Keynote Paper

The Role of Precision Engineering in Manufacturing of the Future

P. A. McKeown ( l ) * , CUPE, Cranfield/UK *wi th Contributions from CIRP Members noted in the References

High precision manufacturing, and thus the development of new and improved high precision processes and machines, has gained much greater prominence in the last decade. Many advanced technology products depend entirely on one or more components being manufactured to tolerances or dimensions in the micro- or even nanotechnology range. The paper gives a few examples and summarises today's state-of-the-art in dimensional measurement and servo motion control for instruments and ultra precision machine systems needed to meet this growinq demand. A forward look is made at 'atomic-bit' engineering based on scan- ning tunrelling microscopy.

KEY WORDS: Advanced Manufacturing Technology: Precision Engineering; Dimensional Tolerances; Nanotechnolgy; Design of Uitra Precision Machines: Topoqrafiner: Scanning Tunnelling Engineering.

1.0 ADVANCED MANUFACTURING TECHNOLOGY

The main common interest of all members of CIRP and their rapidly growing number of associates, is Advanced Manufacturing Technology. Over the last 10-15 years we have seen dramatic examples of how the efficient application of Advanced Manufacturing Tech- nology is increasingly determining success or failure in world markets.

The objective of this keynote paper is, however, to remind 'us that there are two main thrusts, world wide, in Advanced Manufacturing Technology. They are:

AUTOMATION OF MANUFACTURE with its well known major subsets

CADCAM FMA

and CIM

and MANUFACTURE WITH HIGHER PRECISION - for which the most widely used categories are

PRECISION ENGINEERING MICRO-ENGINEERING

and NANOTECHNOLOGY

Precision en incerin may be defined as manufacturing tojtolezance~ smallez than 1 part in 10' or perhaps 10 [2], whereas micro-engineering is whcrc the physical dimensions of the component or features are small, namely in the order of 1 urn. Nanotechnolo~, a tcrm coined by our colleague Taniquchi as early as 1974, is where we are working with 'bit sizes' in the order of 1 nm (lo-' or 0.001um.l [ll, 121. It may be considered to cover the range from 10 nm to 0.1 nm (1 Angstrom), and includes 'atomic ait' engi- neering.

Across the industrial world, precision enqinecr- ing is increasingly seen as a set of technologies that are the key to succesful international competi- tive development. This is because many advanccd technology products necessitate manufacturing proces- ses and machine operating in the regimes of precision enqineerinq, micro-technology and nanotechnology. It is important for u s in CIRP, and indeed for many others, to recognise that precision engineering is work at the forefront of current technology, impli- citlv ln the fields of metrolow and advanced manu- factGring technology, and that-for many new products today's precision engineering is of prime economic importance - and that in many areas the precision engineering of today will be the general engineering of tomorrow.

2.0 THE NEED FOR HIGH PRECISION I& MANUFACTURE

Table 1 summarises the gcneral reasons for the increasing demand for higher precision in engineering manufacture. [ 2 1 . Table 2 sets out in broad terms, the manufacturing tolerances of components used in mechanical, electronic and optical system products. It will be secn that many advanced technolow pro- ducts of strategic importance in international com- petitive development fall under the tolerance band in the micro-technoloqy reqime and some in the ?an= technology regime.

A few important specific examples are now repro- duced in detail from [21.

TABLE 1

1. To eliminate 'fitting' and promote ASSEMBLY especially AUTOMATIC ASSEMBLY

2 . To improve INTERCHANGEABILITY of components

3 . Tu improve QLIALITY CONTROL through HIGHER MACHIYE ACCURACY CAPABILITIES and thence reduce scrap, rework and conventional inspection

4. To achieve longer UEARlFATIGUE LIFE of components

5 . To achieve greater MIXlATURIZATIOB and PACKING DENSITIES

6 . To achieve further advances in TECHNOLOGY and SCIENCE

2.1 The advanced turbo-propeller enqine

The next generation of civil aircraft propulsion units will have to meet the airlines' demands for greatly reduced operating costs. Engine manufacturers, such as Rolls-Royce, are now working at fundamental design changes, including the return of the propeller, to (iive substantial improvements in fuel efficiency. The propfan may well give between 3 5 - 4 0 per cent im- provement in specific fuel consumption over the pcr- formance of today's aero engines. Rolls-Royce's first RB 211 engine achieved major improvements in thermal and overall propulsive efficiencies over its prede- cessors without initially rclying on significant in- creases in component efficiency. The next generation of turbofans may be large ducted configurations, or use swept scimitar shaped propeller blades in contra- rotating configuration (see Fig. 1) with propulsive efficiencies of about 90% when operating at cruising speeds of Mach 0.8 .

