Performance evaluation of aluminium Alloy 7075 for use in tool design for the plastics industry

Abstract

The performance of a high-strength aluminium alloy AA7075 as a candidate injection mould material has been assessed. Particular attention has been focussed on the thermal and wear performance of the AA7075 alloy compared to a standard EN19 tool steel alloy. In view of the fact that aluminium often fails due to poor wear resistance, surface treatment of the aluminium alloy was implemented by hard anodising. The assessment was performed by manufacturing three mould insert sets of identical design from each of the materials, namely EN19 steel, AA7075 and AA7075 in the hard anodised state. Each insert set was subjected to 10 000 shots in an injection moulding machine. The core temperature of the inserts was measured during moulding and wear was assessed by comparing profile measurements of the mould cavities before and after moulding. The EN19 steel and uncoated AA7075 inserts did not show signs of wear whereas edge retention was impaired by hard anodising. The higher thermal conductivity of aluminium compared to conventional tool steel was not affected by hard anodising.