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PRESSES AND PRESS EQUIPMENT 83

them to the surface of the cooling roll is pri-

marily by conduction. The heat transfer from

the surface of the cooling roll, through the

wall of the cooling roll, to the cooling medi-

um, is also by conduction.

With the ever-increasing cost of energy,

cooling-roll heat transfer efficiency will

become an ever-increasing cost problem.

Cooling-roll efficiency is equal to the roll’s

output of energy divided by the energy input.

Energy input is the heat transferred from the

substrate to the cooling-roll shell; energy out-

put is the heat transferred from the shell to

the coolant and finally carried away.

The basic heat transfer expression, without

any refinements is:

H  U  A T

Where

H = The total heat removed from the sub-

strate in British Thermal Units (BTU)

per hour.

U = Overall conductance or rate of heat

transfer of the system (BTU/hr/ft

/°F)

A = The area of the web in contact with

the cooling roll surface

T

= Log

mean effective temperature dif-

ference between substrate and coolant

(°F)

These heat calculations can be very com-

plex because of the many factors that affect

the heat flow:

• press speed and dryer temperature;

• mass and conductance of the web

material;

• conductance of the cooling drum mate-

rial;

• type and temperature of the coolant;

• level of smooth versus turbulent

coolant flow in the cooling drum; and

• corrosion scale on the inner wall of the

drum.

If an open coolant system is used, with the

source being the local water supply, inlet

water temperature variation in the summer

and winter must be considered, along with

the total pressure range available and the

flows required.

Understanding the expression can also

help bring about a practical balance of fac-

tors for an application. How many sub-

strates can be run? At what speeds? At what

weights and widths? For instance, where a

single roll diameter may be too large and

impractical, then two or more smaller rolls

may be more suitable and add flexibility to

an operation. For a sophisticated cooling

roll application, the only foolproof approach

is to fabricate an experimental model and

then use the experimental value obtained

to confirm theoretical value calculated.

Cooling Roll Design

If the press is small (36" or less), runs at

speeds of only 300 to 400 feet per minute,

and substrate temperature reduction needed

is minimal, a simple single-body cooling roll

may do the job. (Figure

). The coolant

flows in one end, fills the roll about half full,

and flows out the opposite end. The sub-

strate must possess some strength since it

will have to withstand some roll imbalance.

If more substrate cooling is required and

imbalance must be minimized, the self-vent-

ing roll (Figure

) may do the job. In this

Outlet

End

12" to 48" Face

3" to 6" Diameter

Coolant

Inlet

End

A typical single-body

cooling unit for small

presses, where coolant

flows in one end, fills

the roll about half way

and flows out the

opposite end.

84 FLEXOGRAPHY: PRINCIPLES & PRACTICES

design, most of the air bank is automatically

exhausted as the roll rotates and most of the

roll body is in contact with the coolant.

A further improvement in substrate cool-

ing and roll efficiency is the double-bodied

roll (Figure

). The coolant is forced to

flow in the annular or ringed space. Con-

sequently, more flow and velocity control

can be designed into the roll, resulting in

more heat transfer from the substrate.

Generally the flow rate will remain in the

laminar flow range and heat transfer will be

limited by that condition.

A refinement of the double-bodied cool-

ing-roll design is the addition of a spiral

wound coolant chamber (Figure

). The

ideas and designs that have come out of this

refinement effort over the past few years are

many and varied. Some of these designs are

patented, which may attest to their impor-

tance in this phase of the roll business. Only

the spiral-wound version is shown and dis-

cussed. The outside diameter of the inner

body is spirally wound with an appropriate

material. When this inner body assembly is

placed into position within the outer body, a

distinct coolant passage is formed in the

annular space. This design gives accurate

control of the rate of flow and the velocity of

the coolant.

Q  A  V

Where :

Q = rate of flow or discharge (ft

/sec)

A = passage area (ft

)

V = coolant velocity (ft/sec)

If a single passage area is required, the

pitch or angle of the spiral is equal to the

passage width plus the width of one spiral.

If, for example, four passages are required to

handle the rate of flow, the pitch is figured as

mentioned and the lead would be four times

the pitch. With this control available, the

designer can increase the coolant velocity

and change laminar flow to turbulent flow.

Turbulent flow is desirable since it increases

heat transfer most by reducing the coolant

film and agitating, with eddy currents, the

coolant itself. In this cooling roll, using

For substrates that

require more cooling, a

self-ventilating cooling

roll automatically

exhausts the air as the

roll rotates comes in

contact with the coolant.

