Ultrahigh Power Fiber Laser Cutting: The Basics You Should Know

Preface

Ultra high power fiber laser can achieve fast and high-quality thick plate cutting, including the use of air as an auxiliary gas to cut stainless steel, and many advantages over other cutting schemes.

In the past few years, ultra-high power (UHP) fiber lasers with power ranging from 10kW to 40kW have been rapidly applied to the cutting market, and the maximum laser power for cutting applications is expected to continue to increase.

We will show the cutting application effect in this power band, and discuss the main factors driving the application of ultra-high power fiber lasers: significant productivity advantages, cutting quality improvement and the ability to cut the limit thickness (for example, as shown in this article: cutting 230 mm thick stainless steel at 40 kW).

In this article, the power of ultra high power lasers is defined as lasers larger than 10kW, which enable new process methods to promote laser cutting to expand to new markets (for example, using air as auxiliary gas to cut stainless steel with a thickness of up to 50 mm, and the cutting speed is 4 times faster than high power plasma cutting).

The application results show that the ultra-high power laser is changing the way of cutting stainless steel – using air cutting technology instead of nitrogen and oxygen cutting technology to achieve high-quality, high-speed and economic cutting.

6-year development trend: maximum laser power for cutting applications

Fig. 1: Maximum power growth of fiber laser used in cutting equipment since 2016

More than 50 years ago, laser cutting technology came out.

Since then, laser cutting technology has entered a period of rapid development.

In the 1970s, a commercial laser cutting machine was introduced, and early users used it for mass production;

In the 1980s, CO2 laser cutting equipment was widely used;

In the late 1990s and early 2000s, high-power fiber lasers were introduced;

At the end of the 2000’s, the development of kilowatt-class optical fiber laser cutting machine made laser cutting from small-scale application to mainstream manufacturing technology.

Fiber laser cutting machine has an important position in the metal plate laser cutting market, which is mainly attributed to the easy integration, reliability, low maintenance, relatively low investment and operating costs, high cutting output and the feasibility of power expansion of fiber laser.

At the end of the decade of the 21st century and the beginning of the 1920’s, the growth path of the laser cutting market has two directions: the first trend is to cover the low power end of the market.

As the cost of equipment capital decreases, the demand for 1-3kW cutting machines increases sharply;

The second trend is in the high power end market, which also leads to the increasing demand for ultra high power lasers.

This is driven by the fact that ultra-high power lasers provide high productivity and technical capabilities at a high cost performance ratio, and the laser cutting field has experienced a revolutionary “power transformation”, which is unprecedented in other sheet metal manufacturing processes in the same period.

From the processing and manufacturing exhibition, we can see that the maximum laser power of the cutting machine on display has increased from 6kW in 2015 to 40kW in 2022, an increase of nearly 7 times (see Fig. 1).

In the past three years alone, the maximum power of laser equipment has risen from 15kW to 40kW, a sharp increase of 2.5 times!

Why is this the best time?

A few years before the ultra-high power cutting trend began, reliable high power fiber lasers had appeared.

As early as 2013, 100kW industrial fiber laser appeared.

However, only in the past few years, after the price of laser per kilowatt dropped rapidly, the threshold of ultra-high power laser cutting was lowered, and the cutting head capable of carrying such high laser power in the harsh cutting environments also came out.

In addition, the cutting database that can adapt to ultra-high power cutting equipment is also becoming more and more perfect.

Cutting test

In this test, IPG 40kW YLS-40000 and IPG 30kW YLS-30000-ECO2 high electro-optical conversion efficiency fiber lasers are used, and 100 µm fiber core diameter and IPGCut-HP cutting head are configured to evaluate the cutting speed and quality of different metals.

As far as we know, 40kW laser power and 100 µm fiber core diameter are the highest laser power that can be provided by laser light source in industrial laser cutting.

We chose a fiber core with a diameter of 100 µm because the cutting speed is 10-25% faster than a fiber core with a diameter of 150 µm.

