Mona Naderi

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

Abstract 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.

Multi-technology products

Development of technical solutions that lead to widening the use of multi-technological products as well as in assessing ecological and economic potentials of multi-technological products have not yet been studied intensively. The activities conducted in the context of this research area focus on these aspects. The aforementioned aspects have been examined, evaluated and quantified on the basis of three example products resulting from the first funding period. The research activities conducted on the example components deliver the basis for the layout of different integrated multi-technology production systems. Technical solutions that enable coupling of different process steps with each other as well as the integration of different functionalities and different materials in final multi-technology products have been proposed. The complex interdependencies of the products themselves and their associated production processes have been researched and evaluated intensively. Finally, a profitability assessment of the proposed solutions was conducted and future research topics identified.

Improved molding of micro structures using PVD-coated mold inserts

Abstract Micro structured optical plastics components are intensively used, i.e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting, or laser technology. Injection molding has been proven successful for the large-scale production of these parts. However, the production of these parts still causes difficulties due to challenges in the molding and demolding of plastics parts created with laser-structured mold inserts. A complete molding of the structures often leads to increased demolding forces, which then cause a breaking of the structures and a clogging of the mold. An innovative approach is to combine physical vapor deposition (PVD)-coated, laser-structured inserts and a variothermal molding process to create functional micro structures in a one-step process. Therefore, a PVD coating is applied after the laser-structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of molding trials with polycarbonate (PC) and polymethyl methacrylate (PMMA) using different coated molds, the mold temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the molded parts was evaluated by digital three-dimensional laser-scanning microscopy. The influence of the molding parameters and the coating of the mold insert on the molding accuracy and the demolding behavior were analyzed. It was shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal molding process. Due to the mold coating, significant improvements could be achieved in producing micro structured optical plastics components.