Fig. 2 shows the past and predicted improvement in compressor efficiency with higher precision aero- foil profiles, especially of leading and trailing edges of rotor and stator blades in axial compressors. By using the modern complex shaped 'end-bend' blades, and by improving profile tolcrances by five times and surface finish by two and a half times, then dramatic improvements can be achieved in compressor efficiency. There is no doubt that today's high pre- cision machine tool technology can readily achieve the necessary work-zone accuracies if not yet on com- mercially available machines. The limits are clearly set by the machinability of the workpiece materials. Forming to near-net-shape before finish-machining is obviously of major economic importance.

For the propfan to successfully replace today's turbofans, it must produce no increase in cabin noise and vibration. Rolls-Royce and others believe that a pusher configuration with the engines mounted at the rear of the aircraft (Fig. 1) will reduce noise propagation through thc air. Lower propeller tip speeds will certainly reduce noise, and this can be achievcd with high efficiency rcduction gearboxes for maximum efficiency and economy of operation. These gearboxes will dcpend critically on the develop- ment of effective tooth contact modelling for helical gears whose involute, or possibly conformal, teeth must be made with high precision root and profile

Annals of the CIRP, Vol. 36/2/1987 495

Tolerances on components for a range of modern products TABLE 2 Tolerance

band Mechanical Electronic Optical

200 pm Normal domestic appliances General purpose electrical Camera, telescov and and automotive fittings etc. parts. e.g. switches, binocular bodies

Normal machining motors and connectors 50 pm General purpose mechanical Transistors. diodes Camera shutters

parts for typewriters. engines etc. rccorders and microscopes

Magnetic heads for tape Lens holders for cameras

5 pm Mechanical watch parts Electrical relays Lenses Machine tool bearings Resistors, condensers Prisms Gears Silicon wafers Optical fibre and conneclors Ballscrews TV colour masks (multi-mode) Rotary compressor parts

Precision machining 0.5 pm Ball and roller bearings Magnetic scales, CCD Precision lenses Precision drawn wire Quartz oscillators Optical scales Hydraulic servo-valves Magnetic memory bubbles IC exposure masks (photo, Aerostatic bearings Magnetron. IC line width X-ray) Ink-jet nozzles Thin film pressure trans- Laser polygon mirrors Aerodynamic gyro bearings ducers X-ray mirrors

Thermal printer heads Thin film head discs

Elastic deflection mirrors Monomode optical fibre and

connectors

0.05 pm Gauge blocks IC memories Optical flats Diamond indentor tip radius Electronic video discs Precision Fresnel lenses

Ultra-precision X-Y tables Optical diffraction gratings Optical video discs

Ultra-precision Microtome cutter edge radius LSI machining

0.005 pm VLSI Ultra-precision diffraction Super-lattice thin films gratings

uB2t I - v23m andpmpfam

Spcy R B 2 I I - RB2tt hmoMvnor 228 535EA T u ~ f ~

5356

Notes CCD charge coupled device IC inicgralcd circuit LSI large sale integration VSLl very large ruk integration

Rdlr-Royce engine 1yp 1

optimization to transmit the higher power levels now demanded. Figure 3 shows the possible improvement in gearbox capacity, (torque per unit weight of gearbox v. improved position accuracy of gear tooth contact area). This critically depends not only on the ability to design and manufacture accurately to allow for shaft bearing and gearbox housing deflections, but also on the accuracy with which gears themselves

Propfan aft-mounted contra-rotating pusher configuration

. U

Propfan aft-mounted contra-rotating pusher con- figuratidn [courtesy Rolls-Royce Limited]

FIG. 1 ~

can be made, particularly angular tooth spacing and helical lead generation and modification.