Cutting carbon steel with air as auxiliary gas
Cutting speed Vs. Laser power

Fig. 2: Schematic diagram of cutting speed and power of carbon steel slag free air cutting

Faster cutting speed

Our experiments show that for all tested metals (including stainless steel, carbon steel and aluminum), the laser cutting speed increases with the increase of average power (up to 40kW).

Fig. 2 shows the increase of cutting speed and laser power between 12kW and 40kW when cutting 6-40 mm carbon steel with air.

The rate of growth increases with the increase of metal thickness.

For example, when cutting 12 mm thick carbon steel, the cutting speed of 40kW is 280% of 15kW (the power is 270%);

Cutting 20 mm thick carbon steel with a cutting speed of 420% of 15kW at 40kW;

For 30 mm carbon steel, the power was increased from 30 kW to 40 kW (33% increase in power) and the cutting speed was increased by 66%.

It can be seen that the ultra-high power laser with higher power will further improve the production efficiency of thick plate cutting.

In order to use the faster cutting speed brought by the ultra high power laser to significantly shorten the production cycle, it is necessary to cut workpieces, especially thinner workpieces, at high acceleration.

In recent years, in order to adapt to higher laser power, the maximum acceleration of laser cutting machine has changed from 1G to 3G.

In the high-end market, the acceleration of the ultra-high power laser cutting machine can reach 6G at most, and its mechanical design can ensure that there is no obvious deviation in the cutting path.

Reduce the processing cost of unit parts and realize rapid return on investment

Compared with lower power, ultrahigh power laser cutting significantly reduces the processing cost of unit parts, and brings fast return on investment and higher profitability.

In laser cutting, the processing cost mainly comes from gas consumption, and the gas cost often increases significantly with the increase of component thickness.

Ultra high power laser cutting requires the same or smaller gas pressure and nozzle size as low power cutting.

But the cutting speed of ultrahigh power laser is faster, which reduces the cutting time of unit parts and greatly reduces the gas consumption.

For example, compared with a 15kW laser, a 30kW laser can cut a typical 16mm thick stainless steel part in half the production cycle, which can reduce gas consumption by half.

The power consumption of lasers and chillers is usually linearly increased with laser power.

However, other power consumption of the cutter is almost the same.

Therefore, in the previous case, the production rhythm of the unit component was half faster, and we reduced the total power cost of each component by increasing the laser power.

With the continuous development of IPG technology, the electro-optic conversion efficiency of high power fiber lasers is more than 50%, which is more conducive to power saving.

In addition to faster cutting speed, ultra high power lasers can also save the use of gas.

Compared with the use of more expensive nitrogen or slower cutting speed of oxygen, ultra-high power lasers allow the use of high-pressure air to cut thick carbon steel quickly and slag free.

In nitrogen and air cutting, ultra-high power allows to reduce the air pressure required for slag-free cutting.

For example, using a 15kW laser to cut 20 mm thick carbon steel without slag requires the use of air pressure greater than 16 bar, while using 20kW or higher power, 10-12 bar is sufficient.

Since the gas usage and pressure vary approximately linearly (at the same nozzle size), significant depressurization helps reduce gas consumption and simplify the specification of the gas generation equipment.

The production efficiency of high-power laser cutting equipment is twice that of low-power laser cutting equipment, while the price of the equipment is not twice that.

This is because the cost per kilowatt decreases with the increase of laser power.

In addition, the cost of higher power laser is included in the total cost of equipment, showing marginal growth (compared with lower power laser equipment).

Therefore, the ultra-high power laser cutting machine can achieve twice the production efficiency through higher laser power, while the equipment cost has only increased by 30-40%.

Due to the significant improvement of production efficiency, ultra-high power equipment can replace multiple low-power equipment, which can correspondingly reduce the floor space, operators and facility preparation.

On the other hand, in order to ensure production efficiency, the ultrahigh power fiber laser cutting machine requires higher reliability of the laser source and cutting head.

That is to say, for optical fiber laser source, long-term stable power output and beam quality are required, which will be affected by the quality of diodes, components and optical integration.

As for ultra-high power cutting head, it needs to bear high laser power, high pressure gas, dust, process heat and high acceleration to achieve stable and reliable processing.

