INNOVATION | OPTICAL MOULDING
from the mould to cool, the cycle time is shortened further. Cooling in the air takes longer than in the mould, but it does not affect the cycle time. The lens base bodies were produced on an Engel Duo 1060/400 injection mould- ing machine in a 4-cavity mould. An Easix articulated robot is integrated in the production cell and removes the four parts and passes them to an external cooling
Above: Engel connected two Duo injection moulding machines to produce thick-walled LED lenses
Right: Engel’s Optimelt multilayer technology with external cooling can produce thick-walled lenses to
combine high optical quality with high production efficiency
18
ing 5 nm on the surface, the highest possible parts quality and precision are required. Looking at future developments in optical moulding, Arburg adds that the current market trends will be further refined and their require- ments will increase continuously. “This means that the demands on precision in injection moulding will also continue to increase,” Rolf-Uwe Müller says. “In this respect, Arburg is well prepared for the challenges ahead with its electric Allrounders, its injection compression moulding process, its powerful control systems and the ability to easily integrate special processes, as well as its adapted and fully integrated Multilift robotic systems. This is supplemented with advice on application technol- ogy and coordinated service that guarantees high technical availability over long periods of time.” Plastics are increasingly being used to produce high quality optical components, reports Engel. This is because polymeric materials are lighter than glass and offer product designers more freedom. Engel is providing a wide spectrum of technolo- gies processing both PMMA and polycarbonate materials, as well as LSR for optical applications. The company adds that it has developed a manu- facturing cell for LED lenses made of PMMA with a thickness of 22 mm for vehicle headlights using two Duo injection moulding machines. In order to increase efficiency in producing thick lenses, Engel has developed Optimelt technology with external cooling. Initially, a preform is produced and further layers of the same material added to it in subse- quent stages. Overmoulding compensates for any sink marks in the surface of the previous layer and achieves high optical quality. Optical tests have shown that the boundary between the layers has no influence on the performance and function of the lighting optics. Because the cooling time in injection moulding increases with the square of the wall thickness, the multilayer technology signifi- cantly improves efficiency especially in the produc- tion of thick-walled components. Several thin layers cool in total faster than one thick layer. If, in addition, the base body of the lens is removed
INJECTION WORLD | September 2019
station. From there the robot takes four already sufficiently cooled preforms at a time and transfers them to the 4 + 4 cavity mould of the Duo 600H/600H/500 combi multi-component machine with rotary table. There, two more PMMA layers are applied successively before Easix removes the finished lenses. The cycle time is significantly lower than three minutes, although the preforms take around 30 minutes to cool. The cooling time can be controlled via the number of cooling positions in the external cooling station. The combination of a standard injection moulding machine and a two-component machine is synonymous with very high production flexibility. Both machines can also be utilised independently of the other with different moulds. Engel adds that liquid silicone rubber can be
processed efficiently in injection moulding and also has good material resistance. LSR is therefore becoming increasingly important as a material for optical lenses in lighting technology. By manufac- turing LED headlamp lenses on a tie-bar-less Engel E-victory 310/120 injection moulding machine in an automated, rework-free process, the company says that geometrically highly complex LSR products can be manufactured economically in large quantities. The automotive industry is increasingly exploit- ing optical silicones for lighting systems. In addition to this, LSR is also becoming increasingly important as a lens material for street and building lighting.
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www.injectionworld.com
PHOTO: ENGEL
PHOTO: ENGEL
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