2.2 Computers - VLSI and the optical transphasor Computer systems and precision engineering are

symbiotic. The present feverish competition in com- puter system development is aimed at higher device and data packing densities and dramatic increases in data rates. Fig. 4 illustrates the achievement in line-width reduction for electronic computers and thus the increased packing densities in VLSI device technology. Here in this prime example of microtech- nology photolithography will eventually give way to electro-lithography (electron beam and X-ray tech- niques. )

One of the ERATO projects (Exploratory Research for Advanced Technology, organised by the Japanese Research and Development Corporation), is currently experimenting with 2 0 nm line widths of gold on sili- con substrates; 5 nm is theoretically possible. This project is working towards the next generation of electronic devices called static induction transistors

Reproduced from [2]: a f t e r Taniguchi

(SIT), and the machines for making them.

wilkinson et a1 (University of Glasgow, UK) demon- strated in 1985 30 nm line heights and widths by re- active ion etching on gallium arscnide by electron beam lithography.

F I G . 2

In the USA, the Department of Defense is part funding the VHSIC Program (Very High Speed Integrated Circuits) in which I B M , Texas Instruments and other large companies are participating. The objective is to achieve much higher data rates through a factor of 100 reduction in feature density. Line widths will thus be reduced to at least 10 times less than best practice today. 'Hard' X-ray lithography using syn- chrotron sources is under development.

A major and exciting potential competitor to the electronic SIT is the optical (photonic) transphasor

496

Potential for increased performance with improved precision

3-

State-of-the-an current in-service iranvnissions

0.5-

0.25-

I . . , . . . . . 1 1 2 3 4 5 6 7 8

Individual twth error (includes tooth form - Irm and position tolerance) FIG 3

Aerospace geared power transmissions: state-of-the- art and benefits of improved precision [courtesy Rolls- Royce Limited]

IC for pocket calculator

\o 16 K memory

\o 64 K memory

\ 256Kmemory

b- %.

I -\ 1972 1976 1980 1984 1988 1992 1996

Year Reduction in pattern dimensions of integrated circuits - volume manufacture ---- prototyping

FIG. 4

which promises switching speeds of perhaps three- orders of improvement, (a few pico-seconds I10 12s) ) This optical system , unlike the electronic transistor also promises more than two stable states which of course, will revolutionize present-day computing logic. Without the need for wires, photons can be transmitted at the speed of light three-dimensionally by holographic techniques. Super lattice crystal materials fabricatfd into three-dimensional 'quantum dots' or 'quantum wells' by atomic accretion tech- niques [ 4 1 will make this possible and eventually achieve better performance than the indium antimonide, gallium arsenide and zinc selenide used in many of today's research programmes.

__

Typical air bearing pressure distribution for flying head

Fig. 5

magnetic systems

I

I960 1970 I980 Year

Slider flying height versus year (commercial systems)

Fig. 6

2 . 3 Computer mass storaqe - direct access and retrieval systems

Fig. 7 shows that optical systems are capable of considerably higher recording denslties , but mass storage and retrieval are dominated today by the mag- netic disc file system. Inductive magnetic recording was selected in the mid-1950's as the base technology for disc files because of its advantages of non-vola- tility, immediate read-back without intermediate processing, unlimited reversibility and the relative- ly low cost and simplicity of the magnetic transducer and recording medium.

Fig. 5 shows a magnetic flying head supported on an aerodynamic bearing that enables the slider to f l y above the surface of the magnetic disc at the

densities

a 0 Japanese announcements IBM disc products

1960 1985 1970 1975 1980 1985 1990

Year

FIG.7. DEVELOPMENT OF MAGNETIC DISC STORAGE DENSITY (REPRODUCED FROM [S] 1 (factor of 5 I every S years)

close spacing that is essential for high density mag- netic recording (today this flying height IS typically 0 . 3 pm (0.15 Wm is the current target). Figure 7, reproduced from [51 shows the dramatic increase in aereal magnetic recording densities achieved through increasing the bits per inch along the track and the tracks per inch across the radius of the disc over the last two decades. Increasing the linear bit den- sity has depended upon the scaling down of three major geometric parameters:

- head to disc spacing (flying height) - read/write gap length - disc magnetic coating thickness

Figure 6 shows the dramatic reduction in head flying height from 2 4 pm in the late 1950's to approximately 0.30 vm using the thin film heads of today. This has been achieved through establishing an in-depth under-

497

'MACHINING' ACCURACY

).(o( (1 nm)

0.3 nm

MACHINING TOOLS L EOUIPMENT

I I TUNING AND W K L I f f i MACHINtS .A.

b.