 ItemOxygenNitrogenHigh-pressure Air
Gas equipment costlowlow to highhigh
Gas operation costlowhighvery low
fluxlowvery highvery high
slagNone/Lowmediumnone/low
Long term repeatability of production qualityMedium/Highvery highvery high
Sensitivity to material surface environmentMediumlowlow
Sensitivity to material compositionhighlowlow
Heat affected zoneMediumsmallsmall
Ability to cut complex or high aspect ratio workpiecesMediumhighhigh
Oxidation degree of cutting surfaceseriousnothingmoderate
Cutting surface roughness (Rz)lowsecondarymedium/High
Aesthetic degree of cutting surfacegoodsecondarypoor
Notch widthlargesmallsmall
Laser power required for slag free cuttinglowN/Amedium

1. It depends on the production scale;

2. Equipment for pressurizing air and filtering moisture and oil;

3. Oxygen cutting uses low pressure (usually 5-20 psi) and small orifice nozzle;

4. High pressure and large nozzle shall be used for nitrogen cutting;

5. Air as cutting gas resource has no cost;

6. Oxidation level and oxide skin thickness.

New Process Scheme for Cutting Stainless Steel

Carbon steel can be cut with oxygen, nitrogen or air as auxiliary gas.

Although oxygen cutting is good at cutting thick carbon steel with lower laser power due to additional oxidation energy, because the cutting speed is not proportional to the laser power, the production efficiency will be reduced.

On the contrary, the carbon steel air cutting speed is proportional to the power (see Fig. 2).

For example, for 16 mm carbon steel, when the power is between 10kW-30kW, the oxygen cutting speed remains unchanged, about 2 m/min, while when the power is 30kW, the air cutting speed is higher than 9 m/min, which is 4.5 times faster than the oxygen cutting speed.

For the thickness cut with oxygen only at lower power and speed, ultrahigh power lasers and air can now be used for processing, which is several times faster and of good quality.

For low power laser, air cutting will lead to slag hanging which is difficult to remove and poor surface quality.

The development of this innovative and efficient ultra-high power processing scheme is very popular for industries such as manufacturing construction equipment and heavy industry, which have a huge amount of thick plate processing.

We introduce the development history and cutting advantages of ultra-high power fiber lasers. In this issue, we will continue to show more competitive advantages of ultra-high power laser cutting through actual cases.

Fig 4. Cutting very thick stainless steel in pulse mode using an ultra-high power laser cutter

(a) 30 kW power, nitrogen cutting 70 mm thick stainless steel;
(b) Power 40kW, air cutting 230 mm thick carbon steel.

Improve the thickness, output and quality of sheet metal cutting

The test shows that with the increase of ultrahigh power laser power, the cutting thickness capacity also increases.

For example, Fig. 4 shows cutting 70 mm thick stainless steel with nitrogen at 30 kW and 230 mm thick carbon steel with air at 40 kW, both in pulse cutting mode.

Fig. 5 Full speed cutting in continuous mode

(a) IPG 40kW YLS laser is used to cut 28 mm thick carbon steel by air at the speed of 4.5 m/min (177 ipm);
(b) The IPG 40kW YLS laser is used to air cut 40mm thick stainless steel at the speed of 2.3m/min (90 ipm);
(c) Use IPG 30kW YLS-ECO laser nitrogen to cut 3-25mm thick stainless steel profiles;
(d) Cut 30 mm thick carbon steel with 15kW power and oxygen.

Under continuous wave (CW) full speed cutting mode, 20 kW slag free air is used to cut 20 mm thick carbon steel, 40 kW slag free air is used to cut 30 mm thick carbon steel, and 40 kW slag free air is used to cut 40 mm thick carbon steel (see Figures 2 and 5a in the previous section).

For cutting stainless steel, it is easier to achieve slag free effect, so the limit cutting thickness is thicker than that of carbon steel (see Figure 5b and Figure 5c).

For continuous nitrogen and air cutting, slag free cutting and good cutting surface can only be achieved within a certain thickness under any given power.

