Replication of micro-structured injection molds using physical vapor deposition coating and dynamic laser mold tempering

Plastics parts with micro-structured surfaces enable the development of innovative products such as optical components in sensors or light management systems for laser and LED applications. Moreover, micro-structured parts can be utilized in the medical and packaging industry for hydrophobic or antibacterial products. The production of micro-structured parts causes challenges in molding and demolding. Rough surfaces of the laser-structured mold inserts offer flow resistance during injection phase as well as increased demolding forces which cause failures of the replicated structures during ejection. Therefore, an innovative approach combines coated mold inserts by means of physical vapor deposition (PVD) and a highly dynamic laser tempering system to improve the replication of micro-structured plastics parts. Both uncoated and coated micro-structured mold inserts were used in a series of molding experiments by means of conventional and dynamic mold tempering. Based on the results, it can be shown that significant improvements of the replication of micro-structures of different sizes can be achieved by use of PVD mold coatings. This is attributed to the tribological interactions between coating and plastics melt. Furthermore, results indicate an influence of the thermal conductivity of PVD coatings to enhance replication quality.