A Methodology of Availability Assessment for Complex Manufacturing Systems GABRIELA TONŢ 1 , MIHAIELA ILIESCU 2 , DAN GEORGE TONŢ 1 1 Department of Electrical Engineering, Measurements and Electric Power Use, Faculty of Electrical Engineering and Information Technology University of Oradea Universităţii st., no. 1, zip code 410087, Oradea, ROMÂNIA, dtont@uoradea.ro , gtont@uoradea.ro , http://www.uoradea.ro 2 Manufacturing Department 2 “POLITEHNICA” University of Bucharest 2 Splaiul Independenţei no. 313 Street, ROMÂNIA iomi@clicknet.ro Abstract: -The degree in which a system is operational in a given horizon of time is the key indicator of service quality perceived by business users. The availability of critical systems is a function of the system reliability, maintainability and accessibility of support resources. Based on a comparative analysis, selecting an adequate method of availability assessment requires typical structures identification, reliability indices characterization and evaluation of non-reliability impact of the parts on system availability. Frequently used, binomial method leads to optimistic results due to bivalent states of components (operating/fault). For serial or parallel reliability structures, a realistic evaluation of system availability is obtained by applying polynomial or direct analysis based on reliability block diagram. A complex structure implies a successive assessment of structural components allowed by Monte-Carlo simulation providing accurate indices values. The paper presents a method of availability evaluation using Monte-Carlo simulation techniques which allows a comparative analysis of component impact on the system availability. Key-Words: - availability, assessment, simulation, structures, complex manufacturing system, operational and reserve parts 1 Introduction Reliability and availability are valid measures of quality, performance and effectiveness of a complex manufacturing system. Machine tools continually increase in sophistication (higher levels of diagnostics, diagnostic and prediction capability,), inherent flexibility, and user friendliness. Environmental demands require an increase inherent flexibility regarding multiple subsystems support, and user friendliness. Availability assures the ability of system or component to perform its required function at a stated instant or over a stated period of time. The availability management inputs deals with business impact analysis and availability requirements while the outputs are concerning risk assessment, reliability and maintainability monitoring, improvement plans. High availability focuses specifically on minimizing or masking the effects of a component failure within the system. Availability improvement needs establishing feedback and feed forward methods for continuous improvement regarding performance monitoring, life cycle management and effective corrective actions applied to component criticality assessment. Due to the increasing complexity of systems, availability assumes implementation at each capability level. Concept development, determining product functionality based upon customer requirements, technological capabilities, and economic realities. Design development, focusing on product and process performance issues necessary to fulfill the product and service requirements in manufacturing or delivery. WSEAS TRANSACTIONS on SYSTEMS Gabriela Tont, Mihaiela Iliescu and Dan George Tont ISSN: 1109-2777 822 Issue 6, Volume 7, June 2008