A REVIEW BY DISCUSSION OF CONDITION MONITORING AND FAULT-DIAGNOSIS IN MACHINE-TOOLS

The main theme of the paper is a description of the activity around the world in the way of research, development and application of techniques for condition monitoring and fault diagnosis of machine tools. The paper initially discusses the necessity for planned maintenance, the extension of this into condition based maintenance and the necessity for condition monitoring. It then discusses some definitions relating to this field of activity and in particular differentiates between hard and soft faults and the reason the latter can be used for prediction, whereas the former is easier to diagnose. The paper endeavours intentionally to restrict itself to the condition monitoring and fault diagnostics of the machine tool itself. Thus there is no real discussion of research into tool or process monitoring-although many areas of this type of work cut across that of the machine itself. For this reason there are notes on area of tool condition monitoring where these have techniques and expertise which lend themselves to the machine itself. There is a discussion on on-line and off-line monitoring followed by a brief survey of the automatic monitoring presently available on machine tools. Much of this is related to hard fault diagnostics but there are signs that soft faults are now being monitored. The paper then describes methods for the choice of parameters for condition monitoring and their data acquisition. Two large sections then follow on fault monitoring and diagnosis of both hard and soft faults where much reference is made to recently completed research under contracts ESPRIT 504 and SERC GR/E/12818. These sections also include references to ongoing research and EC contracts, including application of neural networks, expert systems and fuzzy logic. The paper concludes that the area of condition monitoring and fault diagnosis is being seen as of increasing importance. All available techniques have their drawbacks, all are not absolute and there is a plea for more information as to how real faults develop and exhibit themselves in measured parameters.