NATL INST. OF STAND 4 TECH

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NBSIR 75-927

NIST

PUBLICATIONS REFERENCE

The National Measurement

System for Surface Finish

Russell D. Young

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

March 1976

Final

Issued July 1976

5. DEPARTMENT OF COMMERCE

10NAL BUREAU OF STANDARDS

* 15-1x1

'f7<^

NBSIR 75-927

THE NATIONAL MEASUREMENT

SYSTEM FOR SURFACE FINISH

Russell D. Young

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

March 1976

Final

Issued July 1976

U.S. DEPARTMENT OF COMMERCE, Elliot L Richardson. Secretary

Edward O. Vetter. Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Acting Director
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CONTENTS

Page

EXECUTIVE SUMMARY , 1

1. INTRODUCTION , ! 3 2. STRUCTURE OF THE MEASUREMENT SYSTEM 4-15

2.1 Conceptual System 4 2.2 Basic Technical Infrastructure 4 2.2.1 Documentary Specification System 5 2.2.1.1 Standardization Institutions . .

. 5 2.2.1.2 Survey of Documentary Standards 7 2.2.2 Instrumentation System 8

2.2.2.1 Measurement Tools and Techniques . . .

. 8

2.2.2.2 The Instrumentation Industry .............. 10

2.2.3 Reference Data 11 2.2.4 Reference Material 11 2.2.5 Science and People 11 2.3 Realized Measurement Capabilities 13

2.4 Dissemination and Enforcement Network 13 2.4.1 Central Standards Authorities 13

2.4.2 State and Local Offices of Weights and Measures 14 2.4.3 Standards and Testing Laboratories and Services 14

2.4.4 Regulatory Agencies 14

2.5 Direct Measurement Transactions Matrix 15

3. IMPACT, STATUS AND TRENDS OF MEASUREMENT SYSTEM 17-26

3.1 Impact of Measurements 17 3.1.1 Functional, Technological and Scientific Applications 17 3.1.1.1 Dairy and Food Industry Storage and Distribution Containers 17 3.1.1.2 The Surface Finish of Surgical Implants 17 3.1.1.3 Gravure Illustrations 18

3.1.1.4 Surface Finish Requirements for Automobile Motors, Transmissions and Brake Drums 18

3.1.1.5 Surface Finish and Automobile Oil Consumption 19

3.1.1.6 Efficiency of Electric Motors 19

3.1.1.7 Shaft and Radial Lip Seal Surface Finish 20

3.1.1.8 Paintability of Surfaces - New Powder Coatings 21 3.1.1.9 Electroforming - Duplication of Highly Finished Surface . 21 3.1.1.10 Surface Requirement in the Electronics Industry , . .

, 22 3.1.1.11 Summary of Measurement Needs 22

3.1.1.12 Distribution of Surface Finish Instrumentation 22

3.1.1.13 Measurement Needs in High Technology Industries .... 22

3.1.2 Economic Impacts -- Costs and Benefits 23

3.1.3 Social, Human, Person-on-the-street Impacts 26

3.2 Status and Trends of the System 26

4. SURVEY OF NBS SERVICES 27-33

4.1 The Past 27

4.2 The Present -- Scope of NBS Services 28

4.2.1 Description of NBS Services \ 28

4.2.2 Users of NBS Services 30

4.2.3 Alternate Sources 30

4.2.4 Funding Sources for NBS Services 30

4.2.5 Mechanism for Supplying Services 30

4.3 Impact of NBS Services 31

4.3.1 Economic Impact of Major Users Classes 31 4.3.2 Technological Impact of Services 31

4.3.3 Pay-off from Changes in NBS Services 31

4.4 Evaluation of NBS Program 31

4.5 The Future 31

4.5.1 Driving Force of NBS Programs 31

4.5.2 Alternative NBS Responses to Surface Measurement Needs .

. 32

5. SUMMARY AND CONCLUSIONS [ 33

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CONTENTS

Page

Appendix A. METHOLOLOGY OF THE STUDY 34-38

A.l Literature Survey , 34

A. 2 List of People Consulted in Preparing This National Measurement

Study (as of 1973) 34

A. 3 List of People Contacted by Phone, at Meetings, etc 34

A. 4 Typical Correspondance on Industrial Surface Finish 36-38

Appendix B. SUMMARY OF BACKGROUND DOCUMENTS 39-45

B. l ASA B46. 1-1962 Standard for Surface Finish ^0

B.2 Surface Finish, Friction and Wear: The Need for More than One

Parameter 41 B.3 Precision Reference Specimens of Surface Roughness: Some

Characteristics of the Cali-Block 41 B.4 Calibration Report - Precision Reference Specimen of Surface

Roughness , 42

B.5 The Public Health Significance of Surface Measurements 43

B.6 Eight Techniques for the Optical Measurement of Surface Roughness . . 43

B.7 Surface Micro topography 44

B.8 The Topografiner: An Instrument for Measuring Surface

Microtopography 44

B.9 Evaluation, Revision and Application of the NBS Stylus/Computer

System for Surface Roughness Measurement 45

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LIST OF FIGURES

Page

Figure 1: Pictorial representation of roughness, waviness,

lay and flaws

Figure 2: Surface finish measurement system infrastructure

Figure 3: Surface finish calibration flow chart

Figure 4: Typical stylus instrument

Figure 5: Precision reference specimens of roughness

Figure 6: Surface finish measurement capability

vs time (1930 - 1980)

Figure 7: Calibration accuracy vs magnitude of surface

roughness

Figure 8: Calibration accuracy vs height of thin film

steps

Figure 9: Synthetic rubber friction theory

Figure 10: Cost comparison charts:

a) turned surfaces

b) face milled surface

Figure 11: NBS information and calibration Input-Output chart

LIST OF TABLES

Table 1: Subcommittee chairmanships for ISO/TC-57

Table 2: List of recommended ISO surface standards

(published and under review 1974)

Table 3: U.S. and foreign manufacturers of instrumentation

for measuring surface roughness

Table 4: Surface roughness of automobile motor production

parts in microinches AA

Table 5: Surface roughness of automobile drive-chain components

in microinches AA

Table 6: Direct measurement transactions matrix

Table 7: Dependence of seal torque on surface roughness

Table 8: Cost of individual seals in U.S. manufactured cars

and estimated total yearly cost

Table 9: Measurement improvement impact matrix

Table 10: Distribution of surface finish instrumentation

Table 11: Economic dimensions of impact areas in surface

finish measurement in the metal working industry

Table 12: Table of surface measurement needs related to some present

day national issues m

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THE NATIONAL MEASUREMENT SYSTEM FOR SURFACE FINISH

Russell D. Young

National Bureau of Standards

EXECUTIVE SUMMARY

Surface finish measurements involve the

outside surfaces of products, the part

which is most evident to the user and which

is frequently responsible for the quality

of its performance. The average consumer

can visually detect less than one millionth

of an inch of surface roughness in a highly finished chrome plated surface. The

reliability of clock motors, the performance

of switches, the effectiveness of razor

blades, the safety of a wheel bearing, all of these depend on careful measurements of

manufactured surfaces.

The National Measurement System for

surface finish consists of the standards,

the measurement techniques and procedures,

the personnel, and the equipment through

which surface finish measurements are conducted in the United States. The purpose

of this study was to determine as quantitatively as possible the structure,

vitality, integrity and future requirements

of this measurement system. The study was initiated by a literature search, followed

by visits to instrument manufacturers,

industrial laboratories and academic institutions . Each of the hundreds of metalworking

industries has a special surface finish

requirement. The highly polished pipes

and tanks of the dairy, food and hospital

supply industries permit rapid sanitation

inspection. Quality of magazine illustrations depends upon the surface finish of

gravure plates and cylinders. Automotive

safety and reliability is related to the

surface finish of hundreds of bearing,

seals, brake drums, valves, cylinders, etc. The lifetime of surgical implants is directly related to their surface finish.

Military applications abound. The list

is endless. Yet, each application requires

different surface micro-features. Ths most

important oonalusion of this Study was that

NBS should develop measuring procedures

and methods for analyzing surface profiles

so that each metalworking industry can properly inspect its surfaces according to its needs.

The second most important measurement

need is for instrumentation capable of

measuring new, high technology surfaces such

as integrated circuits, computer discs and

drums, surgical implants and precision

bearings. New molecular electronic devices

require surfaces which are smooth on the

atomic scale. A third important need is for on-line surface finish measurement in manufacturing processes.

NBS calibrates precision reference

specimens of surface roughness (carefully

manufactured rough surfaces) according to the voluntary American National Standard

B46.1. These specimens provide calibration

users with a readily available physical

standard to check their instruments. The

integrity of the measurement system is

maintained by national and international

intercomparisons and by direct calibration

of users' standards. There are no regulatory

agencies in surface finish. NBS also

calibrates thin film steps for the microcircuit industry. Since both thin film

steps and surface finish measurements are basically length measurements, NBS bases

these calibrations on the defined unit of

length through i nterferometry

The information gathered in this study

has already provided a solid basis for

management decisions within NBS with regard

to the distribution of the very limited resources in the surface program (2 1/3 man years; $84K of NBS funds). For example,

first priority has been given to a new calibration facility which includes computer

analysis of surface profiles. Second priority is assigned to the development of new, high resolution instrumentation. Work with

standards committees also has a high priority.

The study revealed a broadly based need

for research leading to an understanding of

the relationship between the surface finish

and the function of a part. Such a study

cannot be underwritten by instrument manu- facturers since the 25,000 instruments now

in use are very long lived. Yearly sales of

the largest U.S. instrument manufacturer

amount to only Si million per year. The

metalworking industry spends S54 million

yearly in making surface finish measurements

on products whose market value exceeds $40

billion. Yet this effort is thinly spread

over hundreds of industries, so that little

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reported research is done. These circumstances have resulted in stagnation in U.S.

surface programs relative to governmentsupported foreign research. NBS is now able to provide measurements and instrumentation to those who wish to pursue such

programs in the U.S. Several small cooperative efforts with industry and a university are now underway.
1. INTRODUCTION

A typical consumer can visually detect

a barely measurable one half of a millionth an inch in the surface finish of a chrome-plated toaster. From morning till night we use, enjoy,

seek out, depend upon, and excoriate

highly finished surfaces. We awake to an inexpensive alarm clock whose motor bearings are finished to about one microinch,

shave with a razor blade which has highly

characterized, ultra-smooth surfaces; we

turn on the electric stove with switches

whose contacts are specially prepared

surfaces and use a waffle iron whose

chrome plated surfaces rely on very highly

finished steel from rolling mills. Many

of the foods we eat are manufactured and

transported in stainless steel containers

with mirror finishes. Almost all household appliances have one or two surface

finish requirements; some, such as the

washer, dishwasher, electric iron, blender,

freezer, refrigerator, etc., have many

requirements. It staggers the imagination to realize that tin can surfaces are

smooth to 10 microinches to economize on the use of tin.

The ubiquitous automobile is a product with hundreds of surface finish re- quirements, some very stringent. A selected list of 26 surface finish re- quirements for automobile motors and 17 requirements for automatic transmissions

is given below. Early component failure

sometimes results if a surface fails to meet inspection requirements, and some failures can involve serious safety

hazards

Hospital and surgical surfaces are highly finished to meet rigid sanitation

and sterilization requirements. Surgical

implants, such as hip joints, are polished

to a finish which is beyond the measurement capability of the finest instrument

today. Eyeglasses and contact lenses are highly finished to avoid confusing and

annoying light scattering. Undesirable

effects sometimes result when highly

finished windshields, chrome, and painted

surfaces generate annoying or dangerous

glare. The list is endless. Indeed, a very large fraction of the products com- prising the Gross National Product are in some way dependent on highly finished

surfaces. To achieve functionally adequate

surfaces and/or cosmetic acceptability,

manufacturers employ sensitive, precise

surface finish measurements throughout

their production processes.

To accomplish the necessary measurements, U.S. manufacturers employ over

25,000 instruments, thousands of man-years

of work and considerable R&D. Our

technological society is such that a ball

bearing made in Germany or in San Francisco

must meet specifications and fit mating

components in Detroit and Tokyo. Without accurate and reproduceable surface

finish measurements this compatibility

could not be achieved. Indeed, a host

of measurements require the existence of

an accurate, hierarchical, consistent

measurement system.

In 1972, the National Bureau of Standards

(NBS) undertook a full scale evaluation of

all components of the National Measurement

System to determine as quantitatively as possible the structure, vitality, integrity

and future requirements of each component.

The surface finish measurement system was identified as one such component. Much of

what follows will focus on the what, where,

why, when and how of surface finish measurements, the infrastructure of the surface

finish measurement system, and the role of

NBS in this system.

The National Measurement System for

Surface Finish consists of documentary and

artifact standards, measurement techniques

and procedures, personnel, and equipment

through which all surface finish measurements are conducted. The purpose of this

study is to 1) develop and test a model of

the National Measurement System infrastructure, 2) identify the industries and social

groups upon which the measurement system

impacts, 3) insofar as possible, determine

the economic dimensions of the impact areas,

4) examine critically the quality of the

present measurement system in terms of

present and projected needs, 5) make specific recommendations for future NBS programs, and 6) develop reprogramming guidelines so that NBS can more effectively

accept its National Measurement System

responsibilities.

In carrying out this study, 1) the

literature was searched and evaluated, 2)

visits were made to standards laboratories,

instrument manufactures, industrial users

and academic institutions, 3) users were consulted by letter and phone, and 4) technical meetings were used to initiate dialogues on measurement deficiencies. The

findings were digested, organized and are presented herein.

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2. STRUCTURE OF THE MEASUREMENT SYSTEM

2.1 Conceptual System

Surface finish (roughness, texture, etc.)

is a major branch of surface technology con- cerned with the micro-geometry and microtopography of the surfaces of solids. In manu- facturing physical objects, the process of

generating the nominal (intended) surface

is always imperfect. The four major deviations from the nominal surface are called

roughness, waviness, lay and flaws. Roughness consists of the finer irregularities

in the surface texture including those irregularities which result from the inherent

action of the production process. Waviness

is the widely spaced component of the sur- face texture and is usually eliminated from

the surface finish measurement process by

electrical or mechanical filters. Lay is

the direction of the predominant surface

pattern, ordinarily determined by the production method used. Flaws are irregularities which occur at one place or at re- latively infrequent intervals. These

concepts are depicted in figure 1. The

present report is concerned chiefly with

roughness 3 which is a quantitative description of surface finish. Standards have not been established for waviness and lay.

Traditionally, the roughness is characterized by the average deviation of the profile of the true surface from the nominal

surface (Arithmetical Average roughness

(AA)). Almost all manufactured goods have

some surface finish requirement, whether

functional or cosmetic. In the extreme

case, some optical components require

that surfaces have roughness no greater

than a few atomic layers (less than one

ten millionth of an inch).

LAY DIRECTION

ROUGHNESS'WIDTH CUTOFF

Figure 1: Pictorial representation of rough- ness, waviness, lay and flaws in a manufactured surface.

The formal definition of Arithmetic Average

Roughness (AA) is:

L AA =

|y| dx

where L is the distance along the surface

corresponding to the greatest spacing of

repetitive surface irregularities to be included in the roughness measurement (roughness width cutoff), y is the vertical displacement of the actual surface from nominal and x is the distance along the nominal surface.

The metric system of units will be adopted

as soon as a new standard has been completed

and accepted. Until then, surface roughness

(in the U.S.A.) will continue to be given in

microinches AA. Under the new standard,

roughness will be in micrometers with NBS

calibrations derived from interferometric

measurements which relate AA quite directly

to the defined unit of length: the wavelength of certain light sources. The physical reference standards used to calibrate surface roughness instrumentation

and to disseminate these calibrations is

called a Precision Reference Specimen.

While there are many types, these specimens

consist of finely ruled parallel lines

on flat hard surfaces such as glass and

electrodeposited nickel. They are a few

tens of square cm in area and are believed

to be extremely stable, suffering only from wear or accidental damage. They are periodically calibrated by NBS for various types

of standards laboratories who in turn employ

them in secondary calibrations of instruments

and other Precision Reference Specimens.

2.2 Basic Technical Infrastructure

Figure 2 is a hierarchically stratified

block diagram of the surface finish measurement system insofar as NBS can determine it.

The numbered blocks are interconnected with

lines which are coded (see legend) so as to describe the relationship between the boxed

components. The hierarchical levels are as follows: I - Scientific and Technological

Base/International Agreements, II - Recognized National Standards Organizations, III National Standards or Instrument Standards,

IV - Artifacts used for transfer or control , V - Instruments for Transfer, and VI - point

of application of standards. NBS partici^

pates actively at all six of these levels.

