Gravure Fall 2011

Gravure Fall 2011 - GrC 329 Gravure Printing Techhnology...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: GrC 329 Gravure Printing Techhnology Rotogravure Printing GrC 329 Cal Poly – Graphic Communication Dept. -Gravure and Litho share the magazine markets Gravure products Publications Magazines Sunday magazines Catalogs Retail inserts Packaging Folding cartons Flexible Labels Products Gift wrap Wallcovering Decorative laminates Floor coverings Engraving/intaglio (sheetfed) Currency Stamps Stationary (lawyers). Typical Gravure Packaging Products -Gravure usually does long run mags, coffee table, high-end (national geographic) -packaging--> tide box, a lot of ink coverage -sin products (alcohol and tobacco) -giftwrap- need continuous imaging so use gravure -Gravure and Litho share the magazine markets -Gravure usually does long run mags, coffee table, high-end (national geographic) -packaging--> tide box, a lot of ink coverage -sin products (alcohol and tobacco) -giftwrap- need continuous imaging so use gravure Content from RIT Gravure Day 2010 – Packaging Corporation of America Presentation 1 GrC 329 Gravure Printing Techhnology Other Gravure Samples Content from RIT Gravure Day 2010 – Packaging Corporation of America Presentation -print directly from engraved cylinder PROS of Gravure Direct printing Gapless Fast drying inks (solvent) Varying ink-film thickness Dry trapping Computer-to-cylinder Light-weight substrates -Big advantage of gapless: even surface, no speed limiter- faster Variable repeat Consistency Cylinder life Faster press speeds Larger press forms Shadow detail Beautiful, rich color. process -can lay down more ink than litho (dry trapping), good continuous color -prints on lighter weight substrates than lithio bc gravure is a onefluid process- no water to damage to substrate -cylinder life: bc of chrome (harder than doctor blade) should last for millions of impressions -smooth stocks required- rough surfaces can't pick up ink well CONS of Gravure Cost of engravings Time of engravings Smooth stocks required Serrated type Serrated line art Solvents (publications) Static Fewer suppliers Weaker highlight detail Difficult cylinder corrections Fewer paper sources Physical location of plants Local color adjustment Long makereadies “Donut” halftones. -can't prink serifs well- not clean, sharp -solvents- harmful to people, enviro, flammable (but allows you to run faster) 2 GrC 329 Gravure Printing Techhnology Con of Gravure – Size of Rolls You Deal With Large Amount of Automation Required 3 GrC 329 Gravure Printing Techhnology flying splice Relative Simplicity of Gravure Printing Compared to Litho Gravure vs. Litho – Quick Comparison of Key Attributes RR Donnelley RIT Gravure Day Presentation 2009 4 GrC 329 Gravure Printing Techhnology Design considerations for gravure Screened type and line art – serrated Wider density range than offset variable ink-film Hold 4% to 90% on good substrate Average with high-key, excellent with low-key Care with… Color separations Reverse, small or script type Font selection Low stroke-contrast Prep is critical – remakes $ Length of Run consideration due to costs Lithography – Small and Big Dots Gravure – Cells Change Size, Depth, and Geometry 5 GrC 329 Gravure Printing Techhnology Color separation for Gravure Determine highlight/shadow area of image Determine tone reproduction curve Area of interest Determine TVI (dot gain) Correct for gray balance Apply GCR, UCR, UCA Total coverage not to exceed 300% or ?. Or color manage w/ profile GAA/SWOP? Custom? Engraving Cylinders are engraved with calibrated cell sizes to insure color matches customer’s requirements Gravure specifications GAA/SWOP Specifications for Gravure Publications CGATS TR 011 Graphic Technology—Package Development Workflow CGATS TR 012 Ink and Color Characterization for Packaging. 