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5th Edition

VOLUME

FLEXOGRAPHY:

Principles & Practices

FLEXOGRAPHY: PRINCIPLES AND PRACTICES

Flexography: Principles And Practices

Foundation of Flexographic Technical Association, Inc.

900 Marconi Avenue, Ronkonkoma NY 11772

TEL 631-737-6020 FAX 631-737-6813

Find us on the World Wide Web at:

http://www.fta-ffta.org

1999 by the Flexographic Technical Association, Inc.

and the Foundation of Flexographic Technical Association, Inc.

Fifth Edition

Notice of Liability:

any form or by any means, electronic, mechanical, photocopying, recording, or other-

wise, without the prior written permission of the publisher.

Notice of Liability:

The information in this book is distributed on an “as is” basis, without warranty.

While every precaution has been taken in the preparation of this book, neither the authors

nor the publisher shall have any liability to any person or entity with respects to any loss,

liability or damage caused or alleged to be caused, directly or indirectly by the informa-

tion presented in this book.

Published by the

Foundation of Flexographic Technical Association, Inc.

Printed in the United States of America

INTRODUCTION

WHAT IS FLEXOGRAPHY? 3

Advantages of Flexography....................................................4

Flexographic Printing Applications.......................................4

Other Printing Methods...........................................................6

Lithography ........................................................................7

Rotogravure........................................................................8

Screen Printing (Serigraphy).........................................10

Letterset (Dry Offset)......................................................11

Offset Gravure..................................................................11

Flexo Offset......................................................................12

THE EVOLUTION OF FLEXOGRAPHY 13

Aniline Printing ......................................................................13

Early Development................................................................14

Introduction of the Anilox Roll............................................14

Impact of Man-made Plastics...............................................14

Off-press Mounting and Proofing ........................................15

Aniline Process Name Change.............................................15

Molded-rubber Plates............................................................15

Photopolymer Plates.............................................................15

Plate Mounting.......................................................................16

Ink and Drying System..........................................................16

Accurate Multicolor Registration ........................................16

Recent Developments............................................................17

Prepress............................................................................17

Presses..............................................................................17

Anilox................................................................................17

Printing Plates..................................................................17

Plate Mounting.................................................................18

Inks and Dryers................................................................18

THE FLEXOGRAPHIC PROCESS 19

Basic Elements of Flexography...........................................19

Artwork Design and Prepress........................................19

Inks....................................................................................20

UV Flexo...........................................................................21

Substrates.........................................................................21

The Printing Plate............................................................21

Design Rolls......................................................................22

Mounting and Proofing Devices....................................22

Presses.....................................................................................23

Parts of a Web Press.......................................................25

VOLUME 1

Table of Contents

The Sheetfed Flexo Press.....................................................26

The Basic Flexo Print Unit...................................................26

Fountain Roll....................................................................26

Ink Metering and Anilox Rolls.......................................28

Plate Cylinders and Sleeves...........................................30

Impression Cylinder........................................................31

Repeat Lengths and Gears..............................................32

Station Control.................................................................32

Variations on the Flexographic Process.............................33

The Impression Bar (Tympan Bar) ...............................33

The Flexographic Press as a Coating Station..............33

GLOSSARY

A to F .......................................................................................39

G to L .......................................................................................65

M to R.......................................................................................76

S to Z........................................................................................93

ORGANIZATIONS

A list of environmental, governmental and

trade organizations mentioned in FP&P, 5th edition .....107

INDEX

Comprehensive index for Volumes 1 thru 6.....................111

VOLUME 1

he fifth edition of Flexography:

Principles & Practices repre-

sents the efforts and contribu-

tions of many people in the flex-

ographic printing industry. In

fact, we can thank all those con-

tributors that date back to the publication of

the first edition in 1962. The text book has

served the industry well as a reference work

on all aspects of flexographic printing. Our

belief is that this publication will continue to

be highly valued as we enter the next millen-

nium.

This fifth edition introduces a new format.

Six volumes contain the various chapters on

specific topics of flexography. The motiva-

tion for this change was twofold: First, the

text has continued to expand with each edi-

tion and has outgrown a convenient size for

one volume. The second and perhaps a more

important motivation was the desire to be

able to update the material in more manage-

able pieces. In the future, select topics, par-

ticularly some of the more rapidly changing

areas of our industry, can be updated in spe-

cific volumes. This will make the process

more timely and also will not necessitate the

purchase of the entire six volume set at each

update.

Another major change in format will be

immediately apparent by inspecting any of

the books – all of the illustrations are now in

color. We have standardized the use of illus-

trations in order to give the work a unified

and easy to understand appearance. We

hope you enjoy the new format!