Briefly, NBS (box (1) in fig. 2) calibrates

precision reference specimens (5) using a stylus instrument/computer calibration

system (4). Instruments (7) are then used

to transfer these calibrations to further

specimens with which the user (8) calibrates

his instruments. The measurement loop is

closed when a user sends a precision refer- ence specimen directly to NBS for calibration. In discussing figure 2 the relationship of the components will be more easily

understood if the levels are not described

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I Scientific & Technological Base/lntemtl Agreement OTHER NATIONAL STANDARDS ,„ ISO

19 CHARACTERIZATION20 1-

1

DIFFRACTION

OPTICS 2, LASER WINDOW

n Recognized National Standards Organizations

ID National Standards or Instrument Standards

IV Artifacts used for Transfer or Control STEP STANDARDS

T Instruments for Transfer T

ANSI NBS

B 46 1 119621

OTHER SPECIMENS

INSTRUMENTS T

PREC REFERENCE SPECIMEN ]

MEASUREMENT DATA

CALIBRATION TRACEABLE TO NBS - -¥ INfORATION ANO CONSULTATION

MIL SPEC^

SCRATCH AND DIG STANDARDS ,4

INSTRUMENTS

VI Poini of Application

of Standards USERS USERS T

NBS PRIMARY

CALIBRATION INSTRUMENT

USERS J USERS

TACTILE STANDARDS

USERS

Figure 2: Surface finish measurement system infrastructure

in numerical order.

The Structure of figure 2 is employed

uniformly for all National Measurement System studies in the Mechanics Division.

Another representation of the system, a calibration flow chart is given in figure 3. Starting from the top, standards organizations produce documentary standards which

NBS interprets through the inputs of

science and technology. The resultant primary calibrations are disseminated through

a variety of metrology laboratories to industrial users.

2.2.1 Documentary Specification Institutions

2.2.1.1 Standardization Institutions

In figure 2, level 1 includes other

National and International Standards Organizations e.g. International Organization for

Standardization (ISO). The corresponding

ISO Technical Conmittee (19) TC-57 is chaired by the USSR and has, until recently, been

ignored by many western countries, including

the U.S., for political reasons. The American

National Standards Institute (2) recently appointed a delegate to ISO/TC-57 and is in the

process of accepting the chairmanship of two TC-57 subconmittees . Since travel to the

USSR must be provided by the delegate or his

company it is often very difficult to maintain continuity in the U.S. participation in

this ISO work. At this writing an experienced specialist in surface work is presently

providing his own financial support to participate as a delegate to ISO-57.

While there are 266 ISO standards published per year, the surface standards

have not as yet reached the maturity re- quired for adoption. Table 1 lists the

TC-57 subcommittees. NBS has been unable to participate in ISO/TC-57 due to travel

restrictions

Level I, figure 2 includes input from

other national standards organizations. The

U.S. ANSI Committee for Surface Texture (B46)

has achieved good uniformity with Canadian.

British and proposed ISO standards. On the

other hand there is considerable conflict

with French, German and other European

national standards groups.

A particularly influential international

group, the International Institution for Production Engineering Research (CIRP) conducts

yearly international conferences throughout

the world, a portion of which are devoted to surface finish work. The NBS representative

was elected to full membership in 1975.

There are no legal or regulatory standardization institutions for surface finish in

the U.S. The military specification is man5
Physical Principles

Basic Units

International i National Standards

(ANSI , ISO, etc.

B46.

•- Fundamental Theory

High Technology

Industries

Std. of Length

"State of Art" Measurement

N B S

Surface Characterization

Theory of Measurement

|«

£

Government Agency

Metrology Labs

Secondary

Cal I brat Ions

Government

Labs

Primary

Cal Ibrations

Industrial Metrology Labs

Secondary

Ca 1 1 bratlons

Special Studies

|-

Instrument Mfg.

Metrology Labs

Techno log lea I Advances

Secondary

Cal Ibrations

Machine Tool Automot I ve

Metal working

Electronic Device

Industrial Calibration Users

Optical

AppI lance Ceramic

Computer

Precision Ref. Specimen Labs

Secon

Cal Ibr dary stions

Dairy and Food PalntabI I Ity Gravure plates

Tin can

Figure 3: Surface finish calibration flow chart

Table 1: Subcommittee Chairmanships for

ISO/TC-57

Metrology and Properties of Surfaces

(Standardization of the Microgeometry of Ma- chined Surfaces)

TC-57

SCI

SC2

SC3

SC4

SC5

SC6

Metrology and Properties

of Surfaces USSR

Instruments and devices for the

measurement of surface

roughness USSR

Roughness Comparison specimens

and devices for the calibration

of instruments UK

Instruments and devices for

the measurement of waviness,

roundness and straightness . UK

Geometrical Parameters of

the Surface USSR

Typology of Surfaces .... France

Relation of surface

irregularities to functional properties .... *

SC7 Physical parameters of

surfaces and surface layers . *

*USA is presently negotiating for these com- mittee chairmanships.

atory only for military hardware procurement.

Level II of figure 2 includes the American

National Standards Committee which appoints

an industrially based coimittee (B46) to develop and periodically revise a voluntary

engineering standard. NBS has one representative on B46 and one of the subcommittee

concerned with measurement and instrumentation. NBS interprets and carries out the

provisions of the standard and is playing a major role in the present revision of the

1962 documentary standard for surface

texture, B46.1. The military specification

(MIL-ABC-STD-50) is derived directly from

the B46.1 standard and will not be discussed

further.

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Table 2: List of recommended ISO surface

standards (published and under review - 1974)

ISO Recommended Standards

IS0/R468-1966

IS0/R1878-1970

IS0/R1879-1970

IS0/R1880-1970

Surface Roughness

Classification of Instruments and Devices for

Measurement and Evaluation

of the geometrical parameters of surface finish

Instruments for the mea- surement of surface roughness by the profile method

- General statements - Terms and Definitions

Instrument for the mea- surement of surface roughness by the profile method

- Contact (stylus) instruments of progressive profile transformation - Pro- file recording instruments

2.2,1.2 Survey of Documentary Standards

Four "Recommended" ISO standards (see

table 2) have been distributed among ISO members for possible revision and are ex- pected to be approved within the next few

years.

The American National Standard B46.1

was adopted in 1962 and is presently under

revision. Some idea of the material covered in the standard can be obtained from

table of contents:

1. General

2. Classification of Terms and Ratings

Related to Surfaces

3. Designation of Surface Characteristics

4. Stylus Type Instruments

5. Precision Reference Specimens

6. Roughness Comparison Specimens

7. Appendices

The full table of contents is given in

appendix B.l. After defining the terms used

in the standard a preferred series of roughness standards is prescribed and the symbols

used to designate surface characteristics on drawings are detailed. The present standard

only recognizes the stylus type of instrument, which is similar to a high fidelity

phonograph pick up. When the transducer is

drawn across the specimen surface, the fine

stylus follows the microdetails of the sur- face profile and records a magnified profile

of the surface. At the same time a built-in

analog computer generates the AA roughness

value which is displayed on a panel meter.

The standard specifies the electrical and

mechanical properties of such instruments

including detailed discussions of the

stylus shape and force, and the methods

for obtaining a reference surface (datum)

relative to which the profile is measured.

The precision reference specimen defined

by the standard will be discussed with

Level IV along with tactile standards.

The standard recognizes only Arithmetic

Average roughness as a quantitative measure of surface texture. It has been

clearly demonstrated in a number of papers

that AA alone does not characterize the

surface well enough so that the surface

texture can be related to function. An unanticipated conclusion of this National

Measurement System study was the widespread and generally unrecognized need

among users for a variety of surface finish

characterizing parameters. A recent

internal NBS report (appendix B.2) gave

a particularly clear discussion of

limitations of the most used parameters

(AA, RMS roughness, peak height and

bearing area) and urged the adoption of other

parameters which are sensitive to the

periodicity of roughness along the surface. This restriction to AA is probably

the most severe limitation of the present

standard and it is to be hoped that this

deficiency will be corrected during the

current revision.

A second limitation of the standard

is the exclusion of all roughness measuring

techniques other than stylus instruments.

Thus, the standard fails to recognize the

increasing use of multiple beam interferometry and light scattering for measuring

surface roughness. The latter technique

is particularly attractive as non-contacting, on-line measurement method. The

current state of the art in optical mea- surement of roughness is reviewed in a recent NBS internal report (appendix B.6).

NBS is frequently called upon to carry

out special measurement studies at the

forefront of measurement technology.

These experiences are studied and form

the basis for special investigations

which result in recommendations to a committee of the American National

Standards Institute.

It is not practical to list every

voluntary engineering standard which

incorporates some surface finish requirement. Some examples are:

Surface Comparison Standard (1958)

(Cast Surfaces) NSA823

Surface Finish (RMS) (1960) SAE107CAS

Surface Finish as Cast for

Die Casting (1964) ADKE18

Surface Finishes (1948) machined AIRS

Surface Requirements for

Metallic Surgical Implants 1968 ASTF86

Surface Roughness Designation NSA30

7
Surface Texture Control (1968) SAEJ449A

Surface Texture Measurement of

Cold Rolled Sheet Steel (1969) SAEJ911

Surface Texture, Roughness,

Waviness and Lay (1964) SAE291DAS

Surfaces for Dairy Equipment - Sanitary Standards DFI2000

2,2.2 Instrumentation System

2.2.2.1 Measurement Tools and Techniques

Industrial measurements of surface finish

employ a wide variety of instrumentation.

While stylus instruments predominate, multiple beam interference microscopes, light

scattering devices and glossmeters, pneumatic instruments, and tactile and visual

comparators are also widely used. Since the

B46.1 standard specifies the characteristics

of stylus instruments (7, fig. 2) only,

they are used exclusively in the calibration

chain to the user (8, 9, 12). For example,

the stylus tip radius, stylus shape, shank

angle, stylus force, stylus support and

tracer head supports are carefully specified.

Of particular importance is the traversing

length of the stylus as it moves across

the surface and the relationship of this

to the roughness width cutoff (the greatest

spacing of repetitive surface irregularities

to be included in the measurement of

average roughness height). In addition, the

electrical properties of these instruments

are carefully specified so as to insure

that the same surface characteristics will

be measured by all complying instruments.

Stylus instrumentation has reached a high degree of sophistication, close to the

fundamental limitations imposed by nature,

i.e. single atom steps. A typical

instrument is shown in Figure 4. Stylus

size cannot be reduced appreciably (to

improve horizontal resolution) since the

stylus pressure now approaches the yield

strength of most materials. Vertical re- solutions in the tenth microinch range

(2.5 nm) can be achieved, although this

distance corresponds to the depth of the

stylus damage in all but the hardest metals.

The advent of the mini -computer has enabled

the coupling of a dedicated computer and a stylus instrument so that much improved

calibrating accuracy has been achieved.

The NBS system was developed and calibrations were formalized in July 1973. The

instrument will be described in section 4.1.

The measurement rests on a combination of the

defined unit of length and the definition of

AA roughness in B46.1 (see section 2.1).

Calibration of surface roughness instrumentation is achieved through the use of

Precision Reference Specimens (5) consisting

of ruled surfaces on hard materials, typically glass and electrodeposited nickel.

B46.1 defines the Precision Reference Speci- men as follows: "Surface Contour - The normal

surface profile of Precision Reference Specimens of roughness height shall consist of a series of isosceles triangles having included

angles of 150°. A flat region is permitted

at the bottom of the grooves, provided that

both the roughness height rating and the

spacing of the grooves meet the following

tolerance for accuracy Accuracy - Roughness values of Precision Reference Specimens

shall not vary from the designated value by

1 microinch or 3 percent, whichever, is the

larger. The average spacing of the grooves

shall be within 2 percent or 20 microinches

(whichever is the smaller) of the theoretical

spacing corresponding to the nominal roughness height. Uniformity - The average deviation of roughness height of individual

grooves of any Precision Reference Specimen

shall not exceed 4 percent of the total

roughness height. The average deviation of

the groove spacings on a given Precision Re- ference Specimen shall not exceed 3 percent

of the average spacing."

Precision Reference Specimens with

roughness heights (AA) 20 microinches or smaller can be used to estimate the radius

and determine the condition of the stylus

in an instrument since a worn or damaged

stylus will fail to "bottom" in the close

spaced grooves.

A recent NBS study of the most frequently used Precision Reference Specimen,

the Cali -Block, showed that that distribution

of AA values over the 120 microinch and the

20 microinch patches can be characterized

in terms of their standard deviation (a) from

the mean roughness value (see appendix B.3).

These a values can then be combined with

other uncertainties to describe the un- certainty of the whole measurement process.

The 3o value for the deviation from the mean

AA value was about 2 microinches for both

the 120 and 20 microinch patches. This

study resulted in recommendations on sampling

the Cali-Block surface when calibrating

instruments.

Until July 1973, a special Cali-Block

artifact standard was maintained by NBS

and all calibrations were comparisons

between the block to be calibrated and the

artifact standard. Since July 1973, the

computer based calibration procedure has

been used (see section 4.1).

Other specimens (6) which do not conform

to B46.1 can now be calibrated with the new computer system. Some typical precision

reference specimens are shown in figure 5. As a result of revision of B46,l it is anticipated that other precision reference

specimens, particularly some good foreign

8
Figure 4: Typical stylus instrument
specimens, will be included in the rewritten

standard. NBS has tentatively studied the

possibility of developing a device which is

capable of calibrating and testing a stylus

instrument over a wide range of roughness

values and with a variety of surface waveforms. The instrument which was evaluated

consisted of a piezoelectric expander with a built in interferometer, illuminated with a well known wavelength. The interferometer

serves as a built in calibrator and can be

coupled to a servo system so that deflection

can be precisely controlled. While the study

revealed that the instrument would be costly

and require a considerable investment of

labor, it is clear that it would have wide

application in micrometrology. Design and

construction of this instrument have been deferred until resources become available.

A special case of surface roughness mea- surement is thin film step calibration. The

calibration chain for step standards relies

on well established interferometric procedures and is not based on a national standard.

Step heights are measured by comparison with

an interferometrical ly measured step of similar size using stylus instruments (7). The new computer roughness measuring system also

provides for careful curve fitting of step

profiles so as to improve the accuracy of

step height measurements. Steps are also

calibrated using two beam and multiple beam

interferometers (11). Again in the case of

steps, there is an increasing need for improved sensitivity and accuracy which will be

met by the new NBS system.

The principle users (12) are the microcircuit and thin film industries, as well as the developing ion beam machining industry

who employ specially manufactured thin film

step standards calibrated by NBS. Tactile Standards (16) are employed by

machinists for visual and tactile comparison

with machined surfaces in order to determine

the approximate roughness of the surface.

In the surface roughness standard, 846. 1,

page 14-15, these Roughness Comparison

Specimens are described and tabulated

according to the roughness values, lay,

and tolerances for uniformity. These

specimens are calibrated with stylus

instruments according to the roughness

width cutoffs given in B46.1. They are widely used in machine shops of all types.

All surface roughness calibrations follow

the path indicated in figures 2 and 3. NBS calibrated specimens serve as secondary

standards for other calibration laboratories which in turn provide calibrations

for instruments used by hundreds of types of

industries. Department of Defense and other

government agencies. There is no enforcement network. The integrity of the system

depends on occasional NBS calibrations directly for the user and round robin intercomparisons.

Scratch and Dig Standards (14) are based

on Military Specification MIL-0-13830A (11

Sept. 1963). The Scratch and Dig specifications are now being revised by an American

Society for Testing Materials Committee so they can serve as a more useful standards.

The principle application of this standard

is in characterizing the surface of high

quality and diffraction limited optics (21).

2.2.2.2 The Instrumentation Industry

Surface roughness measurements, in ac- cordance with B46.1, employ stylus instrumentation as described in the section above.

Among the western countries the U.S., Great

Britain and Germany are the leading suppliers

of the 25,000 stylus instruments and the

Precision Reference Specimens now in use

in the U.S. A highly flexible calibration

quality instrument costs well over $20,000,

while shop quality instruments cost

less than $1,000. Table 3 lists U.S. and

foreign manufacturers (mfg. names deleted)

of stylus instruments, precision reference

specimens, light scattering instruments

such as glossmeters and interference microscopes. Sixty five percent of stylus

instruments are ten years old and almost a third are twenty years old, explaining why

the U.S. stylus instrument yearly sales in

1972 did not exceed $2 million. As will be

shown in section 3.1.2, after a $39 million

instrument investment, industry spends approximately $50 million in labor for surface

measurements affecting $42 billion of proTable 3; U. S. and foreign manufacturers of instrumentation

for measuring surface roughness

INSTRUMENT Stylus Prec . Ref. Glossmeters and Interference MANUFACTURERS Instruments Specimens Light Scattering Microscope

U.S.A.

A X X

B X

C X

D

E XX X F X G X H X

I X X J X K X MXL X

X

N X 0 X

Foreign (dis- tributed in U.S.A.

P X

Q X

R X

T

S XXX

u X

W

V XX X

X X

V X

10
ducts each year. Finished surfaces and

roughness measurements are used throughout

most manufacturing industries. The distribution of stylus instruments among metalworking industries is given in table 8. Interference microscopes are used to measure thin film steps and surface roughness values less than a quarter of a micrometer (x/2). They are particularly

useful where the surface is metallic and a non-contacting measurement must be made.

