Lighting up time

Traditional marking methods such as engraving, dot matrix and inkjet have been superseded by laser technology which is permanent and doesn’t damage the surrounding substrate. Mark Venables reports.

In a bid to provide full product traceability and help protect against counterfeiting, manufacturers are turning to ever more sophisticated technologies. Traditional marking methods such as engraving, dot matrix and inkjet have been superseded by laser marking.

To meet customer requirements and comply with the US Food and Drug Administration (FDA) regulations, Medtronic, market leader in the manufacture of stainless steel and titanium parts for the orthopaedics industry, has to give every item it manufactures a cradle-to-grave alpha numeric mark — which cannot be removed or obliterated by any substance.

The mark includes the part and serial number, the product description and sometimes a logo, which it has to achieve without affecting the inherent integrity of the product or the base material. The mark has to be achieved on very small parts, some as small as a 1/4in (just over half a centimetre) in diameter. A further, obvious, consideration is that marking must fit comfortably within the existing production process and be affordable to both install and operate.

Following a rigorous evaluation of the alternative marking technologies available, Medtronic concluded that laser marking was the only viable technology available and it selected Electrox as its partner.

Laser marking uses the highly concentrated energy of an amplified beam of light focused on to a very small spot and creates the images by changing the colour of the surface of the material without causing damage to the surrounding substrate.

The mark is both permanent and non-intrusive and because there is no physical force applied to the workpiece, the risk of distorting thin-walled and fragile products is virtually eliminated.

Another manufacturer to move to laser marking is glass bottle manufacturer O-I which has installed laser coding equipment at its Harlow facility to enable coding directly on to the bottle while the glass is still hot.

As a supplier to all of the UK‘s top five breweries and many of the country’s leading regional players, O-I recognises the value of providing a reliable code for traceability. The information can be used to readily identify faulty batches, distinguish between suppliers where customers’ source bottles from multiple locations, and can be used to protect against counterfeiting.

‘We were keen to ensure that the container code was easily distinguishable from the information used by the filling company to identify the batch or use-by date of the bottle contents,’ explained quality assurance manager Mark Eldrett.

‘In addition, we wanted a durable solution that could withstand the rigours of being handled through the filling and distribution process. If the text is damaged or removed, it is ineffectual for purposes of traceability or authenticity.’ As a result, inkjet coding was considered unsuitable for O-I’s requirements, and its supplier Linx recommended the use of its hot glass coding laser solution.

The principle behind this technology is that better laser coding results are achieved when it takes place close to the point at which the bottle or jar is formed — in other words, while the glass is still red hot. This is because this process generates a very clean, smooth mark that is less visible and more discreet than codes created on cold glass.

Not surprisingly, coding on to glass containers at the actual point of manufacture presents a number of challenges both in terms of the process itself and the extreme conditions in glass manufacturing plants. For example, during manufacture, the temperature of the newly-formed bottle reaches 650oC, while the ambient temperature close to the production line is around 70oC.

To ensure an effective code, the laser optics are designed to tolerate a long lens-to-product distance and have sufficient depth of focus to deal with the slight inconsistencies in the alignment of the bottles as they travel down the line. The extra-long beam delivery system, comprising flexible arm and printhead, can withstand ambient temperatures up to 70oC.

The coder itself is designed for installation above or beside the production line and has a cooling system allowing it to operate at 45oC.

O-I has installed Link’s Xymark BBH on six of the seven high-speed production lines at its Harlow plant. Each is programmed to apply a single-line alphanumeric code at 50m/min, indelibly marking date and time of manufacture on to the base of the bottle immediately after it has been formed.

This position ensures the required differentiation from the coding information applied by the manufacturer, which is generally printed on to the bottle neck, closure or label.

Motorsport transmissions manufacturer Hewland Engineering has cut component marking times since replacing its dot matrix engraving facility with a laser marking system. Hewland manufactures and supplies racing gearboxes to virtually all levels of motorsport from its facility at White Waltham in Berkshire. Between 1993 and 2000, the company invested some £8m in creating a facility that is the envy of the industry and, since then, has continued to invest as requirements demand.

For instance, the increasing need for greater component traceability in the motorsport sector recently led Hewland to assess its part marking facility.

It was apparent that the company’s dot matrix engraving machines and rotary mill-type engravers were the sources of a growing bottleneck. ‘Our existing facilities were slow and took too long to set up,’ said Hewland’s work superintendent Colin McKee.

‘As a result we took a long, hard look, and eventually selected laser marking.’

Installed last year, the HKR5 machine — from HK Technology — has been put to work marking a wide range of parts for motorsport transmissions, including lay shafts, hubs, gears, washers and shims. According to Mckee, around 90 per cent of Hewland’s components now require some form of marking.

Using computer-controlled optical scanning systems, the HKR5 moves a high-speed laser beam over the workpiece. The non-contact focus of the beam produces a clear, high-contrast and permanent mark on all metals and most plastics to a controlled depth of up to 1mm.

Hewland uses its machine to produce marks that include part numbers, logos, drawing numbers and alignment marks on a range of flat, curved and irregular surfaces.

‘The laser system is Windows-based and extremely easy to use,’ said McKee. ‘We can download from Coral Draw if required, although starting a program from scratch will only take a few minutes. Our dot matrix engravers would take around half a minute to mark every part, whereas the HKR5 takes seconds.

‘Within a few days of the machine being installed we could see work flowing more easily.’ McKee said that mark clarity has also improved dramatically. ‘Any mark below 1mm would be extremely difficult to see using dot matrix engraving techniques. But we have no such problems with laser marking.’