Fibre laser extends micro-welding capabilities

Latest Crafford-LaserStar workstations using fibre lasers provide higher quality output, improved process yield and reduced running costs, report David P Braman, John Tinson and Gregory Flinn.

Crafford-LaserStar Technologies Corp, of Rhode Island, USA, is a worldwide supplier of laser microwelding, cutting and marking workstations for industrial applications.

The company premiered it's first FiberStar laser welding workstation earlier in 2008 and is already examining other workstation products featuring fibre lasers.

There is a growing acceptance of fiber lasers for materials processing applications as a cost-effective alternative to conventional laser design.

The new welding workstations provide a better quality output combined with improved process yield, reduced running costs and have lower maintenance demands, achieving a major breakthrough in welding performance.

* Tougher demands for laser-based manufacturing - for all of the typical laser materials processing applications there is an almost universal requirement for consistently high quality results.

For a large proportion of these applications, workstations that make use of conventional laser engines are more than satisfactory for the task.

Some industries are subject to particularly stringent quality requirements, in particular the manufacture of medical devices and electronics.

Medical devices, medical implants and components for the electronics industry often use 300-series stainless steel, with wall thicknesses of 0.1mm to 0.5mm.

The specifications for the size, quality, durability and performance of such welds are set very high, although the weld process for such thin materials is actually very difficult.

The reasons are that too much power can result in excessive penetration and thus to weak points and perforation, while too little power can result in weak weld strength.

Crafford-LaserStar Technologies supplies benchtop and portable laser microwelding, cutting and marking workstations for industrial applications.

These workstations find extensive use in low and high volume and high value assemblies and precision assembly environments, being capable of welding a wide variety of metals, and are highly valued for their low running costs and compact ergonomic design.

In order to provide the industry with a wider welding performance envelope, Crafford-LaserStar began exploring alternative laser engine options for a new line of workstation products with fibre laser specialist SPI Lasers (Southampton, UK).

Over the last few years, and in close cooperation with strategic partners such as Crafford-LaserStar, SPI's intensive R and D programme has developed the fibre laser into a 'real-world' industrial welding, cutting and marking tool.

Backed up by more than 50 years combined experience in industrial manufacturing, applications specialists at Crafford-LaserStar are now confident that fibre lasers have matured beyond the performance window offered by conventional laser design and are key to the next step in workstation performance.

* New performance envelope - Crafford-LaserStar exhibited the new Model 7500 FiberStar workstation design at the MDM West Show in February of this year (Anaheim, California, USA) and Westec (Los Angeles, California, USA).

Designed for stringent welding and cutting applications, this workstation is equipped with an air-cooled, cw/modulated fiber laser from SPI and is worldwide the first fully integrated portable welding workstation of this type.

Production versions of this workstation are available with 20, 50, 70 or even 100 W fiber lasers.

The new workstation has been designed for the precision microwelding and microcutting industry, providing a level of accuracy and consistency previously unavailable.

This is made possible owing to the following novel capabilities of the fibre laser engine.

* A sub-0.5% pulse to pulse energy variation.

* A +/-0.5% continuous wave (CW) power stability over time.

* Single-mode beam quality.

* Focused spot sizes down to 10 micron.

These features, coupled with high energy efficiency and with no optical parts to align or calibrate, make fibre lasers an attractive laser engine for practical shop floor environments.

According to David Braman, vice president of Engineering and Operations at Crafford- LaserStar: "Full integration of the fibre laser into the FiberStar workstation provides full control over pulse energy, repetition rate and pulse duration for welding, with the workstation meeting all Class 1 safety regulations".

Braman also noted that the workstation can function in CW mode for cutting applications.

* Improved overall system performance - one of the biggest benefits is the improved overall system performance - the FiberStar can be guaranteed to perform to a higher standard for longer, and at the same time maintenance is simplified thus allowing the end-user to focus his expertise on production.