As each volume and its chapters are

reviewed, please notice the credit list of peo-

ple who authored or edited that particular

section. However, several people played an

overall role with their work. Michael Wiest,

technical manager of the FTA/FFTA, was the

leader of the project, coordinating the input

from many sources, as well as editing each

chapter. Michael also authored select chap-

ters or parts of chapters. Involved with sev-

eral of the other chapters was George

Cusdin, president of Flexographic Printing

Services, Smyrna, GA, a respected consul-

tant, who created manuscripts from the

beginning, or modified and updated those

areas from the Fourth Edition where appro-

priate.

Coordinating the layout, imposition, and

graphics was Kelley Callery, director of mar-

keting and creative services for the

FTA/FFTA, and handling the production and

design was freelance publication graphic

designer, Sonja Huie, of H+A Productions.

Illustrations were done by Shane Kelley of

Kelley Graphics in Maryland.

The editorial staff of Flexo

magazine,

Glenn Koch, the former editor, Ed Rogers,

associate editor, and Bob Moran, publisher,

read and edited each manuscript to generate

consistent readability from one chapter to

another, as well as to ensure language and

word appropriateness. Kim Berk, marketing

coordinator for the FTA/FFTA also assisted

with the proofreading.

Due to the enormity of the effort to pro-

duce “FP&P”, we want to acknowledge the

history and people who have brought us to

this point. The fourth edition of Flexo-

graphy: Principles & Practices was an

exceptional effort, as it was also not intend-

ed to be merely a revised copy of the third

edition, but rather a completely-new general

INTRODUCTION 5

Preface

6 FLEXOGRAPHY: PRINCIPLES & PRACTICES

resource book. Frank Siconolfi of Matthews

International Corporation dedicated an

enormous amount of time, as did his com-

mittee of industry volunteers (*committee

listed below).

In 1980, the third edition was published

with Joe W. Cotton as chairman. Members of

this revision committee were: Don Vanden

Branden, Robert Demetrician, Don Donelan,

James K. Ely, Gerald J. Gartner, Charles

R.Heurich, Vernon R Johnson, Joseph B.

Lankford, Wallace D. Nard, Henry F.

Salmaggi, Fred Shapiro, Howard K. Sheldon

Douglas E. Tuttle, Bruce Weaver and George

Wilfling.

The second edition was released in 1970

under the chairmanship of Howard K.

Sheldon. Committee members included:

George H. Anthony, E. Howard Grupe, Jack

Kemerling, John M. Miller, Ned E. Mitchell,

Frederick K. Moss, George J. Parisi, Daniel

A. White and Robert Zuckerman.

The first edition of Flexography: Prin-

ciples & Practices was printed in 1962 under

the overall leadership of Norman H. Abrams

and F. Henry Wittel as co-chairmen. Members

serving on this first committee were: Calvin

Balcom, James J. Deeney, Peter M.

Fahrendorf, Jr., Richard E. Jansing, Heinz P.

John, Mel Kester, David Killary, Franklin

Moss, Frank Murphy, Christopher Shepherd,

Douglas E.Tuttle and Robert Zuckerman.

All of the above-named individuals are rec-

ognized for their exceptional dedication and

forethought in preparing the respective edi-

tions. It is through their laying of the ground-

work that a project of this size and scope

can be undertaken. At this point, we should

also acknowledge the pioneering efforts of

Frank E. Boughton whose book entitled

Flexographic Printing was published in

1958. To our knowledge, this was the first

book to be dedicated solely to flexography.

George Parisi, former president of the

FTA/FFTA, who maintained a spirit of con-

tinuation, updating, and energy to foster the

educational mission of the organization,

directed previous issues. To all our contribu-

tors, past and present, we extend thanks and

appreciation for the work and effort that has

resulted in a most significant product.

William C. Dowdell

President

Foundation of Flexographic

Technical Association

CHAPTER 1

Introduction

2 FLEXOGRAPHIC PRINCIPLES AND PRACTICES

ACKNOWLEDGEMENTS

Author/Editor: George Cusdin, Flexographic Printing Services

lexography is a method of direct

rotary printing, similar to letter-

press, that uses resilient relief-

image plates of rubber or pho-

topolymer material. The plates

are affixed to plate cylinders and

are inked by a cell-structured, ink-metering

“anilox” roll carrying a fast-drying fluid ink

to plates that print onto virtually any sub-

strate, absorbent or nonabsorbent. For

every revolution of the printing-plate cylin-

der, an image is produced.

