Research Components advance technology for moulding optical products
Researchers Christian Hopmann and Paul Walach at the Institute for Plastics Processing (IKV) in Aachen, Germany, have discovered that multi-layer injection moulding or compression moulding lowers the cycle time for, and increases the quality of, thick optical parts. Mould design is key.
Optical parts made of plastics play an increasing role in many areas of application. For example, lenses for LED-headlamps, mobile phone cameras or illumination optics enable the development of innovative products in the field of automotive technology or lifestyle products. Optical components are used intensively in consumer electronics, optical sensors in metrology, LED-lighting and laser technology.
Good quality requires long cycle times
Since the optical design of these components is often thick-walled, the cycle time of the production process in injection moulding takes several minutes to achieve the required quality. In order to ensure an economical production combined with high precision, thick-walled optical components cannot be moulded in one step. The goal of multi-layer injection moulding is therefore to reduce the cycle time of such components through a process in which a pre-moulded layer is overmoulded with the same transparent material.
The separately overmoulded layers are thinner than the final wall thickness. In this manner the resulting cycle time of a multi-layer lens is lower than a single layer lens with the same thickness. Furthermore a lens built up layer by layer using overmoulding can achieve a higher precision in geometrical accuracy because of a lower potential for warpage and shrinkage in each layer.