The new FiberStar workstation can be demonstrated in any one of the four Laserstar Centers operated by Crafford-LaserStar in the USA (in Rhode Island, California, Florida and Texas) and will be available internationally through established distribution channels in Europe, the Far East and Australasia.

Crafford-LaserStar can also provide on-site technical training.

* Advantages of fibre lasers - fibre lasers bring significant advantages for industrial applications.

To begin with, they do not exhibit the shortcomings in output power variation and spot size and focal point variations caused by thermal effects on the glass rods of traditional YAG lasers.

Fibre lasers offers true welding consistency at all power levels, across all pulse sequences and during the entire lifetime of the laser, the laser parameters remain predictable and consistent.

The reason for this is that the generation and transport of the laser beam to the work-piece takes place entirely within the confines of a single-mode fibre.

The beam shaping provided by this fibre neither degrades over time nor changes with laser power - this also makes the laser exceptionally physically robust and stable, and thus suitable for the most challenging of industrial environments.

A further advantage is that the small spot size and high beam quality translate to high irradiance at the focus, so workstations equipped with fibre lasers can produce better results at lower power levels.

The focused beam consistently affects a very small area of metal, with the benefit that very little heat is generated around the weld point.

High quality precision welding can be performed close (0.1mm) to the most complicated and intricate component parts, but applications are not limited to just welding - cutting of medical grade steels and wire end preparation for medical components are both easily realized with the new workstation.

From an economics standpoint, the consistent and improved welding performance means reduced scrap and faster production throughputs, coupled to lower operational running costs, and improved laser up-times.

These financial and performance advantages mean that fibre laser technology is now frequently chosen as an upgrade over conventional flash-lamp pumped solid state, or even DPSS laser technology in many other laser-based manufacturing segments.

In addition, a small footprint and fast ROI open up markets that were previously out of reach for some applications.

* Advantages for industrial manufacturing - Braman highlighted the choice of SPI as supplier for the fibre lasers, in addition to their mutual long term partnership, as being due to a number of reasons critical to performance in an industrial setting.

He said the following.

1 - The output delivery optic is back-reflection hardened, protecting the laser from potentially damaging reflections feeding back into the laser engine.

2 - The pump laser diodes are also fibre-coupled to the laser and are rated with 400,000h MTTF (mean time to failure) giving a full system design life of 30,000 operational hours (on time).

Both of these features help contribute to maximum up-time in the production process by guaranteeing maximum dependability.

3 - High consistency of performance among fibre lasers of a given type means that the degree of repeatability between workstations is also much higher.

4 - For the end-user, this means setting up and maintaining multiple lines to produce identical high quality components has never been easier.

In general, the choice of workstation for any application comes down to determining the required performance followed by a trade-off between initial outlay, component yield, uptime and maintenance.

* Rapid return on investment (ROI) - while the initial outlay for the new workstation will be higher, Braman was confident that rapid ROI due to high yield, near 100% up-time and near-zero maintenance means that less demanding manufacturing processes can also benefit from the technology.

There is little doubt that the fibre laser engine offers distinct performance advantages, in particular the high level of weld quality provided over the entire working range and over the entire working lifetime of the workstation.

Extra benefits to the end-user include a more flexible workstation with a broader performance window and the ability for the end-user to focus on their business demands rather than having to become laser maintenance experts.

In the longer term, as the market for fibre lasers matures, the specialists at Crafford-LaserStar expect to see more widespread adoption of the fibre laser engine for more general tasks.

Likewise, as the performance window improves, we can expect to see greater diversification of workstation use, as well as penetration into new application areas, including marking.

* About the Authors: David P Braman is vice president, Engineering, at Crafford-LaserStar Technologies Corporation, Riverside, Rhode Island, USA: http://www.laserstar.net.

John Tinson is vice president, Sales, at SPI Lasers UK.

Gregory Flinn is with Putting Photonics into Context, Munich, Germany: http://www.gregory.flinn@gmx.net.

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