Yam, Kit L. (ed.). The Wiley encyclopedia of packaging technology

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or binding) mounted over multiple-speed combining

conveyors.

With new computer-controlled, low-pressure techni-

ques, however, nonround shapes can be conveyed at

high speed by photoelectric monitoring of the gaps be-

tween the containers at the output end of the station.

Chain speeds are adjusted automatically to maintain

the desired gap between the containers and the optimum

single-ﬁle exit rate. In addition to being much more

tolerant of nonround container shapes, this method is

signiﬁcantly quieter and assures gentler handling of less-

sturdy containers. Care must be taken in using this

technique, because it will work only for a speciﬁc range

of nonround containers.

SYSTEM DESIGN

The following factors affect the type and design of a

conveyor system:

1. Input or package material, shape, size, weight, and

center of gravity.

2. The conveyor system’s speed of operation.

3. The space available and the production line layout

and ﬂow.

4. The best location for the major pieces of equipment

and their interrelationships.

5. The location points of supply for the system.

6. The routing of ﬁnished products to warehouse and/

or marketplace.

7. The production volume needed by the marketing

department (present and future needs).

8. The cost justiﬁcation for the system.

9. The probable return on the investment.

10. Locating points of labor needs and the most efﬁ-

cient use of the labor supply.

11. Access routes for primary and secondary packaging

supplies, labeling, and maintenance.

12. The power, air, and/or hydraulic services that are

available for systems operation.

13. The logic requirements of the electrical power and

control system.

14. The systems basic pacing factors—whether the

design is based on maximum process speed or on

the projected sales volume.

Proﬁts of successful consumer products companies are

heavily inﬂuenced by the proper design and installation

of conveyors in their packaging lines.

Special thanks to the following manufacturers for

their input and materials. They have a wealth of

knowledge, experience, and products.

uni-chains Manufactur-

ing, Inc.

Tel: (610) 743-6964, (800)

937-2864,

Rexnord

2000 Sam Rittenburg

Boulevard, Suite 2011

Charleston, SC 29407 USA

Fax: (610) 372-3590

Holli Musante

e-mail: hmu@unichains.

com

Web site: http://

www.unichains.com

Rick Corlett Tel. (262) 376-

4678

Phone: 843-852-3456

Fax: 843-852-3471

Web site: http://

www.rexnord.com

BIBLIOGRAPHY

General References

Conveyor Equipment Manufacturer’s Association (CEMA) [9323

Hungerford Drive, 6 Rockville, MD, 20850, telephone (301)

738–2448], http://www.cemanet.org/publications/index.html.

ANSI/PMMI B155.1-2006. American National Standard for

Packaging Machinery and Packaging Related Converting Ma-

chinery—Safety Requirements for Construction, Care, and

Use. ANSI, American National Standards Institute, Inc.,

1430 Broadway, New York, NY, 10018. Harmonized with

ISO/EN requirements, http://www.ansi.org/.

ANSI B20.1-2006. American National Standard for Safety Stan-

dard for Conveyors and Related Equipment. ANSI, American

National Standards Institute, Inc., 1430 Broadway, New York,

NY 10018, http://www.ansi.org/.

F. Nippard, Dynamic Analysis of Container Conveyance Systems,

Zarpac Inc., 1185 North Service Road E, Oakville, Ontario

L6H 1A7, Canada, 1991.

F. Nippard, Kinematic Analysis of Container Conveyance Systems,

Zarpac Inc., 1185 North Service Road E, Oakville, Ontario

L6H 1A7, Canada, 1990.

P. J. Zepf, P. Eng., CPP, How to Calculate Wastage and Rework

in Production Process, Zarpac Inc., 1185 North Service

Road E, Oakville, Ontario L6H 1A7, Canada, 2002, http://

www.zarpac.com.

P. J. Zepf, P.Eng., CPP, How to Implement Performance Measure-

ments into a Production Process, Zarpac Inc., 1185 North

Service Road E, Oakville, Ontario L6H 1A7, Canada, 2002,

http://www.zarpac.com.

