Injection moulding of mechanical micro-manufactured structures for optically encoding plastic surfaces

Abstract The functional properties of micro-structured surfaces have gained increasing interests due to diverse applications such as anti-counterfeiting and medical implants. The present paper presents a process chain of injection moulding of microstructures for the mass production of plastic parts with the optically functional surfaces based on directional reflection contrast, which is obtained between two orthogonally textured positions at the same viewing angle. A data matrix was patterned on the tool as an application. More specifically, micro milling was used for fabricating the microstructures of the codes' orthogonally textured modules on the tool surfaces and micro injection moulding was conducted for the replication to the plastic components. The contrast generated between the modules was quantified by reflectance measurements and then correlated with the quality of the processed surface and microstructures. Accordingly, the processes including the tooling and injection moulding were optimized aiming at the maximum contrast on the surfaces of the tools and the replicas, respectively. The preliminary durability test indicated that the microstructures on the tool could withstand the injection moulding of over 100,000 functioning plastic parts. The work could be used as a reference of mass fabricating microstructure-based functional surfaces by means of relatively inexpensive and direct methods.