Additive manufacturing of variothermal injection moulding insert made of Al-40Si

Abstract

Injection moulding has been a pivotal technology in the mass production of polymer optics for many years. The surface quality of the moulding inserts exerts a significant influence on the quality of the optics produced. In the production of micro-structured polymer optics, such as Fresnel lenses, conventional isothermal injection moulding is unable to achieve the requisite surface accuracy. Variothermal injection moulding allows for improved surface accuracy and reduced residual stresses, but increases technical effort and cycle times. To reduce the cycle time and residual stresses of variothermal injection moulding, the potential of additive manufacturing of Al-40Si for the fabrication of moulding inserts is investigated. In order to achieve these objectives, the offered design freedom of additive manufacturing is investigated with a view to developing optimised conformal cooling channels. Numerical methods will be used for thermal and structural analyses. The performance of the newly developed moulding insert is evaluated experimentally by thermographic measurements and the measurement of stress birefringence on replicated PMMA samples.