CORRUGATED PLASTIC

NEAL FERGUSON

I.C.C. Primex Plastics

Corporation

Updated by Staff

INTRODUCTION

Corrugated plastic refers to a wide range of extruded twin-

wall plastic sheet products produced from high-impact

polypropylene resin with a similar makeup to corrugated

ﬁberboard. It is a lightweight, tough material that can be

easily cut. Theoretically, almost any plastic material can

be formed into a corrugated proﬁle, but costs can be

prohibitive. In the United States market, polypropylene

copolymer (see Polypropylene) and high-density polyethy-

lene (see Polyethylene, High-Density) are the materials in

348 CORRUGATED PLASTIC

common use, although there is a small quantity of poly-

carbonate (see Polycarbonate) material imported for spe-

cialized outdoor applications. The board is marketed

under the following trademarks: Coroplast, Correx, Cor-

rulite, Corriﬂute, and Twinplast.

Correx and Coroplast are extruded proﬁles. Corrulite

is laminated from three separate sheets and has the

characteristic S-shaped ﬂute of standard ﬁberboard. In

all cases, the formability and mechanical properties are

very similar, although the printability of the extruded

sheet is superior. The plastic corrugated board has ad-

vantages over standard ﬁberboard, but certainly cannot

be used as a substitute for all applications. The packaging

designer should consider the following opposing criteria:

Advantages

Long life

Chemical resistance

Insulation

Multiple color choice

Strength: weight ratio

Waterproofness

Disadvantages

Cost

Formability

Temperature resistance

Ultraviolet degradation

PROPERTIES

Plastic corrugated board utilizes test data from both the

ﬁber and plastics industries, and this can lead to confu-

sion. Plastic corrugated’s strength and durability have no

direct relationship to corrugated ﬁberboard. Corrugated

plastic sheet is inert. It is pH neutral. At regular

temperatures most oils, solvents, and water have no effect.

This allows good performance under adverse weather

conditions or for a product exposed to harsh chemicals.

When used in archival, pharmaceutical, and hospital

applications, Coroplast may act as a carrier through a

sterilization system (1). It can be wiped down with alcohol,

autoclaved (check for extreme conditions), and treated

with ethylene oxide gas. A single treatment by gamma

radiation is not critical, but 4–5 exposures to the Standard

AECL-2.5 mega rad dose will be sufﬁcient to cause poly-

mer breakdown. The rough handling capability of Coro-

plast compares well against ﬁberboard, and it has a

signiﬁcantly higher burst, puncture and edge, and ﬂat

crush properties than that of B ﬂute ﬁberboard. Special

products require additives that are needed for UV protec-

tion, antistatic properties, ﬂame-retardant properties,

custom colors, and anti-corrosion properties. For general

performance comparisons of corrugated plastic and corru-

gated ﬁberboard, see Tables 1 and 2.

PRINTING TECHNIQUES

Plastic corrugated board is supplied in various base colors

by blending pigment into the plastic resin. It can be

printed by screen printing or ﬂexography (see Decorating;

Printing) if the extruded board is ﬂat enough. The poly-

oleﬁns are nonabsorbent and have poor adhesion surfaces

unless they are corona-treated or ﬂame–treated prior to

printing (see Surface Modiﬁcation). Minimum ﬁlm thick-

ness of ink is essential to expedite ink drying (see Inks).

Therefore, ink viscosity should be approximately 10%

Table 1. Mechanical Properties Extruded Proﬁle of Polypropylene Copolymer

Property Value

Thickness in. (mm) 0.157 (4.0) 0.157 (4.0) 0.196 (5.0)

Weight lb/ft

(g/m

) 0.143 (700) 0.159 (775) 0.205 (1000)

Impact strength

73.41F (231C) lbf/in. (N/cm) 90.7 (159) 97.9 (171) 126.5 (222)

321F(01C) lbf/in. (N/cm) 88.5 (155.0) 100.3 (175.7) 129.4 (226.6)

41F(201C) lbf/in. (N/cm) 62.7 (109.8) 69.4 (121.5) 89.6 (156.9)

Tensile strength

Load lbf (N) 62 68.6 88.6

Yield point lbf/in. (N/cm) 661.5 732.4 945.9

Point of failure lbf/in.

