Introduction

Final finishing operations in manufacturing of precise parts are always of concern owing to their most critical, labour intensive and least controllable nature. In the era of nanotechnology, deterministic high precision finishing methods are of utmost importance and are the need of present manufacturing scenario. The need for high precision in manufacturing was felt by manufacturers worldwide to improve interchangeability of components, improve quality control and longer wear/fatigue life (Keown 1987). Taniguchi (Taniguchi 1983) reviewed the historical progress of achievable machining accuracy during the last century. He had also extrapolated the probable further developments in microtechnology and nanotechnology, Fig. 8.1. The machining processes were classifieds into three categories on the basis of achievable accuracy viz. conventional machining, precision machining and ultraprecision machining. Ultraprecision machining are the processes by which the highest possible dimensional accuracy can be achieved at a given point of time. This is a relative definition, which varies with time. It has been predicted that by 2000 AD, machining accuracies in conventional processes would reach 1 ^m, while in precision and ultraprecision machining would reach 0.01^m (10 nm) and 0.001pm (1 nm), respectively (Taniguchi 1983). His predictions made around two decades before are in line with the current advances in manufacturing technology. These accuracy targets for today's ultraprecision machining can't be achieved by simple extension of conventional machining processes and techniques.

Nanotechnology (Taniguchi 1983) was first used to classify integrated manufacturing technologies and machine systems, which provide ultraprecision machining capabilities in the order of 1 nm. Since then ultraprecision technologies have grown rapidly over recent years and have tremendous impact on the development of new products and materials. Nanotechnology is the target of ultraprecision machining because the theoretical limit of accuracy in machining of any substance is the size of an atom or molecule of that substance. With the advent of new materials, manufacturing scientists are facing challenge in machining them to meet their functional requirements. As the demand moves from the microtechnology (1 ^m accuracy) to the nanotechnology (1 nm accuracy) region, the systems engineering demands rapid increase in stringency and complexity (Taniguchi 1983). The traditional finishing processes alone are therefore incapable of producing required surface characteristics to meet the demand of nanotechnology. Even in certain cases these processes can be used but then they require expensive equipment and large skilled labour, finally leave them economically incompetent.

Machining Accuracy (Mm)

Machining Tools

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0.001

Machining Tools

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0.001

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Turning & Milling Machines

CNC Machining Centers

Lapping & Honing Machines Jig Boring & Grinding Machines

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Precision Grinding Machines Super Finishing Machines

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Ultraprecision Diamond Turning

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X-Ray Lithography Ion Beam Machining

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Ion Implantation

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Scanning Tunneling Engineering

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1960

1980

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1980

Fig. 8.1. Achievable Machining Accuracy (Taniguchi 1983)

New advanced finishing processes were developed in last few decades to overcome limitations of traditional finishing processes in terms of higher tool hardness requirement and precise control of finishing forces during operation. This helped in finishing harder materials and exercising better in process control over final surface characteristics. Another limitation relaxed by some advanced finishing processes using loose abrasives is to finish complicated geometries by enhancing reach of abrasive particles to difficult-to-access regions of the workpiece surface. In this way, newly developed finishing processes are, to a large extent, helpful in meeting the requirements of 21st century manufacturing.

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