Coatings Technology Handbook Episode 1 Part 6 pptx

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Coatings Technology Handbook, Third Edition

19.5 Die Adjustment as It Relates to Manifold Design

Precise coating weight control depends on the stability of the total system and on operator experience.
Die performance will be at its best when a balance of pressure and flow is reached at the lip area. This
balance is hard to define; changes in materials and rate will affect it. We can best describe this through
the voice of an operator when he talks about the die being “jumpy or nervous” in one case and “lazy or
unresponsive” in the other. In the case of the “jumpy” adjusting die, the pressure balance is too high;
with the “lazy” one, pressure is too low. We will refer to this performance parameter as the operating
window. When a die must be profiled excessively to improve end flow, the operating window will vary
across the die; therefore, the die adjusting characteristics will differ (e.g., jumpy center, lazy ends). This
effect is magnified in automatic control. When a die is set up at 0.010 in. opening in the center and 0.020
in. at ends to achieve balanced flow, a 3% change in opening at the ends is 0.0006 in., and in the center
it is a 0.0003 in. change. As we develop more dynamic computer programs to respond faster or to
predetermine a target point, uniform die response becomes very important.

19.6 Coat Weight Adjustment

Base coat weight is controlled by pump and line speed. Transverse area coat weight is a function of the
lip gap adjustment. It is important to remember that the pump will always deliver a given amount of
fluid to the web. When the operator adjusts the lip, material is not taken away — it is only moved from
one place to another. This difference between roll or knife coating and slot die coating is often overlooked
by the operator.

19.7 Adhesive Selection

Adhesives formulated for roll coating, in some cases, are not compatible with slot die heads. This is
because roll coaters are high shear devices, whereas slot dies develop low shear. Any fluid that requires
very high shear to create smoothing will not perform well on a low shear coating head. The shearing
device or lip face can be modified to change shear level in two ways: changing the face-to-web gap (see
the shear level, as frequent changes of adhesive and formulation are common.

19.8 Die Steel and Piping Selection

Recent developments and reformulations of adhesives have led to highly corrosive or aggressive fluids.
The die steel or plating must be carefully selected to ensure chemical compatibility, machinability, and
reasonable cost. We find the majority of problems centering around highly acidic adhesives. A pH level
of 4 will severely attack a chrome-plated die and render it unusable in a matter of 2 to 3 months. Several
stainless steels offer reasonable prices and a highly corrosion-resistant makeup.

19.9 Proximity versus Contact Coating

Tr aditional die designs require being pushed into the backup roll to produce even coating distribution
(contact coating). Utilizing modern manifold technology, we can reduce the roll contact pressure signif-
icantly and, therefore, reduce roll damage and lip wear. Most important, when this application technique
is chosen, the flex lip concept can be used.
In any system, it is of utmost importance to have inserts that are quickly replaceable, a lip step
differential that can be easily changed, and the capability to increase the shear without having the infeed

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Figure 19.6) and changing the face length (Figure 19.7). Provision should be made for ease of changing
lip rotate into and make contact with the web and roll (Figure 19.8).

Slot Die Coating for Low Viscosity Fluids

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2. The angle of contact depends on lip profile, die-to-roll gap, roll hardness, roll diameter, lip step
difference, lip profile, and material spreading tendency. It is impossible to predict this angle without
all these factors and in-depth experience.
3. Reduced contact pressure is necessary to reduce roll and die lip damage.
4. Because roll deflection is very hard and expensive to eliminate, a die that can be deflected or bent
to conform to roll variance is required if roll deflection is a problem. It is common to use a steel
roll backing up the elastomer roll to lessen the deflection problem, and with heated adhesives to
help cool the elastomer roll.
5.
for the best and most reproducible coating surface.

19.10.2 Lip Profiling

Lip shape and the relative position of the lead and trailing wipers to each other are of utmost importance
in today’s coating technology.
In some cases, using today’s high technology coatings, a uniform and proper level of wiping action is
required to produce satisfactory coating. As a result of the shear thinning characteristics in today’s more
difficult adhesives, proper profiling and angle to attack will produce a smooth and even coating. Any
variance in lip profile will create differential wiping, causing an uneven appearance. Because, with modern
coating heads, uniform distribution is not a function of the lip face, we can confine the lip face to a
single function — namely, creating a proper environment at lay-down.
No hard data are available on lip face design as the interrelation between roll diameter, roll hardness,
line speed, substrate, lip design, and adhesive viscosity characteristics come into play. There seem to be
two technical camps. One group adheres to the flat, fixed wiping lip, with a differential step between the

infeed lip and the wiping, or outfeed, lip. The other group tends to favor a rotating or fixed rod in the
wiping area. This rod style design is as old as die coating, and several patents have been issued.