HARD X-IAV 1ITWOGRAPH.I I\-+FION . -.-.- 8EAM NACNINING .-.

IOLECUIAR .LAM EPITAXV Dll IMPLANTATlOW

--------- .-.- mMGLATTICE.---- --.--

M A T f l l A l S SVNTHfS121NG I SCANNING TUNNELLING fffilNtERlNG

SEPARATON

Jl6 WRING MACHINES JIG GRINDING MACHINES

sum fimisnimc MACHINES

Tec hnigue M y Ranae Besolution

Fig. 8

standing of aerodynamic bearing technology, develop- ment of low mass head/sliders with integral aerodyna- mic surfaces, and the development of very smooth and flat disc surfaces free of mechanical asperities. I 2 1 It has also depended on the development of high pre- cision diamond turning, coating and grinding proces- ses under CNC control. The improvement in data pack- ing storage and retrieval density and the reduction in access time has also been dramatic. In the mid- 1950's when the first disc file was conceived in IBM's newly established development laboratory in Calirornia, an externally-pressurized (aerostatic) air bearing was used as a support for the magnetic head on a 2 4 in. diameter2disc. density was 2000 bits in , this being equivalent to about five million characters per spindle. In 1981, 1250 million bytes of storage per spindle had been achieved. The development of today's thin film head is another prime example of substantial advances in product performance made possible by application of ultra-precision machining and other precision engi- neering techniques.

NOTE :

The data packing

- Today the world market for maqnetic mass data storage and retrieval systems (hard disc and tape) is estimated to be between $25 billion and $30 billion. It will rise to $ 4 0 billion by the early 1990's. This already exceeds the value of integrated circuits made in Silicon Valley, California, USA.

3 . 0 CGRRENT CAPABILITY IN MEASm'ENT AND SERVO- POSIT ION I NG OF DI SPLLC>MENT/ LENGTfl AND ANGTsI:

Man's knowledge of nature, the Universe, and how to adapt nature to his purposes, advances in stel with his ability to measure precisely. In particular, dimensional measurement, namely of length, profile and surface topography applied to the manufacturing of artefacts, has become crucially important to ad- vances in technology and new improved products.

In 1973, Merchant I 1 7 1 showed that over the past 200 years the ability to apply dimensional measure- ment in the context of machining processes had impro- ved by five orders of magnitude. Today'.de can see the emergence of techniques through which this capa- bility is being extended by a further 3 to 4 orders of magnitude.

Of course, in every walk of life, measurement is essential for control. In the context of machining, displacement in linear or angular terms between the tool and the workpiece is fundamental to achievable machining accuracy. Table 3 sets out the state-of- the art today in measurement of displacement/length and angle for heavy carriages, i.e. for machine tools and other types of large production machinery. It

also indicates the state-of-the-art for short length displacement as applicable to instruments.

It should be noted that accuracy of servo-posi- tioninir of the best capabilities in the world today in each of these cateqories is only limited by the performance of the displacement transducer itself, i.e. siqnal/noise. stabilitv. bandwidth etc.. T h u s

~ ~~ ~ _ . servo positioning-in any one axis of control is basically capable of equally the stated resolution of the displacement transducer.

