SPI – 20 years of innovation in fiber lasers

This year marks our 20th anniversary since the registering of the SPI lasers brand; over which time we have transformed from a humble start up to a global leading player in the supply of fiber lasers. Over this time period fiber lasers have been an incredibly disruptive technology transforming from being a scientific curio to the dominant technology in today’s manufacturing processes, almost completely displacing the CO2 and solid state Nd:YAG lasers that dominated the previous 3 decades! Key to our success has been a continual focus on end user requirements developing products and applications solutions into a diverse range of market segments.

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Armed with a strong background in fiber from our launch into telecoms (figure 1) we refocused into an industrial laser manufacturer following the markets crash.

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Figure 1 – Telecommunications was SPI’s first venture.

Based on our patented GTWave pumping technology we launched initial CW products using Yb+ (1µm) and Er+ (1550nm) as well as a ns pulsed laser based on a MOPA design with a novel semiconductor seed. The early days were spent trying to get traction in any application and market that could see a benefit from this new technology. One of the key features of these lasers was the exceptional beam quality, so it was not surprising that the first successes came in the area of fine cutting.

Some of the first applications examples of the CW lasers were for thin sheet metal cutting such as those used in the manufacture of solder stencils and in the medical market for the manufacture of arterial stents. While the Er+ lasers found a niche application in medical aesthetics and more specifically the removal of wrinkles, the technology tussle with CO2 lasers meant that Erbium fiber lasers were only the preferred solution for a few years and as the demand declined, we exited this market, unable to find suitable alternative applications to sustain the product.

The pulsed laser development was strongly focused on the marking market and our initial products were developed in conjunction with Electrox, a well-known UK based supplier of laser marking systems. They clearly saw the benefits of the MOPA design allowing the selection of pulse duration and high frequency operation over the q-switched approach that had been adopted by our competitors…which had a fixed pulse duration and limited operational frequency.

The adoption of CW lasers quickly grew as the powers available increased to 200W.

Figure 2 – A laser cut stent.

The medical industry increasingly used these lasers not only for cutting (figure 2) but also welding from pace makers to brachytherapy seeds. The precision and quality afforded by the fiber laser supported the development of a broad array of medical devices. The electronics industry also picked up on the benefits of the beam quality which opened up new applications such as alumina scribing where the incumbent CO2 lasers were quickly displaced based on the significantly smaller spot size that could be achieved with fiber lasers. This continues to be an application stronghold for fiber lasers today.

Figure 3 – Plastic marking for mobile phones was a big market before touchscreens were popular.

The pulsed lasers made a successful beach head in the marking arena and over a 10 year period grew to an 80% market share of metallic marking applications. Including some plastic marking applications such as key pad marking (figure 3) for the then emerging mobile phone market which led to large unit deployments. Sadly, this market has gone as we have all fallen in love with the touch screen. The tussle with our key competitors with their low-cost q-switch vs the higher performance of the MOPA meant that basic marking applications were primarily based purely on cost. For many marking applications quality is not a driving criteria so we were forced to look at developing micro-machining applications where the superior performance would be rewarded with premium pricing.

One step on from marking is engraving where significant material is removed. Traditionally high-power lamp pumped YAGs were used for this application with long, high energy and low repetition rate pulses, however, fiber lasers approached the problem from a different direction with their short, low energy high repetition rate pulses breaking the conventional wisdom of the time.

Figure 4 – An example of deep engraving with a pulsed fiber laser.

One of the biggest challenges was in achieving high quality deep engraving (figure 4) where the resulting quality tended to be very poor as a result of heat accumulation and furrows created by the repetitive passes required to get depth. At SPI we developed a method using a series of 4 fixed angles for processing, based on techniques used in the printing industry to reduce moire interference patterns, to improve the bottom surface quality which virtually eliminates any directional roughness features. The challenges of heat accumulation is one that still exists and achieving good engraving quality with laser powers of >100W is still challenging. However, this topic is still being worked on in conjunction with Herriot Watt where a technique using line scan interlacing is showing promise.

The ability of the SPI MOPA to produce 10ns pulsed with >5kW peak power meant that we were capable of highly controlled ablation which led to the opening of two significant markets. The first was in the consumer electronics industry where a mobile phone manufacturer required the delicate selective removal of a silvered layer on a plastic casing with no damage to the casing!

Figure 5 – Etching thin lines in solar cells, made possible by pulsed fiber lasers.

The second was in the solar industry where the growth of thin film solar panels required the etching of thin lines through metallic layers on both glass and plastic substrates (figure 5). The challenge was to achieve complete removal without damaging the substrate. The customer requirement was for the narrowest scribed line features and so a true single moded M2<1.3 pulsed fiber laser was developed for this application. This laser found further mass-market high-volume applications in the electronics industry for the manufacture of touch screens and in the silicon solar cell market for “half-cell” cutting where cells are cut into multiple pieces to reduce resistive losses and hence improve efficiency. Unfortunately, the manufacture of touch screens has adopted alternative manufacturing methods, but the solar application is still growing nicely.

Figure 6 – A multikilowatt redPOWER QUBE CW fiber laser.

