AUTOMOTIVE | INNOVATION
Right: The challenge in producing thick-walled lenses is to combine high optical quality with high production efficiency. Engel’s Optimelt multilayer technology with external cooling meets that challenge
necessary in order to visually inspect the rising com- plex micro structures, according to their visual functions. There is also a trend towards turnkey concepts for the production of multi-layer compo- nents including cooling station, integrated sprue picker, laser cutting or fully automatic optical inspection. Multi-layer moulds, however, are becoming more complex as different structures on both sides require more sophisticated moulds with moving elements and bigger, heavier moulds.” Moulds with greater weight and bigger dimen-
Below: Production under clean- room condi- tions – Krauss Maffei’s CX two platen machine is optionally equipped with a special flow box above the clamping unit. The box keeps the mould area almost free of dust
sions present a specific challenge in optical moulding as they require larger platens at constant clamping forces. KraussMaffei says that the modular design of its CX, PX and GX perfectly match these demands in flexibility. “Industry 4.0 is also a current challenge in the market offering many opportunities for efficiency in production at the same time,” says Mitzler. “The KraussMaffei DataXplorer, for instance, is a perfect tool to retrace each part’s history including testing and quality control. This has also been crucial for optical mould applications. Another issue is the rising demand for new control systems, which are easy to install and to operate even for more complex processes, such as multi-layer applications. “The plastication unit is the heart of any injection moulding machine. For optical articles, it must be precisely matched to the shot weight in order to avoid too-long residence times, and therefore material degradation. KraussMaffei has recently developed a new optimised PMMA screw. In addition, we have enlarged its portfolio for the arrangement of two injection units. In addition to the successful Z-arrangement (piggyback) the processor can also choose an H-arrangement (parallel). APC plus, the adaptive process control developed by KraussMaffei, is also demonstrating its benefits in this market in terms of stability,
precision and cost-efficiency in production.” Engel has developed an economic injection moulding technique for thick-walled lenses in a complex multi-component process with interlinked injection moulding machines. At Chinaplas earlier this year the company demonstrated two Duo injection moulding machines producing LED lenses made of PMMA with a thickness of 22 mm for vehicle headlamps. The Optimelt multi-layer technology is designed to combine high optical quality with highly efficient production. The company says that initially a preform is
produced and further layers of the same material added to it in subsequent 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 perfor- mance and function of the lighting optics. Because the cooling time in injection moulding increases with the square of the wall thickness, the multi-layer technology significantly improves efficiency especially in the production of thick-walled compo- nents. Several thin layers cool faster than one thick layer. If, in addition, the base body of the lens is removed from the mould to cool, the cycle time is shortened further. Cooling in air takes longer than in the mould, but it does not affect the cycle time. During Chinaplas, the lens base bodies were
produced on a Duo 1060/400 injection moulding machine in a 4-cavity mould. An Easix articulated robot was integrated in the production cell and removed the four parts and passed them to an external cooling station. From there the robot took four already sufficiently cooled preforms at a time and transferred 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 were applied successively before the Easix robot removed the finished lenses. The cycle time was significantly lower than three minutes, al- though the preforms take around 30 minutes to cool. The cooling time can be controlled via the number of cooling positions in the external cooling
50 INJECTION WORLD | September 2018
www.injectionworld.com
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