The Basics of Flexible Packaging Printing - · PDF fileThe Basics of Flexible Packaging Printing Flexography Rotogravure Presented by: Warren E. Durling Associate Research Fellow Clorox

The Basics of Flexible Packaging Printing

FlexographyRotogravure

Presented by:Warren E. DurlingAssociate Research FellowClorox Services Company / Glad Division

Slide 2Session #11 – A Flexible Packaging Primer


Design to Substrate

Preproduction Design Creation

Substrate Management

Image Preparation Color Separation

Ink ManagementCylinder or

Plate Making

Converting

PrintingPrinting

Press Make Ready


PRINTING INK, Form & Chemistry

Physical formLiquid – free flowingRelatively low viscosity

(closer to water than honey)30% to 60% solids and 100% solids UV/EB

ChemistrySolvent based – gravure, flexographicWater based – flexographic, (gravure)Radiation cured (UV/EB) – flexo, gravure


Basic INK Formulation Examples

WATER65%

SOLUTIONRESIN 10%

EMULSIONRESIN 10%

SOLVENT65%

Primary RESIN 15%

SecondaryRESIN 5%

Reactive Diluents

Up to 30%

ACRYLATEMONOMER

ACRYLATEPREPOLYMER

55%

Water Solvent Radcure

80% ALCOHOL20% ACETATE

ADDITIVES 5%

ADDITIVES 5%ADDITIVES 5%

PIGMENT10%PIGMENT10%

PIGMENT20% - 25%

Dry InkDry Ink

Wet InkWet InkDry Ink

&Wet Ink


Ink Blending / Color Matching

Typical Production Ink Blending:Color Base Systems:

High Solid, Concentrated Color Pigmentsused singly and as blendsspecific to the vehicle systemCMYK + many specific colors

Vehicle / Varnish Systems:Clear Backbone Resins

physical propertiesprocessabilityfilm strength

Additives & ModifiersScuff ResistancePlasticizers (improved flexibility)Coefficient of Friction (slippery or sticky)Aesthetic Appearance (matt vs. glossy)


Cup Number Seconds Efflux Time Centistokes Range

1 40-60 10-36

2 20-60 19 to 156

3 12-60 64 to 596

4 10-60 79-784

5 10-60 161-1401

INK, Viscosity Measurement

ZAHN Cup conversions SHELL Cup

SECONDS (time) is the Operators press side, process measurementCENTISTOKE is the unit of reference in all viscosity cup measurements

POISE is the fundamental unit of viscosity defined as the resistance of a liquid to flow where gravity is not a factor. 100 CENTIPOISE = 1 POISE. Gravity is the driving force causing liquid in a viscosity cup to flow through the orifice so a high density material will flow from a cup in a shorter time than a low density material of the same viscosity.

STOKE is defined as the POISE divided by density. 100 CENTISTOKES = 1 STOKE.

ZAHN Cup


PRESS SIDE Ink Management

1) PUMP & MOTOR

2) INK TANK

3) FILTER

4) PRINTING STATION

5) AUTOMATIC VISCOSITY CONTROL


FLEXOGRAPHY Printing

Flexography: (often abbreviated to Flexo) A form of relief printing where ink is applied to a rubber or polymer plate on which the printing image is raised above the rest of the surface as a 3-D positive, mirrored relief.


FLEXOGRAPHY – The Process


FLEXOGRAPHY - Printing Plates

A photopolymer is a polymer that cures, or becomes solid, when exposed to light

(1) A photo negative image is used to expose (image wise), a photopolymerizable sheet to light

(2) The unexposed or unpolymerized areas of the plate are removed with solvent or water

(3) The resulting plate is dried, then detackify / harden by exposing it to specific frequencies of U.V. radiation

(1) A photo negative and acid wash process is used to engrave the image into a copper or magnesium positive image master plate

(2) The positive image master is used to produce a negative image plastic plate mold

(3) The printing plate is produced by molding raw rubber with the plastic mold then vulcanizing the resulting rubber sheet

Conventional rubber plates that rely upon a less precise molding process have become nearly obsolete except where lower quality is acceptable

Digital, direct to plate engraving is the latest innovation in flexo plate technology. A processed digital file controls a laser that directly burns away unwanted areas of the polymer printing plate. In the past, limited durability plate materials resulted in short plate life. Recent equipment and material developments are generating renewed interest.


FLEXOGRAPHY - Anilox Rolls

The anilox roll is a steel or aluminum core cylinder with a ceramic surface that contains millions of very fine cells. They are specified by their "line screen", or the number of cells per linear inch ranging from below 250 to above 1500. Lower line screens are used to print a heavy layer of ink such as block lettering. The highest line screens produce fine detail for four-color process work such as reproducing photographs.


FLEXOGRAPHY – Printing Presses

Stack Flexo Press Design

Historically, stack presses are lower cost compared to central impression presses and are used where lower quality printing is acceptable. However, recent advances in servo technology have resulted in quality improvements.