(N/cm

) 3417 3783.2 4886.3

Elongation % 166.3 165.8 165.3

Compression strength

ﬂat

Load lbf (N) 36 (160.1) 39.5 (175.7) 51.4 (228.6)

Compression lbf/in.

(N/cm

) 9.2 (6.3) 10.2 (7.0) 13.2 (9.1)

Strain % 1.04 1.06 1.08

Vertical ﬂute

Load lbf (N) 87.7 (390.1) 97.1 (431.9) 125.4 (557.8)

Compression lbf/in.

(N/cm

) 280.8 (193.3) 310.2 (213.9) 401.1 (276.5)

Strain % 2.37 2.52 2.71

Horizontal ﬂute

Load lbf (N) 6.4 (28.5) 7.1 (31.6) 9 (40.0)

Compression lbf/in.

(N/cm

) 21.3 (14.7) 23.6 (16.3) 30.5 (21.0)

Strain % 1.7 1.7 1.4

Tests conducted by Tokan Kogyo Co., Ltd., Japan, on extruded proﬁle.

DuPont Impact Tester to ASTM D781-59 T. Test specimen 1.9685 1.9685 in. (50 mm 50 mm).

Instron Material Tester to ASTM D828-60. Test specimen 9.8425 0.5905 in. (250 mm 15 mm).

Tensilon Material Tester to ASTM D695-69. Test specimen 1.9685 1.9685 in. (50 mm 50 mm).

CORRUGATED PLASTIC 349

higher than normal. Squeegee pressure is normal with

the squeegee medium sharp to sharp. Halftones and

transparencies are possible using direct emulsion screens

or indirect photo-ﬁlms on a ﬁne monoﬁlament fabric

(245–305 mesh). When force-drying, care should be taken

to keep the oven temperature below 1101F (431C) and to

prevent sharp variations in air temperature. Corrugated

plastic tends to be relatively rigid and, therefore, is best

printed on ﬂat–bed types of automatic and semiautomatic

equipment.

One of the major uses for corrugated plastic is in

signage, so high-quality printing and water resistance

are important properties. Coroplast supplies a smooth

polypropylene sheet for digital ﬂat-bed printing (2).

FORMING METHODS

Standard boxmaking techniques can be used to fabricated

corrugated plastic board. Generally, ﬂat-bed presses using

cam action or single stroke are used to die-cut, score,

crease, or fold the material. Three-point or four-point,

single-side bevel-edge rule is used for cutting. Six-point

creasing is used for creasing parallel with the ﬂutes,

three-point for creasing across the ﬂutes, to obtain a 901

bend. The packaging designer must bear in mind that the

polyoleﬁns have a ‘‘memory’’ and, unlike paperboard, will

generally attempt to return to their previous shape. This

characteristic calls for modiﬁed bending and creasing

techniques, but difﬁculties can be overcome.

High-frequency welding has been the most successful

method of joining the material. Because of the nature of

the polymer, glues are not generally successful, but lap

joints have been accomplished using corona-treated board

with silicone-type or hot-melt adhesives (see Adhesives).

Metal stitching can be used, but this creates a weak spot

immediately surrounding the staple (see Staples).

Milseal 2 is a new, smooth plastic process that seals the

edges of heavy duty sheets (3).

