Introduction to printing and finishing

Conventional printing processes 1Offset lithographic printing 4 Sheetfed offset lithographic printing 5 Sheetfed offset lithographic press sizes 6 Sheetfed offset litho press configurat

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Conventional printing processes 1

Offset lithographic printing 4

Sheetfed offset lithographic printing 5

Sheetfed offset lithographic press sizes 6

Sheetfed offset litho press

configurations 8

Lithographic make-ready and printing 13

Inking systems 14

Damping systems 15

Feeding and delivery mechanism 16

Remote control/press management

systems 17

Press sophistication and automation 18

Waterless litho 18

Web offset 20

Web offset press configurations 21

Blanket-to-blanket web presses 21

Common impression web presses 22

Blanket-to-impression web presses 23

Heatset and coldset presses 24

Narrow-width web offset presses 30

Book web offset presses 32

Commercial web offset presses 32

Preflight checking of files 50

Workflows 50 Data preparation for print 51

Digital printing 51

Digital printing processes 53 Toner 56

Substrates 56 Outline of digital printing systems 56 Digital printing systems: 57

Inks, toners, varnishes and coatings 73

Ink drying 73

Properties and uses of printing inks 74 Properties and uses of toners 75 Anti set-off spray powder 75 Accelerated ink drying 76

Ink mixing and matching 77

Colour matching systems 78 Printing ink terms 80 Varnishes and coatings 81

Substrates 83Furnish of paper and board 83

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4

Papermaking machine 86

Finish of paper and board 88

Supercalendered papers 89

Coated papers 89

Engine-sized and tub-sized papers 90

Embossed and other finishes 91

General characteristics of paper and

International paper and board sizes 104

Traditional UK paper and board imperial

sizes 106

US paper and board sizes 106

Sub-divisions of UK and US traditional

imperial paper and board sizes 107

Supply and purchase of paper and

board 108

Paper and board specifications 109

Description of papers and boards 109

Paper in web and reel form 109

Weight and price calculations 111

Printing processes and paper/board 112

Print finishing, binding and

warehousing 115

Offline finishing operations 116

Binding 125

Stitching 125

Perfect or adhesive binding 128

Burst, slot or notch binding 129

Automated binding lines 129

General finishing operations 131

Varnishing and laminating 136

Inline finishing 137

Inline webfed folding 137

Additional inline webfed finishing 140

Magazine binding and bookbinding 140 Bookbinding 145

Print finishing operations associated withdifferent types of printed work 148

General or jobbing work 148 Specialist work 149

Digital/electronic work 150

Printing processes and products,compared and contrasted 153Comparisons between the differentconventional printing processes 153Advantages and limitations of the mainprinting processes 154

Offset lithography 154 Flexography 154 Letterpress 155 Photogravure 155 Screen 156

Visual characteristics of the main printingprocesses 156

Offset lithography 158 Flexography 158 Letterpress 158 Gravure 158 Screen 158

The suitability of printing processes todifferent classes of work 159

Offset lithography 159 Flexography 160 Letterpress 160 Gravure 160 Screen 160

Other printing and print finishing relatedprocesses 161

Digital/electronic 161 Pad printing 161 Diestamping 162

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Thermography 163

Foil blocking 163

Developments in printing and

finishing 165

Integration between MIS, printing

processes and equipment 165

MIS supplier developments 168 CIP4 168

Developments in press automation 169Developments in inline facilities 171Web sheeting and feeding equipment 173Varnishing and coating 175

Glossary 177

7

1.1 Range of sheetfed offset litho press

sizes 7

1.2 Representative range of available

heatset web offset press sizes 27

2.1 Projected market share change of

different printing processes over

time 50

2.2 Main types of digital printing 52

4.1 Multiples and subdivisions covering

the A, B and C range of sizes

in mm 105

4.2 Selection of A, RA, SRA and B

range of sizes in mm 106

4.3 Range of sizes in mm representing

the metric range of traditional UK

paper and board imperial system 106

4.4 US paper grades, sizes and basis weight range in lbs per ream of

500 sheets 1074.5 US paper grades, using the basis weight for book papers as the reference grade, highlighted in italics, along with the equivalent weight in lbs per ream of 500 sheets for the other paper grades, plus overall gsm 107

6.1 Projected market share change of printing processes over time 154

1.2 The relief principle of printing 2

1.3 The intaglio principle of printing 3

1.4 The stencil principle of printing 3

1.5 The offset principle of offset litho

printing 5

1.6 Schematic drawing of a single-colour

Heidelberg Printmaster GTO 52-1,

B3 small offset press (1/0) 9

1.7 Schematic drawing of a two-colour

1.9 Schematic drawing of a two-colour

Ryobi 522HXX, A3+ offset press,

with common impression cylinder

construction 13

1.10 Schematic drawing of a typical

inking system used on a sheetfed

offset litho press 14

1.11 Schematic drawing of a damping

system used on an offset litho press,

showing the pan or trough of

damp, which is enclosed when an

alcohol-based solution is used 15

1.12 Schematic drawing of Heidelberg

Quickmaster DI 46-4, waterless

SRA3+ four-colour satellite

computer-to-press machine 19

1.13 Schematic drawing of a four-unit

blanket-to-blanket heatset web

press with the web travelling in a

horizontal direction 22

1.14 Schematic drawing of a four-unit

common impression satellite-type

coldset web press unit 23

1.15 Schematic drawing of a single-unit

blanket-to-impression web press

section 23

1.17 Schematic drawing of a twin-web eight-unit heatset web press 251.18 Schematic drawing of a 32-page long-grain heatset web press cylinder configuration 271.19 Schematic drawing of a 32-page short-grain heatset web press cylinder configuration 281.20 Single web two-unit coldset H-shaped blanket-to-blanket print unit module used on the Cromomanfour-page newspaper press, with the web travelling in a vertical direction 29

1.21 Schematic drawing of a specification four-unit narrow-widthweb offset press, showing web paper specifications and inline finishing operations 311.22 Schematic drawing of a typical single flexographic printing unit with ink feed via a fountain roller system 33

high-1.23 Chambered doctor blade inking system 34

1.24 Common impression/satellite multicolour flexographic press 351.25 Edale eight-colour Beta flexographicand combination press 361.26 Cooper single-colour Flexopress model 1500 37

1.27 Schematic drawings of letterpress platen and flatbed cylinder presses 38

1.28 Schematic drawing of a two-colour gravure press 40

1.29 Comprehensive schematic drawing

of the gravure printing process 411.30 Schematic drawing of a KBA eight-unit rotogravure TR 10 B/352 press 43