If it exceeds a certain thickness, pulse cutting (slower than continuous cutting) shall be used to achieve acceptable quality;

Otherwise, the laser power must be increased.

Generally, cutting speed lower than 2m/min means that in continuous mode, the laser power is insufficient to achieve the best cutting quality.

For carbon steel oxygen cutting, on the premise that the cutting surface is smooth, increasing the power will increase the limit cutting thickness;

For example, the 4kW limit cutting thickness is about 6-8 mm, while the 15kW limit cutting thickness is 30 mm.

Fig. 5d shows a 30 mm thick carbon steel sample cut with 15kW.

Faster and cleaner perforation

By using the peak power of ultra-high power laser in pulse mode, thick metal can be perforated quickly with less splash.

The piercing time of 16 mm stainless steel is greatly reduced from>1 second for 6 kW to 0.5 second for 10 kW and 0.1 second for 20 kW.

In practical applications, perforation ≤ 0.1 seconds is usually considered as “instantaneous”.

The higher peak power increases the depth-to-width ratio of the molten pool, which makes it possible to bridge the thickness faster with less transverse melting.

The reduction of material transverse melting also minimizes the top surface splash.

Competitiveness of Ultra High Power Laser Cutting

In the past six years, several technological developments have contributed to the improvement of laser cutting performance, including:

1) The required focal spot size is determined by selecting a variety of collimating or multi-core optical fibers;

2) High speed rotating beam that can improve the processing efficiency and quality of some metals;

3) High peak power continuous laser for faster and cleaner perforation/complex cutting;

4) Ultra high power laser.

Although the needs of various industries are different, and all enabling technologies (technologies that enable processes to operate) are used in specific areas, ultra-high power laser cutting is a leading technology trend that promotes the improvement of laser cutting performance.

This can be verified from the fact that a large number of global laser cutting machines use ultra-high power lasers.

With more and more contacts with ultra-high power lasers, application engineers have learned that the output and quality benefits of ultra-high power cutting machines are manifold, and they exceed the lower laser power enabling technology with less complexity.

Ultra high power laser has significant advantages in cutting thickness, quality and cost efficiency in thick plate cutting, especially at 15kW and higher power, it is more competitive than high current plasma cutting machine.

The comparison test shows that for stainless steel up to 50 mm thick, the 20kW fiber laser is 1.5-2.5 times faster than the high current intensity (300A) plasma cutter.

Related reading: Laser Cutting vs. Plasma Cutting: The Differences Explained

For carbon steel, it is also shown that cutting up to 15 mm thick is more than twice as fast.

The calculation shows that the total cutting cost per meter of carbon steel with a thickness of 15 mm using a 20kW laser is about 2 times lower than that using plasma.

Compared with the use of high-power plasma, the use of 40kW laser cutting 12-50 mm thick stainless steel section is 3-4 times faster, while the use of 40kW laser cutting 12-30 mm thick low-carbon steel section is 3-5 times faster, so the difference in productivity is greater.

Ultra high power laser

Compared with low-power lasers and other cutting processes (such as plasma cutting), the main driving force for cutting with ultra-high power lasers is higher productivity and lower cutting costs for each component.

The use of ultrahigh power lasers brings speed gains that provide manufacturers with economies of scale;

For example, the power from 30kW to 40kW increased by 33%, resulting in a 66% increase in cutting speed.

Ultra high power laser can achieve high-quality and fast air cutting of carbon steel, which is more advantageous than slow oxygen cutting and high cost nitrogen cutting.

In our test, using 40kW air to cut carbon steel up to 50 mm thick is 3-4 times faster than using high-power plasma.

Ultra high power laser makes laser cutting more competitive in many other aspects.

For example, increase the cutting thickness and quality (materials with a thickness of up to 230 mm can be cut), reduce or remove the subsequent processing costs (which can minimize slag hanging), reduce the floor area and facility costs, reduce the requirements for labor, and improve the quality and output of piercing.

With the continuous improvement of the power and energy efficiency of ultra-high power lasers, these advantages will become more obvious – improving their ability to quickly and economically change cutting applications in different industries.

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