CONDUCTIVE CONTAINERS

Changes in the electronic industry resulted in a require-

ment for different packaging materials. Plastic resins

have been formulated to prevent, or dissipate, a static-

electricity charge that would normally build up in the

material. In the past, a carbon-loaded ﬁlm was printed

onto the surface of corrugated paperboard, but this had a

tendency to slough off easily. The sloughing rate can be

reduced by dipping the entire material, but this is another

area in which plastics have an advantage. If the carbon

is introduced into a polymer before extrusion, the wear

factor is sharply reduced and the board can be used in

near-’’clean-room’’ conditions. The electronic industry has

requirements for conductive containers for dip tubes,

kitting trays, stackable tote boxes, multitrip shipping

containers, dividers, covers, and lids. Coro-Gard (Coro-

plast) is a conductive plastic sheet made to transport

electronic materials and meets the Electronic Industries

Association’s standard STD 15-5A, MILP 83668 (United

States Air Force), and DOD-HBBK 263.

ENVIRONMENTAL CONCERNS

Twin-wall ﬂuted structures produce strength and rigidity

at lower weight, thus reducing the amount of material

required for a product. Durability in all weather condi-

tions means a longer life of the product. Polypropylene

recycles in processing streams. Polypropylene copolymers

Table 2. Comparative Tests Between Plastic and Paper

Test #1 Box size: in. (mm) 12.4 9.4 11.8

(315 240 300)

Material: Polypropylene Paper

Board thickness: in. (mm) 0.157 (4) 0.197 (5) 0.205 (5.2)

Board weight: lb/ft

0.150 (730) 0.191 (930) A Flute

Compression load: lbf (N) 485 (2157) 1455 (6472) 661 (2940)

Test #2 Box size: in. (mm) 23.6 19.7 16.1

(600 500 410)

Material: Polypropylene Paper

Board thickness: in. (mm) 0.157 (4) 0.197 (5) 0.299 (7.6)

Board weight: lb/ft

(g/m

) 0.150 (730) 0.191 (930) Double wall

Compression load: lbf (N) 717 (3189) 1482 (6592) 1753 (7798)

Distortion: in. (mm) 0.630 (16) 0.787 (20) 0.512 (13)

Test #3 Box size: in. (mm) 15.7 9.4 8.8

(400 240 225)

Material: Polyethylene Paper

Board thickness: in. (mm) 0.150 (3.8) 0.191 (4.85)

Compression load: lbf (N) 794 (3532) 708 (3149)

Distortion: in. (mm) 0.472 (12) 0.630 (16)

Testron #2000, compression speed 0.472 in./min (12 mm/min). Ten samples cases at 681F (201C).

A ﬂute (B-240)(B-240)(SCP-135)(B-240).

Double-wall corrugated (B-240)(SCP-135)(SCP-135)(SCP-135)(B-240).

350 CORRUGATED PLASTIC

are considered inert and nontoxic and safe for use in

contact with food.

BIBLIOGRAPHY

Neil Ferguson, ‘‘Corrugated Plastic’’ in M. Bakker, ed., The Wiley

Encyclopedia of Packaging Technology, 1st edition, John Wiley

& Sons, New York, 1986, pp. 226–228; 2nd edition, A. J. Brody

and K. S. Marsh, eds., 1997, pp. 285–287.

Cited Publications

1. ‘‘Sterilization of Coroplast TM, Coroplast, Dallas, Texas, http://

www.coroplast.com/steril.htm, 2008.

2. ‘‘General Properties of Coroplast Plastic Sheets,’’ Tech Bulletin

CSS-011-93, Coroplast, Dallas, Texas, http://www.coroplast.com/

genprop.htm, 2008.

3. ‘‘Milseal 2,’’ Mill Industries, www.millsind.com, 2008.

CORRUGATED PLASTIC 351

DATE CODING AND MARKING

DALE VONEY

Markem-Imaje, Kennesaw,

Georgia

Date coding and marking serves many crucial purposes.

Within a single date code or product label, one or many of

the following functions can be ﬁlled: product marketing,

product identiﬁcation, traceability, date and/or time of

product creation, expiration of product, product ingredi-

ent/chemical composition information, and product usage

information. Depending on the type of product produced,

where the product is produced, and where the product is

sold, state and federal agencies may have speciﬁc require-

ments for the date code.