TABLE 3

1 ~~~1~~~~ 0 4 l n m I 1 20nm j 0403nm t 200pm Fcannina X ray

#ntertarometry Bo-'nm] [angular 0.000 04 arc MC loarc sec]

NOTE ! Jones, R . V . , has reviewed devices that use

variable capacitances aid reports that dis- placements of [ 2 0 1

* Deslattes,?R.D.. has measured displacements of 10 nm which is about 1% of the nuclear diameter i201

nm can be measured

To translate these servo-positioning capabilities into equivalent dimensions and tolerances on high pre- cision "machined" workpieces, necessitates continuing rigorous programmes of research and development not only in - ultra precision CNC production machines and control systems ( [ 2 ] the CUPE Electronic Gear Box CNC systems) but also in

- ultra precision machining processes and

- the production of high purity, structurally homo- geneous materials.

498

'TABLE 6 MACHINE AND CONTROL SYSTEM DESIGN

State-of- the-art in DISPLACEMENTS MEASUREMENT Largo Displacementa

-- Technique .-dyno Laser Interforornotry[ 231 (commercially i available)

.Linear Optical tonm I 1OOnm l m - Scale (moire) r accuracy > l p m /m 1

4.0 PRECISION MACHINING PROCESSES

The most noteworthy processes capable of providing high and ultra-precision 'machining' are:

(a) single-point diamond and cubic boron nitride (CBN) cutting:

(b) (multi-point) abrasive cutting, for example as in diamond and CBN grinding, honing, belt polishing etc.. (Both (a) and (b) can be usually classified as 'solid' tools).

(c) free abrasive (erosion) proccsses such as lapping, polishing, elastic emission machininy and selective chemico-mechanical polishing;

(d) chemical (corrosion) processes such as con- trolled-etch-machining, perhaps following photo- and electrolithography: [241

and accretion) [ 2 4 1 , includinq (el energy beam processcs (removal, deformatlon

photor. (laser) beam cutting, drilling, transformation hardening and coating: electron beam lithography, welding; electrolytic jet machining for smoothing and profiling: clectro-discharge (current) machining (EDMI for profiling: electrochemical (current) machining (ECM) for profiling; inert ion beam for 'milling' (erosion) micro-profiling: reactive ion beam (etching) ; epitaxial crystal growth by molecular- bit accretion, e.g. for manufacturing new super-lattice crystals, etc..

(f) molecular 'machining' through 'tunnellinq' and 'atomic force' microscopy.

It is pleasing to seen an increasing number of papers on these topics, especially the nanotechnology Drocesses, cornins forward in the CIRP Annals [ 2 4 1 , [I]. -~ i t is imrrortaEL- i,i.at-.w_e&L~~~, structure our activi- ... (1s to enable 2s K:I treat a-1 aspects of ulcra arc- c : s : or. ma nu fec t :: r i nq , - .

( v r o c e s s e s , ser.5c11s ,- 2 ~ s $ t z g system desiqn and materials synthesisinq) as an entity.

Fig. 8 shows the well-known "Taniguchi curves" 111 and is repeated here for completeness. Our re- vered colleague, Taniguchi, continues to make major contributions to progress in ultra precision (atomic bit) machining by energy beam processes. Beyond this in category ( f ) above, we have the exciting prospect of what is sometimes now referred to as 'Scanninq Tunnellinq Engineering' by which true molecular machining may soon be possible. This promises the capability of transforming surfaces of crystalline and bio-materials by pick-and-place atomic modifica- tions. (See Section 6.0 below).

I . Srrurrural-stiffness support, damping and secular stability. high bal-

2. Kinemarir:cemi-kineotic design 3. Abbe principle or options 4. Bearing orerapinq klaslic or fluid f i lmklow friction. lempcralure and

5. 'Direcr' displacrment transducers-scales. laser interferometer 6. Metrolop~~/ramer-isolalc measuring systems from machine distortions 1. Sertwdriiw and control-high stiKness. high responx. high bandwidth

8. Drives-positioned on axes of reaction 9 Carriages-'non-influencing' drive couplings andbamps

ance and low vibration 01 moving parts fluid Row etc.

