A study of degradation of laser-sintered moulds using wear tests

Abstract

Purpose – Surface changes like wear or local plastic deformation occurring during service of a mould make it unsuitable for further use and determine its life-time. The performance of the mould and its design are important aspects that influence its longevity. The purpose of this paper is to study the behaviour of mould materials manufactured by laser sintering, a type of rapid manufacturing process, and to explain their relative in-service performance. Design/methodology/approach – Mould specimens were made by two laser-sintering machines (a DTM Sinterstation and an EOSint M250 Xtended equipped with CO2 lasers) using two iron-based commercial powders, i.e. LaserForm ST-100 and DirectSteel 20 V1, respectively. They have been subjected to two types of wear tests, i.e. bidirectional fretting and unidirectional pin-on-disc tests, under loading conditions leading to wear and/or plastic deformation of the specimens. The results obtained show similar trends to that obtained from the real-life performance of polymer injection moulds manufactured using such materials and processes. Findings – LaserForm is a better material for injection moulds material than DirectSteel; however, and its performance will deteriorate under impact injection moulding conditions where plastic surface deformation will occur in addition to abrasive wear. Both materials show high coefficient of friction, their performance will be enhanced by redesigning the composition of the powders by incorporating hard and low friction components. The methodology adopted here for investigating the surface degradation behaviours of materials is able to give sufficient and reliable information about the wear behaviour of mould materials for practical applications. Originality/value – It is concluded that the wear tests used here are suited to characterize the in-service mould wear strength, and such tests could be preferably used to shorten the mould development/validation time.status: publishe