Study of Morphology Wear Model of Moulds from Alloys of Aluminium EN AW-6082 in Injection Process

Abstract

Abstract. The main objective of this research is study the wear of a mould, made in easy machining material; aluminium EN AW-6082 T4 and the surface characterization of mould cavity, used in a polymeric manufacturing process, after several injection cycles. To evaluate the effectiveness of this materials in the plastic injection process, a test part with different thicknesses and shapes was designed and some inserts of aluminium were made. In the way of plastic material, a 30 % fiberglass reinforced polyamide PA6 has been employed in the experimental procedure. A reusable injection mould was used and surface measurements of mould cavity have been performed after 9200 cycles. The surface topography has been measured by using optical interferometry profiling technology and there have also been obtained roughness and surface parameters according to ISO 25178 and EUR15178N. In order to surface characterization, different areas of the mould cavity with different geometries, has been analysed. The behaviour of wear rate has been analysed by the study of the evolution of the surface parameters and functional parameters in different points of the surface mould. IntroductionIn order to cope with flexibility and short time for new product development, mould industry has made use of soft materials for cavity inserts in injection mould. However, one of the main problems using this kind of material is related to its wear rate. This paper provides a contribution for measuring the topographic wear in injection moulds cavities.One type of material used in automotive parts industry is glass fibre reinforced plastics. These kinds of materials are extremely abrasive for mould cavities. Silva et al studied behaviour of TiAlSiN and CrN/CrCN/DLC sputtered coatings in steel moulds to determine the one with better wear resistance for plastic injection processes using glass fibers as reinforcement. [1] More specifically, Zhong, Z.W. et al has studied the behaviour of a rapidly solidified aluminium alloy compared with beryllium copper and 6061 aluminium alloys in terms of their wear rates, hardness and performance as mould insert materials, for moulding a plastic lens with spherical surfaces. [2] Various fibre orientation patterns in the melt may arise in processing filled polymers. There are a number of distinct layers within the moulding with different fibre alignments [3]. In the skin layer, the fibre orientation is predominantly parallel to the flow direction due to the elongation forces developing during flow at the melt front as well as due to the shear flow after the front has passed. In contrast, a random-in-plane alignment of fibres is observed in the core layer due to slower cooling rate and lower shearing. Exactly this mutual relative motion of self-orienting filler and mold wall causes adhesive and abrasive wear of injection moulds. Wear intensity is affected predominantly by the kind of processed polymer, moulding shape and dimensional complexity, its segmentation and required precision, and the temperature and pressure of t...

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