1.31 Schematic drawing of a single

colour basic screen press 44

1.32 A Svecia five-colour SAMX fully

automatic screen printing press 46

2.1 Xerox Docuprint digital

2.5 Océ CPS700 seven-colour colour

copier/printer, showing the straight

paper path around one common

imaging drum 66

2.6 Schematic drawing of the

DocuColor iGen3 digital colour

production press 67

2.7 Schematic drawing of the NexPress

digital colour production press 69

2.8 B2 sheetfed b7000 HP-Indigo

digital colour production press 70

2.9 Xeikon DCP 320 D digital colour

webfed production press showing

the one-pass duplex printing

operation 71

3.1(a) The ‘neck’ of the delivery unit of a

sheetfed press showing the position

of an infrared drying unit, and (b)

the radiant heat coming from the

infrared unit 76

3.2 DuPont Eurostandard colour

bar 80

4.1 Schematic drawing of Fourdrinier

papermaking machine – from the

wet end to the dry end of the

machine 88

4.2 Stack of calender rolls as used on a

supercalender unit 89

4.3 Paper fibres aligning with the

machine direction during

papermaking 92

4.4 Illustration of how paper fibres and

sheets of paper stretch and expand

more in the cross-grain direction 94

4.5 Watermark and laid wires on a dandy roll 95

4.6 Construction of a whitelined chipboard 102

4.7 The ISO series of A, B and C sizes are proportionate to each other, shown by the dotted line passing through the apex indicated by eachsize range 104

4.8 The range of A sizes obtained by halving or doubling the size above

or below in the range from A0 to A7 105

4.9 Sub-divisions of UK and US traditional imperial paper and board sizes from quad to 32mo 1085.1 Heidelberg Polar cutting

system 6 1185.2 Different types of fold, including right angle, parallel and cross 1195.3 Schematic drawing of the knife action of folding used on folding machines 120

5.4 Schematic drawing of the buckle action of folding used on folding machines 121

5.5 Examples of common fold configurations 1225.6 Illustration showing sections being gathered 124

5.7 Illustration showing sections being insetted 124

5.8 Collating or back step marks used

to identify visually any miscollated sections 125

5.9 (a) Saddle-wire stitching and (b) side-wire stitching 1265.10 Müller Martini Bravo Plus gather/inset, saddle stitch, trim (GST) machine 127

5.11 Müller Martini Acoro perfect bindinggather, adhesive, trim machine 1305.12 Müller Martini Ventura book sewing machine 131

5.14 Atlas automated label production

5.17 Schematic drawing showing former

and ribbon web folding

operation 138

5.18 Examples of page and size

configurations on a web offset

press fitted with a single chopper

5.23 Plastic comb binding 144

5.24 Standard spiral wire binding 144

5.25 Wire-O binding, allowing alignment

on page spreads to be

maintained 145

5.26 Schematic drawings indicating the

typical sequence of a soft cover

adhesive bound book 146

5.27 Schematic drawings indicating the

typical sequence of a hard cover,

adhesive-bound book block 147

thread-sewn-bound book block 1475.29 Schematic drawings indicating the typical sequence of book block processing 148

5.30 HP-Indigo webfed digital press withprinted product being cut and folded inline 151

5.31 Horizon online binding system linked to sheetfed digital printing system 152

6.1 Visual characteristics of different printing processes 157

7.1 Printcafé’s integrated Logic MIS in schematic form 166

7.2 Flow diagram of a typical CIP4 andMIS link-up 169

7.3 Speedmaster 74 DI digital imaging sheetfed offset litho press 1717.4 Schematic drawings illustrating inline finishing of cutting, creasing

or perforating set-up on sheetfed offset litho machines with the preparation of blanket and impression cylinder 1727.5 Heidelberg CutStar sheeter and feeder device 173

7.6 Rolls Systems DocuSheeter LS connected to a Heidelberg Digimaster 9110 digital printing system 174

the different operation of the planographic, relief, intaglio and stencil types of printing.

All conventional printing processes follow the same initial stages in order toconvert the original matter, which can be of conventional or digital origin, into an imagecarrier – such as a plate, cylinder or stencil – that produces the finished printed form

In conventional (otherwise known as traditional) graphic reproduction, theprinting elements of type matter and graphics are converted into an intermediate filmstage of negatives or positives These are then assembled, planned and approved beforeimage carriers for each of the printing processes are produced

Image carriers, in the form of plates, cylinders or stencils, can be created either byexposing the assembled films onto a light-sensitive image area which is then processed, or

by laser engraving, digital or chemical transfer

All printing processes are identified and categorised by the way they create

printed images Printing image carriers have two separate surfaces: image or printing areas and non-image or non-printing areas Printing areas accept the ink by physical or chemical

means of transfer Non-printing areas do not accept or retain ink

Basic principles of the In planographic printing, the printing and non-printing areas are, to all intents and

main conventional purposes, on the same plane This means that the substrate, such as paper or board,

printing processes is pressed into contact with the whole surface

The processed plate is treated, so that the printing areas, when they receive ink

Planographic printing from the inking rollers, transfer it to the substrate The non-printing areas then reject ink,

having previously been wetted with a dampening solution

Figure 1.1 (overleaf) illustrates the side view of a planographic plate The ink,represented by the solid areas, and the damping solution, seen here as wavy lines, show the printing and non-printing areas respectively In addition, a face-on view of

a planographic plate is shown, indicating the printing areas in the form of the words

‘offset litho printing’ and the blank non-printing areas

Lithography is an example of the planographic printing process

Relief printing In relief printing, the printing areas are raised above the non-printing areas These printing

areas receive the ink that is then transferred to the substrate when it is pressed against theprinting areas The ink rollers and the substrate come into contact only with the raisedprinting areas

Figure 1.2 illustrates the side view of a relief plate, showing the raised solid inkedareas and the non-printing areas (below the surface) The face-on view of a relief plate isalso shown with the words ‘flexographic printing’

Flexography and letterpress are examples of relief printing processes

Intaglio printing In intaglio printing, the printing areas are the reverse of that in relief printing, i.e they

are recessed and on a lower level than the non-printing areas The recessed printing areasare filled with ink and then the surplus ink is removed from the non-printing areas Thesubstrate is then pressed against the printing cylinder to transfer the ink onto it

Figure 1.3 (opposite) illustrates the side view of a gravure cylinder showing therecessed printing areas filled with ink and the non-printing, flush surface areas of thecylinder The face-on view of an intaglio cylinder is shown with the words ‘gravure printing’

Gravure is an example of the intaglio printing process

OFFSET LITHO PRINTING

Ink accepting/water repelling image areas that print

Water accepting/ink repelling non-image areas that do not print

Offset litho printing plate Non-image wetted with

font solution Ink receptive image areas

FIGURE 1.1 The planographic principle of printing

Source: Pira International Ltd

Raised image areas only receive ink and print Non-image areas not in relief do not receive ink and therefore do not print Non-image areas

