Supporting maintenance strategies using Markov models

The basic principle of total productive maintenance (TPM) is to reduce and ultimately eliminate breakdowns by pre-emptive maintenance strategies, which rely on the co-operation of all employees. When properly applied, TPM can bring about tremendous improvements in a company's performance. However, recent research, using interviews and questionnaires, suggests that many managers in manufacturing industries in Europe still have to be convinced of the usefulness of TPM. Many more are perhaps unsure of the losses which can accrue as a consequence of not having an appropriate maintenance programme implemented in their organizations. A simple yet powerful Markov model is proposed as a diagnostic tool for the manager who wants an effective way of identifying the prime costs involved in production line downtimes, and hence the potential benefits of TPM. The influence of the performance of a single machine on a line can be investigated. This is vital information for strategic planning of machine replacements, which involve major capital investments. In particular, an approximate analysis of the benefits of a machine building up a buffer stock is presented, and assessed against the costs involved. The model has been implemented as an Excel macro.