an introduction to gravure imaginggravure.cias.rit.edu/gravure/pdf/gravure_day2007/yanny_1.pdf ·...
TRANSCRIPT
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Cylinder Engraving
Gravure is an intaglioprinting process.
That means, theimage is cut or etchedbelow the surface.
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Copper Cylinders
• Copper is used to cover cylindersbecause it’s soft and pliable, making iteasy to engrave.
• Each cylinder weighs approximately2,500 pounds – about the same weightas a VW Beetle.
• Cylinders last for tens of millions ofimpressions, so gravure is usedfor long press runs. The gravure image carrier is a
re-usable steel-based cylindercovered with a layer of copper
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Gravure Workflow
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Cylinder Preparation
• The gravure imaging processbegins with the cylinder comingoff press.
• Gravure cylinders come invarious circumferences.
• The cylinder size is determined by:
– Final size of the page
– Number of pages in the form
– Repeat of the design
Stripping Station –RemovingBallard Shell
• After the cylinder is cleaned,the top layer of copper andchrome is removed fromthe cylinder.
• This is called the Ballardshell, which allows thecylinder to be reusedmany times.
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Copper Plating
• After the cylinder is cleaned, it’s movedto a copper plating tank, and the steelcylinder is electroplated with a thinlayer of copper.
• The cylinder is stored in racks to usefor future jobs.
• The copper is only 80 microns thick –about the thickness of a human hair.
• Later, the copper will be removed fromthe cylinder and replaced, so thecylinder can be used over and over.
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Copper Polish
• To prepare for engraving,the copper surface isautomatically polished.
• Polishing removes anyimperfections and smoothesout the cylinder.
• Polishing also adds aroughness to the surfaceso it can retain the ink that willlubricate the cylinder.
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Helio Form Station
• A press imposition formneeds to be created beforewe engrave the cylinder
• The form positions andaligns pages accordingto the book layout.
• Forms are digitallytransferred to theengraving station.
Cylinder Engraving
• Now the cylinder is ready to beengraved (after impositionform stage).
• Digital data for text and imagesfeed these engraving heads,that images the copper cylinder.
• The printed image consists ofhoneycomb shaped cells that areengraved into the copper cylinderusing a diamond-tippedengraving head.
• The un-etched areas of thecylinder represent the non-image(unprinted) areas.
100 % 50 % 5 %
Electromechanical Engraving
Cross Section of Cells
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• Engraving the image onto the cylinderis a high-speed, fully automatedprocess.
• Diamond tips engrave hundreds ofthousands of individual cells into thesurface of the cylinder.
• The depth and size of the cells controlthe amount of ink that gets transferredto the paper.
• The size and shape of the cells alsodepend on the color of the ink and thetype of paper it will be printed on.
K6 Fully AutomatedEngraving Technology
K-6 Advantages
• Fully automated cylinder engraving
– HelioSprintHigh speed electro-mechanical engrave heads
– CellGuardPre-engrave & post-engrave verification of cells
– GipsyNTHigh speed processor of digital page information
• Enhanced productivity(shorter setup times; reducing client cycle time)
• 40-44 cylinders engraved per 24 hrs.(2 engravers)
• Consistent quality(automated ribbon balance verification)
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Pre-ChromePolisher
• After engraving, the cylinderis polished for a consistentsurface, and removesburrs (imperfections).
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Cylinder is submergedinto degreasing tank
Cylinder isDegreased
• The cylinder is electronicallycleaned to remove all greaseand oil from the surface.
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Chrome Plating
• Once the cylinder is engraved, it’s cleaned andcoated with a final layer of chromium.
• Chromium:
• Provides a hard surface layer that helps preventthe doctor blade from wearing outduring printing.
• What is a doctor blade?
– Device that removes excess ink from thenon- engraved portions of the cylinder.
– Allows cylinders to be used for press runsof over one million
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Chrome Polisher
• Chrome polisher looks similarto the pre-polisher.
• The chrome-plated cylinder ispolished once again to “roughup” the surface, making theink act as a lubricant.
• After the final chromiumsurface is polished, thecylinder is inspected.
• If it’s okay, it’s ready to goto press.
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Cylinder Handling& Storage
• The cylinder is stored in racks to use for future jobs.
• Lomira stores up to 2,000 cylinders
• Cylinders are automaticallytransported from one step tothe next – from imaging tothe press room and backto storage.
• During makeready, thepress operator carefullyloads the printing cylindersinto the press.
Cylinder Handling& Storage
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What Type of CustomerFits Gravure?• Gravure prints high-quality
images with intense, rich colorwith one pass through the press.
• That’s why it’s often used forhigh-volume printing such asadvertising pieces like inserts,magazines and catalogs.
Thank you,questions?