Greg Blackman explores advances being made in fibre lasers, now the dominant technology for material processing
Amada's Silky Cut technology is designed to give a high quality cut edge
Fibre lasers are now the dominant force in materials processing. Efficient, reliable, able to reach multi-kilowatt power levels, and now a mature technology, they are gradually taking over from older CO2 laser machines. So, what does the future hold for fibre lasers?
The first thing to consider is power. While power isn’t everything, the trend to higher power seems likely to continue for the moment. IPG Photonics has delivered a 100kW laser to one of its customers, according to Michael Stark, product manager, marketing and sales at IPG, adding that the company has ‘headroom to increase the output power to 500kW’.
‘Higher process speed is a trend in many applications,’ Stark commented. ‘In cutting applications, for example, real industrial machine installations are reaching 15kW output power.’
Fewer machines are inevitably going to be sold at the top end of the power spectrum. Jack Gabzdyl, vice president of marketing and business development at SPI Lasers, puts power levels for most cutting machines as moving towards 6kW, while Jim Christian, senior product line manager, macro materials processing at Lumentum, quotes 3kW to 6kW as the norm.
Matt Wood, senior product manager at Amada Europe, commented: ‘Higher power is all well and good, but it gets to a point where you get diminishing returns.’ Amada showed a 9kW fibre laser at Blechexpo, the trade fair for sheet metal processing held in Stuttgart, Germany in November. ‘Those higher powers are for people that are consistently cutting mid- to thick-range material. That’s where the benefit lies, but you’ve got to be cutting a lot to make the cost per part competitive because you’re paying more for the machine.
‘The biggest thing to increase the adoption of fibre lasers isn’t going to be power, it’s going to be the sheet handling, the automation side of it,’ Wood continued. Wood ran a test comparing how long fibre laser machines ranging from 2kW to 9kW took to cut a 1mm stainless steel window frame. He found that the 9kW fibre laser was only one second faster than the 2kW system; the part had a lot of internal detail, so it was only on the straight edge that the higher power lasers reached maximum speed. ‘The power is dependent on the type of processing,’ he said. ‘If it’s a job shop cutting straightforward parts 24/7, then higher power will be a benefit.’
As fibre lasers are able to cut faster, the bottleneck then becomes the time it takes to load and unload the part. Wood said that, in the future, the advances will be adding quicker automation to the machine to take advantage of the higher fibre speed. He said: ‘We often come up against this; customers will be fixated with having a 6kW system, whereas for the work they are doing they’d get more productivity out of a 4kW laser with a loading tower. We don’t want to get caught up in the power race. Automation is more important for how you keep up with these high-power fibre lasers, and if it’s best for your process or not.’
There are also regional average power requirements, according to Christian at Lumentum. Wood gave an example that in Italy there is a strong demand of 2kW to 3kW fibre lasers because there’s a buoyant thin stainless steel market there.
‘The power will plateau at 8kW to 10kW,’ Wood believes. ‘Above 10kW there won’t be much to gain, because then you’re getting into the thicker processing range and you move to plasma cutting. Generally we find that the market wants between 2kW and 6kW. A 6kW and a tower will eat through work compared to an old 4kW CO2 laser.’
Fast and efficient
Fibre lasers are taking over from their older CO2 counterparts in part because they are more efficient at turning electrical power into laser light. Stark quotes wall plug efficiencies for IPG’s fibre lasers as up to 50 per cent, which is a big difference compared to 10 per cent efficiency for a CO2 machine. Wood at Amada believes efficiencies will continue to improve because the diodes that pump fibre lasers will become brighter and more efficient.
SPI Lasers has added process monitoring to its fibre lasers
Stark added that the efficiency of fibre lasers allows IPG to build compact, high power systems – IPG’s 15kW fibre laser has a footprint of 800mm2 and a height of 800mm.
The efficiency of fibre lasers is now well established, and now machine tool manufactures are looking to fibre laser companies to give added value. Christian at Lumentum commented that fibre laser firms have to ‘provide novel and possibly dynamic laser characteristics that allow for enhanced ability to cut thin to thick materials more reliability and with less tool reconfiguration.’ He said that beam shaping to give more flexible systems will be one of the technological advances for fibre lasers. Lumentum’s Corelight fibre laser systems are available in 2kW, 4kW and 6kW options.