The process was developed primarily for

printing on packaging substrates – board,

paper, foil and film. Materials are commonly

supplied in roll form for feeding into form-

and-fill, over-wrapping, bag making and

other continuous web-processing machin-

ery. For these applications, roll-to-roll or

roll-to-cut printing is required.

The four most common flexographic press

designs are central impression, stack, in-line

and sheetfed.

Many operations can be performed in line

after the substrate has been printed and

dried, while still unwound. Some types of

flexo presses are equipped with a shearing

and stacking device that delivers sheets

instead of wound rolls; others are equipped

with a die-cutting operation which delivers

finished individual cartons, rolls of labels,

or other finished products.

In the corrugated postprint converting

operation, the flexographic presses are

sheetfed, in-line units and are generally cou-

pled to other in-line processes such as die

cutting or folding and gluing.

The heart of the flexographic printing pro-

cess is its simple inking system (Figure

The ink-fountain pan supplies ink to a rub-

ber ink-fountain roll, which supplies ink to

the ink-metering (anilox) roll and may come

equipped with a reverse-angle doctor blade.

The anilox roll transfers a precise amount of

ink onto the printing plate, which is mount-

ed onto the printing cylinder. The printing

plate on the printing-plate cylinder and the

impression cylinder form a nip where the ink

is transferred onto the substrate.

The fact that flexo printing plates are

inked directly by the anilox roll makes the

system simple and unique. To a flexographic

press operator, the ink-metering system is a

means of controlling the amount of ink being

presented to the plates and subsequently to

the substrates. On the most sophisticated

presses the ink fountain, fountain roll and

doctor blade have been replaced by a cham-

bered ink applicator.

Flexography uses low-viscosity inks, either

solvent- or water-based, which dry very

quickly between the print stations of a press.

The viscosity of the ink is like that of a free-

INTRODUCTION 3

What is Flexography?

A typical flexographic

print station, configured

as a two-roll inking

system with doctor

blade.

Substrate

Printing

Plate

Cylinder

Doctor Blade

Anilox

Roll

Rubber

Ink-Fountain

Roll

Ink Fountain Pan

Impression

Cylinder

4 FLEXOGRAPHY: PRINCIPLES & PRACTICES

flowing, liquid, such as light oil or a light

syrup. In the early 1990s, pigmented, UV-cur-

able flexo inks became commercially avail-

able from a number of suppliers. Since that

time, UV-flexo printing has grown rapidly

among narrow-web converters.

Flexographic printing plates can be made

of either vulcanized rubber or a variety of

ultraviolet-sensitive, curable-polymer resins.

The plates have a base-relief (raised image)

and print directly to the substrate with a

very light impression.

The key component of the plate is, of

course, the raised image area, which carries

the image to be printed. Figure

illustrates

the additional components of the printing

plate, and are summarized as follows:

• image area – the printable surface;

• caliper – the total thickness of the plate;

• floor – the nonprintable area of the

plate;

• relief – the distance from the floor to

the top of the image area;

• shoulder – the support for the printable

area; the edge of the image area;.

• plate backing – the material on the back

of the plate to provide stability.

Unlike the hard metal plates that are used

in letterpress work, flexo plates are resilient

and displaceable. The plates are attached to

the plate cylinders with double-sided adhe-

sive tape called

“

stickyback” which may be

solid vinyl or cushion type.

ADVANTAGES OF FLEXOGRAPHY

Flexographic printing is an efficient, cost-

effective and versatile printing method. By

the end of the 1990’s, approximately one

quarter of all printing is flexographic; in the

packaging segment of the printing industry,

flexo enjoys a market share of over 65%.

Growth throughout the 1990s has been

steady, estimating an increase of 6% to 8% for

the final year of the decade. Table 1 summa-

rizes the positive points of using flexography.

FLEXOGRAPHIC PRINTING

APPLICATIONS

Figure

shows the variety of products

printed and vivid colors produced by flexog-

raphy. For any manufacturer, flexography is

a logical and economical choice.

Consumers, of course, are usually unaware

of the process used to reproduce the graph-

ics on products they use every day. Ordi-

narily, the product is opened, the contents

used and the packaging discarded.

As new products are manufactured, addi-

tional package printing requirements are

generated. This has a lot to do with the

steady growth of flexography. In fact, flexo-

This diagram of a

flexographic relief

printing plate shows

the components of the

plate: image area, floor,

caliper, shoulder, plate

backing and relief.

A wide variety of

packaging is produced

using the flexographic

printing process.

Caliper

Image Area

Floor

Shoulder

Relief

Plate Backing