6 GrC 329 Gravure Printing Techhnology Prepress workflow for Gravure Microns 1 micron = 1/1,000,000 of a meter 2.54 centimeters in an inch 25400 microns in an inch 1 micron = .0000393”. 7 GrC 329 Gravure Printing Techhnology Cells are engraved by diamond stylus cutting tool into copper cylinder Electronic engraver must operate to microscopic tolerances within plus or minus 2 microns Cylinder bases Types Integral Shafted Hollow (shaftless cylinder) Sleeve Ballard shell Materials Solid steel base Electroplated w/ other metals (Nickel, Copper, Chrome) Hybrid polymer – Starbase Cylinders may be plated to different diameters (stepped up) to aid web tension. Cylinder base quality: Total Indicated Runout ± .0005” Cylinder deflection Structural rigidity needed on long cylinders ± .006” Balance Static balance vs. dynamic balance. 8 GrC 329 Gravure Printing Techhnology Sleeves and shells Sleeves Lightweight (transport) Mounted on base cylinder Ballard shell Nickel (separation layer) Easily stripped. Ballard Shell – Cylinder Recycling Ballard Shell Removal & Cranes 9 GrC 329 Gravure Printing Techhnology Preparing bases Remove previous image Degrease Electroplate above the correct diameter Check for proper hardness Polish. Sample Exam Questions 1. How many inches is 200 microns? (closest) A. .0003 B. .0079 C. .0154 D. .0366 E. 2.35 No Calculators! Sample Exam Questions 2. New cylinder base research involves engraving using… A. hybrid polymer coatings B. nickel plating C. copper plating D.chrome plating 10 GrC 329 Gravure Printing Techhnology Sample Exam Questions 3. To aid tension, cylinder sizes may vary throughout the press, with the largest cylinder on unit… A. 1 B. 2 C. 3 D.4 Image courtesy of Max Daetwyler Coporation Electroplating Electroplating needed for: Nickel Copper Chrome Transport metal in ionized form to deposit in metallic form with electric current Components: Anode – positive charge Cathode – negative charge Electrolyte – solution that contains ions – conduct current Copper (Cu), sulfuric acid (H2SO4), water, (H2O). Electroplating Illustrated + Cylinder: acts as cathode, carrier of the negative charge, supplies electrons Electrolyte: conducts current, contains water and ions of copper and sulfuric acid Anode: carrier of the positive charge, made of copper that is removed during the plating 11 GrC 329 Gravure Printing Techhnology Faraday’s law We can control the exact deposit of metal Metal deposited is directly proportional to current Proportionality factor directly related to equivalent weight (atomic weight ÷ valence) of metal in electrolyte. Other important plating issues Immersion of cylinder Anode/cathode distance Temperature of electrolyte Cleanliness of cylinder – degreasing. Image courtesy of Max Daetwyler Coporation Inside a Copper Plating Station 12 GrC 329 Gravure Printing Techhnology Electoplating Copper Copper Engravable, stable, reproducible Pure, small grain required Electroplated to base in 2 steps -soft enough to be engraved, hard enough the maintain the shape of the cell Nickel flashed base Copper plated. why would packaging printers use sleeves more often than Copper grinding After plating To achieve round cylinder Grind – change diameter Polish – change surface “Polishmaster”. publication printers? -it can be reused, content doesn't change very often -grinding= changing the diameter of the cylinder 13 GrC 329 Gravure Printing Techhnology Image courtesy of Max Daetwyler Coporation Polishing polish with stones Before engraving, surface is polished Also used: After After After After lathe proofing/corrections engraving chroming Polishing stones (wheels), paper, pastes, and buffing wheels. Polishing a Cylinder 14 GrC 329 Gravure Printing Techhnology cutting tool makes the main cut Engraving burr cut- cleans off the edges Diamond stylus 