W e a r

and zero following errors in multi-axis systems

10. Thermnl d,~-compmration/slabil~tion I I . Emor cont~KNorion-quasi-static and dynamic

Temperature External vibrations (yismic and airhorne) Humidity Pressure Particle size

4 I MACHINE WORK-ZONE 1 'Displacement' (ID)

'Volumetric' (3D) Spindle error motions BUEeffccts

Geomclry. wear SllflneSS

Spcedr. fccdr Coolani supply

WORKPIECE Stiffness. weight Datum preparation Clamping Stress condition Thermal propenle* Impurities

OPERATING WORK PIECE tFFECTS ACCURACY METHODS

Factors aRecting and controlling workpiece accuracy (note: BUE = built-up edge)

Fig. 9

5 . 0 ULTRA PRECISION MACHINING - THE DESIGN OF ULTRA PRECISION PRODUCTION MACIiINES

The dimensions and tolerances indicated in Table 2 necessitate the constant development of appropriate ultra precision machine tools and manufacturing equip- ment. Tanisuchi [ l l susqested that this represcnts the "greatest challenge-;acing the manufacturing engineer of today". The larqe number of critical features to be controlled, necessitates the use of multi-variable ~ O O D control bv hiqh speed computer. - . These features inciude not oniy

- tool-to-workpiece position, velocity and acceleration:

but also

- thermal drift compensation: - vibration levels at the tool/workpiece inter-

face: (sctive vibration control) - tool/workpiece 3D-error compensation, both

in-process (dynamic) and immediate post- process (quasi-static).

The objective 1s to design machines with very high, totally predictable, workzone accuracies. Error budgetting at the schematic design stage of a new machine is an essential step. [ l o ] , [lll.

Figure 9, reproduced from [ 2 1 , shows the factors affecting workpiece accuracy and how the machine tool designer has eleven major principles andlor techniques to consider.

[12], [ 1 3 1 , [ 1 4 1 , and [IS] are just a few papers which have been welcomed in recent years addressing state-of-the-art techniques to achieve significant improvements in overall accuracy of both small capa- city light-weight instruments and heavier machine tools and other production equipment.

6 . 0 NANOTECHNOLOGY/SCANNING TUNNELLING ENGINEERIN- A GLIMPSE OF THE ULTIMATE?

Table 1 succinctly sets out the reasons for the cver-increasing demand for higher precision in engi- neering manufacture. Nanotechnoloqy encompasses processes controlling dimension and tolerances from

499

say, 10 nm (perhaps 100 nm) down to 0.1 nm (1 Angstrom). It is capable, therefore, of atomic-bit machining and molecular materials processinq. I t has as its main motivating objectives

No. 5 "to achieve greater miniaturisation and packinq densities"

and

No. 6 "to achieve further advances in techno1oq;i and the under-lying sciences"

Nanotechnology is an enabling technology. The rewards for successful development of nanotechnology processes and machines are immense and that is why we are now seeing the emergence of national programmes in nano- technology.

In Japan, the ERATO project (Exploratory Research for Advanced Technology, organised by the Japanese Research and Development Corporation), includes nano- technology as one of six topics selected for high priority government/university/industry joint develop- ment. In this project, physical actions and mechani- cal properties of materials in the nanometer region, are being analysed and, through study of new measur- ing and processing methods, essential technology for constructing the required measuring systems and pro- duction machines will be developed.

In the United Kingdom, a National Initiative on Nanotechnology (NION), has been started. A Nanotech- nology Strategy Committee has been set up to assess priorities and to establish collaborative research programmes, some of which will qualify for support under the government's LINK scheme to sponsor impor- tant technology collaborative R&D programmes. I 1 6 1

In the USA, the VHSIC Program referred to in 2.2 above, is well under way [ 3 1 . The Office of Naval Research (ONR) has sponsored Precision Engineering programs at several universities. The Precision Engineering Program at Lawrence Livermore National Laboratory is highly significant. The American Soci- ety for Precision Engineering has been formed. There are 7 groups at universities at the NBS and in indus- try who are carrying out significant work in Scann- ing Tunnelling Microscopy (STM) into the atomic domain. (Scanning Tunnelling Engineering, to con- struct molecular structures). The Nanotechnology Experimental Workstation (NEWS) is in the final stages of design at the University of Arizona. it combines multiple STM's, multiple optical microscopes and multiple detector fibre optic waveguides. Over the last three years, conferences on this sub~ect have attracted a rapidly growing number of deleqates, namely 15, 50 and 400.