It is possible to use a soft metal to obtain an impression or replica of a portion

of a surface which is inaccessible to stylus

instruments and to examine the replica with

an interference microscope.

2.2.3 Reference Data There is a pressing need for both measurements and theories relating surface

finish to part function. Industries

possessing such data consider it proprietary, so it remains unpublished and often

even its existence is unknown. Two ex- ceptions are tables 4 and 5 listing

surface finish requirements for automobile

motor and automatic transmission components.

The source of this information is proprietary. Industry as a whole suffers from

this unwarranted secrecy, since small manufacturers do not have sufficient R and D capability to investigate problem areas,

and large companies cannot benefit from

each others' R and D as is possible in

much of science and engineering.

2.2.4 Reference Materials

The only "reference materials" used

in surface finish are the precision

reference specimens of hard plated nickel

and glass, and hard thin film deposits

used in step calibrations. These have

been discussed in 2.2.2.1.

2.2.5 Science and People

New measurement technology grows

out of demands generated by refinement

of existing technology and the birth of new technology. The measurement system is alerted by demands upon NBS and instrument

manufacturers for improved measurements,

and by articles in the scientific and

technical literature exposing measurement

deficiencies. As a result, new problems

are analyzed (fig. 2, boxes 20, 21, and 22)

and new instruments proposed or developed.

These serve as input to the measurement

system, which, if the system is responsive,

results in continued improvement of the

system. In surface characterization the

new technologies which demand improved

measurements include laser mirror finish

for laser fusion experiments, magnetic

tape heads for video and computer applications, high quality optical surfaces,

semiconductor surfaces for integrated

circuit devices with ever increasing device

density, thin film devices, surgical implants such as hip joints, optical fiber

surfaces for low loss communication systems

and gauge blocks for length calibration.

A study of the literature collection

in surface finish maintained by NBS reveals

that most technical papers in the field

come from European countries, Russia and

Japan. U.S. University studies are limited

to a very few mechanical or production

engineering departments, and their interest is usually peripheral. Research

in the relationship between surface finish

and such parameters as friction, wear,

paintabil ity , corrosion, light scattering,

heat exchanging, radiative properties,

gauge block wringing and a host of others,

is very badly needed. NBS has made a considerable effort to attract research

associates from industry and universities

to carry out such studies at NBS, but to

no avail

Surface characterization draws heavily

from statistical analysis and communication

theory in order to develop methods for

dealing with the vast amount of information

contained in a single surface profile.

Such statistical parameters as the autocorrelation function, amplitude density

function, mean slope, and average wavelength can be routinely calculated at

NBS and by some instruments made in

England and Germany. Hope for progress

in relating finish to the function of the

surface (i.e. bearing, appearance, etc.)

presently lies in the application of

these statistical parameters to function

models

Professional societies such as the

American Society of Mechanical Engineers

(ASME), Society of Manufacturing Engineers

(SME), International Institution for Pro- duction Engineering Research (CIRP), and

American Society of Testing Materials

(ASTM), participate in standard writing

activities, publish research in surface

characterization, and organize national

and international meetings. Unfortunately,

an unusually large fraction of the knowledge involving the relationship between

surface finish and function is considered

proprietary and thus has no impact on the

surface community. Instrument manufacturers

conduct one day courses and other special

programs on surface measurement techniques.

Qualifications of people in this field range

from machinist to Ph.D. in mechanical

engineering.

11
Table 4: Surface roughness of automobile motor production parts in microinches AA

Component Cylinder Block: Cylinder Bore Tappet Bore Main Bearing Bore

Head Surface

Piston: Skirt

Pin Bore

Piston Pin Crankshaft:

Main Bearing Journal Connecting Rod Journal Camshaft: Journal Cam Rocker Arm: Shaft

Bore

Valves:

Intake Valve Stem

Intake Valve Seat Exhaust Valve Stem Exhaust Valve Seat

Tappet: Face

O.D. Hydraulic Lifter: Face

O.D.

Car No. 1 Acceptance

Roughness Mfg. Process

16-20 Hone

UU / J 60-80 Bore 40-50 Mill 45-55 Grind-Polish

30-38

9-12 Gri nd-l an

4-6 Grind-Polish

4-6 Grind-Pol ish 4-6 Gri nd-Pol ish 15-20 Grind-Polish

14-20 Gri nd 29-32 Hone-Pol ish 34-38 Grind

25-40 Grind

18-20 Grind 34-45 Grind

4-5 Grind

14-18 Grind

22-25 Grind-Polish

14-16 Gri nd-Pol ish

Car No. 2 Acceptable

Roughness Mfg. Process

20-25 Hone 80-120 Ream

130-150 Bore 190-210 Mill 40-50 Grind

11-13 3-5 Grind-Lap

6-9 Grind-Polish

6-9 Grind-Polish

14-18 Grind-Polish

22-26 Grind

20-22 Grind

30-40 Hone-Pol ish 16-22 Gri nd 30-40 Grind

14-20 Grind

30-35 Grind

15-20 Grind

13-14 Grind Table 5: Surface roughness of automobile drive^chain components in microinches AA. Acceptable

Automatic Transmission Parts Roughness Mfg. Process

Front Pump Shaft Journal 18-22 Grind

Front Pump Shaft Thrust Surface 11-14 Grind Reverse Gear Drum - Braking Surface 150-170 Turn Intermediate Shaft Journal #1 6-7 Grind Intermediate Shaft Journal #2 50-60 Grind Center Main Shaft Journal 23-27 Gri nd Center Main Shaft Thrust Surface 20-30 Grind Output Shaft Journal #1 14-16 Grind Output Shaft Journal #2 10-15 Grind Output Shaft Journal #3 27-32 Grind

Front Drum - Braking Surface 90-110 Turn Clutch Plate 16-24 Turn

Main Shaft Journal #1 20-25 Grind Main Shaft Journal #2 25-30 Grind

Low Range Reaction Member - Thrust Surface #1 35-40 Grind Low Range Reaction Member - Thrust Surface #2 65-75 Grind

Front Drum - Braking Surface 90-110 Turn Brake Drum - Front 65-75 Turn

Rear 75-85 Turn

Clutch Pressure Plate 40-50 Turn-Pol ish King Pin 6-8 .Grind Universal Spider Race 14-16 Grind

12
100 1 1

1 f

1930 1940 1950 I960 1970 1980 1990 YEAR

Figure 6: Surface finish measun

2.3 Realized Measurement Capabilities

Figure 6, a logarithmic plot of surface

finish measurement capability from 1930 to 1980 (projected), puts the measurement

system in historical perspective. Some key features included the two decade improve- ment in accuracy between the 1930 's and the

60's, the terminations of improvement

at the 0.1 microinch (0.025 ym) level in the mid 60 's and the urgently needed single

atom step capability which is already being requested by the semiconductor industry

and surface scientists. The thrust toward microminiaturization will necessitate the single atom step level of measurement in the very near future. The accuracies of NBS calibrations in surface finish and thin film steps are dependent on the magnitude of the quantity measured and are shown in figures 7 and 8. Both measurements are limited by step cali- bration accuracy. A new polarizing inter- ferometer under development at NBS will considerably improve the accuracy of both measurements. A sample calibration re- port is reproduced as appendix B.4. The accuracy required by users varies

from a few high technology industries measuring close to the NBS level (computer

discs and drums, semiconductor devices, bearings, surgical implants, etc.) to the

t capability vs time (1930 - 1980) machine shop level where accuracies of 25%

at the 100 microinch (2.5 ym) level are

the rule. The accuracy of calibrations using pre- cision reference specimens is not appreciably

influenced by temperature or humidity. Major inaccuracies in the transfer have been shown

by NBS (appendix B.3), to be due to variations

in AA roughness across the surface of the artifact itself and are sufficiently small so that only high technology users and cali- bration laboratories need concern themselves,

2.4 Dissemination and Enforcement Network

2.4.1 Central Standards Authorities

There is no hierarchical system of physical standards (artifacts) in the surface

roughness measurement system. The documentary standard (B46.1) provides the full prescription for surface propagation of sur- face roughness calibrations. Historically,

the importance of surface measurements to the military and other government agencies

focussed central responsibility for primary calibrations on NBS. Industry has strongly

supported this NBS role because they have chosen to rely on NBS, as an independent,

impartial measurement source. Thus, through

the years, NBS calibration instrumentation

has become the de-facto "artifact" standard
0.025

/iin

10 20 50 SPECIMEN ROUGHNESS. AA

Figure 7: Calibration accuracy vs magnitude of surface roughness

in the USA through the primary calibration

of precision reference specimens.

2.4.2 State and Local Offices of Weights

and Measures

So far as NBS has been able to determine, state offices of weights and measures are not part of the surface finish

or thin film step measurement chain.

2.4.3 Standards and Testing Laboratories

and Services

Secondary transfer of surface roughness

calibrations occurs in industrial and

government laboratories and in instrument

manufacturer laboratories (7). These organizations usually maintain one or two Pre- cision Reference Specimens (5) which are recalibrated by NBS at one to ten year intervals. Stability of these artifacts is

known to be very good. In the last five

years precision reference specimens have

been calibrated by NBS for 35 members of

the prestigious National Conference of

Standards Laboratories. Ten of these

calibrations were performed in 1974 and

projections for 1975 suggest an even greater number. As far as NBS can determine, the majority of the 90 NCSL members

who perform dimensional calibrations also

perform surface roughness calibrations at some level. In addition, instrument and

specimen manufacturers as well as a number of users employ NBS calibrated

artifacts.

All of the above users calibrate specimens at the second, third, etc., level

by comparing the NBS calibrated artifact

with the one being measured. These are then

distributed to secondary metrology labs and

machine shops for day to day use in the

calibration of production line instruments.

2.4.4 Regulatory Agencies

There are no governmental regulatory

agencies for surface finish or this film

steps although agencies like the Public

Health Service exert indirect control in some instances (3.1.1.1). As discussed in 2.4.1,

the integrity of these measurement systems is

based on voluntary standards with the co- operation of NBS and professional societies.

14
Figure 8: Calibration accuracy vs height of thin film roughness

2.5 Direct Measurement Transaction Matrix factors than business considerations.

The interaction among the various components of the surface finish measurement

system can be succinctly described by means

of the input-output transactions matrix of

table 6. Where applicable, Standard Industrial Classification (SIC) codes are given.

In the left hand column each organization

is listed as a supplier of information, goods

or services and across the top of the matrix

these same organizations are listed as users. The information within each box is coded according to the key shown.

All of the suppliers have been discussed

above or will be described in section 4.3.

The measurement needs for a particular

category, for example the automotive industry,

vary so widely within the industry that

some manufacturers measure with accuracies

approaching that of NBS while others use only tactile comparison standards. All

metalworking industries employ some measurements at the lowest level of accuracy in

their machine shops and some manufacturing

processes. Highlights regarding the major

measurement system users are discussed in

the next section, since the discussion has

been developed more around technological

15
Table 6: Direct Measurement Transactions Matrix

DIRECT MEASUREMENTS

TRANSACTIONS

MATRIX FOR SURFACE FINISH

SUPPLIERS

I CO

=3: —1 ^ 2! ^ <: o s- o o o —! —

LlJ >- — —^1 c^UOt— oi— 1— occii— Q-a: Lij^ — <:<: —

iuja:<;;r3;^<i os: It— f— ojt.j'^o so siujQiot— cc:

a oc

O f—

X O

uo o

> SI LiJ S I ID O o t nr uj 1 Q oo o I h- o s oo Q oo o car — ea:

O I— ct 1- O =J —I =)

h- O Q- O

ID 2: r. . < _ et —

LU Q —^ CD —IS er s uj " Q —

10 12 13 14

5: q:

q: on

LU ID 1 CD

I— s o —

15 16

^ KNOWLEDGE COMMUNITY

2 INTERNATIONAL METROLOGICAL

3 DOCUMANTARY STANDARDS

ORGAN I 7AT IONS

4

4 21

^ 3 3

2 4 3 4

3

3 4

3

1 3

0 32 22 32 32 33 22 23 12

' 02 o2 2

3 2 3 Q 2 Q 3 2

: 2 2

2 ,2

2 113 2 3 1.3 2 3 12 2:3 4 2 3 0 i 0 2 0 2 0

INSTRUMENT MANUFACTURERS

2 4

0

1 2

•IBS

DOD (MIL. SPEC. )

DOD AND PRIVATE STANDARDS LABS

2 II3 23 24 24

2 ! 3 3 3 3 2 2 , 2 0 ^ _2„

3 f 3 2 4 2' 3 3 3

3 12 2 3 0 _ 2___2 0 2

3 1 3 2 3 1 2 1 3 1 2

3 3 4 2 3 2 _2___J J_ 0 0

1 1 2 2 2 2 2 l'3 r

1 2 3 2 3 0 0 0 0 0

1 1 2 2 3 1 2 0 4 M 3"

2 3 3 2 4 0 0 0 0-2 0

1 2 1 2 2 _ 2' 0_ _

3 2. 3 3 0

1 2 1 2 2

1 3 i 2 3 0

' 3 1 ? 3 0

2 li 2

2

' 2 0_ 0_

3 2 2

3 2 0 2__

2 1 2

2 2 0 0

3 "T2

2 2 Q_ o_

3 1 3

3 2 0 0

1 3 3 3 3 3 3 3 3

3 3 3 3 2 2 2 0

1 3 2 3 1 2 1 3 1 3 3 3 2 2 0 0 0 0 2

0 2 0__

3 3 2*

2 2 .0 13 13 13 13 12 22 1 3 3 2 3 1 2 0 ^_ _ 0 g 0 1|3 12 r 2 13 2'2 12

3 2 ? 2 2 2 i2 2 0 2 0

'2 1!3 1 1 1 1 1 3 1 3

1'

3 2 2 3 0 3 0 0 0 0 0 42423313 13 1302 13 13 11 13 1 2 1 000, 0 21

0 000 0 DOD - EXClUDING

STANDARDS LABS

2 0 3 0 3 0 3 2 0 3 3:2

0 0 0 |0 OTHER FEDERAL AGENCIES

0

1 0

10

TT

17"

H"

T4~

INDUSTRIES TRADE ASSOCIATIONS

AUTOMOTIVE

INDUSTRY

APPLIANCE

INDUSTRY

ELECTRONICS

INDUSTRY

DAIRY AND FOOD

INDUSTRY

2 0 3 1 3 0 1 0' 3

3 3 3 2.3

0 2 2 2 , 0 2

3 0 3 2 3 0 2 0 3 FT

3 2 3 3 3 2 2 3 0 0 ___0 _0 _0 _ 0 _ _0 _ 0 _

3 3 3 13 2 2 13 1^

2 3 3 2 2 2 2 1 0 _ 0 0_ 0 0 10 1 1" 2 2 3

2' 2

2" -

1 2 2 2 1 0 0 0 g_ _o^ g 0 0 ^ 4 12 24 13 23 14 04 0

4 2 4 3 3 4 4

2 ]_ 2 2 2 2 2 T" 3 4 2 3 2 4 1

2 1 3 2 3 1 ? 2 2 2 0

1'3 03 13 02 03 02 01 02 0

3 2 3 2 3 1 1 2 0 0 0 0 0 0 0

1 1

0 0 0

2 0 3 1 2

2 2 0 0 0

1 3

0' 2 0 3

3 0. 0 3 0

3 0 0 0

3 3 2 0 g 0._

'2 13 2

3 3 0 2

3 0

3 0

0 3 0

2 2

0_ 0 4 0?

3 3 0

1 1

0

4 0 4

2

15

16

OTHER METALWORKING

INDUSTRY

2 n r4 oT oT n o" "

3 2 3 3 3 3 1 0 0 0 0 2 0

3 0

4 1 4 0

GENERAL PUBLIC 0 0 0 0 0 0 0 0 0

4 0 3 2

0

4 1142

4 13 1 4 4 1.2 0

2 0 0

4 0^4^ ' 0*1—cr T

4 4 3 1 0 0 0 0 ~i ^0^ ~D r

0 3 3 0 0 0 0

3 1 3 04 r4

3 : 2 _ 0^

' I' 2^

3 . 0 TT 1"^"

4 3 : 0 ' 0 TT" ri"

3 3 0 0

1

0

" 0' 3 W

3 2 0 Importance of Transaction

1. Convenience

2. Very Desirable

3. No Alternate

Source

4. Essential

Rate of Change

N = Declining Volume

0 = Stable

2 = Growing

4 = Explosive Grov;th

Adequacy of Transaction

0 = No Improvement Needed

1 = Under Control

2 = Marginal ly OK

3 = Seriously Deficient

4 = Out of Control

Magnitude of Transaction

Trivial Minor Moderate

Important Major

16
3. IMPACT, STATUS AND TRENDS OF MEASUREMENT SYSTEM

3.1 Impact of Measurements

3.1.1 Functional, Technological and

Scientific Applications

Since all metal working industries employ

surface roughness measurements, ten typical areas will be discussed briefly in this

section. They have been selected because of

their broad interest or because of NBS involvement in their measurement problems.