19.10.3 Die Support Design and Operation

The interrelationship of die and mounting require that the two units act as one, both being equally
important. Absolutely necessary to the successful operation of a slot coating head are the items in the
Application and utilization of existing equipment designs will determine the best die-to-roll position.
Operator convenience and the ability to view the point of laydown are very important. It is our opinion
The support bed must be completely rigid and vibration-free. Any sag or bow in the die will create
problems in the die-to-roll alignment. For this reason, we do not recommend that the die be supported
from its ends. On heated dies, the designer must also allow for thermal growth while maintaining
die straightness.

19.10.4 Support and Adjustment System Design Specifications

Item 1 in Figure 19.10

: The die should be supported on precision-ground pads, with die straightness
(contouring) adjustments for roll warp correction. On heated dies, insulation should be provided
between die frame, and allowance made for die growth.

Item 2 in Figure 19.10

: A heavy-duty rectangular tubing cross frame should be used for maintaining
straightness during operation and adjustment.

Item 3 in Figure 19.10

: An “X” in/out adjustment utilizing machine tool slideways, with fast air actuation

and hydraulic soft stop cushions is used. A micro stop correction adjustment with dial indicator
or LVDT should be provided for each end.

Item 4 in Figure 19.10

: This “Y” adjustment is provided for roll axis position alignment.

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Angle of attack of the die to roll must be pivoted around the pivot point indicated in Figure 19.8
series of design specifications indicated in Figure 19.10 and explained in Section 19.9.4.
that mounting position A in Figure 19.9 is the most advantageous, and position B is the least.

Slot Die Coating for Low Viscosity Fluids

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arrangement, with indicator markings in degrees. Note that the angle of attack movement is
centered at the die lip (coating contact) point.

19.10.5 Die-to-Roll Positioning

Flexibility and repeatability are primary requirements. Difficult adhesives, speeds, and substrates will
require different setup positions, and the ability to vary the die-to-web position easily with exact repeat-
ability is of prime importance. The support frame must allow in/out movement and angle of attack
adjustment (see Figure 19.10).
In/out adjustment will have two functions: (a) fast movement with 5 to 8 in. (130 to 200 mm) of
travel, allowing lip cleaning; and (b) micro in/out to fine-tune roll-to-lot gap distance. This adjustment

should allow differential end-to-end gapping.
The in/out adjustment must be on a straight line, always moving directly at the roll centerline. (Pivot-
style mountings are not recommended.)

19.10.6 Angle of Attack Position Adjustment

To create different shear levels for proper film forming at varying speeds, the angle of attack must be
adjustable. This movement should be accurate and smooth, and movement should cover about

±

5

°

.
It is important that when one positioning point is adjusted, the other roll-to-die relationships remain

19.10.7 Lip Opening Setup

Depending on materials and laydown, a 0.008 to 0.012 in. even lip opening gap (Figure 19.11) should
be set before start-up and adjusted for proper flow and laydown after start-up.
The lip opening setting adjusts coat weight thickness, not die-to-roll gap. Roll coaters will have difficulty
with this, as they have traditionally used roll-to-roll gap as the coat weight adjustment.

FIGURE 19.11

Lip opening setup.
lip opening

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Item 5 in Figure 19.10: This is an angle of attack positioning adjusted through a rack-and-pinion gear
unaltered. Angle of attack adjustment must pivot about the point indicated in Figure 19.8.

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Coatings Technology Handbook, Third Edition

19.10.8 Die-to-Roll Gap Setup

The distance from die to roll or substrate is, in general, determined by web thickness and the viscosity
of the fluid to be applied. The more clearance that can be maintained, the less damage there may be due
to positioning or start-up mistakes.
We suggest, as a rule of thumb, that a clearance equal to the substrate thickness be set between
substrate and infeed lip face. This distance may be less for materials of very low viscosity or for hard
roll to lip face.

