A Dutch company has come up with a way to print lenses, which one day could be used to make prescription glasses on demand
MAKING things with a three-dimensional (3D) printer is quickly becoming a commonplace activity. In part this is because of the expanding range of “printable” materials, which now includes precious metals, biological tissue and even the ingredients for a pizza. But the machines are still not very good at producing smooth surfaces. This is because 3D printers deposit material layer by layer, which can leave ridges.
Sometimes, as with a Margherita, rough surfaces do not matter. But many things need to be smooth to look good and work well. Machining or polishing 3D-printed items by hand costs time and money. Some companies have tried polishing 3D-printed metal and plastic parts in machines like those used for polishing pebbles, but it is a slow process. Now a way has been developed to print objects in a transparent material with a precise shape and a surface that is smooth enough to be used as a lens.
LUXeXcel, a company based in the Netherlands, has pioneered the technology and used it to print some reading glasses. These are not yet as good as prescription spectacles, the lenses of which are individually polished. But it is early days and as the firm improves its process it is busy with other applications.
In March LUXeXcel opened a new factory near its headquarters in Goes to print lenses for light-emitting diodes (LEDs). With low-energy consumption and a service life extending to many years, LEDs are steadily replacing traditional bulbs and tubes in most domestic, urban and industrial lighting.
Bespoke every time
An LED comes in two main parts: the electronics which turn a semiconductor into a light source, and a lens to direct the light. The lenses are made by injecting a transparent thermoplastic into a moulding machine, a mass-production process where economies of scale count. It makes one-offs and small production runs prohibitively expensive because new high-precision metal moulds have to be manufactured every time a new design is put into production. But 3D printers excel at customised production and manufacturing one-off things. They build things additively, depositing material under the direction of computer-aided design software. As software can be changed with relatively little cost, there is no penalty in making one or a few things.
LUXeXcel calls the 3D-printing process it has developed Printoptical. It is based on a large-format commercial inkjet printer fitted with specially adapted print heads. These heads deposit droplets of fluid plastic to build the shape of the lens. But instead of forming layers, the droplets are allowed to flow into one another to create a pool of liquid. The emerging pool is measured by lasers and once it has taken on the required shape it is solidified by curing the plastic with ultraviolet light. Repeating the process allows complex lenses to be constructed. The pooling process leaves smooth surfaces that require no polishing.
As LEDs are developing rapidly, lighting companies struggle to bring out new products quickly. Printoptical can produce prototype lenses which can be assembled and tested in a matter of days instead of months with injection moulding.
As it makes small production runs cheaper, the new process allows architects and lighting companies to customise illumination in homes, offices and shopping centres. Each light could have a different lens, created for its purpose. A museum, for instance, might use specially tailored lenses to illuminate paintings uniformly. Streetlights, too, could be optimised with lenses that avoid shining light into a bedroom window in one location and in another to project more light down a dark alley.
There is also a potentially huge repair market. Besides LED lenses, LUXeXcel can print stained-glass inserts to repair church windows. Replacement lenses for broken vehicle lights are another possibility. These are hard to obtain for some classic cars and even for modern vehicles it would cut down on the number of spares that need to be stocked.
As the company continues to develop the technology it expects many more applications to emerge. “We think the level of precision will go well beyond that provided by injection moulding,” says Richard van de Vrie, LUXeXcel’s chief executive. In time he thinks that will enable the printing of prescription lenses for glasses from a computerised eye scan. Since the 3D printer could make not just the lenses but the frames as well, it could lead to bespoke glasses being printed on demand at high-street stores.
From the print edition of Technology Quarterly