It is Scanning Tunnelling Engineering which enables us to glimpse the ultimate in precision engi- neering/nanotechnology. Enough has been accomplished now to indicate that it is not inconceivable that experiments in quantum chemistry and molecular bio- logy might well be carried out by physical transfer of atoms, molecules and enzymes from the tip of the STM to the 'bulk material' substrate. 1161. [181, L 3 1 .

CIRP can take some pride in the development of the STM which received the Nobel Prize in Physics last year. L191.

SCHEMATIC OF STM STYLUS TRA-CKING AT ATOMIC RESOLUTION

FIG. 10

It was invented and demorstrated in the field- emission mode by our C T R P colleague, Or Russell Young ~n 1971 at the United States National Bureau of Standards (NBS). Then called the Topografiner, the ST?I is a surface topography mapping instrument enabl- ing a very sharp point to be raster scanned just above a specimen surface. Ctilizing the enormous sensitivity of the electron tunnelling process, the tinnelling current and thus the point-to-surface dis- tance is kept constant by amplifying the current emitted by the sharp point and feeding it back to a piezo-electric transducer which controls the point-to- surface height or spacing. After several publicatiops and a successful demonstration of the performance of the instrument, its development was terminated at NBS in 1972 by a management decision to re-direct effort into a new program in micromeasurements in response to the calibration needs of the microcircuit industry.

In the early 1980's Binnig and Rohrer at IaM Zurich continued the development, and throuqh the "exceptional precision of the mochanical desrgn" [ 191 , were able to demonstrate atomic resolution wlth their improved instruments (Fig. l o ) , thus earning them a Nobel Prize in Physics (shared with Ernst Ruska for his fundamental work in electron optics and for the design of the first electron microscope).

The Nobel citation states the general features of the STM and then describes Dr Young's contribution as follows: "The first to succeed in doing this was the American Physicist Russell Young, at the National Bureau of Standards in the United States. He used the phenomenon known as field emission.... Young succeeded in building an instrument that worked on this principle. The distance between the stylus tip and the surface was approximately 2OOA ... However, Young realized that it should be possible to achieve better resolution by using the so-called tunnel effect".

The citation goes on to describe the instrument in detail. It is important to note that in 1971, Young and colleagues published the first experimental demonstration of vacuum tunnelling, using the same instrument to measure current vs. voltage characteri- stics. In 1978 Clayton Teague completed the first detailed study of vacuum tunnelling at NBS.

graphic mapping of highly refined surfaces, i.e. diamond turned surfaces, other applications are being studied such as microlithography, micromachining, polymer science, and biotechnology. The possibility of measuring the position of molecules on specially prepared surfaces, and the manipulation of these molecules to achieve goals in micrometrology, is under intensive investigation in several laboratories. [181, 1201. Yet, there are some in the STM community who believe that the original Topografiner, i-e. the STM applied at point-to-specimen spacings of 20-200 Angstrom, will 'nave the greatest long term impact of this developing instrument.

In addition to a promising future in microtopo-

7.0 CONCLUSION

Over the last fifteen years CIRP, through its work in its Scientific Technical Committees (mainly) Q, S and E, has contributed much to growing awareness of the economic significance of Precision Engineering in its widest sense.

This keynote paper has tried to show that within Advanced Manufacturing Technology, Precision Engineer- ing has a rapidly expanding future. A wide and increasing number of advanced technology products demand manufacturing processes, machines and indeed complete systems operating in the microtechnology range ( 1 0 um to 0.1 pm (100 nm)). Nanotechnology leading to atomic bit machining and molecular struc- turing of materials, first brought to our attention by our colleague Taniguchi, is now a reality. Scann- ing Tunnelling Engineering deriving from the invention of the topografiner (STM) by our colleague, Young, is pushing Precision Engineering far beyond what many of us thought possible only ten to fifteen years ago. Its promise is immense.

The role of Precision Engineering in Manufactur- ing of the Future is, to summarise:

- to research, design, develop and commercialise processes, sensors, instruments, machines, control systems and materials in order to ACHIEVE FURTHER ADVANCES IN TECHNOLOGY, SCIENCE and WEALTH CREATION.