In a double-bodied

cooling roll, coolant is

forced to flow in an

annular space. The

increased flow and

velocity control promote

greater heat transfer

from the substrate.

A spiral-wound

double-body cooling

roll provides a coolant

passage that allows

accurate control of the

flow rate and velocity of

the coolant.

Outlet

End

12" to 48" Face

3" to 6" Diameter

Coolant

Inlet

End

Outlet

End

12" to 240" Face

7" to 40" Diameter

Coolant

Inlet

End

Outlet

End

12" to 240" Face

7" to 40" Diameter

Coolant

Inlet

End

PRESSES AND PRESS EQUIPMENT 85

water and water-base coolants with a range

of velocities from 11 to 15 feet per second

will generally result in turbulent flow.

Where an application requires a minimum

temperature gradient across the face of the

roll, the spirals can be mounted with a

decreasing helix angle. Continually decrea-

sing the flow area increases the coolant

velocity as its temperature is increasing and

brings about this desirable effect. As these

rolls become more efficient due to improved

design and better flow characteristics, it is

important to stay within the pressure capa-

bilities of the system. Remember that the

friction head varies in close relation to the

square of the velocity. This type of roll is usu-

ally used in a closed system along with a

treated coolant and an automatic chiller as

part of the package.

A hydrostatic or pressure test is necessary

on all of these rolls. The speed of the sub-

strate and roll will determine whether a sta-

tic or dynamic balance is required. On the

more critical cooling-roll applications, dy-

namic balancing is performed with the roll

full of coolant.

The flexographic process is growing

because it can be adapted to handle a wide

variety of packaging substrates. The heating,

drying and cooling equipment components

make up a very important segment in this

process. The cooling roll is also being adapt-

ed so it too can handle a wider variety of

substrates.

STATIC ELECTRICITY

Whenever nonconductive materials touch

or rub against one another, a charge of static

electricity may be generated. This electrosta-

tic charge attracts dust particles, causes

materials to cling to each other and can cause

mild to violent electric shocks.

What is static electricity and how do we get

rid of it, or at least control it? When the phe-

nomenon is understood and controlled, the

principles can be harnessed to provide advan-

tages for the printer, such as substrate clean-

ing, film surface treatment and dust control.

Causes of Static

Static electricity is generated by unbalanc-

ing the molecular construction of relatively

nonconductive materials such as plastics

and paper. All matter is composed of single

elementary atoms, or groups of atoms called

molecules. An atom consists of a nucleus

surrounded by one, or many, orbiting elec-

trons, which have a negative charge. The

nucleus consists of positively charged parti-

cles (protons) and neutral particles (neu-

trons). Atoms are most stable when they are

electrically neutral and carry no charge. An

atom in this state requires the number of

orbiting electrons and protons to be equal.

In certain complex molecules, the forces

between the protons and outer electrons are

very weak and electrons may be easily

removed. The loss of any electrons causes

such molecules to become positively

charged, because the number of protons

exceeds the number of electrons. Conversely,

nuclei of certain atoms exert very strong

forces on their electrons and on others in

close proximity. As a result, these nuclei pick

up additional electrons and become charged

negatively because the number of electrons

now exceeds the number of protons. This

exchange of electrons may simply be caused

by contact with a dissimilar material.

The ability of a material to surrender its

electrons or absorb excess electrons is pure-

ly a function of the conductivity of the mate-

rial. For example, in a pure conductor, such

as copper, the molecules offer little resis-

tance to the flow of electrons and any charge

imbalance within the material is soon dissi-

pated. However, in the semiconductor range

of materials, such as some bond papers, the

ability of the atoms to surrender their elec-

trons is relatively high and can be accom-

plished by friction, heat or pressure. With

purely nonconductive materials, such as

plastics, it is extremely easy to disrupt the

molecular construction, causing the material

to charge with the slightest friction, heat or

pressure and, because the material is non-

conductive, the charge remains static.

Static electricity has as its basis an imbal-

ance of electrons in a material. Instead of the

material being electrically neutral in its nor-

mal state, it has either a positive or negative

charge. In other words, the atoms or mole-

cules on its surface have either gained or

lost electrons. The number of electrons that

have been added or removed from a materi-

al’s surface determines the magnitude of the

static charge.

To achieve electrical neutrality, a charged

material exerts a force on other adjacent

materials. This force is known as an electro-

static field. As is the case with magnets, sim-

ilarly charged materials repel each other,

whereas oppositely charged materials

attract each other.