Most products will receive multiple date codes as they

are created, packaged, and processed throughout a supply

chain. In the different stages of a production cycle, various

technologies are used to efﬁciently and accurately apply the

proper marking. Depending on the objective of the date code

and all of the variables involved in a particular application,

one may choose from the following coding and marking

technologies: continuous ink jet, drop-on-demand, laser,

thermal transfer, direct thermal, and contact.

In this article, we will examine each of these technol-

ogies and discuss their proper application.

TECHNOLOGIES

Industrial printers used for marking and coding can use a

variety of technologies. The most prevalent technologies

are described in the following subsections.

CIJ (Continuous Ink Jet)

The principle of CIJ technology is to apply ink to the

substrate by deﬂecting calibrated droplets from a continu-

ously circulating stream. These droplets are distributed in

a dot matrix pattern to form desired characters. The dot

matrix pattern, or character, is made up of vertical dots

controlled electronically. The horizontal placement of

drops is achieved by the movement of the substrate under

the print head. Ink is distributed from holding tank,

through the printer, and into the print head. Droplets

are created and dispensed to the substrate by the print

head (see Figure 1). Droplets used in printing the message

are selectively chosen by the equipment software.

Droplet creation, calibration, and consistency are cru-

cial to this technology. Within the print head is an ink

chamber that contains a small nozzle and a vibrating

crystal, called a resonator. The pressurized ink ﬂows

through the chamber and toward the opening, called the

cannon. During this journey, the resonator changes the

characteristics of the ink stream from a continuous stream

to a series of droplets that are marginally connected. As

the ink stream leaves the cannon, marginally connected

‘‘teardrops’’ begin to form. Due to ﬂuid dynamics, these

teardrops eventually form individual, spherical droplets.

The size of the drop varies and is dependent on the

modulation of the resonator, cannon size, and ink pres-

sure. The droplets continue down the print head and

through a charge electrode. Since CIJ inks are conductive,

the ink droplets can be selectively charged simply by

changing the electrical current on the charge electrode.

Only those droplets needed to form the desired matrix

pattern or characters will be charged. Droplets then

pass through two parallel plates, called deﬂection plates,

whereby the charged droplets are deﬂected by applying

voltage. The remaining uncharged droplets fall directly

into a small vacuum tube at the bottom of the print head.

The vacuum tube returns the ink to the ink reservoir.

For industrial packaging, CIJ technology is mainly

used in small-character ink jet printers (SCPs).

Small-character printers are typically used to print di-

rectly onto products or primary packages. Depending on

character height and dpi requirements, SCPs can also be

used for secondary package printing. Here is a brief list of

examples of SCP applications: lot identiﬁcation for glass

bottle printing, expiration information on metal cans

containing vegetables, time of production on bags of bread,

and kosher symbols on hot dog packaging. Due to the large

variety of ﬂuid chemistries that can be used in a contin-

uous inkjet printer, it is a preferred printing technology

for primary packaging applications.

DOD (Drop-On-Demand)

Drop-on-demand (DOD) ink jet technology uses the prin-

ciple of applying ink to the substrate by ejecting drops

though multiple openings. Each opening corresponds to a

speciﬁc location on the vertical axis of the message to be

printed. Drops are ejected from these openings based on

message requirements and character locations relative to

the print head (on-demand). DOD technology is mainly

Cannon

Charge electrode

8 Detection electrode

9 Deflector plates

10 Recovery gutter

11 Head cover

Gutter plug

Figure 1. Continuous ink jet printhead.

353

used in Large-character ink jet printers (LCPs).

There are different mechanisms used in DOD technology

for ejecting drops.

Valve-Based. The principle is to supply ink under

slight pressure to an array of valves that are all

equipped with a drop-ejecting nozzle. By controlling

the opening of the valves, the drops can be ejected to

print characters or graphics. DOD-valve-based prin-

ters have coarse resolution. They are mainly used to

print large alphanumeric characters onto shipping

cartons (also called secondary packaging), hence

their naming as large-character printers or LCP-

valve printers (see Figure 2).