Raised inked image areas

FIGURE 1.2 The relief principle of printing

Source: Pira International Ltd

Stencil printing In stencil printing, the printing and non-printing areas are carried on a mesh screen,

with the printing areas being open, or unblocked, in the form of a stencil The printing areas are formed by blocking out the appropriate areas of the mesh

non-During the printing process, the substrate is placed in contact with the prepared mesh screen Ink is then forced through the open, unblocked printing areas

to meet the substrate

Figure 1.4 illustrates the side view of a processed screen stencil, showing theweave of the mesh as thin, diagonally striped columns The clear areas indicate theunblocked areas through which the ink is forced onto the substrate

Screen printing is an example of the stencil printing process

Recessed/intaglio image areas

Cylinder surface non-image areas

Recessed image areas only retain ink and print

Surface non-image areas

do not retain ink and therefore do not print

Source: Pira International Ltd

Squeegee Ink Processed stencil diagonal lines indicate mesh with solid areas representing blocked off non-image areas, clear areas represent image areas though which ink penetrates onto the substrate

Printed substrate with

inked areas corresponding

to the clear/unblocked

areas of the stencil mesh

Image areas clear to receive ink which passes through unprotected mesh

Non-image areas blocked off across the mesh to prevent ink passing through

FIGURE 1.4 The stencil principle of printing

Source: Pira International Ltd

The main Lithography, based on the planographic process, is the most widely used printing process.

conventional printing This is due to its versatility, speed, quality and cost-effectiveness across a wide range of

processes outlined printed products

The basic principle of lithography is essentially that of a chemically-based process

Lithography that grease or oil and water do not mix Printing areas are created that are oleophilic (oil

attracting) and water repelling, and non-printing areas created are hydrophilic (water

attracting) and oil repelling A notable exception to this basic principle is waterless litho,

an explanation of which follows later in this chapter

When viewing a litho plate, such as the one seen in the face-on image in Figure

1.1, printing and non-printing areas can be clearly identified No physical difference can bedetected, however, if for example a hand is run over the plate surface

Flexible litho printing plates made from paper, polyester, plastic or metal havereplaced the rigid, thick porous stones that typified the early days of the lithographicprocess Each of these materials is processed and treated to acquire the properties needed

to meet the requirements of the lithographic process

Offset lithographic Offset lithographic printing gradually replaced direct litho printing from the early 1900s

printing In offset litho printing the right-reading printed plate is not transferred directly onto the

substrate, but is initially offset, or transferred, wrong-reading onto an intermediate surface

of a rubber blanket From there the printed image becomes right-reading again when thesubstrate receives the image from the blanket cylinder (Figure 1.5, opposite)

The offset litho process was first used for tin printing before paper, board andvirtually all other substrates adopted it It is the only major conventional process that doesnot print directly onto the substrate The offset rubber blanket offers many advantages tothe litho process These include the ability to print very fine resolution detail, and on awide range of substrates including relatively thin gauge metal and plastics

Offset lithographic presses are designed to print sheetfed, reelfed or webfed on a widerange of substrates Sheetfed presses are more flexible and numerous than webfed ones,but both are popular depending on a company’s target print market

The simple schematic drawing of a sheetfed offset press in Figure 1.5 illustratesthe arrangement of the three main printing cylinders: plate, blanket and impression, plusthe auxiliary delivery cylinder

Sheetfed offset A series of machine lays and grippers control the exact position of the sheet by a sheetfed

lithographic printing offset lithographic press on the substrate Irrespective of the size of sheet being printed,

three lays are used, two front and one side lay The front lays are set and adjusted tosquare up the printing on the substrate and are also used to fine tune the image position

on multi-pass work

The side lay fits on to the press’s feed board, across which it can be set in anyposition It can also be removed and placed the other way round This will allow the same

OFFSET LITHO PRINTING

OFFSET LITHO PRINTING

Plate cylinder

Blanket cylinder

Impression cylinder

Delivery cylinder

Plain paper feed unit

Printed paper delivery unit

Offset litho single-colour printing unit

Arrows indicating direction of paper path

OFFSET LITHO PRINTING

Printed sheet

of paper

Inking system

Damp/font solution

Source: Pira International Ltd

edge of the sheet to be fed to it when printing the second side An example of this is when

a job is printed by the work-and-turn method.

When the sheet is moved forward by the feeder mechanism to the front and side lays on the feed board, the front edge of the sheet overhangs to allow it to be taken

by the grippers that carry it around the cylinder for printing The purpose of the lays,therefore, is to position the sheet correctly for gripping, after which it is held in thatposition during printing operations

The printing plate is clamped around the plate cylinder and, as the cylinderrevolves, the damping rollers apply the damp solution The quality of printing largelydepends on the correct balance of damp solution and ink being applied to the plate

To bring it into register, the position of the plate may be adjusted on the platecylinder This can also be achieved by micro-adjustment of the front or side lays to whichthe sheet is presented prior to being taken into the press

Lithographic blankets are usually made of a fabric-backed material with a surfacecoating of synthetic rubber They are available in a range of shore hardness to suit the type

of work being undertaken

Printers of general commercial work tend to favour a compressible rubberblanket The blanket material must be treated carefully as any indentations will leavecorresponding non-printed areas on the substrate However, with care, it should last for

a reasonable time

The blanket does not normally need to be changed when the printing plate

is changed, unless it has been damaged or badly worn on the previous print run

The image is cleaned from the blanket with a suitable solvent, leaving theblanket clean to receive the image from the next plate Cleaning must be done carefullyand regularly to ensure that the blanket does not become contaminated

During its life the blanket material is constantly under pressure due to cominginto contact with the plate cylinder and impression cylinder In addition, it is regularlywashed and cleaned with solvent and other agents, which often results in a surface glazethat has to be removed During a print run the operator will regularly stop the press toclean the blanket and remove an accumulation of unwanted particles such as loose fibres,dust and ink particles, which will adversely affect the print quality

The impression cylinder, as its name suggests, provides pressure to ensure thesubstrate comes into contact with the blanket cylinder to create the printed result It isimportant that the correct amount of even pressure is applied between the two cylinders toensure the overall required print quality is achieved If too much pressure is applied, therewill be a heavier printed result than required, including dot gain – and vice versa when notenough pressure is applied

Sheetfed offset Sheetfed offset lithographic presses are made in a variety of sizes Typically, these equate

lithographic press sizes to just above the B range of the International Standards Organisation (ISO) Some presses,

Printers seldom buy trimmed, finished size paper and board such as A3, A2 or A1 During the printing and finishing process several allowances for the overall sheet sizehave to be made, such as trim or bleed, gripper allowance and colour bar, etc Withoutthese additional allowances the printer could not achieve the quality and overall finishedsizes required

In the UK, printed products are generally based on A sizes and their derivatives.The relationship between the different sizes can be seen by comparing the size A1, which is

594x 841mm, with SRA1, which is 640 x 900mm and B1, using the accepted rounded upfigures of 720 x 1020mm or 720 x 1040mm More detail is included on paper and boardsizes in Chapter 4

Table 1.1 outlines a range of sheetfed offset litho press sizes However, it should be notedthat the list only covers some of the available press sizes