FLEXOGRAPHY – Printing Presses

Central Impression (CI)Flexo PressTraditional Open Architecture Gear Drive


State of the Art Central Impression Flexo Press

FLEXOGRAPHY - Printing Presses

10 colorservo drivefully automated, automatic printing plate washingup to 1,900 feet per minute


ROTOGRAVURE Printing

Rotogravure: (typically referred to as Gravure)An intaglio process (in-tal-yo means engraved or cut in) in which a negative image is etched into the surface of a copper printing cylinder as tiny cells or dots of various sizes and depths. The copper is chrome plated for durability. Ink is applied to the surface and a flexible metal blade called a doctor blade removes excess ink, leaving the surface clean, with ink only in the depressions.


GRAVURE – The Process


Acid Etching (Diffusion-Etching and Direct-Transfer) - Light sensitive gelatins or photopolymers on the coper surface are exposed through a film positive of the image, resulting in varying levels of acid resistance. The surface is exposed to acid, resulting in cells of the same size and cell wall thickness but varying depths.

Electromechanical Engraving - The original copy is scanned into a computer and digitized. The computer then controls a diamond stylus that cuts the cells into the surface of the gravure cylinder. Cell depth and cell area are varied simultanously by using a tapered engraving head.

GRAVURE - Cylinder Engraving

Laser Engraving - The method of choice to produce Flexo anilox rolls with some applications in gravure printing. An original is scanned into a computer, the various image densities are determined, then a laser etchs the cylinder. Highly reflective copper is a poor material choice so alternative special alloys, plastics and ceramics are used.


GRAVURE - Cylinder Cell Structure


GRAVURE - Electrostatic Discharge

Electrostatic Discharge (ESA) - A charge imballance is created between the printing cylinder holding the ink and the substrate. This results in an effect much like a maganet where the charged ink is attracted to the obsit charged substrate.Properly functioning ESA is escential to achieve high quality Gravure printing.


Doctor Blade Design

Doctor Blade shape, construction material, tip honing, set angle and pressureare becoming more sciencitific and process controlable but there still remains a great deal of “ART” in the process.

Stainless SteelBlue SteelCeramicPlasticAlloys

Round TipSquare Tip

CombinationsStraight BeveledStepped Beveled


GRAVURE - Printing Presses

Gravure PressTraditionalOpen Architecture

Solid line shaftManual print station change overLimited if any electronic process controlLower efficiency ovens



Rapid Changeover Gravure PressState of the Art, High Speed

Fully automated print station, trolley change over systemOff-press trolleys washing unitElectronic line shaft, full PLC controlHigh efficiency compact dryersPrinting speed up to 1,300 feet per minute



Automated Gravure Print Decks


Flexo or Gravure - HOW TO TELL?

Rotogravure

Flexography


Flexo or Gravure - HOW TO TELL?

Flexography

Rotogravure


LINE Printing

Single colors are printed at varying densities

Individual colors do not overlap or combine to form new colors

The number of colors in a design is limited by press capability


Flexo LINE - Reverse Print Film


Flexo LINE - “Screened” Print


Gravure LINE Printing - Surface Print


Red, Green and Blue (RGB) are the primary colors of light as perceived by the human eye.

4 Color PROCESS Printing - CMYK

Printing utilizes a subtractive color process based on light reflecting from an object through pigments or dyes that absorb certain wavelengths, allowing others to be reflected. Unlike the additive system, which begins with black and adds color, the subtractive system begins with white and subtracts color.

When the three colors are together in a spectrum they create white and the absence of color altogether is black. This works great for digital images on computer and TV screens. Colors are created on monitors by adding light. RGB is an additive color system, which means that color is added to a black background.



The base colors for process printing are CMYK and not RGB

CMYK are subtractive colors or secondary colors of red, blue and green

Blue + Green = Cyan (B+G = C)Red + Blue = Magenta (R+B = M)Red + Green = Yellow (R+G = Y)

And Black = K



The image is separated into 4 different color valuesCyan / Magenta / Yellow / Black

A printing plate or cylinder is created for each process color using the individual separations

Individual colors are printed as dots at varying densities

Individual dots combine to form additional unique colors

In Packaging printing , 4 color process is typically combined with line colors to accurately represent

trademarks and logos and to maintain color consistency over large areas of solid colors.

The number of final colors in a design is nearly limitless


Flexo PROCESS Printing


Gravure PROCESS Printing


Gravure PROCESS Printing


GRAVURE vs. CI FLEXO

GRAVURE FLEXOPrinting Press Footprint larger smaller

Printing Press Cost much higher lower

Operating Costs (utilities and overhead) slightly higher lower

Maintenance slightly higher lower

Cylinder / Plate cost much higher lower

Impressions per Cylinder / Plate very high w/ rechrome lower

Make-Ready Time generally longer shorter

Water Base / Solvent Base solvent – water? both

Substrate Flexibility less more

Process Flexibility (coating & laminating) more less

Print Quality (detailed process printing) exceptional improving

Basic Printing Process Selection Guide


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PRESENTED BY

Warren E. DurlingAssociate Research FellowClorox Services [email protected]

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The Basics of Flexible Packaging Printing - · PDF fileThe Basics of Flexible Packaging Printing Flexography Rotogravure Presented by: Warren E. Durling Associate Research Fellow Clorox