Amada’s 3kW Ensis Rotary Index machine, which the company showed at Blechexpo, can process flat sheets as well as cutting different styles of tube, angle and channel. The machine can move from flat sheet to angle or channel or round square rectangle tubes with a two-minute changeover, according to Wood. ‘It’s ideal for production of 25 per cent tubing and the rest sheet metal – any more than that and you’d need a tube laser,’ he said.
The mode of the beam can be changed with the Ensis fibre laser, going from a conical mode to a doughnut shaped CO2 mode. The benefit is that a 2kW fibre laser can cut 25mm mild steel. The company has also introduced its Silky Cut technology on its fibre lasers, which Wood said gives the same cut quality on 10mm stainless steel as a 4kW CO2 machine can produce.
‘People are asking for simple operation,’ Wood added. The Ensis has an automatic nozzle changer so that engineers don’t have to do it manually.
IPG Photonics' 15kW fibre laser measures 800mm3
‘One thing we’re focused on is having higher-power individual modules within a fibre laser engine,’ Wood said. Five years ago, Amada was combining 600W modules for its fibre lasers. In 2014, the company moved to 2kW modules, and now it uses 3kW modules. ‘That will be an ongoing thing,’ Wood continued. ‘We’ll look to go to higher power single modules to remove things like the combiner. Whenever you can remove something from the machine, it not only removes the cost of that part but any potential unreliability. It’s going to be about streamlining the fibre laser engines themselves.’
SPI Lasers has added process monitoring to its fibre lasers, using the back-reflected light for pierce detection in cutting. ‘The fibre laser becomes more of a smart tool, adding value to processing through signal capture,’ explained Gabzdyl. ‘We have a technique in our beam delivery optic that strips out the back-reflected light. By monitoring this light, it can tell you when you’ve pierced into the material so you can initiate the cutting process.’ Given the act of piercing can take up to 10-15 per cent of the cutting process time, efficient detection of the pierce can significantly increase production rates.
Christian at Lumentum commented: ‘Laser manufactures will absolutely continue hardware consolidation and optimisation to improve costs, but the expectation is those companies successfully executing vertical integration strategies will benefit the most in the area of costs.’ He said that there will be interesting market dynamics as the industry consolidates, adding that Chinese fibre laser manufacturers are now coming online and that diode packaging houses are merging with local fibre laser firms.
Amada's 3kW Ensis Rotary Index machine operates with a 3kW single-diode module meaning it has no beam combiner
IPG’s vertically integrated business model means it can work on optimising each component that goes into its fibre lasers. Stark said: ‘Fewer components with higher efficiency is reducing the cost [of fibre lasers].’
IPG has also been developing its ultrashort pulsed fibre lasers, launching a two picosecond laser with an all-in-one fibre design and an average power of 50W. The laser is designed for dark marking stainless steel or processing glass.
SPI Lasers has shown that its nanosecond fibre laser can weld dissimilar metals of around 0.5mm thickness, such as copper to aluminium. The success of the welding process is down to the ability to tune the beam parameters of the laser.
Cutting on gas
‘There have always been two main problems with fibre lasers,’ commented Wood. ‘One is the quality of the cut edge when working with thicker stainless steel and aluminium compared to CO2. The other is the amount of nitrogen fibre lasers get through compared to CO2. You are cutting faster, but the amount of gas used can be higher.’
Amada is investigating ways to reduce the amount of gas consumed during cutting and, at Blechexpo, showed a preview of technology on its 9kW fibre laser to do that. Wood said Amada plans to introduce this technology early in 2018.
Another option that is becoming more popular is to use compressed air instead of nitrogen. The cut edge has a slight yellow oxidised tint to it when cutting with air, but if the part is going to be sprayed then air cutting is a good way to reduce the cost of processing.
‘There are still four or five years of people converting from CO2 machines to fibre lasers,’ Wood commented. ‘There are still an awful lot of CO2 machines out in the field and a lot of people are still perfectly happy with them.’
Lumentum's Corelight fibre laser engines are available in 2kW, 4kW and 6kW options
He added that fibre lasers will occupy the domain up to 20mm to 25mm thick metal, but when thicknesses get up to 50mm the quality of a fibre laser cut isn’t as good compared to plasma cutting or water jet cutting.
Wood concluded: ‘A mid- to high-power fibre laser can replace two lower powered old CO2 machines. We’ve sold a 4kW fibre laser to companies replacing two 2.5kW CO2 machines. In four or five years’ time the majority of laser cutting companies will have moved to fibre lasers.’