2 diamonds Main cut Burr cut -shoe- stationary, moves with engraving head, Shoe 1 sapphire or diamond Rides against surface Determines shadow cell Publication have 8/16 engraving heads Package/product has 1. Image from Gravure: Process and Technology, GAA Gravure engravers Hell Gravure Systems - Helioklischograph Max Daetwyler Corporation Publication Packaging. Images courtesy of Hell Gravure Systems 12 Head Publication Engraver 15 GrC 329 Gravure Printing Techhnology Engraving a Cylinder-Publication Image from Gravure Primer, GATF Diamond stylus Diamond 105° to 135° angle Diamond stylus vibrates more than 9600/second Cell width/depth controllable Depth controlled by stylus impact Shape controlled by cylinder rotation & lateral head movement Up to 200μ wide and 50μ deep. Impact of Stylus Angle on Cell Depth 16 GrC 329 Gravure Printing Techhnology Cell Depth Versus Cell Width deeper cells= more ink, more color Input Input comes from digital file Voltage is generated based on density required. Screen angle: Cell shape Screen angle changed by changing cell shape Compressed, normal, and elongated Example: Height and width of cell change proportionately 30 degree screen is shortened and widened by 0.76 Same number of overall cells per in2 in each style of cell Images from Gravure: Process and Technology, GAA and Gravure Primer, GATF 17 GrC 329 Gravure Printing Techhnology Basic Cell Measuring Points -normal, full cells Enlargement of Cell Name That Cell Shape……. 18 GrC 329 Gravure Printing Techhnology Calibration of Each Head Prior to engraving each head is calibrated and results are stored for quality control if questions or issues arise later -Copper is stable, hard enough to hold the image, soft enough Copper hardness Measured in Vickers (HV) Standards for engraving range from 200-220 HV (hard copper) Vickers Diamond pressed into copper with known force Rotodur instrument. to engrave -Rotodur: has diamond on the head, tests the hardness of the copper to see if it will hold up doctor bade- in between the hardness of copper and chrome 19 GrC 329 Gravure Printing Techhnology Copper Plating Prepares copper cylinders for the engravers Copper Plating no chrome nuggets, chromeo solution Chrome 6 Xs harder than copper 950 to 1200 HV Low coefficient of friction Plated only 6 microns thick (0.0002”) Electroplated in similar manner to copper Finished w/ crosshatch pattern for lubrication. when polish the chrome, very fine crosshatch pattern -allows a little ink to ride on the cylinder -lubricates the cylinder, doesn't print 20 GrC 329 Gravure Printing Techhnology Chrome Plating Chrome engraved cylinders for press runs with a 5-6 micron thick shell to protect from press wear Advancements in engraving technology Laser engraving Zinc Laser exposing Chemically etched high speed laser engraving- 70,000 cells/sec Direct laser engraving Zinc- absorbs heat and energy exposing and chemically etching no chrome nuggets, chromeo solution Cylinder engraving advancements Laser imaging w/ Chemical engraving Black lacquer coating - Resist MDC Schepers Digilas Think Laboratory Laser Stream-FX Laser imaging w/ reverse electroplating when polish the chrome, very fine crosshatch pattern -allows a little ink to ride on the cylinder -lubricates the cylinder, doesn't print Creo/Acigraf 21 GrC 329 Gravure Printing Techhnology nothing physically touching the cylinder Direct Laser Engraving Laser Engraved Cells Close-up view of laser engraved cells – note the uniformity of size and shape Laser versus EM Print Results DLS is Daetwylers Direct Laser System Uses Zinc as cylinder engraving surface Courtesy Daetwyler.com 22 GrC 329 Gravure Printing Techhnology Zinc Properties Compared to copper & chrome, zinc: Evaporates at lower temperatures Melts at lower temperatures Achieves better thermal conductivity Spray Etching Fine-line EM engraving advances Hell Gravure Systems Xtreme Engraving Separate head MDC Transcribe Engraving System Single head 23 GrC 329 Gravure Printing Techhnology Transcribe Engraving dissolve copper into electrolyte DisCoP Dissolvable Copper Plating technology Anode solution instead of copper nuggets in an anode basket. Herbert Metzger – Chema Technology, Inc. 25% increase in cost Gravure print unit Simple Major components Cylinder Ink fountain Doctor blade Impression cylinder Electrostatic assist (ESA) Dryer. Image from Gravure: Process and Technology, GAA 24 GrC 329 Gravure Printing Techhnology Gravure Publication Press Printing Unit Components Printing Unit Components 25 GrC 329 Gravure Printing Techhnology Printing Unit Components Printing Unit Components Printing Unit Components 26 GrC 329 Gravure Printing Techhnology Printing Unit Components Cart (trolley) systems Simple print unit allows cartridge swapping Offpress makeready. Images courtesy of Cerutti Group 27 GrC 329 Gravure Printing Techhnology Trolley Movies Trolley flick Trolley flick 2 Doctor blade Primary role Keep ink off non-image areas Important issues: Distance from nip Image ink dry vs. non-image ink dry Blade angle Set angle Contact angle Blade tip Bevel Reduced thickness blade Radius Other. Short History of Dr. Blade edge profiles 1865(?) 45 degree hand shaped "chisel point" 15 degree bevel (c. 1963 Allison) Reduced thickness (c. 1972 MDC ) (.006") 150 microns 2-5 -degree bevel 1987 Source: Allison Systems Corporation 28 GrC 329 Gravure Printing Techhnology Doctor blade, cont. Blade assembly Quick Ripple-free Repeatable Backup blade Oscillation Minimize local wear Remove debris Pressure Angle “Running in” . Sample Exam Questions 1. Electromechanical cylinder engraving can reach maximum speeds of _______ cells/sec. A. 9,600 B. 22,000 C. 70,000 D. 123,000 29 GrC 329 Gravure Printing Techhnology Sample Exam Questions 2. As the dr. blade set angle is reduced, the actual contact area is… A. reduced B. increased C. consistent 3. One unit of measure for metal hardness is… A. durometer B. shore A C. vickers D. rotodur Wiping (trailing) angle Optimum angle will... minimize cylinder wear give cleanest printing results allow highest speeds Set angle Contact angle Image from: Gravure: Process and Technology Movies Blade Blade Blade Blade flick flick 2 flick 3 flick 4 30 GrC 329 Gravure Printing Techhnology Doctor blade specifications Flat Straight Slight bow expected Thickness varies - .004” to .015” Width varies – 1 to 3+ inches Hardness – 500 to 600 HV. Wear Abrasion Fatigue Corrosion. 31 GrC 329 Gravure Printing Techhnology Impression Cylinder Rubber roller Minimum functional pressure Hardness important – Durometer Vary from 60 to 100 Shore A depending on substrate 60 to 80 for film and laminates 80 to 90 for paper/board The rougher the substrate, the harder the impression cylinder Thinner substrates, softer impression cylinder TIR – lower than print cylinder - .003” Driven by print cylinder Use minimum functional pressure. total indicated runout ESA How do you get ink to come out of cells? Electrical charge on impression cylinder Creates electrostatic field around nip Exerts upward pull on ink surface Particularly with solvents where molecules readily ionize. ESA Results Print quality – particularly in highlights Lower pressures Higher press speeds Reduced impression roller heat Less expensive stocks Negative = Static. 