Press sizes typically based around SRA3 and B3 are often referred to as smalloffset presses They are available in up to at least six print units and as portrait or

landscape presses With a portrait press the short edge of the sheet is fed into the frontlays In the case of a landscape press, it is the long edge

Feeding a sheet in by the long edge, i.e landscape, gives greater sheet controland is used in sheetfed presses of SRA2, B2 and above Small offset presses are used toprint relatively small format, small quantity and fast turnaround work, including stationery,such as letterheads, compliment slips, business cards and leaflets

Medium format size presses, based around SRA2 and B2, are available in up to atleast ten colours They are used for a range of commercial printing, mainly of larger formatsize than SRA3 and B3 presses and/or typically longer print runs

Large-format size presses, based around SRA1 and B1, are available in up to atleast 12 colours Again, they are used for a wide range of commercial printing, including

TABLE 1.1 Range of sheetfed offset litho press sizes

Maximum sheet size Equivalent stock size

short- to medium-range, high-pagination work such as magazines, journals, brochures, etc.Plus they are used for specialist work such as cartons and wet gummed labels

Extra large format size presses, based around SRA0, B0 and above, are available

in up to at least 12 colours and are not as prolific as the other sizes in terms of the number

of presses sold They tend to be used for more specialised work, including large-formatposters of medium to large print runs Book printers use them to produce large paginationsignatures (folded sections), or large format publications Plus, they are used by cartonprinters producing large print runs and/or large-format cartons

With print runs in general getting smaller, there has been a move towards smallerpress sizes, at least in terms of the volume of presses sold However, all the press sizesmentioned are supported in the different sectors of sheetfed offset litho

Sheetfed offset litho Sheetfed presses are available in a range of configurations, including single-, two-, four-,

press configurations five- and six-colour, up to at least 12-colour

All printing presses are made up of three main parts:

A feed unit that feeds the substrate into the press;

A print unit, or series of print units, depending on the number of print heads

on the press;

A delivery unit that delivers the printed sheets into the delivery mechanism

Most offset litho presses are constructed of modular, i.e unit-based, printing units,between each of which the sheet travels on transfer cylinders or chain grippers Eachprinting unit consists of impression, blanket and plate cylinders, together with thenecessary inking and damping rollers Figure 1.6 illustrates a schematic drawing for asingle-colour B3 press, showing the three elements of the sheet feed unit, one printing unitand the delivery unit

Standard multicolour presses are constructed so that they can print one side only in one

press pass These are known as straight printing presses Other multicolour presses are

constructed so that they are able to convert from printing one side only These are called

convertible printing presses

On convertible presses a conversion unit is fitted between the selected printingunits The printed sheet is turned over by the conversion mechanism that changes the

direction the sheet is travelling This results in the sheet being presented tail end and

opposite side first to complete printing on the non-printed side of the sheet

An example of a convertible press is the two-colour press shown in Figure 1.7 Thishas been constructed so that it can either print two colours on one side of the sheet, or be

changed over to a perfecting mode to print one colour on both sides, depicted as 2/0 and

1/1 Impression cylinders on convertible presses that are either side of the conversion unitnormally have a grained surface Or they can be coated with a material to prevent themtaking up ink from newly printed sheets

1 Sheet feeder unit

2 Sheet control system

7 8 9

Source: Heidelberg

designed to print both sides of the sheet in one pass, are ideally suited to work that needs

to be printed both sides Heatset perfector presses are built on the blanket-to-blanket

principle as illustrated in Figure 1.12 (page 19) The top blanket cylinder also acts as theimpression cylinder, the bottom blanket cylinder printing on the reverse of the sheet

Due to the success of convertible presses, which give the printer the option ofstraight and perfected printing on a wide range of multicolour presses, sheetfed perfectorpresses are aimed at a niche market – such as book and journal printers that specialise

in monochrome (single-colour) publications

An interesting innovation and development in perfected printing is the KomoriSuper Perfector (SP) range of multicolour, two-sided sheetfed presses The 440SP model, for

example, is built on a four-over-four unit basis, rather than the four-back-four basis used by

other eight-colour convertible presses

Lithrone SP presses have a very small footprint and are therefore efficient in

terms of the floor space they take up Overall, the presses occupy around a third less spacethan that occupied by the equivalent multi-unit, straight-line convertible presses A furtherfeature of SP presses is that the same grip edge of the sheet is used throughout the

printing operation, whereas convertible perfecting presses grip on different sheet edges

serving two or more blanket cylinders These have become relatively uncommon The feedand delivery systems of all presses are similar in construction, irrespective of the number ofunits in the press.

Figure 1.9 illustrates a two-colour sheetfed offset litho press with two sets of plate

and blanket cylinders, plus a common impression, double diameter cylinder Common

impression cylinder sheetfed offset litho presses, typically built in five cylinder, two-colourprint units, are a relative niche market where space saving is an important consideration.This is due to the smaller footprint of common impression presses They also allow high-quality register, two-colour printing without sheet transfer via gripper change betweenunits Although these presses are available in up to at least six print units

Lithographic The time taken for make-ready (or setting up) a sheetfed press depends on the type

make-ready and of work being printed, the standard of production required and the degree to which the

printing press is automated

The main press make-ready operations include the setting up of the feed anddelivery units, along with the path of the substrate through the press The inking systemhas to be set to supply more ink to heavy print coverage areas than to light ones, and thedamping system must be set to deliver the correct amount of damp for each job

1 Common impression cylinder

2 Plate cylinders (2)

3 Blanket cylinders (2)

4 Semi-automatic plate change facility 1

3

2 4

FIGURE 1.9 Schematic drawing of a two-colour Ryobi 522HXX, A3+ offset press, with common impression cylinder construction

Source: Ry-Offset

Printing plates also have to be correctly positioned, with the cylinder pressures set to suitthe stock being printed and give the correct print length

The average net output speeds of sheetfed offset litho presses vary from 3000 to

12,000 sheets per hour This depends on the length of run, type of material being printedand the sophistication of the press type, with maximum press speeds of up to 18,000sheets per hour It can take up to one hour to make-ready a single-colour basic press, andover two hours on a four-colour basic press On a highly automated press these times can

be reduced to 20 minutes or less and 40 minutes or less respectively

Inking systems On sheetfed offset litho presses, ink is generally applied to the printing plate by three or

more plate rollers These rollers are at the end of the inking system that starts with the inkduct A typical example of an inking system is shown in Figure 1.10 The ink duct is areservoir for holding a supply of ink ready to be fed into the inking system

Ink flow from the duct is controlled in two ways One method is to control aspecific area, or areas, across the width of the system by loosening or tightening a series

of thumbscrews, or keys, that act on the duct blade They thereby release more or less ink

at the particular points the ink duct keys apply or reduce pressure to the blade Analternative way of controlling the ink across the full width of the rollers is to adjust thedwell, or length of time the ink feed roller remains in contact with the main distributorroller A longer dwell would result in more ink and a shorter dwell less ink

