Improvement of the replication quality of randomly micro-textured injection-moulding components using a multi-scale surface analysis

In this work, the relations between the replication quality of random, coarse textured, surfaces with the injection-moulding process has been analysed through 3D areal characterisation techniques. The multi-scale surface approach has been applied to effectively separate the main surface components, roughness, waviness and form. Amplitude, functional, hybrid and spatial parameters, as well as alternative surface characteristics such as the number of micro-cavities (NG), grain area ((G) over barA) and grain volume (G (V) over bar), were used as a way to determine the influence of the manufacturing process on the replication quality of the mould texture, either at the macro- or micro-scale. A model to quantify the effect of the injection-moulding parameters on surface texture replication has been obtained through a 24 factorial design of experiments. It was found that the holding pressure was the main parameter to enhance the mould texture replication, followed by the melt and mould temperatures. The injection volumetric flow rate did not have a significant effect on the texture replication ratio. The surface analysis, at the human eye resolution, only allows the detection of macro-defects such as form deviation. On the other hand, the surface characterisation at the micro-scale allows the detection of roughness differences, up to 30% on average, as a function of the injection conditions.