Controlling Static

Three basic methods for controlling static

electricity are:

• antistatic conductive coatings, additives

or sprays;

• grounding of the charged material; and

• cyclic ionization of the air surrounding

the charged material.

Anti-static Coatings. If the surface conductivi-

ty of the processed material can be raised,

then preventing static electricity becomes rel-

atively easy. For example, adding surface

conductivity to plastics will move them up

into the higher conductivity range and pre-

vent the build-up of static electricity that is

caused by friction. This is normally accom-

plished by the use of additives such as mois-

ture and antistatic sprays. The average anti-

static spray is made from a soap-based mate-

rial that has been diluted in a solvent, such as

mild alcohol. A fire retardant is added to com-

bat flammability of the solvent, then pressur-

ized gases are added to form an aerosol can of

antistatic spray. As this spray leaves the noz-

zle of the aerosol can, the propulsion gases,

fire retardant and solvents evaporate a short

time after contact with the nonconductive

material, leaving a conductive coating on the

surface of the material. As long as this coating

is not disturbed, it will be difficult to generate

static electricity in this material.

Grounding. The simplest and oldest method

of removing or neutralizing static electricity

is by a combination of induced ionization

and grounding. These nonpowered (or pas-

sive) systems use conductive bristles placed

in close proximity to the charged material,

inducing an electrostatic field between the

bristle tips and the material. The electrostat-

ic field ionizes the air, which in turn neutral-

izes the static charge on the material.

Such passive devices are relatively inex-

pensive. However, if the static charge is not

sufficiently high, or the bristle tips not suffi-

ciently conductive, the electrostatic field

between the bristle tips and the material

may not form, in which case ionization of the

air cannot occur and the static charge will

not be neutralized.

Tinsel is the most common tool for this

application. However, tinsel is often misused

and, therefore, not successful. For a passive

induction device to be effective, the follow-

ing conditions must be met:

• the tinsel must have a metal core to be

conductive;

• the tinsel must be well-grounded elec-

trically;

• the tinsel must be within 0.25”

(6 mm) of the material to be neutral-

ized; and

• there must be “free air space” under

the material to be neutralized.

In this fashion the tinsel can reduce static

electricity on both sides of the static-laden

material.

86 FLEXOGRAPHY: PRINCIPLES & PRACTICES

PRESSES AND PRESS EQUIPMENT 87

It must be recognized that any passive

induction device, such as tinsel, will never

reduce or neutralize static electricity to the

zero potential level. This limitation is due to

the fact that a threshold or beginning voltage

differential is needed to “start” the process.

Operator Grounding. It is also possible to dis-

turb the molecular construction of the

human body. As strange as this sounds, if an

operator is isolated by standing on a wooden

floor or wearing crepe rubber-soled shoes,

he or she will soon pick up a static charge,

which will create a voltage difference above

ground (zero) voltage. It is possible for an

operator to gain a charge of several hundred

volts each time he or she handles a piece of

charged plastic. As the operator handles

many different pieces, he or she may

become charged to a sufficient voltage to

cause a flashover. The operator may receive

a mild to severe shock, or damage a static-

sensitive device.

This build up of static potential can be pre-

vented by having the operator stand on a

grounded conductive mat or by the use of

commercially available personnel grounding

equipment. Personnel grounding equipment

is important if operators are sitting while

working. Sitting is the best means of isolat-

ing an operator from grounded conductivity;

making them extremely vulnerable to static

discharge.

Machine Grounding. In addition to personnel

grounding equipment, grounding all plant

machinery and related equipment is most

important. Besides the safety factor, a well-

grounded machine will help drain off

extremely high charges of static electricity

from partial conductors. Remember, ground-

ing is only an aid to reducing problems with

static electricity; it is not a solution.

Powered Static Eliminators. Static elimina-

tors are ionizing units that produce both pos-

itive and negative ions. The unbalanced

material attracts the ions so that neutraliza-

tion occurs.

Most powered static neutralizers ionize

the air by placing a high, alternating voltage

(4,000–8,000 volts) on sharp points, in close

proximity to a grounded shield or casing. As

the high-voltage, alternating potential pulses

through the 60-cycle-per-second operation,

the air passing between the sharp points and

the grounded casing is ionized, generating

both positive and negative ions. Since the

United States operates on a 60 cycles per

second voltage, the polarity of the ionization

changes every 1/120 of a second.

Cyclic air ionization is the most widely

used method of static control. It involves

removal of electrons from air molecules, cre-

ating positively charged cations and, con-

versely, adding electrons to form negatively

charged molecules called anions. If the mate-

rial being neutralized is positively charged, it

will immediately attract negative anions from

the static neutralizer, absorbing their free

electrons, while repelling the positive ions.

Conversely, if the material being neutralized

is negatively charged, it will attract the posi-

tive ions and give up the spare electrons,

while repelling the negative ions. When the

material becomes neutralized, there is no

longer an electrostatic attraction and the

material will cease to absorb ions.

An outside source of AC power is used to

operate an ionizing unit. Such systems are

very efficient and can be operated at moder-

ate cost with a long life expectancy.

Radioactive Isotopes. Nuclear-powered equip-

ment may also be used to generate ionized

air for static neutralization. These devices,

have a half-life of only 138 days, continually

lose their strength and must be replaced

annually. They are more expensive and less

effective than electrically powered devices.

These nuclear devices cannot be purchased

and are leased by users. One-year lease costs

are usually more than the purchase price of

comparable electrically powered devices.

CONCLUSION

In order to solve problems related to stat-

ic electricity, certain basic steps must be

taken. The logical approach is to identify the

problem; determine the solution; and then

select the proper equipment to solve the

problem.

To identify the problem, some sort of mea-

suring equipment must be used. For exam-

ple, an electrostatic locator will measure the

amount of static electricity that is present

and identify the polarity as either positive or

negative. Measuring and locating static elec-

tricity will remove the mystery often related

to this phenomenon.

Once the problem is identified, the solu-

tion should be considered next. Can the sta-

tic electricity be controlled by grounding,

induction, ionization or a combination there-

of? In making this decision, keep in mind the

facts mentioned relative to conductivity.

With pure conductors or partial conductors

(such as the human body or some paper),

grounding should be considered. However, if

working with insulators, such as plastics,

ionization must be added.

Choosing Equipment

The most effective neutralizing equipment

is electrically powered. If powered devices

are located where employees may come in

contact with them, they should be mechani-

cally shockproofed to prevent contact with

the “hot” ionizing points.

For explosion-prone environments, explo-

sion-proof induction-type neutralizing equip-

ment should be chosen. Also, a number of

specialized pieces of equipment are avail-

able to the electronic industry to provide sta-

tic-free work areas.

By following the above steps, the risks of

building up dangerously high charges of stat-

ic electricity can be greatly reduced. It is

important to understand that static electrici-

ty cannot be entirely eliminated. In fact, the

term “static eliminator” is definitely mislead-

ing. For example, a charged piece of materi-

al can be neutralized by utilizing a static elim-

inator. However, it does not eliminate static

electricity because, if friction is applied to

the material after being neutralized, static

electricity will again be generated.

88 FLEXOGRAPHY: PRINCIPLES & PRACTICES

PRESSES AND PRESS EQUIPMENT 89

Substrate Cleaning

ust is by far the biggest enemy

of quality printing, especially

in polymer film, paper or cor-

rugated processing operations,

and therefore must be ad-

dressed by press builders and

converters alike.

No dust removal system is absolutely per-

fect. However, if the problem is addressed at

its source, i.e., immediately where dust and

electrostatic charges are produced, it can be

controlled, yielding higher production and

quality. The most effective system for remov-

ing dust from a substrate prior to printing

uses the electrostatic repulsion principle as

explained in the preceding section.

The most advanced ionic cleaning systems

involve a corona field formed between two

oppositely charged electrodes in a quartz

enclosure. The substrate to be cleaned is

passed through this corona field, which is

generated using an alternating high voltage

(15,000 volts) at high frequency (5,000–7,000

cycles/sec).

At peak voltage a corona field is built up

between the two electrodes (+/–) and every-

thing within the corona field (air, substrate,

dust) becomes conductive. When this hap-

pens, electrons begin to flow between the

two electrodes. As the substrate is passed

between the electrodes, the surface of the

substrate is charged positively on the side

facing the negative electrode and is charged

negatively on the side facing the positive

electrode. Any dust particles on the surface

of the substrate will also be charged in a sim-

ilar fashion Figure

As the polarity of the electrodes change,

the corona field breaks down. The air

between the surface of the substrate and the

adjacent electrode functions as insulation.

Powerful electrostatic fields are formed,

which are charged positive above the sheet

to be cleaned and negative on the underside.

The dust particles now show an opposite

polar charge, are repelled by the substrate,

float into the positive field and are sucked

away by a fan.

+ + + + + + + + + + +

– – – – – – – – – – –

+ + + + + + + + + + +

– – – – – – – – – – –

+ + + + + + + + + + +

– – – – – – – – – – –

–

+ + + + + + + + + + +

– – – – – – – – – – –

–

+ + + + + + + + + + +

– – – – – – – – – – –

–

+ + + + + + + + + + +

– – – – – – – – – – –

+ + + + + + + + + + +

– – – – – – – – – – –

- - - Electrode - - -

Substrate

Ionized Air

+ + Dust + +

+ + + Electrode + + +

- - - Electrode - - -

Substrate

Ionized Air

+ + + Electrode + + +

0v Electrode 0v

Substrate

+ + Dust + +

0v Electrode 0v

In electrostatic cleaning,

as the substrate is

passed between the

electrodes, the surface

of the substrate as well

as the dust particles are

charged (positively on

the side facing the

negative electrode,

negatively on the side

facing the positive

electrode.) This causes

dust particles having an

opposite charge to be

repelled and sucked

away by a fan.

90 FLEXOGRAPHY: PRINCIPLES & PRACTICES

After reversing the polarity of the elec-

trodes, the corona field forms again as soon

as maximum current is reached. With the

repeated polarity change and subsequent

breakdown of the corona field, the cleaning

process takes place again. Each change of

polarity, which occurs upwards of 10,000

times per second, results in a cleaning action.

FILM TREATING

A number of the flexible packaging materi-

als, particularly polyethylene and polypropy-

lene, need to be treated prior to subsequent

printing or coating operations in order to

make them more wettable, that is, more

receptive to accepting printing inks, coating

and adhesives. Corona discharge treating of

the substrate is one means of making the sur-

face more polar, hence more wettable.

Corona Discharge

Corona discharge is a unique means of

applying a concentrated electrical discharge

to the surface of a moving web. It is accom-

plished by passing a moving web over a spe-

cial dielectric-covered treating roll and apply-

ing a source of high voltage, high frequency

power to an electrode properly spaced over

the surface of the traveling web. The resultant

voltage gradient breaks down the air into a

gaseous conductor, and the corona and ozone

that are generated make the substrate surface

more polar, and more wettable.

Typical Film Treating Applications

Film treating stations are specially designed

and engineered enclosures that house the

treating electrode and roll assemblies. They

have access doors for web threading and rou-

tine servicing, inspection windows to observe

corona discharge and hoods, and extraction

ports for ozone removal. Each station is tai-

lored to the particular application and sized to

match line speed and web width. Stations can

be specified to treat one or both sides of the

web. Station enclosures are normally of a

steel frame and panel construction. Ferrous

parts are primed and finish-coated with corro-

sion-resistant paint. Access doors have

Plexiglas inspection windows. The doors are

electrically interlocked to prevent corona dis-

charge from operating when opened. Ozone

exhaust openings are normally located and

cut to size at the installation site, but this can

also be done during fabrication of the unit.

Electrodes are wired to a porcelain high-

voltage insulator. Stations have pneumatical-

ly actuated electrode assemblies, interlocked

to prevent treating operation when the elec-

trode assembly is retracted. Treating rolls are

equipped with adjustable electronic zero-

speed control switches to prevent treating

operation unless the roll is turning.

Foil and Conductive Substrates. Foil and con-

ductive substrate-treating stations may be

single-sided or double-sided stations, with

hard chromium-plated ground rolls and

dielectric-covered rotating electrode rolls.

They will treat web widths up to 100" at line

speeds up to 1,000 fpm (Figure

Split-Box Film Treating Station. These sta-

tions have drop through automatic web

thread-up and single- or double-sided sta-

tions for treating variable-width substrates.

They are usually available with 4" diameter

rolls and will treat web widths up to 98" at

speeds up to 250 fpm. (Figure

Adjustable Shoe Electrode Station. These sta-

tions are also single- and double-sided. They

treat variable widths up to 144" at line

speeds up to 1,500 fpm. They are usually

available with 6" to 24" diameter rolls

(Figure

Pressurized Film-Treating Station. Specially

engineered, the pressurized film-treating sta-

tion has single- and double-sided stations for

operation in hazardous atmospheres. It can

be obtained with a pressurized treating sta-

tion and high voltage transformer enclosure

and with a pressurized remote-control sta-

tion (Figure

PRESSES AND PRESS EQUIPMENT 91

POWDER SPRAY SYSTEMS

Powder spray systems are used to evenly

distribute micron-sized particles onto the

surface of the moving web. The particle

material may be starch, to promote ink dry-

ing or to prevent ink offset and blocking in

the rewound roll; or in a laminating process,

it may be a heat-set powder adhesive. The

system uses the principles of electrostatic

attraction and repulsion to control the distri-

bution of the particles.

Electrostatic Powder Spray

The electrostatic system feeds the micron-

sized dry powder particles from a hopper to

the surface of a micro-etched chromium

plated roll. The rotating speed of the roll

controls the feed rate of the particles. The

particles adhere to the surface of the roll

until they enter an electrostatic field created

by a high voltage discharge tube, at which

point they become ionized. The web, passing

in close proximity, is charged with the oppo-

site polarity to the powder particles, thereby

attracting them. The electrostatic dispersal

of the particles tends to space them very

evenly over the surface of the web, which

eliminates pyramiding and with the electro-

static bond, prevents particle drifting.

Dust Control

Within the electrostatic spray unit there

are twin air curtains to envelop the spray

and prevent excess floating powder.

Downstream of the coating station is an

extraction hood to collect any particles that

Rotating

Electrode

Web

Roll Type

Electrodes

Adjustable

Shoe

Electrode

Rotating

Electrode

Rotating

Electrode

Web

Adjustable

Shoe

Electrode

Idle

Roll

Idle

Roll

5^ 5*

Rotating

Electrode

Rotating

Electrode

Web

Shoe Type

Electrode

Shoe Type

Electrode

Idle Roll

Rotating

Electrode

Web

Adjustable

Shoe

Electrode

A foil and conductive

substrate-treating

station may be single-

or double-sided, and is

capable of handling

webs widths up to 100"

at line speeds up to

1,000 fpm.

A split box film-treating

station treats variable

width substrates.

Adjustable-shoe

electrode stations may

be single- or double-

sided stations capable

of handling widths up

to 144".

Pressurized film-

treating stations are

specially engineered for

hazardous atmospheres.

This six-color central

inpression press has

been modified for

laminating after

printing.

92 FLEXOGRAPHY: PRINCIPLES & PRACTICES

may become airborne. These particles are

drawn to vacuum plenums on each side of

the hood and transported to a collection fil-

ter bag. The dusting ability of the electrosta-

tic sprayer is not affected and the system

helps to assure a cleaner press and cleaner

plant air.

IN-LINE LAMINATING

Film laminating has had a growth curve

parallel to flexography in flexible packaging

and has usually been performed by convert-

ers who were already flexographic printers.

Competition forced converters who did not

have the capital or market volume for sepa-

rate out-of-line techniques to adapt existing

presses to include a lamination section.

The first development in this modification

was to add a thermal combine (heat and pres-

sure) unit to the exit end of the press and

combine two Saran-coated cellophane webs.

As more types of film entered the flexible

packaging field, and as increased production

speeds became necessary, solvent-based

adhesives were used for film laminations,

both in-line and off-line. For in-line opera-

tions, the adhesives were applied by the last

printing station of the press, then dried in the

drying tunnel before being combined with the

second web.

Modified Press for Laminating

Figure

shows a six-color flexo press

modified for in-line laminations. This arrange-

ment has the disadvantage of slow speed

operation. In order to eliminate ink blistering,

it is necessary to slow the press to speeds that

allow all the ink to dry before applying the

adhesive in the last printing station.

Should the converter wish to modify an

existing press so that in-line laminations can

be performed, there are a number of steps

that must be taken. They will be addressed in

the following four sections.

Space. Approximately 12" of space at the

rewind end of the press is necessary to pro-

vide for installing the second unwind stand.

The unwind can be any suitable type, but it is

preferable for it to be the same as the exist-

ing unwind. This match-up permits running

roll-for-roll at both unwinds and minimizing

mid roll splices in the laminated material.

Structure. An overhead structure with idler

rolls is required to transport the web from the

second unwind to the laminating nip. Since the

web passes above the rewind, the structure

must be high enough so as not to interfere with

the personnel servicing the rewind or with the

rotation of the rewind if it is the turret type.

The idlers should be spaced not more than 4'

apart and preferably grooved to prevent air

from getting between the web and idler rolls.

Laminator

Lamination

Unwind

Print and

Lamination

Rewind

Stock

Unwind

Central Impression

Press

Adhesive

Applicator