1. ¹Luleå University of Technology, Luleå, Sweden
2. ²Laser Expertise Ltd., Nottingham, UK

Correspondence: T Ilar, Division of Manufacturing Systems Engineering, Luleå University of Technolgy, Luleå 97187, Sweden

Received 27 December 2007; Accepted 5 November 2008.

Abstract

This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown-related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN-based manufacturing systems, namely the Overall Equipment Effectiveness. The paper also demonstrates the effect on model accuracy of a miss interpretation of part scrap behaviour or none deliberately simplified modelling of part scrap. This uncertainty in model accuracy will reduce the usefulness of the simulation model as a decision support tool.