Factors influencing the surface quality of polished tool steels

Abstract

Today's demands on surface quality of moulds for injection moulding of plastic components involve no/low defect contents and roughness levels in the nm-range for high gloss applications. Material properties as well as operating conditions influence the mould finish, and thus the final surface of moulded products. This paper focuses on how particle content and different polishing strategies influence final surface qualities of moulds. Visual estimations of polished tool steel samples were combined with non-contact 3D-surface texture analysis in order to correlate traditional assessments to more quantitative methods, and to be able to analyse the surfaces at nanometre-level. It was found that steels with a lower proportion of particles, like carbides and oxides, gave rise to smoother polished surfaces. In a comparative study of polishers from different polishing shops, it was found that while different surface preparation strategies can lead to similar final roughness, similar preparation techniques can produce high-quality surfaces from different steel grades. However, the non-contact 3D-surface texture analysis showed that not all smooth polished surfaces have desirable functional topographies for injection moulding of glossy plastic components.

Development and evaluation of a methodology to integrate technical and sensorial properties in materials selection

“…Determined by the surface roughness, the refractive index of a material and the angle of incident light, gloss is generally used to describe the visual appearance of a material, as it has an impact also on colour perception [82,83]. "The ratio between the reflected and incident light for the specimen […] compared with the ratio for the gloss standard […] is recorded as gloss units (GU)" [84].…”

The influence of tool’s surface topography on mechanical properties of injection moulded product

“…Otsuka et al [17] focused their research on the effect of various roughness values of the mould's surface on flow length and mobility of polymer in thin walled injected articles. Rebeggiani et al [18,19] focused on evaluation of polished surface's quality in injection moulds and its influence on properties of polymer products.…”