Offset litho printing ink rollers are made of various materials Plate rollers that come into direct contact with the printing plate are usually coated with synthetic rubber,polyurethane or other suitably compressible material Other rollers used in the inking

F U

P

P P

FIGURE 1.10 Schematic drawing of a typical inking system used on a sheetfed offset litho press

Source: Pira International Ltd

improve the coverage of larger printing areas

Where ink flow is controlled from a console, i.e remotely controlled rather thanmanually adjusted by the operator, keyless ducts are used where conventional

thumbscrews and duct blades are replaced by wedges, cams or other devices to feed the ink to the inking system Automatic wash up of the inking system is now generallyavailable on presses of all sizes

Damping systems The damping system of offset litho presses is designed to apply an even film of moisture

to the plate while the press is running

Conventional damping systems have two plate damping rollers, which arecovered with fabric and driven by a metal distributing roller The damping solution istransferred to the metal roller via a cloth-covered feed roller that moves alternately fromcontact with the metal roller to contact with the fountain roller This then rotates indamping solution in the fountain pan or trough As the feed roller revolves against themetal distributing roller, it passes on some of the damp solution it has picked up

As the amount of ink that is applied is controlled by the amount of dwell thefeed roller and other rollers have by coming into contact, so the same basic principleapplies with the application of the damp solution

Alternative damping systems to that covered by Figure 1.11 are brush feed – replacing the feed roller – and an air mist system which replaces damping rollers altogether Further examples include an integrated, or continuous, method of damping and inking, via the

inking rollers, which is popular on small offset presses This is also used on larger machines

in some special alcohol-based damping systems

Damping solutions used by offset litho printers are seldom water alone, due tothe fact that, ironically, water on its own is not a particularly good wetting agent Also, thequality of water, in terms of the different treatments it is subjected to and the additives putinto it to make it suitable for drinking, varies from area to area As a result, to improve the

‘wet ability’ and print quality of the water-based damp solution, additives and buffers are

Plate cylinder

Damp/font solution Metal distributing rollers Fabric-covered feed rollers

FIGURE 1.11 Schematic drawing of a damping system used on an offset litho press, showing the pan or trough of damp, which is enclosed when an alcohol-based solution is used

Source: Pira International Ltd

added to neutralise any adverse effects that may arise from water treatments These alsoincrease plate life and improve plate-running qualities.

Due to the damping rollers collecting dirt, mainly from the ink, aerial dust,substrate particles and fluff, they must be cleaned periodically This can be done manually,but an off-press device is often used in which the dampers are automatically scrubbed withdetergent, rinsed, and the excess liquid squeezed off The most common current practicewith the vast majority of printers is to use disposable coverings These reduce the need toremove the rollers from the press for cleaning

Alcohol damping systems The most common practice to reduce the surface tension,and therefore improve the ‘wet ability’ of a water-based solution to suit the needs ofconventional offset litho, is to add a small percentage of alcohol Surface tension is theproperty that controls how much a liquid will or will not wet a given surface The higherthe surface tension the more resistance the liquid displays, resulting in poor liquiddispersion and poor wet ability, and vice versa

The addition of 5% isopropyl alcohol, or a similar alcohol substitute, reducessurface tension by around a third compared with water alone The acidic pH also enhancesthe desensitising action and maintains the hydrophilic (water loving) properties of the non-printing areas

Alcohol damping systems have many advantages over solely water-basedsystems, including shorter set-up times and less substrate waste, sharper printed imagesand a thinner liquid film on the plate Less moisture used also means fewer problems withpaper or board stretch and less likelihood of emulsification problems

Alcohol damping systems react to control changes faster than water systems withcloth-covered rollers Temperatures on such systems are best kept low, at around 10°C, toprevent the alcohol evaporating While the alcohol content is best kept to 5–15% of theoverall damp solution

Feeding and delivery The feeder unit on the printing press holds the supply of sheets for printing Two types of

mechanism feeder are used on sheetfed offset litho presses: single sheet and stream feeder

For some small offset size presses with small format sheet sizes the single sheetfeeder is used The sheet separator is located at the top and front of the substrate pile andforwards the sheets one at a time onto the feedboard Compressed air jets then separatethe sheets in the stack

The stream feeder is a faster and more efficient system, used mainly on largerformat size presses, although this type of feeder can be used on some small offsetmachines The sheet separator is located at the top and back of the substrate pile andforwards the sheets in an overlapped stream onto the feedboard

The next stage is for suckers, or rubber-covered wheels, to move each sheetforward to the feedboard where it can be picked up by the main gripper mechanism of thepress The speed of the feeder must match that of the press so that a sheet is ready in the

Safety systems are fitted to the feeder that stop or trip the press if a double sheet

is fed, if the sheet is crooked or if no sheet is fed at all

The delivery mechanism is an integral part of the press and consists of sets ofgripper bars carried on a continuous chain structure The grippers pick up the sheet fromthe impression cylinder and convey it to the delivery pile where it is released and nudged

to form a neat stack Air jets may be used to control the speed at which the sheet dropsand there may also be a suction roller, sheet de-curlers and anti-static devices to avoidpoor stacking Some machines have chute deliveries that simply eject the sheet, a smallsheet being less likely to wander or buckle than a large one

During its travel in the delivery, the sheet may be subjected to a drying or curingtreatment or, more commonly, when released on the pile will be sprayed with an anti-set-off powder Equipment for rapid ink drying or curing systems using ultraviolet (UV) orinfrared (IR) light is often placed in the swan neck section of the press where the sheetrises to the high pile delivery

The delivery area is usually illuminated so the operator can view each sheet as

it reaches the finished printed sheets pile A system is often incorporated whereby a sheetcan be removed for inspection without stopping the press

Both feed and delivery systems can run non-stop, the press being equipped sothat the printed substrate can be loaded at the feeder end, and the printed sheets removed

at the delivery end, without interfering with the running of the press

Auxiliary operations such as numbering, perforating, slitting and, in some cases,cutting and creasing can be carried out on presses fitted with special attachments

Remote control/press Most of the sheetfed offset litho printing press control panels and indicator gauges are

management systems located at the delivery end of the press, with some controls duplicated at the feed end

On a wide range of automated modern machines the presses are controlled by an press, networked control console This involves considerable automation apart from themere centralisation of controls

off-Such controls allow the operator(s) to monitor the whole machine printing process,from the initial make-ready through to press sheet comparison with approved proofs With theuse of a proof and press pull viewing booth, the controls allow constant monitoring of thepress settings, while at the same time examining the sheets being printed

Operation of the press from a central console that is linked to it is becoming

a common feature on multicolour presses With functions such as light emitting diodes,

or LED displays, providing data on all aspects of the press, including running speeds,maintenance data and press faults Plus, where available, linking up to the machinemanufacturer’s production and information system and/or the print company’sManagement Information System (MIS)