These ten micro-studies revealed a broad need

for improved characterization in most areas,

and a need for refined instrumentation in

others.

3.1.1.1 Dairy and Food Industry Storage

and Distribution Containers

The average household purchased $712

worth of dairy products during 1974 and

generated a 35 billion dollar dairy

industry whose capital expenditures ex- ceed $350 million for 1974 alone.

(Statistical Abstract of the U.S., 1974).

A large fraction of this capital ex- penditure is for milk handling, transporting and processing equipment. In the 1920 's two trade associations and

one professional organization formulated

the first uniform standards for fittings

used on milk pipe lines. Ultimately,

the standards become popularly known

as 3-A standards, for the three founding

organizations. In 1944 the U. S. Public Health Service joined these

three organizations in developing voluntary sanitary standards in the dairy

industry. Today over 50 sanitary

standards for the milk industry and a dozen for the egg and egg product industry have been adopted.

The role of surface finish in insuring

sanitation through appropriate cleaning

procedures has become a matter of some concern to the dairy industry (see

appendix B.5, "The Public Health Significance of Surface Measurements").

Traditionally, the 3-A standards have

relied on the requirement that the

stainless steel surface have a Number 4 finish (8 microinches) , equivalent to polishing with 150 grit silicon carbide

(see Dairy Standard 3A "Accepted Practices

for Permanently Installed Sanitary Pro- duct Pipelines and Cleaning Systems").

This standard also includes the specifications for a Cast Surface Comparison

Standard used to evaluate the surface

finish of castings used in pipelines. These

standards have served the dairy industry

well over the past thirty years. At first

it was believed that the highly finished

stainless steel surface was necessary to prevent bacterial growth on surfaces and

permit reliable sanitizing. However,

studies on the cleanability of a variety

stainless steel surfaces, some much less

smooth than a Number 4 finish, revealed

no significant difference in bacterial

cleanability among a variety of finishes

(see for example, 0. W. Kaufman et.al..

Journal of Dairy Science 53 1, Jan. 1960).

However, there is consTdTerable opposition,

particularly from the Public Health Service,

to relaxing the surface finish requirements.

They point out that while the bacteriological

swab-count of less than 100 per 8 in2 of

swabbed surface has officially been declared

to be the acceptable safety level, and is

achieved on rougher surfaces, the surface

requirement serves another important function.

In routine inspections, most dairy surfaces

are subjected to the more practical visual

inspection of a sanitarian. It is vital to detect the present of pits, cracks and inclusions, since these form tiny corrosion

cells when they collect soil. These cells

then generate corrosion pits which deepen

at a remarkable rate. The grinding and

polishing of these surfaces serves the

purpose of removing cavities, pits and

inclusions, while at the same time permitting easy visual inspection of surfaces. The pits, when present, serve as breeding grounds for bacteria as well as reservoirs for corrosive sanitizing solutions.

Thus, in this case surface finish is a sur- face preparation and inspection requirement.

During October 1973, the Dairy and Food

Industries Supply Association enlisted the

aid of NBS in attacking the problem of proper

characterization of product contact surfaces.

There is considerable pressure from manu- facturers to permit the use of new materials

and surface finishes so that manufacturing,

and thus product, costs can be reduced.

Since the whole inspection system is involved,

NBS is consulting with the Association in

several areas in an attempt to delineate more clearly the range of acceptable surface

finishes.

3.1.1.2 The Surface Finish of Surgical

Implants

An unparallelled opportunity to serve one's

fellow man by improving surface finish mea- surements exists in the area of surgical

implants. The lifetime of these devices, for

example an artifical hip joint, is not likely

to exceed 10 years. R. C. Spragg, Director

17
of Research for the Rank Taylor Hobson

Company, discussed this problem in an article

entitled, "The Interdisciplinary Nature of

Surface Measurement" (Joint Measurement

Conference, Boulder, Colorado, June 1972).

Spragg discussed the evidence that boundary

layer lubrication depends on both the

velocity of the bearing and its surface

finish. As the surface texture is improved,

full hydrodynamic lubrication is obtained at

lower and lower bearing velocities. Severe

wear occurs when the critical velocity is

not attained. The tendency to pit is related

to the ratio of the total height of the sur- face roughness to the lubricant film thickness. It is obvious that hip joints seldom

achieve high velocities and frequently

achieve very low velocities.

Spragg points out that it is preferable

to have one bearing surface, typically the

socket, of low friction material. The ball

is manufactured from a special alloy and is

polished to a surface finish which is not

measurable at present, but which is certainly

well below the microinch level. A major

problem is the detection of tiny (20

microinch) defects in the surface.

Robert Averill, Vice President of Meditec,

Inc., a manufacturer of surgical implants,

has urged NBS to accelerate the development

of the Topografiner as a quantitative tool

for measuring these very refined surfaces.

American Society for Testing Materials

Committee F-4 on Surgical Implants met on November 14-15, 1973, in Miami, Florida to discuss, among other things, the quantitative

measurement of the surfaces of Implants.

Robert Averill pointed out (in a private

conversation) the total inadequacy of

the present standard (F-86-69, "Surface

Requirements of Metallic Surgical

Implants"), much of it stemming from an incomplete knowledge of the relationship

between surface finish and joint lifetime.

Corrmittee F-4 is presently studing this

problem. NBS maintains a continuous dialogue

with this industry in an attempt to assist

in every possible way in this very difficult

measurement problem.

3.1.1.3 Gravure Illustrations

The beautiful colored illustrations

found in magazines, newspapers, packaging,

catalogs, vinyl fabrics, and wall coverings

are the result of the fully developed art of

gravure printing. Gravure is a term for an intaglio process of printing illustrations

from designs engraved or etched on copper,

chromium and other metal plates and cylinders.

Gravure is distinguished by its dense

rich solids, by the unobtrusiveness of its screen, and by the delicate detail on loaded

papers. The popularity of this medium is

evident from the $2.8 billion* of printed

products produced in 1971. Cylinder gravure

printing has enabled long runs of colored

illustrations to be produced cheaply and

rapidly. A detailed survey of Gravure

printing for 1971, including market

breakdowns, growth curves, and a prediction

by the Department of Commerce that certain

areas of printing will double in dollar value

by 1980.*

At the very heart of the Gravure process

is the etched cylinder containing the information to be transferred through the printing

process. In discussions with the author, an engineer in charge of producing the machines

which manufacture, grind and polish the

gravure cylinders, pointed out that much of

the art of cylinder manufacture is proprietary. He was willing to state that the

cylinders are machined to a 3 microinch

finish with high technology diamond turning

equipment. Copper cylinders are used with a

3 microinch finish in newspaper applications, but the beautiful magazine illustrations require a chrome plated

cylinder where a polishing procedure generates a 1 to 1.5 microinch finish. Poor

surface finish on these cylinders results in

the "double exposure" appearance sometimes

observed in colored illustrations.

While the industry is usually reluctant to discuss measurement processes which tend

to expose their proprietary techniques, one design engineer did state that their 1-3

microinch surfaces were very difficult to measure and characterize, and a higher re- solution surface finish instrument would

make a important contribution to their

technology, which is now measurement

limited. Electron micrographs are used to obtain qualitative information, but cannot

be used as a regular, quantitative inspection

technique.

3.1.1.4 Surface Finish Requirements for

Automobile Motors, Transmissions and

Brake Drums

The huge number of surface measurements

made per year by the automobile industry con- stitutes almost half of total number of such

measurements made in the United States. Of

these, the majority involve the drive chain.

Table 4, lists part of the total number of

automobile motor surface finish requirements

together with the associated manufacturing

process for two automobiles made in the United

States. Note that, while the higher priced

car in the left column generally has more

stringent surface requirements, this is

* Garvure Technical Association Bulletin

Vol. XII, No. 2, 1972.

18
not always the case. For example the piston

pin and bore, intake and exhaust value stems,

and hydraulic lifter have smoother surfaces

specified for Car #2, because of requirements

generated by different motor designs.

Table 5, lists the surface finish re- quirement associated with the automatic

transmission, clutch, brake drums and other

components of Car #1, together with the manu- facturing process. Moving part failure is often related to the surface finish of the

part, so that surface inspection is a major

cost factor in automobile manufacture.

During 1971 about 8.5 million passenger

cars were manufactured in the U.S. with total

value of $40.6 billion (3.9% of G.N. P.)

(from Statistical Abstract of U.S. 1972).

The number of surface finish measurements involved in maintaining the quality of these

cars is staggering.

The surface finish requirements for diesel

truck motors is considerably more stringent

than for automobiles because of tighter

dimensional tolerances. In a study of the

performance and reliability of piston pins it was found some years ago that pins with 6-7

microinches roughness failed rapidly, while

those with 5 microinches failed on run in.

When finished with a final polish which is

basically a fine circular grind to a finish

of 4 microinches, performance was good and

this pin is used in engine production. The

nature of the finish rather than its roughness determined its performance. Today a 1 microinch finish is specified for these pins,

even though this is really beyond the measurement capability of practical surface instrumentation. It is clear that the small

reduction from 5 to 4 microinches is not responsible for the tremendously improved

reliability. Since the manufacturer was unable to relate the character of the surface

finish to the lubricating function and its

failure, he merely tightened the surface

requirement, thus increasing the cost. This

is an example of the two major problem areas: characterization and its relation to function, and the need for high resolution sur- face measuring instruments.

3.1.1.5 Surface Finish and Automobile Oil

Consumption

Automobile motor manufacturers have re- ponded to an accelerated need for control of

oil consumption in motors by developing precise and refined criteria for cylinder wall,

piston, and piston ring surface finish. The

development of thin walled blocks, increased

periods between oil changes, air pollution

controls, and most recently, the oil shortage, have served as strong incentives for

studies of oil consumption.

Prior to the oil consumption studies, the

surface finish was specified only in terms of

the roughness height (AA or RMS) of the

cylinder wall surface. The more recent

studies have shov/n that the boring and honing

operations in automotive cylinder manufacture

are crucial in controlling oil consumption.

While most of these studies are proprietary,

a leading manufacturer set up the following

specifications for a honing finish in 1964:

1) The honing process should generate a cross hatch pattern of the cylinder surface with a cross hatch angle of 44° to 64°.

2) It should uniformly cut in both directions . 3) It should be clean cut, not sharp and free

of torn and folded metal.

4) The AA roughness should be between 20 and

30 microinches, and should in no case be less

than 15 nor more than 35 microinches.

5) The cross hatch should have a average

width of 0.0004" - 0.0006".

6) The cross hatch should have an average

depth of 0.00015" - 0.00025".

7) The plateau should be 1/2 to 2/3 of the

surface.

8) The surface should be free of burnish or glaze and imbedded particles.

While the basic requirments of close piston

ring to cylinder wall fit are very important,

the above requirements are designed to in- sure a lubricant retaining surface with

enough oil for good lubrication without ex- cessive oil consumption.

The finish of cylinder walls is inspected

by a replication process and photomicroscopy.

A cross-section of the finish is obtained by

cutting out a piece of the cylinder bore,

copper and chrome plating, polishing the

section and taking photomicrographs at 500X

magnification. Since this is a destructive

test, is has limited use. Other studies

used stylus instruments and peak counters in

evaluating cylinder wall surfaces. The importance of this problem is evident from the

$5 billion yearly product value of automobile

motors (Statistial Abstracts of u'.S., 1972)

and the finish related oil consumption.

3.1.1.6 Efficiency of Electric Motors

A major source of controllable power loss

in electric motors involves tiny electrical

shorts in the stator laminations. It has

long been knovm that surface roughness plays

an important role in controlling these losses but only recently has the proper characterization factor been discovered. Prior

to this discovery the only v/ay to determine

if a stator assembly had excessive core

losses was to build up the laminated stack,

weld it together, and then decarburize and

anneal the assembly. Only after this manu19
facturing process was completed could a core

loss inspection be performed on the stator

assembly.

Engineers had suspected for years that the

finish of the laminations was at fault, since

if the steel has too smooth a surface, then

gases involved in the decarburization process

could not pass evenly between the laminations

because of the excessive surface contact.

This results in lamination welding, and thus

shorts. On the other hand if the surface

finish was too rough, the interlocking peaks

and valleys between opposing laminations resulted in local shorts. Traditional roughness measurements proved to be inadequate so other means of characterizing the surface were sought. After considerable study it was found that peak counting techniques could

be used for quality control of the laminations . It was determined that a peak count of 150

peaks per inch a 0.030 inch width cut off,

and a 50 microinch band width setting was the

minimum acceptable level for adequate quality

control. A higher peak count is desirable.

Surface roughness limits were set between

60 and 125 microinches. Incoming lamination

steel must now meet these specifications.

The total value of electric motors and

generators produced in the U.S. exceeded

$2.5 billion in 1970 and is rapidy growing

(Statistical Abstracts of the U.S. - 1972).

This success story represents the "tip

of the iceburg", in that a similar determination of the relationship between proper

characterization of a surface and its

function could save untold millions of

dollars in industries where surfaces are over specified because they are improperly

characterized.

3.1.1.7 Shaft and Radial Lip Seal Surface

Finish

There are few people in the United

States who have not been inconvenienced by

a seal failure. For example the author has

had a clothes washer transmission seal fail

with the consequent loss of the transmission;

a dishwasher face seal failed allowing water

to enter the electric motor, causing it to short permanently; a water pump seal failed

requiring pump replacement, two automobile

wheel seals leaked causing the brakes to lock, a potentially dangerous situation; a differential seal failed, necessitating re- placement of the differential and a rear main

bearing seal leaked, requiring an expensive

repair. Shaft and radial seals are used in

chemical pumps, high pressure pumps,

hydraulic pumps and a variety of other devices.

The problem of shaft and radial lip seal

design is discussed in great detail by James

Symons, General Motors Corp., in an article

entitled "Shaft and Radial Lip Seal Performance" (Proceedings of International Conference on Surface Technology, Pittsburgh,

Pa., May 1-3, 1973, page 584). In his introduction, Mr. Symons points out that the sur- face finish of the shaft is an important parameter in seal performance and reliability.

Figure 9 from Symons article shows that the

friction between a surface and synthetic

rubber depends on surface roughness.

4 5

o

SURFACE ROUGHNESS

Figure 9: Synthetic rubber friction theory

The adhesion component decreases with increasing surface roughness since it is dependent on the contact area. As surface roughness increases, the contact area decreases

and hence friction decreases. The hysteresis

component is just the reverse, with increasing surface roughness causing increasing

deformation and higher friction due to hysteresis losses. The combined action

results in a minimum about where the two curves intersect, the effect is demonstrated

in table 2 from Symons for a four inch seal on a plunge ground shaft of 5, 15 and 35

microinches AA surface roughness.

Table 7: Dependence of seal torque on sur- face roughness.

Surface Roughness Torque Shaft Speed

Microinch AA in-oz RPM

5 15

35

41.2

18.7

30.0

1000

1000

1000

Further investigation indicates that AA roughness is not the only surface finish

factor which is important, as also shown in

3.1.1.5. The manufacturing process must also

be carefully specified. Thus, in seal

practice as in other areas, it is the characterization which is lacking in a proper

description of the surface requirements. Table 8 lists the replacement cost

for the seals in a medium priced American

automobile and estimates total yearly seal

cost for U.S. manufactured automobiles at $200 million.

20
Table 8: Cost of individual seal in U.S. manufactured cars and estimated total

yearly cost.

Transmission seals $ 3.00

Rear wheel seals 1.00

Power steering pump seals 2.60

Crank: front and rear seals 2.50

Differential pinion seal 2.00

Axle seals 7.00

Cost of Manufacturing Shaft Surface 8.00

Total estimated cost/car $25.10

Cost for 8.5 Million Cars

Manufacturer Yearly $210,000,000.00

3.1.1.8 Paintability of Surfaces - New

Powder Coatings

A new technology has quite suddenly sprung

from limitations and problems associated with

the traditional painting process, a $2.9

billion metal coating industry. Stemming from

an ecological concern over the huge quantity

of toxic solvents released into the atmosphere each year, the rapid development of

powder coatings has been sourred on by the

obvious advantages of a tough, chemically re- sistant, mechanically stable coating with ex- cellent adherence and abrasion resistance

that can be applied in films which are only

500 microinches thick. The economic advantage of such thin coatings is particularly

attractive.

The new powder coatings are electrostatically sprayed onto the surface, usually without a primer, and then heated to spread and

polymerize. Epoxies, polyesters, acrylics,

vinyls, pholyethyl enes , butyrates and nylons

are all available, each with particular advantages. The service temperature range of

these coatings is from -370° to 250''F dry and from -100° to 150°F wet. An article in Iron Age (June 21, 1973) estimates that 250 million pounds of dry powder

coatings may be used yearly be 1980.

New technology, however, is not without

its problems. The surface finish of a metallic part determines the appearance of a coated surface, particularly when the coatings

are only 500 microinches thick. In measuring

the surface panels of automobiles for example

the surface finish for wet coatings must be

20 to 30 microinches AA plus a certain (proprietary) distribution of peak counts. The

new coatings do not have the desired surface

texture when the panels meet these specifications, and new means of characterizing the

surface roughness and its relationship to dry powder coatability are being sought by

the automative, furniture and appliance industries. The future of this rapidly growing

industry may well depend on our ability to manufacture and measure the necessary improved surfaces. NBS interacts with the users of these products, particularly with

regard to the characterization problem.