19.11 Backup Roll Design

Processors and equipment manufacturers alike would like to utilize steel backup rolls to improve
runout (T.I.R.) and to mitigate heat transfer problems. In some cases on lab or narrow production
systems, steel rolls have been successful. In most cases, however, steel rolls are not as forgiving as an
elastomer roll and therefore have not yet been accepted for production. We expect this to change as
the technology matures.
Elastomer rolls have improved over the past several years to allow the precise roll-to-lip conformation
absolutely required for proximity coating. When specifying an elastomer roll, the following items must
be carefully considered:

•Runout tolerance
•Release characteristics
•Heat transfer
•Hardness
•Hardness uniformity
•Roll deformation (bow)
•Resistance to attack by the coating or cleaning agent
We see the use of rolls covered with urethane or Viton being most evident with diameters of around
300 mm and hardness of up to 90 durometer, Shore A. Runout tolerances of 0.0005 in. and better are
being achieved.
The elastomer roll will be deformed by a given width web, and rolls must be provided to match web
width changes. Spare rolls are also necessary, as damage often occurs.

19.12 Automatic Control

19.12.1 Die Control

All commercially acceptable automatic die adjustment systems available today use flexible lip and heated
does not seem to be greatly affected. The greatest confusion surrounds the effect of pure mechanical
response time and how it relates to process analysis and its relation to response. All systems to date simply
read the variation from target and make a corrective response. Polymer lot-to-lot differences, temperature
changes, in-plant drafts, and many other factors that affect gauge have made it impossible to anticipate
flow changes. Anticipation-based programs can be used in product changes, however, if known effects
will happen over a relatively fixed period or on start-up.
During a production run, if a variance is seen, make sure that it is not a short-term effect, gone in
the time it would take to make a change. We also may want to determine the variance trend. Only after
careful analysis of the problem can we make a die adjustment. The time from discovery until an adjust-
ment takes effect varies from line to line, however start-up to

±

5% control, assuming the total system
has reached some stability, will be 10 to 20 min, and

±

3% control in 15 to 30 min.

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to smooth materials. Make sure the gap is from web to lip face, as shown earlier (Figure 19.6), not from
bolt arrangements (see Figure 19.12). Minor disagreements exist on details, but total overall performance

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Coatings Technology Handbook, Third Edition

Thickness variations are converted to lip opening correction by increasing or decreasing power to the
individual lip bolt control blocks to trim variations to a minimum.
The key to the transverse thickness control is a microprocessor-based controller that is tied into the
conventional computer control system.
On ambient operation dies, care must be taken to isolate the heat from the Autoflex bolts from the
die body.

19.12.2 Die-to-Roll Position Adjustment System

The ability to repeat the original roll-to-die setup position is critical during start-ups and normal web
splice coating interruption.

During operation, minor changes in die position may have to be made to accommodate roll expansion,
changes in adhesive viscosity and smoothability, and substrate thickness variance. An automatic posi-
tioning device is available that will allow continuous adjustment, if necessary, of the web to the lip face.
This is accomplished through a device similar to the Autoflex die bolt adjustment system. A heating and
cooling device is installed in the manual adjustment system (U.S. Patent 3,940,221) for die-to-roll gap
setup. Heating or cooling of this device will expand or contract the steel block and increase or decrease
the die-to-roll gap. A usable method for monitoring smoothing must be employed and interfaced with
the Autoflex computer.

19.13 Deckling

Deckling may be necessary to reduce die width or to make stripe coatings. Be careful when attempting
this, to make sure that shim materials are soft. We recommend Teflon/filled, Teflon/aluminum, foil/
aluminum shim stock, or soft brass. For room-temperature applications, an adhesive/foam/adhesive
mounting tape works very well.
does not clamp into the lip and can be changed very quickly.
If excessive force is applied when the deckle is clamped into the lip, the lip will distort, causing lip
wear or uneven coating at this point (Figure 19.14B).
Deckling or stripe coating cannot be used in a system featuring the rotating rod lip design.

19.13.1 Air Entrapment behind Deckling

When the die ends are deckled in, it is common for air to become trapped in this area. This air is slowly
released, causing voids in the coating at the edges. A purge port with shutoff valve should be installed at
the die ends to eliminate this problem.

19.14 Die Cleanup

In most cases, it is important to change coatings or coating formulation frequently. Therefore, it is
necessary to be able either to purge out the system or to clean the die completely. This holds true for the

complete system, including pump filters and piping.
Purging is the easiest and most common method; but extreme care is necessary to streamline all flow
areas to eliminate dead areas.
The opening and cleaning of a die can be an easy 30 min experience or a 3 to 4 day nightmare. Slot
die designs differ greatly; some are simple two-piece designs, while others have complex assemblies.
It is common to have a dual pumping and piping system, allowing quick changeover from one coating
to the next, cleanup then taking place after the line is up and running.