Piezoelectric-Based. Ink is supplied by a chamber to a

print head. Each print head is comprised of an array

of chambers that are all equipped with an ejecting

nozzle. The principle is to activate a piezoelectric

element attached to each chamber in order to deform

the chamber. The change of volume of the chamber

leads to the intermittent ejection of drops from the

nozzle. Piezoelectric-based systems offer ﬁner and

more precise control, leading to high-resolution

printing. The industry commonly refers to this

equipment as ‘‘high-resolution printing systems’’

(see Figure 3).

Laser Marking

This technology uses a laser beam that interacts directly

with the substrate material to create an indelible mark

(see Figure 4). The laser beam can be of different

wavelengths according to the laser source that is used.

Different wavelengths are chosen in order to interact

efﬁciently with the target substrate material. CO

(carbon

dioxide) and YAG (yttrium aluminum garnett) laser med-

iums are the most common types used in the coding and

marking industry. Of these two types, CO

lasers are used

in the packaging industry. YAG lasers are used for mark-

ing metal surfaces.

In order to print characters or graphics, the laser

beam(s) are directed to the correct location on the sub-

strate. Different technologies are used to create the mark-

ing beam and control it:

Mask-Based. A mechanical mask (template) is used to

create the pattern on the substrate. The laser marks

the substrate according to the pattern placed in

front of it. A different mask has to be used for each

printed pattern.

Dot Matrix. A pulsed laser beam is formed into a

column of dots. These dots are individually activated

−

P = Pressure (ink)

F = Force

U = Voltage

O = No volta

Figure 2. Drop-on-demand technology (valve-based).

Signals

Electrodes

Nozzles

Ink channels

Shared walls

Shear mode actuation

PZT Poling

Figure 3. Drop-on-demand technology (piezoelectric-based).

Figure 4. Laser technology.

354 DATE CODING AND MARKING

for printing a matrix-based image from a repeat

combination of columns.

Steered Beam. A pulsed laser beam is displaced along

the X–Y axis by a set of electronically controlled

mirrors.

Lasers used in the packaging industry range from 10 to

150 W of power. Various energies are required for creating

legible marks on different substrates and speeds.

Thermal Transfer

This technology uses a thermal print head comprised of a

dense array of thermal elements (or thermistors) that can

be selectively activated. Printing is accomplished by

bringing the thermal head in contact with an inked

ribbon. The inked ribbon is pressed against the printable

surface. The inked ribbon consists of a base polymer sheet

material and a releasable coating made of fusible ink. By

heating the ribbon with thermistors within the print head,

small areas (dots) of ink are subsequently transferred by

contact to the printed substrate (see Figure 5).

Thermal transfer technology can be used in three

printing systems:

Thermal Transfer Online (TTO). This technology is

used to print directly on packaging ﬁlm.

Desktop Label. Thermal printheads transfer ink to

adhesive labels. In these systems the labels need to

be applied manually to the products.

Print and Apply Systems. Thermal printheads trans-

fer ink to adhesive labels. An automated mechanism

(applicator) then applies the label to the substrate.

Direct Thermal

This technology also uses thermal print heads, as above.

The thermal elements of the printhead come in direct

contact with specially treated labels. These labels are

sensitive to heat and change color when in contact with

an activated thermistor. This thermal technology does not

require a thermal transfer ribbon. Two printing systems

use direct thermal printing technology: desktop label

and print and apply systems. The concepts of these

systems are the same as listed above in the ‘‘Thermal

Transfer’’ section (see Figure 6).

Contact Printing

Contact printing relies on mechanical methods to transfer

print to a surface. The general principle of contact coding

makes use of predeﬁned forms (metal letters, engraved

print wheels, rubber pads/stamps, etc.). These forms are

pressed into the substrate. The image is transferred as the

pressure is removed. Contact printing may or may not

involve the use of ink or inked ribbon. Embosser, hot

stamp, or roller printers are among these older contact

technologies that are still in use today. These contact

technologies are gradually being phased-out by electro-

nically controlled printing technologies.

