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(Plastics Today) -- Engel has introduced new injection molding technology specifically aimed at the production of optical components, offering machines with plasticizing unit components optimized for running transparent polymers and an overmolding process to create thick lenses. Called optimelt, the process starts with the production of a pre-molded part that is recoated with additional layers (usually of the same material) in one or more subsequent stages.
Engel pursued the technology at a time when it says more and more high quality optical components are switching from glass to polymers, propelled by greater cost efficiencies and more flexibility in product design. "The challenge now is to strike the right balance between superior optical quality and high cost effectiveness," Engel noted in a release.
Utilizing injection molded plastics does pose its own challenges, however, including microstructures on the surface of light-guide elements that must be precisely molded across the entire flow path, and the need to minimize residual stress in molded parts, especially where a subsequent coating will be applied. Finally, the optically effective surfaces on lenses with large differences in thickness must be accurately contoured.
Engel says a primary advantage of its multi-layer overmolding process compared to single-layer designs is that the recoating covers sink marks and other defects on the surface of the previous layer, helping ensure high optical quality. The company says this particular benefit makes the process especially attractive to manufacturers of thick- section components such as LED lenses. Engel also notes that studies on multi-layer components in the area of lighting technology have shown that boundary layers between coatings have no effect on the function of illumination optics.