32 GrC 329 Gravure Printing Techhnology Dryer Solvent vs. Water Works dry by… how long it's in the dryer Time Turbulence Moving air Temperature more drying action by sending airflow through explosion proof need to recover at least 92% of solvent recovery Explosion proof Solvent recovery Total enclosure. Inks Solvent inks Used in publication/film Toluene Must recover 96-100% Highly flammable touluene- highly flammable/explosive when contained in small space most typical solvent used uv prints well but is not people friendly any ink exposed to a uv light, the ink instantly hardens Water-based inks Used in paperboard/ product Good ink release UV/EB? Wiping the non-image Viscosity problems Impact of Solvent on Ink RR Donnelley RIT Gravure Day 2009 33 GrC 329 Gravure Printing Techhnology Typical Geography of Gravure 34 GrC 329 Gravure Printing Techhnology Ink Viscosity On press – Efflux cup Zahn Shell ISO Measured in seconds In lab – Automatic viscometer. Movie time! Quad 35 GrC 329 Gravure Printing Techhnology Gravure printing problems Haze Slight haze in non-image area related to blade failure Blade contact (wear, pressure, etc.) Snowflaking/skipping Random, minute spots showing through in midtones and highlights Impression or rough substrate Doctor blade streaks (railroading or tracks) Damage to doctor blade Whiskering (feathering) Fine hair-like lines that “whisker” beyond border of image. Static buildup from ESA. electrostatic assist can help with wiskering Gravure printing problems, cont. Pinholing Failure of printed ink to form a complete film Usually related to ink/substrate incompatibility or high ink foam Volcano Solvent vapors trapped under dried ink film. Ink sequence in Gravure KCMY. 36 GrC 329 Gravure Printing Techhnology Substrates Paper Newsprint Newsprint – 56-59 Standard Roto News – 58-62 Supercalendered (SC) SNC – Soft nip Calendered SC-B – 63-65 SC-B+ SC-A SC-A+ - 68-70 Coated book No. 3-5 LWC Paperboard. Typical Gravure Roll Size Substrates, cont. harder to get a waterbased ink to stick to foil than solvent based inks Film/foil Common types: Polyethylene Polypropylene PVC PET Polyester Polystyrene Composites are common Surface energy must be higher than ink 37 GrC 329 Gravure Printing Techhnology Web treatment – surface tension Surface treatment Film/foil – low absorption Raise dyne level to 38 or 40 How? corona treatments- run through electrical field plasma- similar to corona but with gas Corona plasma flame treatments. Film/Foil properties WVTR Oxygen Transmission rate Haze – optical clarity Tensile modulus – PSI Co-efficient of friction Surface Energy. Examples water vapor transmission rate- the rate of water vapor that passes through a material over a certain time tensile- how resistant to stretching coefficient of friction- how well it slides tensile- how resistant to stretching coefficient of friction- how well it slides Label Print/foil/adhesive paper Dry foods Print/paper/polyethylene/foil/polyethylene Tobacco pouch Polyester/reverse print/adhesive/foil/polyethylene. 38 GrC 329 Gravure Printing Techhnology Gravure Publication Presses kba- 90% of currency and folding cartons KBA Cerruti. Gravure packaging presses used when speed isn't as important unlike publication printers) Windmoeller and Hoelscher Bobst Group Schiavi Rotomec Uteco. Image courtesy of Uteco, Inc. Gravure label presses Chestnut Toshiba. 39 GrC 329 Gravure Printing Techhnology shaftless- every individual drive point has it's own motor Gravure press trends carts (trolleys) Shaftless presses Carts (trolleys) Color Control System. Printing process usage by percentage Printing Process 2001 2002 2003 All Lithography 48 <47 >1 16 21 <4 >5 >6 48 <47 >1 16 21 3 5 7 46 44 2 16 21 3 <5 >9 Conventional DI Gravure Flexography Letterpress Screen On press digital 2005* 2015* 44 41 3 15 >20 <3 4 14 40 36 4 11 >20 <1 <4 25 Source: 2003 GATF Technology Forecast, p. 50 Gravure shipments – Europe* European Gravure Euros 2009 Dollar Total $8.28 billion 2009 Process Share 7.83% 2009-13 Growth -8.5% 2013 Dollar Total $7.53 billion 2013 Process Share 6.67% 2005-13 Growth % -12% *Europe figures compare to US market Source: 2010 GATF Technology Forecast 40 ...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online