INDUSTRY FOCUS CHEMICALS & PHARMACEUTICALS LENS MOULDERS SET SIGHTS ON GLOBAL GROWTH Sumitomo (SHI) Demag’s new all electric, IntElect injection moulding machine T
he biggest markets for contact lenses are currently North America, Asia
Pacific and Western Europe, with the sector currently worth nearly US$15 billion. Since 2011, there has been a steady increase in demand and the lens manufacturers, many of whom are based in Ireland, expect this trend to continue. “Much of this demand is driven by people who no longer want to wear glasses, as well as improvements in lens technology,” says Nigel Flowers, managing director of Sumitomo (SHI) Demag UK. “When you have to wear glasses, it is a bit of a compromise, yet today it is easier to not accept the shortfalls.” There are many potential customers in
emerging markets who want to get their eyes corrected through glasses, but are equally open to the benefits of lenses. It’s anticipated that extra demand for lenses will, in the near future, come from new regions, such as Latin America and Eastern Europe.
ONE MOULD FOR EVERY LENS… EVEN DAILY DISPOSABLES Because no two eyes are the same, there are a broad spectrum of styles and parameters to meet when it comes to the production of lenses. Every contact lens that is produced requires a bespoke mould, which is where Sumitomo (SHI) Demag’s injection moulding expertise comes in. Knowing that each lens must meet the highest levels of quality and cleanliness, it’s essential that the moulds are repeatedly perfect too. The process starts with the injection
moulding of a front and base curve mould. This mould is then filled with a monomer (a molecule that can be bonded to other identical molecules to form a polymer) and is then closed and cured before the lens is then hydrated and packed. “Every single mould used to make a contact lens is produced to a very high level of precision and cannot be reused,” explains Flowers, who confirms that the discarded moulds are recycled – but not for lenses. “Because the final lenses are moulded against a surface that
14 JUNE 2018 | AUTOMATION
Advances in medical science have enabled contact lenses to be accessible to more people around the world, while the quality of the lenses themselves have improved so much that demand is growing all of the time. Today, there are estimated to be 125 million people who wear contact lenses globally. As a result, the production of soft and disposable lenses in particular is big business, something that Sumitomo (SHI) Demag is well aware of. The company is a major player in supplying the machinery that produces the moulds that make the contact lenses
has already been injection-moulded, any imperfection within the mould will find its way into the lens,” he clarifies. To accomplish the quality and accuracy,
Nigel Flowers, managing director, Sumitomo (SHI) Demag UK
Above: Then and now. The first contact lens was made of glass in 1887. Today, more than 125 million people globally are regular contact lens wearers
Sumitomo (SHI) Demag installs its award-winning activeFlowBalance technology into machines that produce the contact lens moulds. This helps to combat uneven filling of multi-cavity moulds. “When we’ve got to a certain part of the fill and the materials are moving under their own inertia, we stop pushing and let the mould fill naturally. We are not forcing it in at high pressures and forces,” explains Flowers. “The key is to ensure that the manufacturers that specialise in making contact lens moulds can do it repeatedly and with the highest precision in order to mass-produce the moulds cost efficiently. For this reason, production using activeFlowBalance only really works on all-electric machines, such as the IntElect. That’s because we can repeatedly stop the screw in the right place to allow the mould to fill naturally. This intervention reduces the cavity pressure and stress in the material. Once one cavity fills it moves on to another one.” Typically, there are between eight and 16 cavities in each moulding tool.
COUNTLESS OPTOMETRIC PERMUTATIONS A variety of moulds are used in the production of contact lenses, representing the different magnification levels (graded in quarter diopters) that are prescribed for each lens. The differences are in the variation in the space thickness between the front and rear of the mould, which dictates the thickness of the lens. There are a finite number of
combinations and a standard number of magnifications and variations on the curve. Nevertheless, production still has to be carefully planned and controlled, to
ensure the machines maintain the highest efficiency levels possible. In a relatively new development, bifocal
lenses are now being manufactured on a larger scale to correct both near and far vision. With these lenses, the centre has a different magnification than the outer ring of the lens. In addition, some companies produce Toric lenses that are thicker or shaped at the bottom, which sit on the tears on your eye and they will rotate round. “If you’ve got a stigmatism, the lens rotates and always ends up in the right place,” says Flowers. All of this places greater challenges of the machines to meet the specific needs of the customer, but breakthroughs are happening all the time,” he reveals. “We’ve not quite reached the point where we are 3D printing the lens according to someone’s eye, however this might be possible in the future.”
HOW DO THEY DO IT? For the production of lens moulds, both all-electric and hydraulic injection moulding machines are used – with the bias heavily weighted (90 per cent to 10 per cent) towards all-electric. Repeatability is the main rationale, as well as meeting ISO Class 8 clean room standards. Direct drive machines offer major improvements in efficiency, including a reduction of up to 75 per cent in energy usage during operation and improved repeatability and cycle times. However, manufacturers of hydraulic IM machines have recently made big strides to standardise the process in order to accommodate the variations in moulds yet still meet the high quality requirements. Automation is playing an equally big
role in maintaining the efficiency levels and reducing cycle, where each mould is typically produced in under three seconds.
/AUTOMATION
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