3.1.1.9 Electroforming - Duplication of

Highly Finished Surface

Considerable care and expense is usually

required to manufacture very smooth surfaces,

or surfaces with a precisely defined texture.

Electroforming is an electrochemical process

of metal fabrication involvina the duplication of an original artifact, for examole a precision reference specimen of surface

roughness, without the aid of mechanical

forming, machining, welding, grinding, etc. The technique uses an electrolyte, an anode

to supply the met|l ^ control of the electric

current and special techniques to control

the deposit of metal on the madrel (form)

which is to be duplicated. The surface

finish of the duplicate conforms to the

original within a microinch AA and dimensional tolerances can be held to 100 microinches. Typical electrodeposited metals include copper, iron, silver and nickel.

El ectroformed articles often have difficult shapes to manufacture, inside surfaces

which are highly polished or surfaces with a highly controlled texture. Optical reflectors

which are nearly perfect copies of the original are an excellent application of this technique. Radar waveguides which have extremely

smooth interiors, surface comparators with

carefully controlled texture, tiny tubing

with polished bore, nickel ice augers, prototypes for cosmetic containers and diffraction

gratings are among the many products manufactured by electroforming.

The ability of the electroforming process

to duplicate the original surface is ex- ploited in the manufacture of precision re- ference specimens where the first duplicate

of the master is carefully measured for sur- face roughness. The extreme fidelity with

which the surface is reproduced enables one

to safely assume that all succeeding duplicates have the same roughness within the ac- curacy of the measurement system, with only

occasional recal ibrations

The chief sales engineer for the leading

electroforming company among the 28 independent companies estimates that the yearly product value of the U.S. electroforming industry may presently be as high as $100 million. In addition, the big automotive com- panies also operate electroforming plants,

as do a few other large corporations.

21
3.1.1.10 Surface Requirement in the Electronics Industry

In the last two decades a huge industry

has developed from the invention of the transistor and other semiconductor devices. Today, thin film devices manufactured on ce- ramic substrates are presenting new and challenging measurement problems in surface finish. An article by R. C. Sundahl and

L. Berrin of Bell Laboratories ("Surface and

Subsurface Analysis and Characterization",

Preceedings of the Symposium on the Science

of Ceramic Machining and Surface Finishing,

Gaithersburg, Md., November 2-4, 1970) describes the need for proper characterization,

and related measurement problems associated

with Ceramic surfaces. They point out that,

"The analysis and characterization of sur- face resulting from ceramic forming, ma- chining, and finishing methods are necessary

to obtain a fundamental understanding of the

effects of such operations on surface properties. It is through this understanding

that ceramic surfaces can be improved so as

to meet the rigid requirements of new technologies."

A typical silicon integrated circuit package provides a 1,024 bit I6FET (insulated

gate field effect transistor) memory on an

80 mm X 30 mm by 1 mm thick ceramic substrate. (Since the electronics industry

uses metric units this practice will be re- flected in the present discussion). Photolithographic techniques are employed in this

vapor deposited metallization process whereby electrical leads 5 micrometers wide

spaced 10 micrometers between centers con- nect the active elements. One 5 micrometer

imperfection in the surface can cause either

an open or a short circuit. Excessive sur- face roughness, scratches, pits, etc.,

threaten the integrity of the finely detailed interconnect patterns.

These surfaces are examined with stylus

instruments, optical microscopes and scanning electron microscopes. It is claimed

that surfaces are achieved with roughness

less than 0.005 micrometer (0.2 microinch),

which is well beyond the present measurement capability. But the real challenge

lies ahead. There is discussion in the industry of devices under development which

will employ the switching properties of interlocking molecules on surfaces so smooth

that only a few atomic steps (0.001 micrometer or 0.04 microinch) could interfere

with the reliability of the device. While

the electronic component industry has already reached the $7.5 billion level (Statistical Abstracts '72), it is clear that

future growth could be staggering, particularly if the surface measurement problems do

not present a roadblock.

3.1.1.11 Summary of Measurement Needs

In table 9 the author has estimated from

his discussions with engineers from each

technology and from his knowledge of mea- surement applications, the impact that an appreciable improvement in resolution, characterization, non-contacting instrumentation,

on-line measurement and improved accuracy

would have on the quality of product in each

of twenty technologies. Specifics are discussed in the previous paragraphs. Clearly,

improved characterization is most urgently

needed with on-line measurement a close

second. NBS efforts to improve characterization will be discussed in section 4.2.

3.1.1.12 Distribution of Surface Finish

Instrumentation

Table 10 lists the distribution of stylus

instruments among metalworking industries

in the U.S. in 1973 according to the 1969

Standard Industrial Classification Code (SIC).

3.1.1.13 Measurement Needs in High Technology Industries

Among high technology industries, one of

the most sophisticated is optical system design and fabrication. Imperfect optical

surfaces scatter light and thus degrade the

performance of optical instruments. The

growing need for improved measurement and

characterization of optical surfaces is

being met by research scientists at the Naval

Weapons Laboratory, China Lake. All

known optical techniques for measuring sur- face roughness have been reviewed in an NBS

Technical Report abstracted in appendix B.6.

Another important technology, the electronics industry, finds that tiny imperfections on substrate surfaces result in a high

rate of device failure. In the computer industry the surface finish requirement for

tape recorder heads, memory discs and drums

and tape transport devices are presently

beyond the state of the measurement art. Microminiaturization also places new demands

on surface characterization.

Laser window, mirror, and lens damage is

strongly influenced by surface topography.

Our ability to make further progress in com- plex laser fusion devices is limited by several factors, one of which is laser mirror

failure when high powered lasers are focussed

on the fusion chamber. It has been established that a major source of mirror damage

is the high electrostatic field at the mirror

surface due to surface imperfections (discussed in several articles in Applied Optics,

22
Table 9: Measurement improvement impact matrix: The impact of specific measurement improvements on product quality and quantity is ranked as Low (L), (little effect).

Medium (M) , or High (H), (considerable impact).

Improved

Improved Character- Non On-Line Improved

Resolution izater Contacting Measurement Accuracy

1. Surgical Implants H H M L M

2. Gravure Printing H H M M M

3. Dairy Industry L H L H L

4. Auto Oil Consumption L H L H L

5. Auto Motor M H L H M

6. Auto Drive Chains L H L H L

7. Paintabi 1 ity L H L H L

8. Electric Motor L H L H M

9. Semiconductor H M H H M

10. Prec. Ref. Spec. H M L L H

11. Ball Bearings H H M H M

12. Computer Discs H M H M M

13. Shaft and Lip Seals L H L H L

14. Surface Science H H H L H

15. Electrical Contacts L M H M L

16. Surface Instrument Industry H M M M H

17. Tin Cans M M L H L

18. Sleeve Bearings H M M H L

19. Chrome Plating M M L H L

20. Optical Surfaces H H L M H

spring of 1973). A major unresolved problem

in the microelectronics industry involves

measuring the topography of the silicon - silicon oxide interface in metal -oxide-semiconductor microcircuit devices. The effect

of roughness on the mobility of free carriers

in the silicon surface layer is well established but the measurement of the inaccessible solid-solid interface represents a new challenge A leading communications industry

cannot find an adequate way of characterizing

the surface roughness of fiber optics proposed for long range communications (see

letter appendix A)

A challenging example exists in the field

of thin film lubricants (sometimes involving

dry film monomolecular layers) that are being

developed for instrument bearings and pivots.

Failure of these bearings is directly related

to the residual surface roughness of a bearing that has been polished to a mirror finish.

An extreme requirement involves the developing field of molecular electronic devices

where one-dimensional conductors can be

switched to insulators. These devices require that surface roughness be of the order

of interatomic distances.

3.1.2 Economic Impacts - Costs and Benefits

The largest user of surface texture measuring instruments is the metalworking industry. Table 10 shows the wide distribution

of these instruments in industries grouped

according to the Government's "Standard In- dustrial Classification Manual". It is difficult to determine the number of instruments in non-metal working industries, universities, small companies (<20 people) and

particularly the electronics and high technology industries (for example computer disc

and drum memory and optics industries). The

sales manager for the largest U.S. surface

finish instrument manufacturer estimates

that there are at least 25,000 surface text- ure measuring instruments in the United

States. He reports that total instrument

sales in the U.S. average $2 million per

year. Instruments cost from $1,000 to $20,000 each with an average replacement
Table 10: Distribution of surface finish instrumentation - Surface measuring

instrument located in metalworking plants grouped into industries according to U.S. Government "Standard Industrial Classification Manual" as of 1968. All

non-metalworking industries, government-owned installations, universities and

plants with less than 20 employees are not included . Data is based on 1973

American Machinist Inventory of Metalworking Equipment, McGraw-Hill.

1969 Under

SIC ^ercent Total 10 years 10-20 Over 20

Code Brief Description of Industry With Number Old Years Old Years Old

019 Ordnance 30 471 308 146 17 025 Furniture and Fixture 6 37 15 21 1 033 Primary Metal Industries 7 314 248 55 11 034 Fabricated Metal Products 7 1124 846 235 43

035 Machinery, Except Electrical 14 3930 2537 1103 290

036 Electrical Machinery, Equip. 11 996 713 268 15

037 TransDortati on Eauioment 18 1103 565 470 68

038 Professionally, Scientific,

Ooti ral 13 322 208 100 14

039 Miscellaneous Mfa Indus. 1 79 7 45 27

251 HniisphnlH Fiirnifiirp 3 2 2 252 Offirp \_/III^C^ Furniturp ILIIIIIUUIC^ 11 18 9 9 253 Riiilflino UUIIVJIIIv^ XCX Rplatpd INCIUOXI^U Fiirnitiirp luillil^uici: 10 6 6 254 Partitions Shplvina 1 orkers 7 11 4 6 1 259

331 6 34 20 8 6 332 Iron & Sfppl Foundries 7 39 28 11 333 Primary Smpltina and Rpfinina 10 31 28 3 335 Rollinn Dri^winn ^ Fxtrudinn 6 42 40 2 336 NnnfprroiK Found ri p*^ 10 69 63 1 5 339 Misc Primary Mptal Products 6 99 69 30

341 Mptal Cans 6 13 13

342 futlprv Hand Tools X Hardwarp 7 119 51 68

343 Hpatina Annaratus. Plumbina 4 8 8

344 Fabricated Structural Metal Prod 3 184 116 54 14

345 Srrpw Marhinp Products 19 308 237 47 24

346 Mptal Stamninas 6 90 74 15 1 347 roatina Fnarf^vinn 10 216 203 13 348 Misc • Fabricatpd 1 vlL.'l IV^UV>V»VJ Witillrp Products 1 1 \J \Jl KA \r \^ J 2 10 10

349 Misr Fabriratpd Mptal Prndiirt*; 11 176 134 38 4 351 Fnainps 1— IIVJIIICO and UIIU Tiirhinps lUI UllldO 43 177 83 49 45

352 Farm lUIIII Marhinprv llUV^IIIIICiy X Faiiinmpnt L.l-JLIIU'llldllU 6 103 48 42 13

353 Mininn lllllll^^, Marhinprv lIU^TIIIICIJf Fi(J( Fniiin l_\^Lll^. 8 161 83 70 8

354 Mp'hP^l iic^uciiwwi work[\iiiy i nn Marhinpvu iicn^iiiiicijf )!i c( Fniiin i_i^u>^. 1 71/ X J. 465 170 76

355 Soprial ^^cv^iui TnHii^trv iii(m1Uouij^ Marhinprv iia\..iiiiicij/ Q 165 102 55 8

356 Hpnprril V^dldCll TnHii<:1"y^*i XIIUUJLI Id)ri 1 Marh liClCII. Aut Fniiin l-l^UllJ 1i, out 3fi4 809 47'S 80

357 O'F'f \J 1 1 iICC, pp Pnmnti'h'inn CUIMVJULIIIM Marhinpc llQCIIillCj 14 L.UU 1 74 ?8CO 358 ^pv*\/ipp OCT vice TillUuoLlJ^ nH 1 1 c "f" MAr^hinPC lluCIIIIICo ao oo A q

3i>Q

1 idcri 1 iici y , iiUii c 1 trc Lr leal 1 7 QQ9 ^ lU

361 Flprf*v^ir ciccui )c Tk*;^ iiaiioiiiiDoiuii n cnri c c 1 nn ot nichv^iK uiour lu. q 1 1

"\ 110 84 47

3fi? LiccLi 1 ccl 1 liluubLi lal MpparaLUb toy 1 91 DO 363 Household Appliances 20 63 52 11 364 Electric Lighting & Wiring 9 113 86 27

365 Radio & T.V. Receiving Sets 5 6 3 3 366 Communication Equipment 15 278 163 115

367 Electronic Components & Access 10 200 177 23

369 Misc. Electrical Machinery 9 34 27 7 371 Motor Vehicles & Equipment 16 353 168 158 27

372 Aircraft & Parts 35 729 394 303 32

374 Railroad Equipment 12 16 2 5 9 381 Engineering, Lab. & Sci . Instr. 16 121 65 52 4 382 Instr. for Meas. Physical Char. 13 102 68 31 3 24
Table 10 (continued)

1969 Under

SIC Percent Total 10 years 10-20 Over 20

Code Brief Description of Industry Width Number Old Ypar<; Old Ypflr<; Did

384 Surgical , Medical , & Dental 15 70 60 9 1 386 Photographic Equipment 6 10 2 2 6 387 Watches, Clocks, Clockwork 22 8 5 3 391 Jewelry, Silverware & Plated 3 39 7 32

395 Pens, Pencils & Materials

Office & Artists' Materials 3 27

Total - 16,253

cost of about $1,500. Thus, total replacement cost for all industries is about

$1,500 X 25,000 instruments or $37,500,000.

So far as can be determined there has

been no study of the "value added" by the

measurement of surface texture. Assuming

all instruments are used only 10 percent of

the 8 hour working day the metalworking

industry spends about $50 million in labor

and overhead costs a year in surface finish

measurement over and above yearly instrument

investments of $2 million. The dollar value

of products from those inAus tries requiring

surface finish measurement, including ma- chine tools, tool products and fabricated

metal parts is about $42.4 billion dollar

today (1973 report of Nat. Mach. Tool Bldrs.

Assoc.). Thus, even though the yearly ex- penditure in surface finish measurements

is only one tenth percent of the gross sales

of final product, this still amounts to a substantial $50 million dollars a year.

Thin film steps are either measured with

stylus instruments or with a two beam or a 10a

900

Cost Comparison Chart

Turning Cut

Varying Surface Quality

multiple beam interference microscope. The

product manager for a large microscope manu- facturer, estimates that there are about 1000

interference microscopes in the United States.

At $1,000 each, they represent an investment

of $1 million. If used 10% of the working

day they represent a labor investm.ent of $2

million per year for thin film step measurements . Precision reference specimens are usually

supplied with stylus instruments for calibration purposes. In addition Precision

Reference Specimens are sold directly to users. Since all instruments require some sort of calibration, it will be assumed

that each existing instrument has at least

one precision reference specimen worth about

$75.00, involving a total capital investment of $1.87 million. The economic dimensions of the impact areas are summaried in

table 11. The surface finish of a part is often

overspecified either from habit or lack of

knowledge. One of the few published studies

10b

Cost Comparison Chart

Face Milling Cut

Varying Surface Quality

Varying Tolerance

TOLERANCE .002 8 UNDER

25 63 125 250 400

RMS SURFACE ROUGHNESS VALUE Figure 10: Cost Comparison Charts

. milled surfaces

TOLERANCE OVER

002

45 63 125 RMS SURFACE ROUGHNESS VALUE turned surfaces, b) face

25
Table 11: Economic dimensions of impact areas in surface finish measurement in the U.S.

metal working industry. Top line-first two columns: number of instrument

purchased in 1972 and investment cost. Last two columns are labor cost for

surface measurements and dollar value of total product involved. The lower

three lines involve total instruments and total costs. See text for source.

Number of Industrial 1972 1972

Instruments Instrument Industrial Do! lar Values

or Specimens Investment Labor Cost of Total

Purchased Cost (measurements) Product Affected

Stylus Instruments

a) 1972 only

b) Total Number in

1,300 $ 2 Million $50 Million $42.4 Billion

Use 25,000 37 Million

Interference

Microscopes

Total Number

In Use

1,000 1 Million 2 Million

Preci si on Reference

Specimens

25,000

(estimated) 1.9 Million See stylus

instruments

See stylus

instruments

of the relationship between surface finish

and cost is illustrated in figures 10a and

b (Lad J. Boyer, Warrer and Swarsey Co.,

American Society of Mechanical Engineering

paper #56-SA-9, June 1956). From figure 10a

it is seen that improving the surface finish

of a turned surface from 50 to 25 microinches almost doubles the turning cost. Similar conclusions are reached from the

study of milled surfaces, figure 10b and

ground surfaces (see Bayers paper). Thus,

there is usually a compromise between

the economics of part manufacture and the

ability of the part to function properly and

have an acceptable life expectancy.

