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Available Print Process. The End Result. Rotogravure. PLUS. IMPRESSION. * Simple proven process. WEB. ROLL. * Quick make-ready. * low speed sensitivity. * low impression. DOCTOR. sensitivity. BLADE. * variable ink film (better. fidelity). * consistent long runs. ENGRAVED. MINUS.
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Rotogravure PLUS IMPRESSION * Simple proven process WEB ROLL * Quick make-ready * low speed sensitivity * low impression DOCTOR sensitivity BLADE * variable ink film (better fidelity) * consistent long runs ENGRAVED MINUS CYLINDER * Cylinders expensive * Cylinders take time to INK make
Lithography PLUS INK * Proven process DUCT * Highest quality process print INK TRAIN MINUS PLATE * High manning CYLINDER DAMPING * High skill level needed TRAIN WEB * Color control issues BLANKET * Not in line with die CYLINDER cutting etc. IMPRESSION CYLINDER
MINUS Flexography PLATE ENCLOSED INK CHAMBER IMPRESSION ANILOX ROLL WEB PLUS * Low cost presses * Process print quality * In line capability * Variable industry * Quick make-ready capability * Less manning/skill level * Consistent color
Ink Types 1.Physical Form - Liquid - Paste 2. Composition and Chemistry - Oil base - Solvent Base - Water Base - Radiation Cure
Ink Formulation – Water Base • FLEXO • GRAVURE TYPICAL PROPERTIES Viscosity 50-100 centipoise Solids 35% Tack Very low Drying Absorption/evaporation Trap Wet on dry Cure Immediate VOC < 1% by wt. Odor Very low Cost OK
Ink Formulation – Solvent Base • FLEXO • GRAVURE SOLVENT TYPICAL PROPERTIES Viscosity 50-100 cps Solids 35% Tack Very low Drying Absorption/evaporation Trap Wet on dry Cure Immediate VOC 65% by wt Odor Low Cost OK (65%) 1.3#/Ream 80% ALCOHOL 20% ACETATE Wet Ink 2#/Ream .1#/Ream ADDITIVES (5%) Dry Ink POLYAMIDE .2#/Ream .7#/Ream RESIN (10%) .2#/Ream NITROCELLULOSE RESIN (10%) .2#/Ream PIGMENT (10%)
Ink Formulation - UV • FLEXO • LITHO SOLVENT (30%) .6#/Ream TYPICAL PROPERTIES Viscosity 10-200 poise Solids 97% Tack Moderate to very high Drying Free radical cure Trap Wet on Wet, or Wet on Dry Cure Immediate VOC <3% Odor Moderate Cost High ACRYLATE MONOMER ADDITIVES (5%) Dry Ink .1#/Ream Wet Ink 2#/Ream 1.1#/Ream ACRYLATE PREPOLYMER (55%) .2#/Ream PIGMENT (10%)
Ink Formulation – Oil Ink • LITHO .2#/Ream DISTILLATE 10% .1#/Ream DRIERS/WAX 5% Viscosity 100-200 poise Solids 90% Tack Very high Drying Absorption/ oxidation Trap Wet on Wet Cure Overnight VOC 10% Odor Moderate Cost OK QUICKSET 1.5#/Ream RESIN 75% Dry Ink 1.8#Ream PIGMENT (10%) .2#/Ream
Litho Inks – Oil Base or UV High viscosity ink and planographic image carrier 1. Low dot gain 2. Uneven solid areas (limited impression) 3. Weak metallic inks (limited ink film)
Flexo Inks: Solvent, Water, UV Low visc ink and raised, resilient image carrier 1. Dot gain very impression dependent 2. Smooth solid areas, even on rough stock 3. Strong metallic inks
Roto Inks: Solvent or Water Base Low viscosity ink and recessed cells image carrier 1. Low dot gain 2. Uneven solid areas (limited impression) 3. Very sensitive to rough stock (skip outs)
Comparing Roto and Flexo * less make-ready * less speed sensitivity * less impression sensitivity * variable ink film (better fidelity) * consistent long runs * lower cost (plates) * quicker response * growing industry focus
THE LITHOGRAPHIC PRINTING PROCESS Offset Printing
THEORY OF LITHOGRAPHY LITHOGRAPHIC PLATE NON IMAGE AREA IS WATER LOVING (HYDROPHYLLIC) IMAGE AREA IS WATER REPELLANT (HYDROPHOBIC)
LITHOGRAPHIC PRINCIPLE Image Image Non-image Water rejecting Water rejecting Water receptive Hydrophobic Hydrophobic Hydrophylic Ink receptive Ink receptive Ink rejecting Oleophylic Oleophylic Oleophobic LITHOGRAPHIC PLATE
Dampening of plate Dampener Roller Water on non-image area LITHOGRAPHIC PLATE
INKING OF PLATE Ink roller Water on non-image area Ink on image area LITHOGRAPHIC PLATE
PLATE CYLINDER Inking rollers Plate Dampening Rollers Fountain Solution
OFFSET LITHO PRESS CONFIGURATION Ink Distribution Rollers (oscillating) Plate Cylinder Blanket Cylinder Dampening Rollers Sheet or Web Fountain Solution Impression Roller
SHEETFED OFFSET PRESS Plate Inking rollers Blanket Dampener Impression
WEB HEATSET PRESS Plate Inking rollers Oven Dampener Blanket Impression Rewind Unwind
OFFSET PROOFING Difficult to accurately control ink film thickness from hand roller to plate. This will cause some variation when transfering to substrate. Plate is inked up by a hand roller Blanket roller picks up ink from plate Transfers it to substrate Substrate Plate
PRUFBAU INKING MECHANISM Back roller oscillating to distribute ink evenly Blanket roller Blanket roller Distribution roller
CONVENTIONAL (DUCTOR) DAMPENING SYSTEM Form roll Vibrator Plate cylinder Ductor Fountain roll Form roll Fountain solution
CONTINUOUS-FEED (DALHLGREN) DAMPENING SYSTEM Second ink form roll Oscillator roll First ink form roll Plate cylinder Slip nip Metering roll Chrome transfer roll Fountain solution
BRUSH DAMPENING SYSTEM Ink form rollers Chrome vibrator roll Plate cylinder Brush roll Metering roll Fountain solution
DUOTROL DAMPENER Ink form rollers Chrome vibrator roll Plate cylinder Metering roll Fountain solution