a “light guide”. The flexibility of the delivery of this laser beam is an important feature for many forms of material processing such as laser cutting, laser welding, laser marking and laser engraving.

Continuous Wave versus Pulsed Wave for metal welding

Fiber lasers are available with both type of energy delivery: Continuous and Pulsed.

As the name states, the Continuous Wave (CW) lasers deliver a continuous, uninterrupted output. This output can have an upslope (soft-start) when switched on, an energy modulation while active, and a downslope when switched off (crater filler). Of course, this type of laser can also be switched on and off to create pulses. However, the maximum power level can never exceed the average power.

In contrast, the Pulsed Fiber lasers deliver a pulse of energy which is typically ten to twenty times higher than their average power. For example, a laser can have 300 W average power and 4000 W peak power. These lasers are often referred to as Quasi Continuous Wave (QCW) Fiber Lasers