3.1.3 Social, Human, Person-on-the Street

Impacts

The impact of surface measurement on the

person-on-the-street has been discussed at

length in section 3.1.1. Much of the impact

of surface finish is cosmetic and spans the

range from automotive bodies and milk storage tanks to jewelry. Safety considerations

are most evident when a wheel bearing fails

in an automobile or a wheel seal permits

oil to reach brake drums causing the wheels

to lock while braking the car. People with

surgical implants, such as hip joints,

place their trust in the manufacturer who

provides highly polished alloy balls, hopefully with lifetimes reaching ten years.

As discussed in 3.1.1, surface finish plays

an important role in sterilization and

sanitation. A well finished surface

eliminates sites for bacterial growth and

permits rapid inspection of the surface.

Thus, all surgical, dental, hospital, and

food handling surfaces are careful finished.

A list of national issues and related

surface measurement needs is given in table

12.

3.2 Status and Trends of the System

The calibration system for surface roughness and thin film steps is functioning in

accordance with the standard (B46.1). NBS

performs calibrations at the highest level

available in the U.S.; calibration turn

around time is 30 days. Secondary laboratories have not requested improved accuracy,

although certain high technology industries

request calibrations at smaller AA values.

At NBS's request, the need to improve the

flatness and quality of U.S. precision re- ference specimens will be addressed in the

revised standard. There is need for a specimen with surface roughness values below 20

yin (0.5 u meter), the smallest value available on U.S. specimens. Thin film step mea- surements will improve as the quality of the

surfaces near the step is improved. Metric

terminology will be introduced in the re- vised standard.

U.S. engineers and scientists exercised

strong leadership in the early development

of surface finish instrumentation. Unfortunately this leadship has been minimal during

the last 10 to 20 years so that most of the

recent innovative work in characterizing

surfaces has come from abroad. A study of

the literature reveals that England, Germany,

Japan and the U.S.S.R are particularly

active. A German company manufactures instruments which measure a variety of surface

roughness parameters and a British company

markets computerized instruments measuring

many parameters.

26
Table 12: Surface measurement needs related to some present day national issues

National Issues Defense

Energy

Material

Health and safety

World trade

Productivity

Agriculture

Communications

Related surface measurement needs

upgrading of characterization; sensitive, non-contacting instrumentation needed for classified applications (this need is not documented here)

high resolution measurement for laser fusion mirrors (energy

generation)

development and measurement of single-crystal surfaces

discussed in 3.1.1 - higher resolution for surgical implants, improved bearings and seals, better characterization of food

handling and sanitary surfaces

participation in ISO standards formulation to prevent discrimination against U.S. exports

determination of least expensive surface finish which is adequate

for function. This work is difficult and expensive but has great

economic leverage

dairy and food handling industry is investigating improved characterization of sanitary surfaces

integrated circuits and microelectronic devices require unrealized

measurement of single atom steps

Some segments of the industrial com- munity are very aware of the surface characterization problem. For example, the

leading manufacturer of industrial polishing

materials, at a recent visit to NBS said,

"American industry is being penalized in areas

where standards are tied to a particular

manufacturing process rather than properly

characterizing the needed finish. Such

standards result in an inflexibility in

procurement and inspection procedures so that use of new materials and manufacturing

processes, which are often superior and less

expensive than traditional processes, are

prohibited. The problem is particularly

acute in foreign markets where local standards are more responsive to changing technology, resulting in an unfair market disadvantage for the U.S." Examples of this

problem included dairy surfaces, hydraulic

pistons, seals, and bearings.

The recent development of the stylus/computer calibration system at NBS makes full

parameter measurement available in the U.S. However, it is necessary that users have

instrumentation close at hand to make such

measurements and that they carry out development programs to study the relationship

between finish and function.

A number of high technology needs have

been discussed in 3.1.1.13. Perhaps the

most challanging requirement is for mea- surement of single atom steps in applications such as molecular microelectronic

devices, surface science studies of single

crystal surfaces and microminiaturization

components. NBS is developing an instrument

to meet these needs.

The scanning electron microscope provides

the highest resolution direct images of solid

surfaces (10 nm). It is characteristic of

the instrument that it has extremely poor

vertical resolution so that the profile of a surface may not be measured with accuracy

greater than 150 nm. Very high priority

should be given to the development of new techniques for profile measurements with

this instrument.

The major impact of automation on the

surface finish measurement system is the

need for on-line non-contacting surface

finish measuring instruments. A number of

instruments are under development in U.S.

to fill this need.

4. SURVEY OF NBS SERVICES

4.1 The Past Throughout the first half of this century,

NBS scientists have been active in a variety

of areas related to surface finish measurement. Several aspects of this early work were focussed in a 1945 NBS Research paper

(RP 1708) by Richard Hunter comparing measurements made with an NBS developed glossmeter with those made with a stylus instrument. Little is known about NBS surface finish calibrations per se prior to World War

II. In the early fifties some calibrations

were carried out but it was not until the

1955 American National Standards Institute

B46.1 standard on surface texture was approved that such measurements became routine

calibrations. Until then, there was no uniformly accepted measurement procedure. By

late 1955 work at NBS had reached a stage of

27
sophistication enabling NBS to measure and

discuss critically the roughness of highly

finished gauge blocks (Symposium on Gauge

Blocks, NBS, Aug. 1955). In the 1960's NBS

developed and tested a piezoelectrically

activated shaker table for calibrating

stylus instruments over their full range of

frequency response. This work was discontinued when the scientist in charge left NBS. The present standard developed when the

American Standards Association authorized a joint effort by the American Society of Mechanical Engineers and Society of Automotive

Engineers in 1932. After exhaustive studies,

drafts, meetings, ballots, etc., three suc- cessively upgraded documents were approved

in 1947, 1955 (similar to today's standard)

and 1962 (compatible with Great Britain and

Canada). The present standard is now under

revision. NBS staff members were deeply involved in developing these standards and are writing parts of the new document and carrying out experimental studies to refine the

section on instrument and measurement re- quirements . NBS impacts directly on a variety of industries by carrying out special studies of

surface topography in expecially challenging

areas such as the topography of plastic

coated surfaces, semiconductor surfaces and

drill bit cutting surfaces.

4.2 The Present Scope of NBS Activities

4.2.1 Description of NBS Services

All surface roughness and thin film

step measurements and calibrations

are carried out in the Optics and Micrometrology Section of the Mechanics Division

(Institute for Basic Standards). Precision

reference specimens and quality thin

film steps are calibrated relative

to the defined unit of length and in

accordance with the national standard

for surface texture. Special studies

are carried out for particularly challenging

surfaces on a fee basis. A variety

of surface characterizing parameters

are computed from the surface profiles.

In addition to fee supported calibrations,

NBS maintains a technical base through

internally funded studies and instrument

development programs, and also coordinates

the national measurement system for

surface finish through dialogues with

users and participation on standards

committees

Although NBS has frequently been re- quested to participate in the formulation

of international standards in order

to protect American industry from arbitrary

and discriminatory international standards.

personnel, funding and travel limitations

prevent such participation.

NBS is very active in The American

National Standards Institute activities

in generating and revising standards.

One staff member is on Committee B46,

the policy making group, and another

is a member of B46.5, a subcommittee

revising the 1962 standard.

NBS has just completed a report

to users explaining the new NBS measurement

system which employs a mini -computer

to store 4,000 profile points from

a stylus instrument, and then calculates

the AA roughness value. The system

is calibrated before each use with

an interferometrically calibrated step,

which makes the measurement traceable

to the standard of length. The new system, which was initiated in July,

1973, resulted in at least a two-fold

increase in accuracy (see fig. 7).

Furthermore, the computer can also

be used to calculate any of the other

surface characterizing parameters discussed

above for any surface. To date U.S.

instruments have not been equipped

to measure these other parameters

with the exception of peak counting,

in spite of the availability of such

instruments abroad. The calibration

of thin film steps is discussed in

2.2.2.1 (see fig. 8). Optical instruments

are also used at NBS in surface roughness

measurements. The most refined stylus

instrument, capable of detecting surface

structure as small as 10 nm with horizontal

resolution of 1 micrometer, is employed

in ultrasensitive measurements.

NBS is presently developing a high

resolution non-contacting instrument

for measuring surface topography (see

Appendix B.7 and B.8). This instrument

employs the novel concept of following

the profile of the surface with a field

emission probe, enabling drastically

improved horizontal and vertical resolutions

(10 nm and 0.3 nm respectively) which

permits measuring single atom steps.

Another development program exploits

the two beam microinterferometer and

a precision scanning microdensitometer

to obtain accurate profiles of surfaces

without damage from surface contact.

As far as can be determined NBS

is in communication with every established

U.S. and most foreign leaders in surface

metrology. A list of the users who were consulted in the preparation of

this assessment together with a few

sample letters from high technology

users are included as Appendix A. The more important NBS contributions

28
INPUT

GOVERNMENT

NASA MIL Specs

Defense Agencies (Metrology Labs)

Postal Service

Lawrence Livermore Lab

NBS/Toy Safety Program

NBS/Electronic Technology Div.

INDUSTRY

Surface Finish Instrument Mfg.

Precision Reference Specimen Mfg.

Optical Instrument Mfg.

Defense Related Industries

Precision Mechanical Instrument Mfg.

STANDARDS GROUPS

International Standards Org.

American National Standards Institute

American Society of Testing and Material

JOURNALS

Microtechnic

Mechanical Engineering

American Machinest

NBS Journal of Research

Measurement Techniques

Wear

Inst, of Mechanical Engineering

Journal of Physics

J. Optical Soc. Amer. Applied Optics

SOCIETIES AND INSTITUTIONS

Amer. Gear Mfg. Association

Amer. Soc. Mfg. Eng. Amer. Soc. Tool Eng. Amer. Ord. Association

Int. Inst, for Prod. Eng. Research

Dairy and Food Ind. Association

Amer. Soc. for Metals

Amer. Soc. Mech. Eng. Soc. of Automotive Eng.

SURFACE FINISH

GOVERNMENT

AEC USN

Defense Dept. NASA

Postal Service GSA

NBS/Toy Safety Program

NBS/El ectronics Technology Div.

20% 207o STANDARDS GROUPS

ISO/TC 57 ANSI B46.1

INDUSTRY

Prec. Ref. Specimen Mfg.

Stylus Instr. Mfg.

Optical Instr. Mfg.

Automotive Industry

Machine Tool Industry

Computer Memory Industry

Semiconductor Industry

Aircraft Industry

Dairy and Food Industry

Bearing Industry

50% 10%

JOURNALS

NBS/Journal of Research

J. Science Instrument

J. Amer. Physics Soc. Physics Today

Machinery

Current Engineering Practice

Instruments and Central Systems

Quality Assurance

OUTPUT

Figure 11: NBS Information and Calibration Input-Output Chart

29
to the surface literature in the last

few years are summarized in Appendix B. One of the most effective ways of

determining the integrity of a measurement

system is through intercomparisons

where a blind round robin is conducted

with other users. NBS is presently

involved in an American Society of

Mechanical Engineers round robin on Scratch and Dig Standards for optical

surfaces which will also include optical

measurement of surface roughness by

light scattering. The danger always

exists that artifacts circulated in

such a round robin will become de-facto

standards of "optical surface roughness"

which are unrelated to the national

standard. A second round robin is

in progress for one segment of the

National Conference of Standards Laboratories,

A third proposed but as yet uninitiated

intercomparison would involve the U.S.,

Canada, England, Australia and Germany.

With reference to the Input-Output

Transactions Matrix (table 6) NBS provides

a full spectrum of services to the

industrial /scientific community ranging

from highly sophisticated special studies,

calibrations of precision reference

specimens, technical and semi -technical

publications, conferences, telephone

and in-person advice, joint studies

with universities and industries, standards

committee work, to responses to mundane

problems such as measurement of the

roughness of wallpaper and cast surfaces.

Figure 11 is an NBS Information and

Calibration Input-Output Chart listing

the sources of information, technology,

challenging measurement problems, and

scientific base for surface metrology,

as well as the distribution of effect

in terms of calibrations, special studies,

consultations, publications and contribution

to Standards Committees.

4.2.2 Users of NBS Services

The users of NBS surface metrology

facilities include all segments

of the metal working community, as detailed above, the various metrology

laboratories concerned with length

metrology, instrument manufacturers,

the various defense and space agencies,

the electronics industries and standards

associations. All of these users

have been discussed above. All are interested in maintaining a viable

measurement system to insure the orderly

transfer of goods and services. Some

have special problems requiring sophisticated

or as yet unattainable measurements.

Many are interested in improving their

products or lowering costs by determining

the relationship between surface finish

and part function.

4.2.3 Alternate Sources

There are no alternate sources

of primary calibrations of surface

roughness in the U.S. Highly accurate

secondary calibrations are available

from a variety of instrument manufacturers

(see Table 3)

4.2.4 Funding Sources for NBS Services

and Distribution of Effort

Personnel - 1 Ph.D. (1/3 time); 1 M.S. (full)

1 Physical Science Technician

(full)

Yearly Budget $84,000

1974 Calibration effort (reimbursed)-$12,000

(excluding internal services)

Thus, the ratio of NBS expenditures for

surface measurement ($84,000) to the metal

working industry expenditures for labor and

instrumentation ($54 Million) is 1/640 or less than 0.2%.

Effort Distribution

Calibration (including internal services) 15%

Improving quality of calibrations 50%

Instrument development 20%

Standards committee work 5%

This study 10%

100%

Limited NBS manpower for surface metrology

prevents achievement of important goals such

as 1) preventing discrimination against U.S.

manufacturers in International Standards by

active participation in generating these

standards, 2) development of instrumentation

for refined measurements such as those for

surgical implants and semi-conductor device

surfaces, 3) exercising leadership in re- lating surface finish to part function thru new means of surface characterization and

4) development of instrumentation to broaden

the usefulness of the scanning electron

microscope in surface profile measurements.

4.2.5 Mechanism for Supplying Services

Services are provided thru calibration

of precision reference specimens,

publications, talks, correspondence,

standards committees and personal interactions with users.

30
4.3 Impact of NBS Services

4.3.1 Economic Impact of Major User

Classes

The economic impact of users was discussed in 3.1.2, including dollar

value of measurements and instrument

investment, social impact, etc. No way has been found to estimate the

impact of withdrawing NBS surface

calibration services, although it

is clear that the major effects would

not be evident for many years.

4.3.2 Technological Impact of Services

Technological impact has been discussed

in 3.1.

4.3.3 Pay-off from Changes in NBS

Services

NBS instituted a new calibration

system in 1973-4 which improved accuracy

and permitted the measurement of a variety of surface characterizing

parameters. The impact of this drastic

change in services has not yet been

fully felt. Perhaps the least appreciated

advantage of proper characterization

is the manufacturing cost reductions

which can be achieved. The sales

manager for a leading surface instrument

manufacturer pointed out, "overfinishing

of parts is very common due to a lack of

knowledge as to the required surface finish

for the intended function. Surface finish

is frequently specified from habit."

When a problem arises which is believed to be due to surface finish, the response

usually is to tighten the AA roughness

specifications rather than attempting

to relate the function to an appropriate

characterization of the surface. Now

that improved characterizing parameters

are available it is hoped that cost

reductions will be achieved. Other pay-offs

have been discussed above. Unfortunately,

many of the specific pay-offs for special

studies conducted by NBS are company

proprietary and cannot be reported here.

4.4 Evaluation of NBS Programs

As discussed in 4.2.4, the overall

U.S. position in surface finish measurement

and in quality and cost of finished

parts would be enhanced if the surface

characterization program were expanded

from 2 1/3 to 3 1/3 man years/year.

The new instruments developed and

calibrated would serve a variety of

high technology users. Participation

in ISO would help protect U.S. manufacturers

in foreign trade as shown above.

On the positive side, NBS now has

the most accurate and sophisticated

surface calibrating and measuring

instrumentation available to users

in the U.S. and, as far as can be

determined, in existence in the U.S. The industrially based Advisory

Panel of the Optical Physics Division

has traditionally had at least one member, and typically two, who have

had a primary interest in surface

finish. These members are invaluable

sources of information, insure contact

with industry and exert a guiding

influence over the surface metrology

program. After careful study, the

panel as a whole has supported and

encouraged NBS programs to develop

new surface instrumentation.

In surface metrology at NBS, calibration

of precision reference specimens for

outside users has priority over all

other work with turn around times

of 30 days. Second priority is assigned

to special studies for industrial

users. Remaining activities in priority

order include calibration for users within NBS, upgrading calibration

Instrumentation, talks, seminars and

standards committee meetings, and

R and D. Calibrations are monitored

by means of a monthly calibration

computer printout to the section chief

listing all items submitted for calibration, the items completed, and those

in-process. Performance of primary

calibrations are limited to NBS, since

at the moment, no other testing or metrology laboratory has the measurement

capability available at NBS and users express their desire to deal with

an impartial, independent calibration

lab.

