Lens moulders set sights on global growth
24/07/2017 Sumitomo (SHI) Demag
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.The 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 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, 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% to 10%) 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% 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.
The levels of automation vary widely for lens mould manufacturers. Some purely specialise in making the lens moulds, which are then shipped globally and the lenses are made closer to the local market. Others batch mould the lenses and then store them before they are put through the next phase of production.
Right now only one Sumitomo (SHI) Demag customer has opted to automate the entire lens production process. Here, the IntElect injection moulding machine forms just one small part of a huge production line whereby raw material is put in and, when it comes out the other end, the final product is packed and ready to ship.
There are obvious advantages and disadvantages to both approaches, with expenditure and downtime issues being two concerns. The investment cost for the 'all-in-one' solution is higher because the level of complexity involved is huge. Also, if there is a problem anywhere in the machine, the entire production line stops and no lenses are produced at all, which is a main downside. With a batch approach, there is more flexibility and operators have the ability to stop the injection moulding machine and compensate somewhere else in the system. "Continuous production might be more effective and efficient, but the risks are higher," notes Nigel. "In both instances preventative maintenance and management of downtime has to be well managed. It can be less disruptive to set aside a window every month to switch the machines off and action all the maintenance. This way you can pre-book your engineers. Alternatively, schedule checks for when you are switching moulding tools before production for another type of lens mould commences."
Using the most state-of-the-art systems available is also a key consideration. For this reason production machines are typically upgraded every five years with new drive systems, controllers and other key components, emphasises Nigel. "As well as reducing the risk of unscheduled downtime, these upgrades also ensure production rates are maximised - and, sometimes, improved - and costs are controlled."
With contact lens demand continuing to increase, machine manufacturers are constantly facing challenges of how ensure their hardware can stay one step ahead. In Asia specifically, the emergence of a market for cosmetic solutions, including coloured lenses, is part of the reason that this region is expected to experience the fastest growth between 2017 and 2024*. "The preference of disposable lenses - and relatively lower cost - makes them a much more appealing solution to resolving short or long sightedness than glasses," ends Nigel.
For more information, please contact:
Nigel Flowers
Managing Director
Sumitomo (SHI) Demag
Tel: +44 (0)1296 739500
Fax: +44 (0)1296 739501
Email: nigel.flowers@dpg.com
Web: uk.sumitomo-shi-demag.eu/
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