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In many applications, a rake-type device may be used for stripe coating (Figure 19.14A). This device

20

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20

Extrusion Coating with
Acid Copolymers and

Lonomers

20.1 Product Considerations

20-

1
20.2 End-Use Considerations

20-

3

20.3 Processing Conditions

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5

20.1 Product Considerations

Acid copolymers and ionomers are high-performance resins that offer adhesion, heat seal, and barrier
acrylic and methacrylic acid copolymers, the two types of acid copolymer commercially available in the
United States at this time. The presence of the methyl side group in the methacrylic acid copolymers
results in some subtle differences between the two resin types, but they can be regarded as equivalent
after allowing for the difference in molecular weight of the comonomers. For example, a 10 wt% acrylic
acid copolymer is equivalent to a 12 wt% methacrylic acid copolymer in carboxyl group content.
group with either sodium or zinc ions. Because the neutralization reaction results in a substantial increase
in melt viscosity, it is commonly referred to as ionic cross-linking.
In both acid copolymers and ionomers, the melt and solid state properties are strongly influenced by
are almost 10 times stronger than the intramolecular forces in the nonpolar polyethylenes.
The ionomers are distinguished by the combination of hydrogen bonding and interchain ionic forces
perhaps an order of magnitude stronger than the hydrogen bonds. As a consequence, the ionomers have
a wide spectrum of melt and solid state properties, including better hot tack and grease resistance than
acid copolymers of equivalent acid content.
With the acid copolymers, melt index and acid content are the major variables available to the resin
producer. Because melt index is a measure of melt viscosity, it is related primarily to the processing
characteristics of the resin. The resins now used for extrusion coating applications fall in the 5 to 15 melt
index range to accommodate a broad field of processing needs.

Resins with acid contents of 3 to 15% are currently available on the market. The effects of increasing
acid content are as follows:
• Better foil adhesion
• Better hot tack

Donald L. Brebner

E. I. du Pont de Nemours &
Company

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Foil Adhesion • Heat Seal Characteristics
Melt Temperatures • Other Considerations
properties markedly superior to those of conventional polyethylenes. Figure 20.1 shows the structure of
Ionomers (Figure 20.2) are derived from acid copolymers by partial neutralization of the carboxyl
intramolecular hydrogen bonding, as illustrated in Figure 20.3. The forces involved in hydrogen bonding

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Coatings Technology Handbook, Third Edition

Hot tack strength is the ability of a heat seal to remain together when a force is applied while it is still
in the molten state. This is a critical property in vertical form-fill-seal applications, in which the product
is loaded immediately after the seal is made. It is also critical in any high speed packaging operation in
which the package is exposed to some form of abuse before the seal has cooled.
One method of measuring hot tack strength is the Du Pont spring test. A series of springs of different
thicknesses and widths at the narrowest point provides varying levels of spring tension (Figure 20.5).

pressure of 40 psi. The 3 sec dwell time allows an accurate measurement of the interfacial seal temperature
by using a very fine thermocouple hooked up to a rapid response recorder.
When the heat seal bars are released, the springs apply an instantaneous force to the seal. The separation
of the 1 in. wide seal is measured to the nearest tenth of an inch. The results are plotted as the force
required to obtain 20% seal separation as a function of temperature.
content in comparison with LDPE. LDPE, a completely nonpolar material, has very low hot tack strength.

FIGURE 20.4

Heat seal strength versus bar temperature (1 mil coatings on 30 lb kraft paper).

FIGURE 20.5

Spring for Du Pont hot tack tester.
2000
1500
1000
500
Seal Separation Force, gms/in
200 220 240 260 280
9% Acid Ionomer
9% Acid Copolymers
LDPE
Seal Interface Temperature, °F
8"
1"
3"

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Figure 20.6 shows how the spring is located inside the sample. The sample is heat sealed for 3 sec at a
Figure 20.7 shows the hot tack characteristics of an ionomer and acid copolymers of equivalent acid

