Surface Microstructure Replication in Injection Moulding

In recent years polymer components with surface microstructures have been in rising demand for applications such as lab-on-a-chip and optical components. Injection moulding has proven to be a feasible and efficient way to manufacture such components. In injection moulding the mould surface topography is transcribed onto the plastic part through complex mechanisms. This replication however, is not perfect, and the replication quality depends on the plastic material properties, the topography itself, and the process conditions. This paper describes and discusses an investigation of injection moulding of surface microstructures. Emphasis is put on the ability to replicate surface microstructures under normal injection moulding conditions, notably with low cost materials at low mould temperatures. The replication of surface microstructures in injection moulding has been explored for Polypropylene at low mould temperatures. The process conditions were varied over the recommended process window for the material. The geometry of the obtained structures was analyzed. Evidence suggests that step height replication quality depends linearly on structure width in a certain range. Further it was found that in this range, the replication quality depends strongly on process conditions. It was concluded that the achieved step height varies linearly with the mould groove width.