4.5 The Future

4.5.1 Driving Force for NBS Programs

The three most pressing future

requirements in surface finish are

(1) improved characterization of technically

significant surfaces through the use of new parameters, (2) improved resolution

and (3) non-contacting instrumentation.

It is clear from Appendix B.7 that

there is no obvious path to improved

resolution. Figure 3 suggests that

molecular electronic devices are anticipated

by 1980. These devices require a substrate which is flat on the atomic

31
level. To achieve this goal, improved

resolution is essential. Integrated

circuits, microminiaturization, surgical

implants, computer discs and drums,

laser fusion mirrors, diesel engine

bearings, gravure printing cylinders

and a host of other technologies,

many listed in above sections, require

improvement in accuracy, sensitivity

and characterization of surface finish.

One of the most desirable solutions

to these problems is to develop new concepts in extracting profile information

from scanning electron microscopes.

This problem is presently under informal

study at NBS.

It is clear that advantages associated

with non-contacting, rapid, optical

techniques for in-process surface

finish quality control will receive

increased use. Calibration, however,

remains a problem. The difficulties

involved are discussed in the internal

NBS report summarized in Appendix

B.6.

The rapidly expanding field of

surface science has encountered a technological barrier in generating

and characterizing singlecrystal surfaces

which are smooth on the atomic level.

Theoretical understanding of experimental

results requires the precise characterization

of single-crystal surfaces. Thus,

a whole technology of single-crystal

surfaces, parallel to the development

of bulk single-crystals, is emerging.

Characterizing these surfaces on the

atomic level is a severe challenge.

Such surfaces may open the door to new devices, corrosion resistant surfaces

and special instruments and standards.

(See Appendix B.7.

The need to develop precision reference

specimens with smaller AA roughness

values (20 microinches and less) has

been suggested in 2.2.2.1. Thin film

deposition techniques and photomask

fabrication are possible approaches

to high quality low roughness surfaces.

4.5.2 Alternative NBS Responses to Surface Measurement Needs

In the following paragraphs four

measurement problems will be outlined

together with a number of possible

responses and the present recommendations

based on available resources. Recommended

reprogramming will be indicated.

Some of the major considerations (documented

above) in evaluating alternatives

are:

1. The largest U.S. instrument

manufacturer grosses only $1 million

per year in surface finish instrumentation

even though users have a $37 million

investment in these long lived instruments.

This gross income is insufficient

to support an R and D program in surface

characterization.

2. As seen from table 10, the users are distributed extremely widely

throughout the U.S. industry, large

and small, so that few of these industries could consider such an R and D program.

3. Foreign competition is strong

since a closer relationship exists

between manufacturers and governments

in more socialistic countries. Most

theoretical and experimental work

in surface characterization occurs outside the U.S. (This is the author's

judgment based on a reasonably complete

file of the surface literature kept

on hand at NBS.) In years to come other nations could completely dominate

in this area and control technologies

which are dependent on improved surface

measurements

4. The demand for improved measurements

by the optics, semiconductor, microminiaturization and thin film industries

requires a well planned and coordinated

effort to develop new instrumentation

and techniques.

The four problems mentioned above

are listed below together with possible

responses and recommendations: a)

a) Calibration of Surface Finish Instrumentation with Precision Reference Specimens;

alternative responses:

1. Develop a highly accurate,

flexible, dynamic calibrator such

as a piezoelectric expander to replace

the Precision Reference Specimens.

2. Continue to encourage industry

to make improved Precision Reference

Specimens by upgrading our ability

to measure and characterize them.

3. Do nothing and accept the present

system as is.

Recommendation: option 2) since the re- sources needed for 1) are not presently available.

b) Defining and Testing Surface Characterizing Parameters; alternative responses:

1. Continue to evaluate known parameters,

generate and study new parameters and

test usefulness of all parameters. Generate

facilities and instrumentation for measuring

parameters

2) Continue to upgrade facilities and

instrumentation.

32
3, Take no initiative in parameter

studies.

Reaommendation: Mixture of 1 and 2; carry

out 2 so that U.S. can catch up to other

countries, and seek a post doctoral candidate

or an Industrial Research Fellow to work at

NBS on the component of 1 concerned with

testing the usefulness of different

parameters. Both of these programs

are presently being implemented.

c) Improved Resolution of Surface Instrumentation: alternative responses.

1. Develop new surface measuring instrumentation with much improved resolution (based

on new concepts), as summarized in Appendix

B.8.

2. Rely on better use of statistical

data and computerizing of existing equipment

to effect more modest improvement of

instrumentation.

3. Develop optical techniques for measuring surface roughness (see Appendix B.6).

4. Rely on existing systems.

Reaommendation: Mixture of 1 and 2. After

completion of 2, which is now in full progress, increase emplasis of 1, which is now marginally supported. Appendix B.6 discusses

in detail the present limitations of optical

techniques for absolute measurements. For

this reason option 1 should be used to provide an independent measurement of the

finish of optical surface.

d) Scratch and Dig Standards of Optical

Surfaces. These standards are under re- vision by an ASTM Committee and may be

sufficiently well defined in the new standard so that NBS should consider providing a calibration service; alternative

responses

1. Participate fully in developing the new standard and provide follow up calibration

service.

2. Participate peripherally in developing

the standard but provide calibration after

standard has been approved.

3. Participate through comparison of

optical measurements of scratch and dig

standards with out non-optical techniques

and promote a non-optical calibration

system.

4. Do not get further involved.

Recommendation: Undecided, the matter is now under consideration. Reprograming may

be required unless the staff can be increased.

It is not clear whether the new committee

will deal effectively with the measurement

problem.

5, SUMMARY AND CONCLUSIONS

The National Measurement System for

Surface Finish appears to be under satistactory control. There is a broadly based need

for developing a variety of parameters to characterize surface roughness, and to determine the relationship between these parameters

and the function of the part, There is need

for improved resolution of surface finish

measurements in a number of areas. A non- contacting, on-line instrument for quality

control application is in great demand.

While it is extremely difficult to calculate value added by surface finish

measurement processes, it is estimated that

the metalworking industry alone spends about

$50 Million in surface measurements each

year in the manufacture of $40 Billion worth

of product. Surface finish measurement is

ubiquitous, pervading most industries.

NBS is in good contact with all segments

of the measurement community in surface

finish. As a result of this study, the

characterization of surfaces has been given

a high priority, second only to our calibration service. Once the calibration and

characterization programs are well in hand,

emphasis will be placed on the clearly documented need for advanced instrumentation

in certain growing, high technology

industries.

33
Appendix A: METHODOLOGY OF THE STUDY

A.l Literature Survey - A complete file of

the literature in the field is maintained

at NBS in a series of "0-Ring" binders. This

literature was evaluated and used as a base

from which this study was generated.

A. 2 List of People Consulted in Preparing

This National Measurement Study (as of 1973).

A. People consulted through personal con- tact either at NBS or at their place of

business

1. Bell Telephone, Columbus, Ohio - Frank

Badger3 Chris Lo, Rudolph Schubert - the

role of surface roughness in quality of

electrical contacts

2. Newark Air Force Base - Metrology Labs

Chief, Ken Forrer - 29 people calibrating for

Air Force facilities. Ed Fratus and Don

Johnson - effect of roughness on gage block

wringing, flatness of optical flats, height

of thin film steps

3. IBM, San Jose, California - DeWayne

Sharp - superf inished surfaces (memory

discs) present measurement requirements not

being met, light scattering measurement of

surface roughness

4. Lockheed Missile and Space Company - Mr. Carrara - Manager of Dimensional

Metrology Lab. - surface finish instrument

cal ibration

5. Hewlett Packard - Palo Alto, California - Glenn Harreman, Manager of Dimensional

Metrology - calibration of surface instrumentation, measurement of thin film steps.

Earl Lindberg, surface instrument designer

6. Dow Chemical Company, Rocky Flats,

Col. - John Stover - use of light scattering

in measuring surface roughness. Scratch and

Dig Standards

7. Ladish Co. - Tri-Clover Division,

Kenosha, Wisconsin, Robert L. Nissen^

Assistant Vice President - relationship

between cleanability of dairy containers and

surface roughness

8. Bendix, Automation and Measurement

Division, Dayton, Ohio - Fred Witzke, Chief

Manufacturer of surface finish measuring

instruments

9. Sloan Instrument Company - Manufacturer of surface finish instrumentation

10. Stanford Research Institute, Palo

Alto, Cal. - Lou Heyniok - electronic

surfaces

11. Bell Telephone Laboratories, Murray

Hill, N. J. - Dr. Charles Tracy - roughness

of the surface of optical fibers for

communication use

12. General Motors Corporations, Detroit,

Mich. - Robert Lenz - Richard Daskivich

ANSI Committee - specialist in surface

technology

13. GAR Electroforming Division of Mite

Corp. - Eugene Castellano, Robert Murphy - fabrication of precision reference specimens

14. Minnesota Mining and Manufacturing

Co., Saint Paul, Minnesota - Peter Banning,

John Sullivan, Tom Voulgares - characterization of manufactured surfaces

15. National Institute for Occupational

Safety and Health HEW, Morgantown, W. Va. - David Puthoff - Safety of ophthalmic lenses - lens failure (a surface related process)

16. Trans - Tech, Inc., Gaithersburg, Md.

- Elwood Hokanson - measurement of Ytt.

Gd. Garnet surface roughness

17. Etec Corporation, Hayward Cal if . - James Dao, Pres. and Kent Lane, Director

of Research - measuring surface topography

with Scanning Electron Microscope

18. Pittsburgh Plate Glass, Pittsburgh,

Pa. - Nancy Robbins - Roughness of plastic

coatings on glass surfaces

19. Federal Products, Providence, Rhode

Island - Mohamed Fadl, Director of Research,

- the role of surface finish in precision

instrumentation

20. Texas Instruments Inc., Dallas, Texas

- Ray Hilton - semiconductor surface finish

21. Pennsylvania State University,

University Park, Pa. - Prof. Eugene White - surface characterization using the Scanning

Electron Microscope

22. Bell Laboratories, North American,

Mass. - Theaphilos Kubiopulos - Surface

finish of waveguides

23. Dairy and Food Industries Supply

Association, Inc., Washington, D.C. - Donald Williams, Technical Director - relationship between cleanability of dairy

containers and surface roughness

A. 3 List of people contacted by phone, at meetings, etc.

1. Bell Telephone, Holmdel, N. J. - Richard Roca, contact resistance in bloted

joints

2. Navel Weapons Center, China Lake,

Calif. - Hal Bennett - leading instrument

developer for light scattering measurement

of surface roughness

3. Rank Industries, England - Robert

Sprague, Director of Research, and D. Whitehouse - Chief European Competition in

field of surface instrumentation

4. Bell Telephone Labs., Holmdel, N. J.

- Herb Libbin - Semiconductor surfaces

5. The Timken Company, Canton, Ohio - W. E. Littman - Manager Metallurgy Research

ball bearing surfaces

6. Autometics, Div. of North American

Rockwell, Anaheim, Cal. - Jack Hall - ruby

laser surface measurement

34
7. Moore Special Tool Company, Bridgeport,

Conn. - Arnold V. Young - characterization

of surfaces - other parameters

8. The Bendix Corporation, Dayton, Ohio - Robert Esken - design of surface finish

instrumentation

9. Eric Schnieder, Lake Shore Drive,

Chicago, 111. - Improved standards, better

characterization of surfaces

10. Sunnen Products - St. Louis, Mo. - Wayne W. Althen - Characterization of

surfaces, better parameters

11. Ehrenreich Photo-Optical Industries,

Inc., Garden City, N.Y. - Dale Freyherg,

Product Manager and John Wilson, Chief

Engineer-Interference Microscopes and precision reference specimens

12. General Electric Co., Evendale Plant,

Ohio - Guy Bellows, Senior Mfg. Engineer

- Measuring finish of machined surfaces

13. Milo Mfg. Co., Union, N. J. - Joseph

Milo, President - Measuring the finish of

diamond turned surfaces (less than 1 y inch)

14. Rexnord Corp., Research Development

Group, Milwankee, Wis. - Robert Trautman,

Senior Engineer - surface of hardened steel,

characterization

15. Meditec Inc., (Surgical Implants)

Fairlawn, N. J., - Robert Averill, Vice

President, surface finish of hip ball joints

and sockets

16. Bendix, Kansas City, Kansas, Paul

Klingsparn - surface inspection

17. Alis Chalmers, Pa., William Erwin

- surface characterization particularly

hydro-turbines

18. 3M - St. Paul, Minesota, Clyde Calhoun

- instrumentation for measuring asymmetric

surfaces

19. Navy Ships Command, Washington, D.C.,

Tom Martin - relationship between difference

amplitude characterization parameters

20. Hughes Aircraft, Oceanside, California,

John C. Hamocher - laser mirror surface

qual ity

21. Oak Ridge National Labs, Oak Ridge,

Tenn., H. B. Adams - calibration of special

high resolution precision reference specimens

22. Carter Products Research, Cranbury,

N. J., Giles Crane - measurement of natural

surfaces (teeth, etc.)

23. Dow Chemical Company, Rocky Flats,

Colorado, Bill Utley - use of optical techniques to measure surface scratches in

lenses

24. Allegheny Ludlum Steel, Pittsburgh,

Pa., Walter D. Edsall - Technical Services

Group, roughness of stainless steel plate

used in nuclear reactor pool liners, surface

measurement

25. Allegheny Ludlum Steel, Leechburg,

Pa., Joseph Bosoo - Special Products Vendor

Control, refined polishing of steels, surface

measurement

26. Bethlehem Steel, Bethlehem, Pa.,

Charles Stattel, Metallurgist, Robert

Moriarity, Metallurgist - finish of automative and chrome plateable steels, surface

measurement

27. Republic Steel, Warren, Ohio - Jaak

Mahaney - Metallurgist, Appliance steel,

galvanized products, tin plate automotive

steel , surface measurements

28. Chrysler Corporation, Detroit,

Michigan - Dan Hammond - Research Senior

Scientist, surface finish of automobile

components and paintable surfaces

35
A. 4 Typical Correspondance on Industrial Surface Finish Needs (Names deleted).

Dr. Russell Young

Metrology Division

National Bureau of Standards

Washington, D. C. 20234

Dear Russ:

We have become increasingly interested in the measurement of surface topography in con- || nection with our intense efforts to fabricate very small dielectric waveguides for use in

integrated optical circuits. These guides consist of a "filament" of GaAs embedded in a metrix of Al^Ga^.xAs (which has a lower index of refraction than pure GaAs). This structure

will support guided modes, the number of which depends on the geometrical and optical parameters chosen. i

One of the dominant loss mechanisms encountered in dielectric waveguides of this kind

results from the non-flatness of the boundary between the two dielectrics. Such roughness

can couple the guided modes with the radiating modes. Thus light initially propagating in

the guide will be scattered out resulting in undesirable attenuation.

The scale over which this roughness is important is just the wavelength of the propagating light (in the medium). Theory predicts that the losses from this scattering mechanism

are a strong function of the correlation length of the roughness.

We have determined that in the devices we are making, this scattering mechanism is

dominating the losses. It is therefore highly desirable to know exactly what the magnitude

(rms) of the roughness is as well as its correlation parallel to the surface (i.e. is it

random, periodic, etc.). The rms magnitude of the roughness is in most cases less than

100 A. For the worst case of correlation length, the losses will be important down to a rms roughness of less than 20 A.

I have made some diffuse light scattering measurements on dielectric-air interfaces

which are believed to have the same topography as the dielectric boundaries which guide

the light (but also may scatter it). These measurements show that one can apparently detect rms surface roughnesses below 50 A on the scale we are concerned with, but an inspection of the literature suggests that it may be difficult to obtain any quantitative

information. This results from the non-formal distribution of the surface roughness as determined by the spatial character of the diffuse scattering.

If you have any comments or suggestions regarding these problems I would appreciate

very much hearing from you.

Best regards

,

Mr. B

"

JCT:SC

Company A October 17, 1972

36
Dr. Russell D. Young

Physicist

National Bureau of Standards

Company C May 3, 1973 MET Building, Room B322

Washington, D.C. 20234

Dear Dr. Young:

I enjoyed very much having the opportunity to meet you and your associates in Pittsburgh

last week. I am writing now to request a copy of the report which you described that compares the various optical methods for surface roughness measurement.

As you can well appreciate, the preformance of tapered rolled bearings is critically

related to the geometry and texture of the operating surfaces on the raceways and at the

rib-roller end contacts. We are well aware of the value of surface texture characterization using stylus tracer instruments and equally aware of the limitations of present

methods for analyzing and utilizing surface profile data.

An equally important related problem area is the economical manufacture of the surfaces

which are critical to bearing performance. Even if we had adequate tools for the research

relating surface microtopography to bearing performance, we still need inexpensive but

adequate tools for inspection and process control of surface texture during the manufacturing

and assembly of bearings. Ideally such methods should avoid physical contact, be rapid and

amenable to automation.

