Leveraging laser benefits

But what are the future prospects for those committed to the technology?

As a model of the archetypal jobshop looking to raise its game, laser and waterjet cutting subcontractor PP Plasma has seen much development in recent years. As the name suggests, the company's origins lie in plasma cutting, but this has, for the most part, been superseded by newer, more effective methods and its latest investments have bought it into the laser arena.
The initial purchase of a Bystronic Bystar L 4020 6kW resonator laser 18 months ago swiftly saw a rise in demand, and was soon followed by a second machine. Coupled with its other services and new marketing strategy, the group has enjoyed a record year for profitability and turnover.

These machines give PP Plasma a current maximum bed size of 6,500mm by 2,500mm and are capable under normal conditions of cutting 25mm deep with tolerances of ±0.1mm, the latter figure in particular being a threefold improvement on waterjet, although this too has been an important technology for the company.

Above and beyond As has become the prerequisite for the sector, the company obtained AS9100 accreditation in June 2008, but this is not the only important factor from an aerospace point of view. Over recent months, PP Plasma has been running a series of trials for a Tier 2 supplier to Airbus and Rolls-Royce into using liquid nitrogen and argon in its laser systems for titanium processing. The benefits are to achieve a smaller heat affected zone by reducing the thermal conductivity of the heat source thus minimising the tendency for titanium to react and cause potential weaknesses. This in turn leads not only to the improved tolerances so often required of aerospace precision components, but also to greater confidence in supplied materials and further reduces material wastage.

“The majority of profilers are already using liquid nitrogen,” adds Mazurkiewicz, “which reduces the heat affected zone somewhat but for aerospace, argon not only meets the standard but gives a better surface finish as well. We've reached our customer's standards with the test now so we'll be taking that forward and will offer it commercially in the near future. The only difference to regular machining is you need a bleed tap to switch between nitrogen and argon and that's a five minute process. Ultimately it has no real effect on set-up times as you don't even have to change the tanks between jobs.”

PP Plasma's new business strategy has rejuvenated it in the market, but it also demonstrates an increasing trend in the market for subcontractors to find further value added services as a result of competitiveness in the European marketplace, in this case becoming part of the research effort that was once the preserve of the higher Tiers. The aerospace sector in particular has seen a change in the supply chain structure, which has become wider as cost factors have risen to the fore as a prominent driver from top to bottom. Laser cutting is just one method that although competitive, has yet to be fully established in aerospace circles, but this is just one facet of a wide ranging technology.

Growing potential

Aiding the promotion of laser technologies across industry, AILU (the Association of Laser Users) was established in 1995 by a varied group of practitioners in the field to promote the use of lasers in industry and to establish a network for users across the supply chain. The belief among these individuals is that laser technology is largely underutilised for a multitude of reasons, the largest being either a lack of data or simply a lack of understanding, depending on the application.

So what are the primary concerns in aerospace? Stewart Williams is currently president of the association, fulfilling an ambassadorial role and leading the steering committee. He comments:
Currently, laser welding is not extensively utilised in either airframe or aero engine structures. In airframes parts are generally mechanically fastened due to familiarity with the process and the knowledge that this method meets all damage tolerance requirements. However, the small amount of welding that is done is currently performed by laser systems. With the advent of new alloys such as aluminium lithium and the competition from carbon fibre composites there will be many future opportunities for the use of laser welding. In addition to lasers friction stir welding may also make a significant impact. In aero engines, welding is much more extensively used but is currently mainly performed by TIG, plasma or electron beams.

Of the technologies that will continue to bring lasers forward, additive layer manufacture is at the beginning of a potentially rapid development path. Williams adds: “The move towards the extensive use of carbon composite material in airframes requires the use of much higher levels of titanium metal. The current route for making integral metallic structures is to machine them from solid. This leads to buy-to-fly ratios of around 10% which is acceptable for aluminium. Titanium though is extremely expensive to buy and machine. By making integral metallic structures from titanium using additive layer manufacture, a massive change in the buy-to-fly ratio can be achieved, with the value potentially approaching 90%. As well as the large economic savings this is extremely good for the environment. Titanium, due to the energy intensive production process, requires 40kg of CO2 to produce 1kg of metal. Lasers are at the forefront of additive layer manufacture with several processes available.

“Large development in additive layer manufacture is still required, in particular, in getting enough property data. Implementing a new process into an aerostructure is time consuming and expensive as you need the research, development and certification, after which there are still NDT issues before you deal with the supply chain and subcontractors.”

Laser cutting however, is a different matter entirely. While certification is still required the process itself is now well established, and that is a message AILU wants to promote. The main method of doing this is in its magazine it publishes and the workshops it organises. Through AILU membership, there are the obvious benefits of networking, and now there is also an emphasis on acquiring research knowledge. AILU encourages its membership to support research programmes and get involved in them. Although the aerospace sector is inherently pioneering, its cautious nature will always make it more difficult for technologies to be established. However, the benefits are there to be had once the confidence is there.

www.ppplasmaltd.co.uk
www.ailu.org.uk