Comparison of Injection Molding Technologies for the Production of Micro-optical Devices

Injection molding is a complex process regulated by many factors (injection speed, injection pressure, melt temperature, mold temperature, and others). Despite, process control and parameter optimization, it is often difficult to replicate thermoplastic components with adequate dimensional accuracy, especially in the case of geometries with high aspect ratios. For these reason, there is a need for innovative moulding technologies such asInjection Compression Molding – ICMor Vacuum Injection Moulding – VIM. In this paper conventional injection molding – IM is compared to ICM and VIM for the replication of optical thermoplastic microscale prism patterns typical of Fresnel lenses. A full Design of Experiments was performed including several micro structured prism geometries, injection molding technologies and specific process parameters for a total of 288 tests. Data analysis evidenced the greater quality of workpieces obtained by ICM, whereas VIM was a minor process improvement.