21

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21

Porous Roll Coater

21.1 Introduction

21-

1
21.2 Extrusion Porous Roll System

21-

1

21.1 Introduction

Recent progress had been made in silicone-coated products that are curable by electron beam (EB) and
products, in which the release levels range between 25 and 50 g per 25 mm wide strip, typical viscosities
of the materials tested are in the range of 500 to 1000 cp at room temperature. These silicone products
are manufactured by Th. Goldschmidt, in West Germany, and Lord Corporation, in Pennsylvania, and
other companies. The UV products are either one-part premixed/ready-to-use materials, or two-com-
ponent products that require nitrogen inerting to overcome surface smear and to achieve a complete

cure at web speeds up to 30 m/min per each UV lamp. A schematic diagram of the nitrogen inerting
lamp). The EB products are also premixed/ready-to-use, and as with the UV chemistries, they also require
nitrogen inerting to obtain a full cure at typical web speeds of 200 m/min. The energy dosage is

21.2 Extrusion Porous Roll System

21.2.1 Development

One recently developed extrusion roll coating system incorporates a slot nozzle coating head, located
transferred to an adjacent “applicating roll,” which in turn, contacts the coating web for fluid transfer.
The relative speed ratio between the “nozzle roll” and the “applicating roll” is approximately 1:30.
Reports on trials have noted that the curable coatings possess poor shear properties and that the speed
ratio between the rolls is somewhat dependent on this limitation. The shear properties can be improved
by heating the rolls, but this method is not always productive, with the result that the coated web has
the appearance of small blotches, 1 to 2 mm or larger, or lateral bands (chatter) of coating, rather than
a smooth, uniform coating. Likewise, conventional roll coaters that contain multiple rolls experience a
and dilatant characteristics. Viscosity of dilatant fluids increases with increasing shear rate, as shown in
surface conditions, silicone product properties, and the method of applications.
Most coating processes are able to apply these coatings between 1.3 to 1.6 g/m

2

within industry
standards; however, the type of web material greatly influences the final coating weight. Our research to
reexamine the current methods for applying curable silicones enabled us to develop an alternative method

Frederic S. McIntyre

Acumeter Laboratories, Inc.

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Development • Details and Disadvantages
ultraviolet (UV). Advantages of UV and EB converting processes are shown in Table 21.1. Of these new
process is shown in Figure 21.1. The UV lamps used for curing are rated at 300 W/in. (120 W/cm per
approximately 2 megarads (Mrad). A schematic diagram of an EB processor is shown in Figure 21.2.
adjacent to a slow speed “nozzle roll” (see Figure 21.3). The fluid is coated onto the “nozzle roll” and
similar effect (see Figure 21.4). This phenomenon is associated with fluids that have poor flow properties
Figure 21.5. The actual coat weight applied in either case is influenced by the web substrate material,

Porous Roll Coater

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FIGURE 21.6

Porous roll coater.

FIGURE 21.7

Diagram of a porous roll.

FIGURE 21.8

Rotary screen printer.
Web
Laminating
Roll

Applicating
Roll
Web Reference Pickup
to Synchronize Pump
Speed to Web Speed
3-Way Valve
Digital
Pump
Drive
Filter
Positive Displacement
Metering Pump
Supply Feed
Return Feed
Rotary Union
Porous Roll
Hopper
Reservoir Cavity
Outer Wall
Reservoir
Cavity
Inner Supply Roll
Single Supply Port
and Rotary Union
Porous Stainless Steel
Sintered Metal Outer Shell
Surface Preparation
which Determines
Application Pattern
End Cap

Single Width
Rotary Screen Cylinder
Interior Doctor Blade
Printing
Fluid Ink

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Coatings Technology Handbook, Third Edition

porous roll having larger openings, depending on flow properties. The larger porous openings will
minimize the fluid backpressure and allow for consistent coat weights at various machine speeds.
The porous roll surface can be sealed for printing of fluids in patterns, as shown in Figure 21.10. This
means that special coating patterns required in flexible packaging products, business forms, envelopes,
tapes, and labels can utilize curable silicone coatings in the final converting process, rather than having
pre-silicone-printed web materials.
The porous roll system can also be configured to handle multiple coating materials within the same
within which the multiple fluids are supplied. This feature permits the converter to coat different materials
simultaneously, yet from the same applicator. Special tape products that require different release levels
on the same web material can utilize this concept. For example, a pattern of 25 g/25 mm release can be
applied on the left-hand side of the sheet, whereas a 100 g release coating can be applied in the center
or adjacent location on the same sheet. Products such as double-sided, release-coated webs used in
transfer tapes can be coated easily by utilizing two separate porous roll coating systems, located on either

FIGURE 21.9

Porous roll applicator porosity.

