Fabrication of the low-residual-stress optical microstructure by using the simulation and practice strategies, in-mold induction heating system, and injection compression molding technology

This study developed an in-mold induction heating system for the injection compression molding process to overcome the problem of incomplete filling of microstructures caused by the formation of skin layers and residual stress caused by flow. Moldex3D software was used with the Taguchi method to optimize the molding parameters for both injection molding and injection compression molding, with the aim of reducing warpage and improving optical quality. The in-mold induction heating system has extremely high heating efficiency. Experiments revealed that a time of only 8 s was required to inducted-heat up the core to the glass transition temperature which keeps the melt under a good state of flow and allows a replication rate of 97%. In addition, the ICM process can effectively reduce the flow-induced residual stress and improve the optical properties of the obtained samples. Finally, the illuminance of the product fabricated through ICM with induction heating for 10 s was 2.3 times higher than that of the product obtained through ICM without induction heating. Accordingly, the proposed induction heating system is feasible for use in ICM the rapid manufacturing of high-quality optical products with microstructures.