The CW market exploded as multikilowatt fiber lasers (figure 6) became available displacing the incumbent CO2 laser technology in flat sheet cutting – the worlds biggest market for industrial lasers. Another fiber laser manufacturer quickly achieved market dominance and we struggled to find a route to market, however, paring back our offering from a fully-fledged laser to an OEM package which we called PRISM gave us a limited market position. But the emergence of Chinese domestic suppliers led to significant commoditisation of multikilowatt sources as well as a price war that is still on-going.

Figure 7 – A product feature available on QUBE & PRISM lasers, variMODE allows the user to quickly switch beam profiles.

To try and lift our offering out of the commodity bracket we have been developing our variMODE (figure 7) solution which enables the beam quality of the laser to be changed in the laser rather than through external optics. This offersend users potential benefits where they can use low beam quality for thick section oxygen assisted mild steel cutting (figure 8) and switch to high beam quality for cutting stainless steel with nitrogen. Launched in 2019 we are hopeful that this will excite potential customers.

Figure 8 – An example of thick section piercing and cutting with one laser, made possible by variMODE.

Our ns lasers have also been very successfully deployed in scanner based cutting, which requires no assist gas and has been widely adopted in the jewellery industry for fine filigree work in silver (figure 9) and gold.

This did require some technical innovation in that using the lasers in a conventional scribing technique would fail to cut any significant thickness of metal. However, using a software scanning feature originally used to widen the lines made in marking, the ns laser is transformed into a capable cutting source.

Cutting 1mm Thick Silver

Figure 9 – A laser, cut, marked and engraved silver pendant.

The wobbling feature oscillates the beam at a very high frequency with a very small amplitude, this enables improved coupling of the beam into the material and also facilitates the removal of the material from the kerf.

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Figure 10 – CW lasers enable the manufacture of metal 3D printed parts, such as this model of the top of ‘Big Ben’.

For lower power CW lasers <1kW the additive manufacturing (AM) (figure 10) market has provided a growing demand. Again, beam quality and stability are critical to this application, and both aspects are well supported by our QUBE lasers. Although still in its infancy the additive market shows good long-term promise. Using the laser beam manipulated by a high-speed scanner, metallic powders are selectively melted and layer by layer fully dense 3D parts can be manufactured. These are being used in the medical industry where AM titanium implants are being created for the dental and general surgery industries. The automotive and aerospace industries are also seriously looking at this technology to reduce part costs and greater design flexibility. Current constraints in costs and part qualification are responsible for holding back the growth of this segment, but these are all surmountable.

Figure 11 – ns welding allows the easy joining of dissimilar metals.

One of the most significant innovations in applications has been the development of the ns welding process. This uses lasers with short low energy pulses that are traditionally used for ablative processing for a joining process. Conventional pulsed laser welding uses long pulses in the ms regime with energies measured in Joules so it was quite surprising that laser pulses in the 200-500ns range with <1mJ could actually be used to weld metals. The process capabilities are perhaps limited, particularly in the material thickness and process speeds, but the benefits are clear in terms of the control of heat input, particularly for thin section and for the joining of dissimilar metals (figure 11). The key is the lack of a large weld pool where the different materials could mix and form undesirable brittle intermetallics which have long been the bane of conventional welding of dissimilar metals. The proof of the pudding is in the sales and we can be proud of a deployed base of over 5,000 units in this application, the majority being used in the manufacture of today’s consumer electronic products.

Figure 12 – Pulsed fiber lasers allow the dissimilar metal properties of batteries to be efficiently joined.

The global focus on e-mobility has opened a multitude of application opportunities for both our redENERGY and redPOWER products. The key difference between conventional combustion engine vehicles and e-vehicles are the battery power source (figure 12) and the electric motors.

Figure 13 – Battery foil cutting, and layer removal are two vital elements of battery manufacture that can be achieved with pulsed fiber lasers.

Both our pulsed ns and cw lasers are being used extensively in battery foil cutting (figure 13) in the manufacture of the actual battery cells, and again for bus bar welding where the individual cells are joined into packs.

These bus bars are typically made of copper and are of limited thickness making them ideally suited to oscillation welding with our 2kW single mode products.

Figure 14 – Oscillation welding is a perfect application for the joining of copper hairpins.

In the manufacture of electric motors a key application is the joining of copper hairpins. These are wires that run through the motor stator and must be joined at the end. This brings about two laser based applications, the first is the cleaning of the ends of these wire hairpins to selectively remove the electrically insulating layer, for which our 200W ns lasers are being deployed and the second is the actual welding of the copper wires.

Although this is ideally suited to our high brightness 2kW oscillation welding (figure 14) technique the productivity requirements are challenging, and we need to develop higher power solutions to capitalise on the potential growth of this application.

Looking back over the past 20 years we can see that collectively we have come a long way and should be very proud of our achievements. However, what is clear is that over this same period the pace of development and innovation has been accelerating. The on-going challenge will be to keep up with industrial demand for higher productivity, better quality and new processes to do things that can’t be done today. That is our job and I am looking forward to seeing what the next 20 years brings in terms of innovation.

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