Polished injection moulds’ and surface defects’ influence on the quality of plastic components

The quality of injection mould surfaces is important as it has a major influence on tool performance. In the specific field of plastic moulding, many products require defect free, glossy, and very smooth mould surfaces (roughness parameters in the nm-range) to achieve a satisfactory surface appearance. The surface quality is also crucial for the mould to function properly in the actual tooling application; too rough surfaces might disturb the flow of the polymer melt and increase wear, while too smooth surfaces give rise to sticking problems. A key factor towards improved tool performance is the development of a metrology framework to characterise the polished surfaces. This paper summarises a study based on a non-contact 3D-surface texture analysis, where tool steel moulds and injection moulded plastic components are characterised in terms of surface quality. Different types of defects, such as non-metallic inclusions and carbides, are studied in more detail to better understand their effect on final plastic component surfaces. Critical defect size?, Types of defects? and Defect distribution? are typical questions at issue. A test mould with intentional manufactured pores and scratches in different sizes and distributions will be designed and verified in order to enable injection mould industry to optimize selection of polymer and process variables with respect to plastic component surface quality and tool material selection