In response to your request, we will describe these needs as they might relate to useful

programs at the Bureau of Standards and will also explore the possibility of the "resident

intern" type of activity by someone from Company C at the Bureau.

We will look forward to your report on the optical methods and further exchanges of

information on surface metrology.

Sincerely yours

Dimensional Technology Section

National Bureau of Standards

Washington, D. C. 20234

Dear Dr. Young:

Your article entitled "Surface Microtopography" in the November issue of Physics Today

was very interesting. Included was a report of your work on a field emission technique

that is being developed to measure surface topography in the 1 A range. This technique

may be useful in rapidly characterizing the surface of highly polished silicon and germanium single crystal slices, which are intended for transistor device applications.

Surface defects including pits, scratches, mounds, stacking faults and also submicroscopic objects have a deleterious effect on the performance of semiconductor devices.

Therefore it is desirable to detect these features at the earliest point in the manufacturing procedure and to eliminate those slices which will not have satisfactory electrical

characteristics based on surface conditions. Current practice for defect detection requires

microscopic examination of a significant area of each polished slice. While this is a time

consuming and expensive operation involving subjective decisions by a technician, it is

considered necessary in order to achieve the high quality devices required for use by the

Bell System.

Mr. D

pjl

Dr. Russell D. Young Company E

37
A technique with the capability of providing a quantitative evaluation of single crystal

surfaces, especially in an automatic or semiautomatic mode, would be of significant advantage to manufacturers of semiconductor devices. It would be desirable if the system could

quickly scan a portion of each slice (about 20 to 40 mm^ in 5 to 10 minutes) and indicate

the presence of surface features as well as the contour of the surface. While automatic

machine evaluation of the system output would be preferable, interpretation of a series of

topographic maps by an operator would be an acceptable alternative.

I would appreciate the opportunity of discussing your system in greater detail with

particular emphasis on its applicability for evaluating polished surfaces used for semiconductor applications. In addition, it would be interesting to examine test results

covering some typical silicon slices. I am not interested in discussing any restricted

of proprietary developments which could not be freely adapted from my own development

work for semiconductor applications and freely disclosed to others. Please advise

whether the above arrangement is satisfactory so that we can arrange for a meeting at your convenience.

Very truly yours.

Mr. F

Dr. Russell Young

National Bureau of Standards

Washington, D.C. 20234

Dear Dr. Young

It was a pleasure to talk to you recently of the telephone concerning the "Topografiner"

As I discussed with you on the telephone, we wish to establish a rapid, "on-line" method

for inspecting highly polished metal surfaces. We wish to measure not only the rms "background" of the surface profile but also to detect and measure the depths and widths

of isolated defects (pits ("digs") and scratches) on an otherwise very smooth background.

As you stated on the telephone, the necessity of the high vacuum (~ 4 x 10-10 Torr) when a tungsten emitter is used practically rules out the Topografiner, in its present form, as an on-line inspection technique. Some rapid surface inspection techniques exist, but

depths of isolated digs and scratches cannot be measured. Therefore, I would like to encourage any development effort on your part to move the Topografiner closer to an on-line

technique because I feel some segments of industry would welcome such an advance.

Sincerely,

Mr. H

PEK:sf

Company G October 30, 1973

38
APPENDIX B: SUMMARY OF BACKGROUND DOCUMENTS

B.l Table of Contents of B46. 1 -Standard for Surface Texture.

B.2 "Surface Finish, Friction and Wear: The Need for More than One Parameter,"

D. A. Swyt, NBS Internal Report 73-196, May 3, 1973.

B.3 "Precision Reference Specimens of Surface Roughness: Some Characteristics of the

Cali-Block," R. D. Young and R. E. Scire, J. of Research of NBS, Vol. 76C, Jan. 1972.

B.4 Calibration Report - Precision Reference Specimen of Surface Roughness

B.5 "The Public Health Significance of Surface Measurements," Donald H. Williams,

Technical Director, Dairy and Food Industries Supply Assoc. Inc. - a statement of

their surface measurement problem and its significance, Nov. 8, 1973.

B.6 "Eight Techniques for the Optical Measurement of Surface Roughness," R. D. Young,

NBS Internal Report 73-219, May 25, 1973.

8.7 "Surface Microtopography ," R. D. Young, Physics Today, Vol. 24, Nov. 1971.

B.8 "The Topografiner: An Instrument for Measuring Surface Microtopography," R. D. Young,

J. Ward, and F. Scire, Review of Scientific Instruments, Vol. 43, pp. 999-1011,

July 1972.

B.9 "Evaluation, Revision and Application of the NBS Stylus/Computer System for Surface

Roughness Measurement," E. C. Teague, Technical Note 902.

39
B.l - ASA B46. 1-1962 Standard for Surface Texture

TABLE OF CONTENTS

Page

1 - GENERAL 7

2 - CLASSIFICATION OF TERMS AND RATINGS RELATED TO SURFACES 7 2.1 Surface Texture 7 2.2 Surface 7 2.3 Profile 7 2.4 Center Line 7 2.5 Microinch 8

2.6 Roughness 8

2.7 Waviness 8

2.8 Lay 8

2.9 Flaws 8

2.10 Contact Area 9

3 - DESIGNATION OF SURFACE CHARACTERISTICS 9 3.1 Where to Specify 9 3.2 Symbols Indicating Direction of Lay 9 3.3 Surface Symbol 9 3.4 Application of Symbols and Ratings 9 4 - STYLUS TYPE INSTRUMENTS 9

4.1 General 9 4.2 Scope 9 4.3 Purpose 9 4.4 Tracer Head Characteristics 12 4.5 Traversing Length 12

4.6 Transducer, Amplifier, and Indicator 13

4.7 Indicating Instrument 13 4.8 Instrument Accuracy 13

5 - PRECISION REFERENCE SPECIMENS 13

5.1 General 13 5.2 Surface Contour 13 5.3 Material 14 5.4 Accuracy 14 5.5 Uniformity 14 5.6 Rating 14

6 - ROUGHNESS COMPARISON SPECIMENS 14 6.1 Use 14 6.2 Description and Ratings 14 APPENDIX A - SUPPLEMENTARY INFORMATION EXAMPLES 16 A-1 Surface Symbol Proportions 16 A-2 Arithmetical Average 16 A-3 Root Mean Square Average 16 A-4 Relation of Surface Texture to Tolerances 16

A-5 General Notes for Drawings 17 A-6 Demonstration of the Application of Surface Roughness Symbols on Drawings . 17 A-7 Control Several Operations 17 A-8 Flaws 17 A-9 Waviness Average Height Measurement 18

APPENDIX B - GENERAL NOTES ON USE AND INTERPRETATION OF TRACER INSTRUMENTS 19 APPENDIX C - USE OF PRECISION REFERENCE SPECIMENS WITH STYLUS INSTRUMENTS 22

C-1 Purpose 22

C-2 Checking the Instrument Stylus Radius 22

C-3 Ovejrall Performance 24

C-4 Interpretation and Precautions 24

APPENDIX D t^NOTES ON CONTROL OF SURFACE TEXTURE 25

40
Appendix B.2

Surface Finish, Friction and Wear: The Need for More Than One Parameter

Dennis A. Swyt

NBS Internal Report 73-196

ABSTRACT

Surface finish is most commonly described by an arithmetic average (AA) value, often

coupled with a description of the process by which the surface is finally formed. Since

the insensitivity of the AA parameter to the periodic nature of surface structure is well

known, many supplemental "second" parameters have been suggested. This short paper gives

an indication of the basis for the insensitivity of the AA parameter to periodic structure

and considers briefly some "wavelength-conscious" parameters (e.g., average wavelength and

correlation lengths) which may be useful in supplementing the basic AA value for a more

complete description of surface finish.

Appendix B.3

Precision Reference Specimens of Surface Roughness:

Some Characteristics of the Cali-Block.

Russell D. Young and Fredric E. Scire

Journal of Research of NBS, Vol. 76C, Jan. 1972

ABSTRACT

The distribution of Arithmetic Average values of surface roughness across the 120 and

20 microinch patches of NBS Cali-Block "B" have been measured. It is shown that each distribution can be described in terms of its mean value and standard deviation. The observed

systematic distribution of AA values strongly suggests that the user select widely spaced

regions at random on the patch when calibrating a roughness measuring instrument.

41
Appendix B.4

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

April 2, 1974

REPORT OF CALIBRATION 232.08/210069

For; One Precision Roughness Standard

Specimen No, PG-1366

Submitted by: The Corporation

Electrical Components Division

The property of surface roughness in the 5 ym (200 microinch) AA range and below is measured at NBS by means of a minicomputer/stylus instrument system. Using an interferometrically measured step the system is calibrated on each value of magnification employed

during a measurement. Surface profiles are taken according to the American National Standard B-46. 1-1962 using a 0.76 mm. (0.030 inch) cutoff length and a 3.80 m (150 yin) stylus

tip radius. Data is stored in the minicomputer memory employing 12 bit analog to digital

conversion and a sampling rate of 1 point/ym (1 point/40 yin) over the traversing length.

AA values are then calculated as described in Appendix A of the same American National

Standard.

A conservative estimate of the systematic error (3a = 3 standard deviations) resulting from

stylus pickup nonlinearity , interface hardware, software computations and analog to digital

conversion is 1% for any type of uniform roughness specimen. Other errors are due to electrical and mechanical noise [3a = 5 nm (0.2 yin)], to the surface finish of the step specmen [3a of step transfer = 25 nm (1 yin)] and to the interferometric measurements of step

heights [3a = 25 nm (1 yin)]. The use of step heights approximately equal to the surface

profile peak to valley height then gives a net systematic error for the calibration procedure of 37c (3a) or less over AA values ranging from 0.25 ym (10 yin) to the upper limit

of the stylus instrument.

The computed value for the average surface roughness of the area marked 120 yin AA is

2.94 ym (115.8 yin) AA with an uncertainty of 0.10 ym (4.0 yin).

The computed value for the average surface roughness of the area marked 20 yin AA is 0.51 ym

(20.1 yin) AA with an uncertainty of 0.07 ym (2.7 yin).

The computed value for the average surface roughness of the area marked 12-20 yin AA is

0.47 ym (18.6 yin) AA with an uncertainty of 0.16 ym (6.2 yin).

The uncertainty for this area can be reduced to 0.09 ym (3.6 yin) with a computed value of

0.4651 ym (18.3 yin) AA if data taken at points 1 and 10 are deleted.

The uncertainties quoted are the sum of the systematic errors just described and the 3a

limit estimated from an analysis of data obtained from 3 traverses in each of 10 positions

on each of the areas. For reference, a copy of the computer printout of measured values and

a diagram of the positions^tyf measurement are incl uded with the report.

Measurements made by

! Director, ^

Chief, Optics

D. Young

and Micrometrology

^ ^

Section

Optical Physics Division, IBS

42
Appendix B.5

The Public Health Significance of

Surface Measurements

by

Donald H. Williams

Technical Director, Dairy and Food

Industries Supply Association, Inc. November 8, 1973

3-A Sanitary Standards for dairy processing equipment provide criteria for the cleanability of product contact surfaces, and for product protection. The fabrication section of

a 3-A Standard requires that product contact surfaces be at least as smooth as a #4 mill

finish properly applied to stainless steel sheets.

Number 4 is a ground finish. A surface polished with 150 grit silicon carbide abrasive

is deemed to be in compliance with the finish criterion. There is some interest in using

a cold rolled or 2B finish if selected sheets can be pit-free. There is some suggestion

that a 2B finish is smoother than a #4, but they cannot be directly compared since the 2B

is not a polished surface.

A method is needed to quantify consistently the surface of stainless steel, whether cold

rolled, #4 polished, or cast. Cleanability and sanitation are associated empirically with

smoothness. Acceptable surfaces are based on the visual examination in comparison with a known or authentic #4 finish, yet there is lack of uniformity in #4 among polishers. As polishing belts wear, there is variation in the resulting surface.

Millions of dollars worth of equipment are purchased by the dairy processing industry.

By far the majority of such equipment today--especial ly in the fluid milk industry--is

built to meet 3-A Standards which are generally recognized by regulatory sanitarians and

health officers.

The volume of fluid milk products and ice cream which are processed in "non-3-A equipment" is insignificant. The acceptance of surface finish for dairy equipment is therefore

of monumental significance. A convenient tool or index for uniformly determining or characterizing surface finish of stainless steel would be of great value to the dairy and

food industries.

Of real significance is the growing use of 3-A criteria in food industries other than

dairy. A separate new 3-A program has been developed for the egg products industry, and

3-A criteria are widely used by most other food industries in writing equipment specifications for meat, brewing, beverage, frozen foods, to name a few. A means for evaluating

surface finish, therefore, has momentous importance to the sanitation of food processing

Appendix B.6

Eight Techniques for the Optical Measurement of Surface Roughness

Russell D. Young

NBS Internal Report 73-219, May 1973

ABSTRACT

The need for a fast, on line, non-destructive technique for measuring surface roughness

has recently accelerated the decade long development of optical methods. It is anticipated

that these new techniques will add a new dimension to the surface roughness measurement

system which may require an appropriate NBS response. In order to formulate this response,

the eight optical techniques which have been identified are briefly described and are sum- marized and compared in Table 1. It is concluded that model deficiencies, questionable theoretical bases, as well as physical and analytical limitations cast serious doubt on the present accuracy of these

techniques for absolute measurements. Optical Techniques seem more suitable for comparison

measurements, i.e., measurement after appropriate calibration using surfaces which have been

measured using other techniques. Thus, it is concluded that the most appropriate NBS re43
sponse to the increased use of optical techniques it to concentrate our limited resources

on developing much improved instruments such as the Topografiner and traditional stylus

instruments so that highly refined optical surfaces can be measured and their surface parameters determined accurately.

Appendix B.7

Surface Microtopography

Russell D. Young

Physics' Today, Vol. 24

November, 1971

ABSTRACT

The growing field of surface science would benefit considerably from measurement of

surface microtopography down to the atomic level. A brief review is presented of several

instruments used to quantitatively characterize the surface microtopography of metallic

surfaces. Techniques are discussed for employing the transmission electron microscope, the

scanning electron microscope, the optical interference microscope and an engineering profil

measuring instrument to measure surfaces suitable for surface science experiments. In addition a new non-contacting instrument which is presently under development will be described. It is concluded that several techniques are presently available for detecting

single atom steps on single-crystal surfaces.

Appendix B.8

The Topografiner: An Instrument for Measuring Surface Microtopography

Russell Young, John Ward, and Fredric Scire

The Review of Scientific Instruments

March 29, 1972

ABSTRACT

A noncontacting instrument for measuring the microtopography of metallic surface has

been developed to the point where the feasibility of constructing a prototype instrument

has been demonstrated. The resolution of the preprototype unit is 30 K perpendicular to the surface and 4000 A in the plane of the surface. Inherent noise in the perpendicular

direction corresponds to 3 A, one atomic layer. By using a typical field emitter with

radius of 100 A, an ultimate limit of 200 A would be expected for the horizontal resolution

Topographic maps of an infrared diffraction grating have been measured in order to demonstrate the performance of the instrument in measuring a well characterized surface. The

instrument has been shown to conform to the Fowler-Nordheim description of field emissiog

while spaced at the usual operating distances for the surface. When moved to within 30 A of the surface, its performance is compatible with Simmons' theory of MVM tunneling. In the MVM mode, the instrument is capable of performing a noncontacting measurement of the

position of a surface to within about 3 A. The instrument can be used in surface science

experiments to study the density of single and multiple atom steps on single crystal surfaces, adsorption of gases, and processes involving electronic excitations at surfaces.

44
Appendix B.9

Evaluation, Revision and Application of the NBS Stylus/Computer

System for Surface Roughness Measurement

E. Clayton league

NBS Technical Note 902

ABSTRACT

This report describes in detail the hardware and software used at NBS to implement on a stylus instrument/minicomputer system the process of calibrating the system with an interferometrically measured step and the calculation of important characterizations of surface

profiles. The characterizations of a profile which may be calculated include the Arithmetic

Average value, the mean square value, the amplitude density function, the autocorrelation

function and the average wavelength. The report also includes a statistical evaluation,

using empirical and analytical techniques, of the calibration procedure's long term stability.

45
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 75-927

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

The National Measurement System for Surface Finish

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S)

Russell D. Young

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

NBS

13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

NBS has conduc±ed a study of the National Measurement System for Surface

Finish. The proposed system model is discussed including the role of standards

committees, instrument manufacturers and measurement users. The econcmic

dimensions of the measurements irrpact areas and the technological base fran

which new measurement technology springs is described.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Surface, Surface Finish, Surface Roughness, Measuronent, Technology Assessment,

Econcmic Factors.

18. AVAILABILITY ^Unlimited

H For Official Distribution. Do Not Release to NTIS

1 1 Order From Sup. of Doc, U.S. Government Printing Office Washington, D.C. 20402. SD Cat. No. C13

1 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22I5I

19. SECURITY CLASS

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