Press sophistication The degree of sophistication and automation on sheetfed offset litho presses varies

and automation considerably across the wide range of models available Three main types of press are

in regular use:

A basic press range that covers the basic model of a press with very little additionalattachments or facilities, so relying heavily on the operator to set up the pressmanually

An advanced press range fitted with a press management system

A highly advanced press range that has all the facilities of the advanced press, butmore automated features, such as automatic or semi-automatic plate change.New developments and automation in printing are covered in greater detail

in Chapter 7

Waterless litho Waterless litho, as its name suggests, is offset litho printing without the use of water or

a damping solution It is a process that has been in regular use for over two decades, albeit

as a niche sector It does, however, possess many advantages over conventional offset litho,such as the avoidance of having to achieve ink and water balance, faster make-readies,more vibrant colours and consistent colour balance Plus, it produces less waste and ismore environmentally friendly

Waterless litho continues to be a relatively small sector of offset litho printing,especially in the UK, although in Japan it has a much higher market share

Due to the increased number of computer-to-press (CTPr) systems released in the last few years using waterless litho technology, the process looks set to claim a higherprofile and market share of the offset litho printing sector

Waterless offset litho printing presses Waterless CTPr format size systems are mainlyA3/B3 and A2/B2, although B1 and web presses are under development Despite the factthat waterless analogue plates cover up to B1 size, the range of CTPr waterless presses fallinto the smaller format range of A3/B3 and A2/B2 at present

An example of a CTPr waterless offset litho press is the Heidelberg Quickmaster

DI 46-4 (see Figure 1.12, opposite) The press is of a satellite construction with a sized central impression cylinder, allowing four-colour printing in one gripper closure andenhancing high standards of registration It is a four-colour press, printing from direct-imaged Presstek polyester plate material, with a maximum sheet size of 340 x 460mm andmaximum printing speed of 10,000 sheets per hour

quadruple-The Quickmaster DI is aimed at short-run colour work, positioned between digitalcolour toner print systems and traditional offset litho printing It retains high-quality offsetlitho printing, combined with short set-up times, and is directly linked to digital prepress

During production of the direct printing plates, PostScript data from the digitalfront end system is converted in the RIP processor of the Quickmaster DI into screen data.This, in turn, is converted into control signals for 64 IR laser diodes (16 x 4 colours) Thelaser beams created by the laser diodes are then bundled into precise rays of controlled

and form the inked printing areas, leaving the untouched silicon layer to form the

waterless non-printing areas Two resolutions are available: 1270dpi and 2540dpi, creating

up to 150lpi screen resolution

The machine operates a plate spooling system that automatically renews theprinting plates in all four units on press after each job is completed Each job is preparedthrough the RIP and held in a page buffer unit on the press It is controlled by the operatorwho selects and controls the print sequence of jobs Automatic imaging of all four printingplates, along with the cleaning/processing of the plates, takes under ten minutes Ink

profiles on the four printing units are preset from the digital data file, and register is

automatic, with the plates being exposed direct on press and the operator overriding thesettings manually if and when required

1 Sheet feeder unit

2 Blanket wash-up system

3 Plate cylinder cleaning system

FIGURE 1.12 Schematic drawing of Heidelberg Quickmaster DI 46–4, waterless

SRA3+ four-colour satellite CTPr machine

Source: Heidelberg

Web offset Web offset printing, as its name implies, refers to printing by presses onto a web or reel,

i.e a continuous roll of substrate The term ‘web’ and ‘reel’ in this context are synonymousand, to a large extent, interchangeable in terms of description when referring to thephysical form of the substrate or press used

The term ‘offset’ comes from the fact that the printing process used is offset litho,where the right-reading image on the plate offsets onto the blanket cylinder before beingtransferred onto the substrate in a right-reading form There are a number of web offsetpresses configured and designed to cover a wide range of product requirements, from smallformat cheques to high pagination, large-format magazines and newspapers

Web presses, unlike sheetfed presses, are generally designed with inline finishing.This gives the press the ability to deliver finished products, or at least partly finishedelements of a job, such as folded sections, that require further final finishing Web pressesare also built with fixed or variable cylinder circumferences

Most large-format web presses, such as heatset and coldset used for commercialproducts and newspapers respectively, are fixed cylinder circumference presses This meansthat they have fixed cut-offs that are established by the cylinder circumference used on aparticular press Many heatset presses, for example, are built to produce 630mm cut-offs.This means that any product produced on such a press is limited to derivatives of thatcylinder circumference size, less an allowance for bleed, etc., such as 297mm and 148mm.The exception to this would be where the printed reel is sheeted off, as the flat sheet canthen be cut and finished to a non-standard cut-off size

As well as large-format presses, narrow width, continuous business forms-typepresses are built to accommodate a range of variable cylinder circumferences, fromwhich derivations of the size can then be produced For example, 18in cylinders can be

used to produce 18in, 9in and 6in deep jobs, or 22in cylinders to produce 22in, 11in and

5.5in deep jobs.

It should also be noted that the web or reel width of the material to be printedcan vary up to the maximum width the press will accommodate For example, the printedweb could be the equivalent of full width, three-quarter or half-width

On a web offset press, reels of paper are fed from unwind reel stands into theprinting units, followed by inline finishing and, finally, the delivery end of the press Here,depending on the design of the press, the reel is finished in one of three ways The finalproducts from the press may be delivered as complete or semi-processed finished products,sheeted off in pre-determined lengths as finished products, or delivered for further offlinefinishing when they may be re-reeled

Web presses are available with printing cylinders up to several metres in widthand circumference, with running speeds in excess of 80,000 copies an hour Once thepresses are set up to run they are generally controlled by an electronically linked offpresscontrol console, or series of consoles

Whereas only one or two operators, even on multicolour presses, often mansheetfed presses, large multi-unit web heatset and coldset presses are manned by a crew

deck As well as the print units being constantly controlled and monitored during set upand running, the infeed, folding and other applicable finishing and delivery units will often

be under the supervision and control of other members of the press crew

Web offset press Web offset presses are available in a wide range of configurations, including single unit

configurations up to several units or banks of colours, plus single and multi-web options This combines

to give a wide choice of permutations in terms of colours, webs printed, finished productsizes and types

Web presses also differ in the way the printed image is transferred from theblanket cylinders to the substrate The three main types of web offset printing

configurations are blanket-to-blanket, common impression and blanket-to-impression.