The technologies mentioned in the preceding para-

graphs (except Mask Laser) utilize advances electronic

technology to create and control character generation.

These electronics give the capability of changing and

printing variable information on the ﬂy. This limits the

amount of human intervention with the date coding

equipment and allows for variable and unique messages

generation from during production runs.

The latest date coding systems also contain commu-

nication capabilities that allow for the option of remote

control, monitoring, and data collection. As quality control

and regulation becomes more stringent, remote commu-

nication to date coding equipment will be more common.

APPLICATIONS

The horizontal segmentation of the packaging market is

described below (see Figure 7).

Product/Primary Package Printing

These applications consist of printing: lot numbers, time

and/or date of product creation, best before dates, or other

product references directly onto the products and/or pri-

mary packaging in the manufacturing line. These applica-

tions are the fastest and highest-output packaging

applications on the the production line, so speed and

accuracy of date code placement are crucial. Four types

of systems can be chosen:

. Continuous Ink Jet Marking Systems. This product

is the workhorse for product and/or primary packa-

ging printing applications. It generates marks onto

Thermal head

Polyester film

TTR - Ribbon

Ink

Transferred

ink

Substrate

Figure 5. Thermal transfer technology.

DATE CODING AND MARKING 355

products without contact, at high speed, with large

print distance, on most substrate materials (a wide

range of ink chemistries are available). Its limita-

tions are related to its moderate print quality, the

limited printed width, and the necessity to use and

handle liquid inks that maybe hazardous for fast

drying chemistries. Common applications: bottle

printing, retail chipboard box printing.

. Laser Marking Systems. Laser systems generate in-

delible marks on many (but not all) packaging

substrate materials. They are preferred over ink

jet because of their superior print quality, indelible

marks, and the absence of consumables. Their main

limitation is linked to the inability to mark all

material types and colors.

. Thermal Transfer Online Printers (TTO). These

printers print by contact on ﬁlm materials. Their

main advantage is in print quality. This enables

them to print most industrial bar codes with good

read rates. Also they do not use liquid consumables.

This printing technology is primarily used in packa-

ging ﬁlm. Printing speeds can be a limitation.

. Small-Character (DOD-Piezo) Ink Jet Systems.

These systems can be preferred to CIJ in applica-

tions where speed and print distance is not demand-

ing. These systems can produce better print quality

than CIJ systems.

Secondary Package (Shipping Cartons) and Tertiary

Packages (Pallets) Printing

These applications consist of printing product information

(product references, lot numbers) and shipping informa-

tion (manufacturer, customer addresses, and order infor-

mation). Three types of systems can be chosen:

Print and Apply Label Systems. These systems are

the workhorse for these applications. They print

high-quality labels that can be read automatically

with high reliability with all scanning equipment.

Their drawback is related to their limited speed and

high cost of labels.

Large-Character Ink Jet Systems. Ink jet systems

have the advantage of higher speed (noncontact

Product

Primary

package

Secondary

package (shipping

carton)

Tertiary package

(pallets)

End of line (logistics)

Manufacturin

Figure 7. Packaging applications.

Paper unwind

Dispensed label

Backing paper rewind

Print Image

Print-

head

Print head

Thermal pape

Print roll or

platen roll

Figure 6. Direct thermal technology.

356 DATE CODING AND MARKING

printing) and better cost of ownership (there is no

cost associated with labels).

Valve-Based (LCP Valve). These low-price sys-

tems print coarse resolution text or graphics di-

rectly onto most packaging substrates. They

cannot print the shipping information that re-

quires bar codes.

Piezo-DOD-Based (LCIJ). These systems use dif-

ferent technology variants and therefore come in

models that can use either liquid ink (Markem-

Imaje’s High-Res) or solid ink (Markem-Imaje’s

HMIJ). They can print high-resolution text and

graphics including shipping information that in-

cludes bar codes on most packaging materials.

