Abstract With the ever increasing persity of manufacturing and maintenance needs for modern products, the realm of machine tool design has expanded considerably in recent years。 While machine tools for producing singular parts are widely documented, there is much less information available about machine tools for specialist tasks such as repair and maintenance。 The paper aims to give an overview of the developments in the field of specialist machine tools and machining systems with a particular emphasis on maintenance operations and in situ machining。 The difficulties of performing maintenance on large-scale systems are outlined along with the potential benefits of in situ machining in these applications。 A number of examples of specialist machines for applications in various fields are described。 The developing area of micro machine tools and micro factories is introduced along with examples of systems which have been developed or proposed。 The possible advantages and draw-backs of the various technologies described are discussed。 The paper goes on to comment on the potential for a new approach which combines these technologies to produce small in situ machine tools for performing macro-scale machining operations on large workpieces。 These machining systems could offer increased versatility of in situ maintenance machining, compared to machines designed for a single repair operation, while reducing costs and environmental impacts。76168

Keywords In situ machine tools 。 Serial kinematics machines 。 Parallel kinematics machines 。Miniature machine tools

1 Introduction

The field of machine tools for generating singular products is well documented; however, the area of specialist machines for dedicated tasks such as repair/maintenance has received less attention。 This paper explores the area of specialist machine tools with a focus toward in situ machining operations for repair and maintenance。 In  general, repair and maintenance machining has been carried out using large conventional machine tools which are, by necessity, installed in dedicated machine shops。 This can pose problems, especially for work on large and potentially complex systems such as aircraft, ships, power stations, metal fabrication mills, heavy machinery, etc。 In these cases, components which require re-conditioning work must be dismantled from the system and shipped to a machine shop for processing before they are returned and re-assembled into the system。 This process is time-consuming, complex, potentially dan- gerous and expensive; in the case of very large systems (e。g。 power stations), this type of maintenance may not be possible at all。 Furthermore, this conventional maintenance

process can result in prolonged downtime of the system。 For

J。 Allen : D。 Axinte (*)

Department of Mechanical,

Materials and Manufacturing Engineering, University of Nottingham,

Nottingham, UK

e-mail:   dragos。axinte@nottingham。ac。uk

P。 Roberts : R。 Anderson Rolls-Royce,

London, UK

these reasons, in situ machine tools which can be brought and attached to the component to be machined, while that component is still more or less installed, can offer obvious advantages。 To address this niche domain of specialised machine tools, an overview of the development of such systems is presented with examples having applications in a range of industries。 In addition, some other developments in specialist machining systems are discussed。

The developing area of miniature or micro machine tools is also investigated。 The motivation and philosophy which led to their development is explored, and a number of example machines are described。 The concept of integrating several of these machines into micro factories is also introduced and some examples which have been produced or proposed are presented。 A selection of specialist miniature in situ sampling and inspection machines are introduced。 The potential advantages and disadvantages of these various machining systems are discussed。