Blanket-to-blanket Blanket-to-blanket configurations are used on both heatset and coldset web presses

web presses Each printing unit on a blanket-to-blanket web offset press has four cylinders,

two plate cylinders and two blanket cylinders Each blanket cylinder acts as an impressioncylinder for the corresponding blanket cylinder on the other print unit The printing image

on each plate cylinder is transferred to its respective blanket cylinder This means that inone direct press pass the web is perfected, i.e printed on both sides, as it runs in the nipbetween the two blanket cylinders

These presses are available in up to at least 12 colours With the use of multi-webconfigurations, they can produce a wide range of options, especially with the

comprehensive inline folding options that are available Figure 1.13 illustrates a four-unitblanket-to-blanket web press configuration

Two configurations of the press are available In one the printing units arestacked vertically on top of each other with the web running horizontally through theblanket-to-blanket units In the other the web travels vertically between the horizontallyarranged printing units, with the printing units turned through 90° This type of

configuration is often referred to as an arch-type blanket-to-blanket press and is common

on coldset newspaper presses

Common impression Common impression configurations are popular on coldset web presses, and are widely

web presses known as satellite presses

These types of web presses are more common than their sheetfed counterparts,generally consisting of one impression cylinder, or a series of them, surrounded by severalplate and blanket cylinders Printing is undertaken by feeding the web in the nip betweenthe blanket cylinders and the common impression cylinder to print the substrate

Perfecting on this type of press is usually done by running a web through onesatellite, printing one side of the web only, followed by running the other side of the webthrough a second satellite unit Figure 1.14 illustrates a single web printing in four colours

on a four-unit common impression printing unit

Another possible configuration is that of a twin-web press printing two separatewebs in two colours Again, perfecting would be undertaken by passing the web through

a second satellite unit to print the reverse side Unlike blanket-to-blanket presses, on whichthe web is unsupported between the printing units, the web in a satellite configuration

is held tightly round the large common impression cylinder This minimises movementbetween successive colours

FIGURE 1.13 Schematic drawing of a four-unit blanket-to-blanket heatset web press with the web travelling in a horizontal direction

Source: Pira International Ltd

Blanket-to-impression Blanket-to-impression configurations are most popular on continuous business forms-type

web presses web presses This is the printing press configuration used predominantly by sheetfed offset

litho presses, with the design of the print units ideally suited to printing the substrate onone side only In the same way that conventional sheetfed presses require conversion units

to turn the sheet for perfecting, the blanket-to-impression reelfed presses require turn bars

to perform the same operation

For reelfed printing, turn or turner bars are used to turn the reel over to print on theopposite side The reel then continues through the press to be printed on both sides Figure 1.15illustrates a single-unit blanket-to-impression configuration as used on a reelfed press Presses

of this type are popular in multicolour configurations up to and in excess of ten colours, withpermutations such as five-back-five (5/5) and six-back-four (6/4) on a ten-colour machine

Source: Pira International Ltd

Plate cylinder

Blanket cylinder

Impression cylinder

Inking system

Damping system

Reel or web of paper prior to printing

Printed web

FIGURE 1.15 Schematic drawing of a single-unit blanket-to-impression web press section

Source: Pira International Ltd

Heatset and coldset Most large web offset presses are classified as coldset or heatset Heatset presses allow

presses a wider range of papers to be used than coldset and produce much higher quality work

They cover an extensive selection of commercial work, including magazines, journals,catalogues and specialist work such as direct mail

As with larger format web presses, the quantities printed are generally long runs,e.g in the tens and hundreds of thousands, rather than the low thousands The work alsotends to be four-colour process, but can be in single-colour and five-colour, normally asfour-colour process with a ‘special’ colour

As previously stated, the most popular cut-off in heatset web offset pressesoperating in the UK print market is 630mm However, in a drive to reduce waste andmaterial cost, press manufacturers are offering cut-offs of 625mm, 620mm and less

Coldset presses are used mainly for printing newspapers and relatively long-runnewspaper-type quality products Examples of this include a range of comics, large-formatpromotional news advertising and sales bulletins, plus text-based monochrome magazinesand books

The paper used needs to be absorbent and the inks formulated to set by acombination of absorption and oxidisation This is so that the finished sections may behandled after folding without undue marking and setting-off On a satellite-type press, theweb passes through the drier twice, once after the first unit and again after the secondunit and before folding

Heatset web offset presses Heatset presses are dedicated perfector presses, i.e.printing both sides of the web in one direct press pass They are built on the blanket-to-blanket principle, with printing units arranged in line with one web, or several webspassing between the selected print units

The presses are built in a specific sequence of units, from raw material in webform to finished or semi-processed product These units are the infeed, splicer, printingunits, heatset dryer, chill rolls, folder and delivery

Figure 1.16 (opposite) illustrates a single-web four-unit heatset press showing the reel infeed, single web path through the press, four print units, dryer and chill unit, plus folder Figure 1.17 (opposite) illustrates a twin-web eight-unit heatset press showingtwo reel infeeds, double web path through the press, eight print units, two dryer and chillunits, plus folder

Infeed unit The infeed unit assists in controlling the tension, sideways position and

speed of the web It takes the form of a reel stand and a number of rollers that guidethe web into the first print unit The web is then fed into the press at a controlled andmeasured speed by a moving or dancer roller, which moves up and down as well asforwards and backwards during the run

replace the used up reels, splicer units are used to join or splice a new, full reel to thenearly used reel This is achieved either via a flying paster that splices the two reelstogether while the press is still running at full speed, or where spare paper in the form

of a festoon is created, allowing splicing to take place at zero speed

blanket-to-blanket basis Most presses are single or twin web, with four or eight units, althoughfive, ten and up to 12 print unit presses are available

application of heat is an integral part of the process Direct heat, via gas-fired jets,drives off the solvent from the printed web This accelerates the ink drying process,with the result that the ink dries with a relatively high gloss finish

The drier and chill roll process comes into play after the last printing unit Theprinted web passes through the heatset unit, followed by chill rolls that cool the soft,heat-affected ink The intense heat applied in the dryer unit can exceed 300°C, withthe printed webs leaving the dryer unit with a temperature of around 150°C

Due to the fact that perfected, printed webs exit the print units, the drying

system must be able to dry both sides of the web simultaneously This is achieved bythe use of a floating dryer system, through which the printed web passes suspended

by tension The highly volatile mixture of hot air and evaporated solvents is removed

by an extraction system to ensure a safe and effective operation

Source: Heidelberg

FIGURE 1.17 Schematic drawing of a twin-web eight-unit heatset web press

Source: Heidelberg

As the printed web exits the drying unit at a relatively high temperature it needs

to be cooled This is undertaken by the chill roll section, which is a series of metaldrums cooled by cold water circulating through them The temperature of the webfalls to around 30°C as it exits the chill roll unit

Before folding can take place, the web is dampened to put moisture back intothe paper This prevents the paper becoming brittle and cracking when folded Asilicone and water mixture is applied to both sides of the web, and this has otherbenefits too, including an improvement in the flatness of the paper web and anincrease in the overall gloss It helps to reduce the risk of smearing and scratching ofthe printed result by allowing the web to slide more easily over the guiding rolls andturning bars of the folder unit The silicone mix also reduces the electrostatic charge

on the paper

folded sections, or signatures Folds are either applied in the direction of the web, i.e.with the grain direction, or across it, i.e with the cross direction See the section onlong- and short-grain presses for more on this The type of folders used on web presses

is covered in Chapter 5

It should be noted that sheeters, i.e sheeting devices fitted at the end of the press,can be used instead of folders These are particularly popular on the eight-page pressesfor sheeted commercial work such as pamphlets The range of stock weights used whenfolding inline is around 30gsm to 135gsm and up to 200gsm for sheeted work

are based on the maximum number of A4 page sizes, or in some cases undersize andoversize A4 page sizes, that can be obtained from each cylinder circumference or cut-off The range varies from an eight-page press, often referred to as a mini-web, up to

