Filling analysis in micro injection moulding using weld lines as flow markers

Micro injection moulding is one of the most used processes for the mass replication of polymer-based micro components. To enable its mass fabrication capability, an optimization of the process and a full understanding of the filling of the micro cavity by the molten polymer are fundamental requirements to be fulfilled. In this paper, a novel approach based on the use of weld lines as flow markers able to trace the development of the flow front during the filling is proposed. The effects on the filling stage of important process parameters such as temperature of the melt, temperature of the mould, injection speed, and packing pressure have been investigated. An optical coordinate measuring machine has been employed for the scope. The micro cavity, which presented micro features ranging from 600 µm down to 150 µm, has been manufactured by micro electrode discharge machining. A commercially available polystyrene grade polymer has been injection moulded using a high-speed injection moulding machine. Results show that the temperature of the mould and the injection speed are the most influencing process parameters during the injection moulding of a micro component.