Their main limitation against labels is that they

cannot meet the highest standards in bar code

veriﬁcation rates, and their output print quality/

performance is substrate-dependent.

Desktop Label Printers. These systems are not inte-

grated on packaging lines. The printed labels need

to be applied manually to the products. Use of

tabletop printers is therefore limited to low-through-

put lines, or as backup to print and apply systems.

DECORATING: IN-MOLD LABELING

RONALD SCHULTZ

RBS Technologies, Inc.,

Scottsdale, Arizona

In-mold labeling (IML) is a process for prelabeling plastic

containers during the molding operation. IML differs from

other prelabeling methods, such as pressure-sensitive and

heat-transfer, in that the labeling mechanism is built into

the molding machine. No additional labeling equipment or

labor is required because the containers are ejected from

the molding machine with the labels already in place. One

of the most important advantages that IML offers pack-

agers is cost reduction. Use of containers that come from the

molder already labeled allows packagers to eliminate

their labeling machines and ﬂame treaters along with the

labor, maintenance costs, utilities, and ﬂoor space for that

equipment. Other advantages include labels with the high-

est-quality graphics, a plastic gram weight savings over

post-mold-decorated containers, and, in the case of injec-

tion-molded containers, the ability to cover all ﬁve sides of a

rectangular container with a single label in one operation.

Over the past several years, IML has evolved and grown

into three related technologies: extrusion blow mold in-

mold labeling (EB-IML), injection mold in-mold labeling

(IM-IML), and thermoform in-mold labeling (T-IML).

BLOW MOLD IN-MOLD LABELING

Procter and Gamble recognized the advantages of EB-IML

and was the ﬁrst consumer products manufacturer

in North America to use it on HDPE bottles in the late

1970s.

In-mold labeling requires some modiﬁcations to the

conventional blow-molding procedure (see Blow Molding):

(1) In-mold labels for EB-IML have a heat-activated

adhesive on the backside; (2) the molds are ﬁtted with

vacuum ports or the labels are electrostatically charged to

hold the labels in place on the mold wall during the blow-

molding operation; (3) label magazines are added to hold

stacks of die-cut labels, usually one for the front and one

for the back of the container; and (4) a robotic pick-and-

place device is added to transfer labels from the magazine

into the mold cavity.

In a typical continuous-extrusion blow-molding (EB-

IML) process, the robotic pick-and-place device takes a

label from the magazine and places the printed side

against the wall of the open mold, where it is held in place

by the vacuum ports. As the mold closes, it pinches off a

section of a molten plastic tube (the parison) as it comes out

of the extruder. The closed mold then moves away from the

extruder and high-pressure air is injected into the parison,

inﬂating it like a balloon. When the hot plastic parison

contacts the back of the label, it activates the adhesive and

ﬂows up and around the edges of the label. The label is

ﬂush with the surface of the container and becomes an

integral part of it. A volume of plastic is displaced that is

equal to the volume of the label (Figure 1). The air pressure

in the mold is maintained until the container is cool enough

to be ejected from the mold.

The largest numbers of EB-IML containers produced in

North America are HDPE bottles made on rotary or

‘‘wheel’’ blow molding machines. These machines are

used primarily for long runs of containers ranging in

size from 8 oz to large, economy-size laundry detergent

jugs of more than 300 oz. Volume of production is a

function of container size and rotational speed of the

wheel. Shorter runs of EB-IML containers are made on

shuttle blow molding machines. These can be single- or

double-sided with multiple mold cavities on each side.

Recent developments in label insertion device technology

have permitted retroﬁtting of older, non-IML shuttle

machines to render them IML-capable. Lesser quantities

Outside surface

Ink and overprint

Label substrate

Adhesive

Bottle plastic

Glue-on

label

In-mold

label

Figure 1. Diagram of in-mold versus glue-applied label.

DECORATING: IN-MOLD LABELING 357