FIGURE 21.10

Pattern printing with porous roll.
Standard Shell Porosity Greater Porosity Shell
Single Width
Multiple Width

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© 2006 by Taylor & Francis Group, LLC
applicator. A cross section of the applicator is illustrated (Figure 21.11) to show the different chambers

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Coatings Technology Handbook, Third Edition

FIGURE 21.13

Application of two-component silicone system.
Filter
Positive
Displacement
Metering Pump
(Single
Discharge)
Positive

Displacement
Metering Pump
(Single
Discharge)
Supply A
Supply B
Hopper
Filter
Digital
Pump Drive
Digital
Pump Drive
Porous Roll A
Porous Roll B
Rotary Union
Applicating Roll
Web Reference Pickup to
Synchronize Pump Speeds
to Web Speed
Laminating Roll
3-Way
Valve
3-Way
Valve
Web
Return A
Return B
Material A
Hopper
Material B

Component A
Component B

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Porous Roll Coater

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-9

FIGURE 21.14

Schematic diagram of a porous roll laboratory coater.
Applicator Manifold
Temperature Control
Applicator Nozzle
Temperature Control
Premelter (100 cc)
Quick Removal Mount
for Premelter
Manifold and Metering
Pump Assembly
Poppet Valve
Web
8.5" (21.3 cm) width max.
Unwind Roll
(Laminate Web)
8" (20.3 cm) dia. max.

Laminating Web
Wide Band Extrusion Nozzle
1" (2.54 cm) min. to 6" (15.2 cm) Std.
for Both Paper and Film Coating
Web Positioning Mechanisms
for Both Paper and Film Coating
S Loop Positive Web Drive Roll
Variable speeds up to 38 fpm (11.6 mpm)
Rewind Roll
8" (20.3 cm ) dia. max.
Unwind Roll
(Web to be coated)
8" (20.3 cm ) dia. max.
Hopper Blanket
Temperature Control

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Coatings Technology Handbook, Third Edition

FIGURE 21.15

A coating line with a porous roll coater.
Coating Applicator, Hot Melt/eb Curables
(a) Extrusion Coating (Paper/Film)

(b) Coating (Silicone)
Dual Unwind Module Electron Beam
Processor
Turn-bar
Module
Coating/Laminating
Module
Duplex Slitter
Rewind Module
Web Edge Guide (typ)
Laminating Roll
Chill Roll
Coating Applicator, Hot Melt
Extrusion Coating (Paper/Film)

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Porous Roll Coater

21

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FIGURE 21.16

Label stock manufacturing line.
Refrigeration Unit
for Hot Melt and
U V Chill Rolls

U V Blower Module
U V Module
Control Console
U V Silicone
Delivery System
U V Power Supply
Corona Power Supply
HMHT-IMP
Hot Melt Adhesive
Delivery System
Dual Turret
Rewind/Slitter
Module
Hot Melt
Control
Console
CL-300 Series
Coater Laminator (171 mm–340 mm)
with Web Drive Controls
Turnbar Module
U V Silicone Coating Module
with Edge Guide Applicator,
Chill Roll and U V Lamps
Corona
Treatment Module

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22

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22

Rotary Screen Coating

22.1

22.2 Equipment

22-

1
22.3 Products

22-

1

22.4 Advantages

22-

4

22.1 Introduction

Not long after the introduction of multicolor printing machines, the one-color printing unit was also
introduced, which through the years has found its way to a wide range of application areas such as wall

cover printing, production of hard floor covering, technical coatings, artificial leather production, and
last but not least, as a one-color printing machine.

22.2 Equipment

•The screen, which is a seamless, perforated, nickel sleeve. The degree of perforation is expressed
in the so-called mesh number, indicating the number of holes per linear inch.
•The squeegee, which is mounted in the screen and serves as the supply and distribution pipe of
the paste. The squeegee blade, which is mounted to this pipe, pushes the paste out through the
wall of the screen.
•The whisper blade smooths the applied coating layer.
The amount of coating to be applied is determined by four factors:
•The choice of mesh number
•The squeegee pressure: that is, the angle formed between squeegee blade and screen (The smaller
this angle, the higher the add-on.)
•The viscosity of the paste
•The squeegee setting with regard to the counter-pressure roller

22.3 Products

The coatings that can be applied by rotary screen are discussed in Sections 22.3.1 through 22.3.4.

F. A. Goossens

Stork Brabant

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Pattern-Type Coatings • Dot Coating • Overall Paste Coatings •
Introduction 22-1

Foam Coatings
Screen coating equipment (Figure 22.1) consists of the following: