FEATURE
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Making a mark

The application of lasers in materials processing is finding markets beyond heavy industry, as William Payne discovers

Lasers have made a natural home in heavy manufacturing. But they are also making increasing inroads into lighter manufacturing industries, and into engineering maintenance and legacy components renewal.

Fashion apparel

Few industries experience the scale of pressures facing the fashion and apparel industries: time to market, cost and globalisation.

Fashion trends can often change week by week. Fashion is dictated not only by the big international shows in Milan, Paris, London and New York, but also in the backstreets as sudden trends emerge and become the dominant street fashion. Fashion designers have to follow both trends, and respond within weeks to a new trend, sometimes altering the whole look of a major line.

At the same time, cost has become a major factor. Imports from the Far East, from China particularly, have slashed the cost of clothing. Making clothing, particularly fashion clothes, is a highly manual and time-consuming industry. Staying responsive to the market means staying close to where fashion is made. But traditional manual methods are increasingly too costly, and too slow, to respond to the price pressures in the contemporary apparel industry.

Since the late 1990s, fashion designers have increasingly adopted laser cutting. Laser cutting in synthetic fabric materials produces well-finished edges as the laser melts and fuses the edge, avoiding the fraying produced by conventional cutting. Leather is also increasingly cut by laser.

Hong Kong-based laser manufacturer Laser Source focuses on building laser systems for the apparel industry, and has seen its technology adopted by a number of leading fashion designers.

Italian fashion designer Gianfranco Ferré has adopted laser cutting in his fashion collections, producing very detailed laser-cut geometric designs in leather jacket and chiffon couture.

Another designer adopting laser cutting is the British couturier Alexander McQueen. Since 2005, his spring and summer collections in Paris and Milan have featured laser cut floral and geometric patterns on his lace-like leather skirt designs.

In fashion jewellery, laser cutting is being adopted to create new and unusual designs, and leading to a fusion of apparel and jewellery fashion. Britain’s Design Council chose London-

based designer, Harriet Clayton, a graduate of Central Saint Martins College of Art and Design, as one of the ‘Ten of the Best’ in an exhibition at The Craft Centre & Design Gallery. Clayton uses laser cutting to produce innovative designs combining leather cuffs with jewellery.

Denim engraving is a new, fast-growing application for sealed CO2 lasers. The laser is used as a bleaching and cutting tool to create elaborate patterns and designs on uncut denim stock, as well as finished garments. It can be used as an alternative to traditional denim distressing techniques such as acid washing, sand blasting, whisker washing and ‘slub’ weaving. But the detail and sophistication possible with lasers goes far beyond these older methods. Lasers can, for example, reproduce photographs, signatures and other personalised motifs, as well as fractal patterns and fake 3D effects such as embossing, embroidering or even apparent tears and mends.

Any image that can be created in a CAD pattern can be transferred to the denim by the laser process. The end result is a pair of fashion denims that can easily command a price reaching several hundred dollars.

According to Frank Gaebler, senior product marketing manager at Coherent, which sells the Diamond product line in the apparel industry, features such as high power stability, good mode quality, fast pulse rise-time and real-time control of laser power are the ‘critical characteristics that enable the laser to produce a colour change in the denim without charring or other damage to the fabric; such damage would be both cosmetically unacceptable and would reduce the product wear life.’

DS4 Laser Technology, Pedrengo, Italy, is a major supplier of these tools and is one of the pioneers in denim engraving. ‘The majority of our systems are sold to locations throughout China,’ says DS4 president Angelo Petrogalli, ‘so system and laser reliability are both key requirements. We supply systems for engraving raw denim based on high power (up to 500W) lasers as well as lower power systems (less than 100W) suitable for custom processing of a single pair of jeans. The trade-off is speed versus cost. Purchase price of a lower power system is less, but higher power systems deliver greater throughput.’ He notes that ROI is excellent in this application because of the throughput rate. For example, even at the 100W power level, typical patterns can be created at a feed-rate of one square meter per minute.

Point of sale

One industry where industrial lasers have made surprising inroads is that of promotions and point-of-sale displays.

The point-of-sale display promotes a product in-store, highlighting special offers, promotions, and branding attributes.

Typically, point-of-sale displays reinforce sales messages contained in national advertising campaigns on television or the press. That means point-of-sale displays have got to stay current. As a national media campaign changes, or enters different phases, the point-of-sale display has to stay current with it. In practice, this can pose major challenges for marketing departments.

In-store promotions are typically designed once the national campaign has been completed and is ready to run. That gives the marketing teams and their agencies very little time to design and produce the displays, which will then be shipped to thousands of stores, before the campaign airs.

George Patton Associates of Rhode Island is a leading US point-of-sale display manufacturer. It designs, manufactures and distributes point-of-sale displays to thousands of stores across the United States on behalf of major consumer brands and their marketing agencies. The company has a particular focus on acrylic displays.

Five years ago, George Patton bought its first laser cutting and engraving machine. Its rationale for this initial purchase was the ability to turn around one-off displays and signage much faster than with its conventional router cutters. But the company quickly discovered additional benefits to laser cutting.

These included: dust-free pieces, especially useful when transferred to the silk-screen department for printing; eliminating the need for flame polishing the edge of the acrylic to achieve a clear sheen; elimination of router bit sharpening; and potential for faster output. A key issue was the possibility lasers offered of bulk peeling the masking film on the acrylic before production. With conventional router cutting, the masking film has to be left on to protect the acrylic from scratches and dust from the router cutter. This means that each cut piece then has to be manually peeled after cutting before transfer to the silk-screen department. Laser cutting could bring major savings in time and boost throughput if it removed this cumbersome manual peeling stage.

George Patton quickly came to the conclusion that its original laser system did not have the capacity for the very large volumes that the company regularly produced. It could run to 1,100 to 1,300 pieces a day, while its current router cutting was achieving 1,800 pieces per day. It believed a higher throughput system could easily beat its current output.

It produced a second requirement, which included criteria around indexed speed of throughput, enclosures that would allow fume-free cutting of acrylic, and haze-free cutting. Having come up with these three criteria, it shortlisted systems from Eurolaser, Beam Dynamics and SEI, eventually choosing Beam as its supplier.

But the company also then added a fourth criterion: workflow effectiveness. George Patton came to the conclusion that workflow is the vital factor in achieving the output breakthrough. It identified four workflow configurations, based on two laser cutting machines. The company discovered through a series of trials it conducted that there was as much as a 300 per cent difference in output between workflow configurations, using the same two laser cutting machines.

The most effective configuration the company found is what it describes as ‘single-sided Z axis loading’. Two extension tables with rollers are located one above the other on a single side of the laser machine. One pallet exits the cutting area, while the Z axis rises vertically to accept an inbound pallet from the top set of rollers. The top pallet is cut, then removed on the top set of rollers, and the Z axis lowers to accept inbound material from the bottom pallet located on the lower set of rollers.

Using this workflow template, the company can produce in excess of 6,250 pieces a day, compared to its conventional router cutting output of 1,800 pieces a day.

Engineering maintenance

Defence systems have a number of unique attributes. One is that they tend to involve very advanced engineering. Another is the need to maintain and upgrade equipment long beyond what would be considered normal in the consumer products world.

Cars have an average maintenance life of around 10 years. Even civilian airliners typically have a maintenance life of around 20 years. Defence systems can have maintenance and upgrade lives of around 30 or 40 years or more. Both the US and the UK, which operate the world’s most modern armed forces, are still flying frontline fighter aircraft that entered service in the 1970s, such as the F-15, the Jaguar and the Tornado. Support aircraft, in some cases, date back to the 1960s. Aircraft supercarriers, such as the HMS Queen Elizabeth and the HMS Prince of Wales, scheduled to enter service over the next decade, have planned operational lives of between 50 and 70 years.

The problems associated with maintaining aircraft that are 30 years old can get a lot worse if a succession of conflicts unexpectedly reduces the spare parts stockbase. This is what has happened to the F-15 Strike Eagle, America’s main frontline fighter. To address this, the US Department of Defense turned to a laser manufacturing technique called laser additive manufacturing (LAM).

Developed by the Pentagon’s Manufacturing Technology Programme (Mantech), LAM is an entirely new manufacturing process for titanium structure fabrication based on a stereo lithography approach. Utilising software to convert a CAD file to a sliced format, parts with properties in the class of forgings are built one layer at a time. Mantech claims that cycle time is reduced by up to 80 per cent; the cost of many components is reduced by 10 to 30 per cent; the process is environmentally friendly and is highly agile, allowing rapid expansion of output.

With constant flying of combat missions over Iraq from 1991 onwards, including the enforcement of the no-fly zone, the F-15’s pylon ribs were beginning to fail prematurely. The Iraq conflict had depleted the remaining inventory. Ship sets made from titanium replaced the failed components in only two months and have a life extension of five-times that of aluminium, significantly increasing the safety of the aircraft.

And finally…

Funerary monuments are almost as old as man. The earliest funerary art goes back at least 50,000 years, as old as modern humans in Europe. The earliest gravestones began as ‘wolf stones’, placed over the grave to inhibit wolves from digging up the body. Now, gravestones are coming right up to date, reflecting shifts in broader society: a change being made possible by the adoption of lasers.

Conventional gravestone preparation is a two-step process. The shape and features of the stone are first cut with a diamond saw. Finer details, finishing off and polishing are then all done by hand, using a hammer and chisel. This produces the ‘classic’ look that we are all familiar with. It allows the craftsman to create a number of designs from a selection of templates. With the decline in conventional religious belief, many people want greater individualisation in their tombstones. They also want a lighter, more expressive and modern look.

Many stonemasons are replacing their age-old chisels with lasers, allowing the production of far more individualised gravestones and markers. Coupled with software CAD programs, laser etching enables far more intricate designs, pictures and photographs to be engraved on to the headstone. The heat from the laser pops the crystals on the surface of the granite, resulting in a elevated, light-coloured etching.