REFERENCES

I.

2.

3.

4 .

5 .

6 .

7.

8.

9.

i0.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

Taniguchi, N. "Current status in and future trends of ultra-precision machining and ultra- fine materials processing". Annals of CIRP, 1.983, 32 ( 2 )

McKeown, P.A., "High Precision Manufacturing and the British Economy" (1986 James Clayton Lecture). Proc.Instn..Mech.Engrs., 1986, Vol. 200, No. 76

Hocken, R., Teague, C., - private communications 1987. (and to whom particular thanks are due).

Taniguchi, N., "Atomic-bit machining by energy beam processes". 3rd International Precision Engineering Seminar, Interlaken, May 1985. Precision Engineering, July 1985, 7 (3)

Talke, F.E., "Precision Engineering issues in magnetic recording technology". 4th Inter- national Precision Engineering Seminar, Cran- field 1987, (4th IPES); to be published in Precision Engineering.

Leteutre, J.R., "Capacitance-based sensing and servo control to Angstrom Resolution". 4th I P E S Cranfield 1987.

Ikawa, N., Shimada, Morooka, "Photo electronic displacement sensor with sub-nanometre resolu- tion". 4th IPES, Cranfield 1987, Precision Engineering, V o l . 9, No. 2, April 1987.

Seyfried, P., Becker, "High precision X-ray metrology". 4th IPES, Cranfield 1987.

Hart, M., J.Phys.D: Appl. Phys. 1 , 1405 (1968).

Donaldson, R.R., and Patterson, S.R., "The design and construction of a large vertical axis diamond turning machine", Lawrence Livermore National Laboratory, UCRL 89638, Aug. 1983.

McKeown, P.A., Dinsdale, J., and Wills-Moren, W.J., "The design of high precision machines and systems". Course notes, CUPE. College of Manufacturing, Cranfield Institute of Tcchnology.

Patterson, S.R., and Magrab, E.B., "Design and testing of a fast tool servo for diamond turn- ing"., 3rd International Precision Engineering Seminar, Interlaken, May 1985. Precision Engineering, July 1985, 7 ( 3 ) .

Kunzmann H . , Busch, A., and Waeldele, A., "Numerical error correction of co-ordinate measuring machine". Proc. Int. Symp. on Metro- logy for Quality Control in Production, Tokyo 1984, pp. 278-282 (Japan Society for Precision Engineering).

McKeown, P.A., Wills-Moren, W.J., Read, R.F.J. and Modjarrad H., "The design and development of a large ultra-precision CNC diamond turning machine", SME technical paper, MR-82-931, 1982

Treib, T., "Error budgetting - applied to the calculation and optimisation of the volumetric error field of multi-axis systems"., Annals of CIRP, Vol. 36/1/1987, p. 365

Franks, A., "Nanotechnology", to be published in Journal Physics.E: Sci. Instr. 1987.

Merchant, E., MTDR, 1973

Proceedings of 3rd International Symposium on Molecular Electronic Devices, 6-8 October 1986, Arlington, Virginia, 22202, USA

Nobel Prize in Physics, 1986 - bulletin from the Royal Swedish Academy of Sciences, 15th October 1986, Box 50005, 5-10445, Stockholm.

Binnig G., and Quate, C.F., "The Atomic Force Microscope", Stanford University, Stanford, California 94305

Feynman. R.P. "There's Plenty of Room at the Bottom", Amer. Phys. SOC. 1959, California Inst. of Technology, Pasadena - published in "Miniaturisation", Chapman & Hall, London

CUPE, Cranfield, UK. "Ultra precision air bearing rotary table - the UK Secondary Angle Standard"; product brochure.

23. ZYGO Corporation, USA. - AXIOM 2/20 laser inter- ferometer system specifications.

24. Snoeys et al. "Current trends in non-conventio- nal material removal processes"., Annals of CIRP, Vol. 35/2/1986, 4 6 7 0 4 8 0 .

25. Chapman, P.D., "A capacitance based ultra pre- cision spindle error analyser", 3rd Internatio- nal Precision Engineering Seminar, Interlaken, Nay 1985; Precision Engineering, July 1985, 7 13) 129.

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