64-page presses Sizes other than A4 can be obtained from the presses, such as 32pages A5 from a 16-page A4 heatset web press

Table (opposite) covers a representative range of press permutations, illustrating that thepresses are available in single and twin web So, for example, a 32-page press can either be

a single web 32-page press or a twin web 16-page press Table 1.2 also highlights the factthat there is a wide range of maximum web widths and cylinder circumferences available,showing that not all heatset presses are designed for the A-size markets Nevertheless, themain cylinder circumference, or cut-off, is still 630mm along with 625mm, with a range ofnon-A-size cut-offs for specialist size presses

Double circumference heatset web offset presses, such as 1260mm and 1240mm,are popular for large-format presses as full size 32-page single and twin web presses

Long- and short-grain presses Most heatset web presses are long-grain, where the

press cylinder circumference is greater than its width Long-grain presses derive theirname from the fact that the grain of the finished product is typically parallel to the

spine In short-grain presses the cylinder width is greater than its circumference, whilethe grain of the finished product is typically at right angles to the spine

Due to a short-grain press having a smaller cylinder circumference than width, it completesmore cylinder circumference revolutions per set period of time than the equivalent long-grain press running at the same speed This makes the short-grain press faster overall

Short-grain presses also offer greater variety of output in terms of pagination through theuse of ribbon folding (see Chapter 5)

Figure 1.18 illustrates a 32-page long-grain heatset web press cylinder

configuration It accommodates four 210mm wide pages, with allowances such as bleed,etc across the cylinder Plus there are four 297mm deep pages with allowances such asbleed, etc around the cylinder circumference

Figure 1.19 (overleaf) shows a 32-page short-grain heatset web press cylinder

configuration This accommodates four 297mm deep pages with allowances such as bleed,across the cylinder Plus there are four 210mm deep pages with allowances such as bleed

around the cylinder circumference In both cases the finished product is A4 upright or portrait

web widths circumference/cut-offs

Coldset web offset presses Coldset web offset presses, as previously explained, aremainly associated with newspaper and newspaper-type products They are available in two

configurations: common impression/satellite and blanket-to-blanket, with the printing

units arranged horizontally The presses tend to be multiple-web as they are built toproduce a high pagination and/or large-format finished product in one press pass

Due to the need to produce a wide product range, the presses are often custombuilt to suit specific requirements, with a range of print unit configurations and web paths.Coldset is a printing process where no accelerated drying of the ink takes place

Coldset presses are made up of several reel infeeds with splicer facilities, plusprint units, folder options and delivery systems The blanket-to-blanket coldset presses arebuilt in a modular fashion to a distinctive pattern or shape, including U, Y and H-shapedprint configurations

Figure 1.20 (opposite) shows an H-shaped blanket-to-blanket double print unitconfiguration, which prints two colours both sides of the web as it passes vertically throughthe blanket cylinders Alternatively, a twin web option could produce two webs printedboth sides in one colour

Printing cylinder

Cut-offA4

FIGURE 1.19 Schematic drawing of a 32-page short-grain heatset web press cylinder configuration

Source: Pira International Ltd

Figure 1.14 (page 23) illustrates a four-unit common impression satellite-type press section,which is particularly popular for fine register four-colour work

Some coldset press configurations combine satellite and blanket-to-blanket printunits in the same overall press configuration For example, a configuration of a four-unitsatellite print module and a two-unit blanket-to-blanket print module could be webbed up

on a twin web press This would produce one section in four-colour process both sides, andanother section in single-colour both sides A further option, using a single web with

different webbing options, could result in a single section printed four-back-two colours(4/2) or five-back-one colours (5/1)

With combination coldset web presses, satellite print units are the preferred

option for colour work, blanket-to-blanket the preferred option for monochrome/singlecolour work Although alternative options are used from time to time as illustrated by theprevious examples

Coldset press cut-offs vary from 470mm to 630mm, with double circumferencecylinders from 940mm to 1260mm and web widths up to 2m-plus Presses are available in

in a vertical direction

Source: MAN Roland

up to ten-cylinder satellite modules, with blanket-to-blanket modules mainly in groups oftwo and four print units Overall pagination from one press line can be up to, and in excess

of, 160 broadsheet pages

Narrow-width web A wide range of printed products, including business forms, direct mail and general

offset presses commercial work, are printed on narrow-width web offset presses As explained earlier in

this chapter, these presses are designed on the blanket-to-impression principle, and usuallyhave the option of variable cylinder sizes A further distinctive feature is the comprehensivefinishing facilities that are available on these presses

Most narrow-width web offset presses are single web However, there are a fewtwin-web presses used for specialist work such as receipts, duplicate forms and sets Thereare a range of cylinder widths and circumferences, and the three cylinder inserts of plate,blanket and impression are easily removed from the press when changing from onecylinder size to another As well as changing the printing units, the operator needs to resetthe press to suit the size and type of product to be printed

Basic business forms-type presses are available in one-, two- and three-colours.Four-colour presses and above are often used for a wider range of work than just businessforms Printing speeds are up to, and in excess of, 400m per minute With comprehensivefinishing, however, the net output is much lower A stock range of 40gsm to 240gsm can

be printed on these presses

A typical press configuration consists of a reel unwind system, printing units consisting of a plate cylinder, inking and damping system – plus blanket and impressionunits There is also inline finishing equipment, such as sprocket hole punching, perforating,folding and sheeting

-Due to the relative decline of the business forms industry, which started in the

1990s, a growing trend with reelfed continuous machines is in the development of higherspecification presses These can be up to ten colours, offering a range of web printingconfigurations, such as five-back-five (5/5), six-back-four (6/4), etc

Additional facilities include interdeck UV drying and inline finishing, e.g additional varnishing, diecutting, remoist glue, scratch-off application, file and linehole punching Others include cross, running and skip perforation units, plus reel-to-reel,reel-to-fold and reel-to-sheet inline finishing The result is a highly productive press aimed

at direct mail/direct response marketing, security printing, continuous and multiple setforms, plus promotional and general commercial printing

Figure 1.21 (opposite) illustrates a high-specification four-unit press, available

in up to ten units It is suitable for direct mail and commercial applications

The main drawing shows the sequence of operations from the reel unwind unit.This includes a web cleaning device to remove paper fluff and loose fibre, plus a webguiding mechanism to ensure control of the reel as it is fed into the press The patternedline as it passes through the machine indicates the path of the reel