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Graphic Communications
GRA 324

TOPIC 2: PRINTING PROCESSES Conventional (Impact) Processes Print Process Types Image Carrier Characteristics RELIEF Letterpress/Flexo wrong reading/raised ring of ink around letter forms PLANOGRAPHIC Litho/Offset Litho plate/flat smooth edges/separated by chem. properties INTAGLIO Gravure metal cylinder serrated edges/liquid POROUS Screen Printing screen frame may have a screen pattern in image areas; thick ink film 1. RELIEF PRINTING  Letterpress raised image carrier is inked, then applied w/ pressure to a substrate image carrier: wrong reading (mirror image) made of metal ink: thick paste sheet-fed/web-fed (roll-fed) first/major printing process in use ‘til 1960s lost to offset lithography less than ½ of printing is done by letterpress o Platen  flat image carrier which open/close like a clam shell  raised image is metal (lead) or wood “cuts”  press can be used for perforating, scoring, die cutting o Flatbed Cylinder  flat image carrier w/ rotating impression cylinder  substrate is held to impression cylinder w/ “grippers”  rarely used in modern plants o Rotary  fastest/most efficient design  image carrier (plate) wrapped around cylinder  impression cylinder is flat, squeezes substrate against image carrier  rarely used in modern plants  Flexography similar “raised image” principle to letterpress image carrier: is rubber/photopolymer & wrong reading ink: water/solvent-based liquid pourable usually web (roll) fed except sheetfed corrugated substrates wide range of substrates (plastic, bags, labels, etc) major process used in packaging industry 2. PLANOGRAPHIC PRINTING writing from a flat surface  Lithography “Stone Writing” image carrier: is flat, plate ink: oil based, thick, paste ink/water-based fountain solution  image areas: attract oil but repel water (hydrophobic / oleophillic) non-image areas: attract water but repel oil (hydrophilic / oleophobic) oil and water don’t mix, chemically different  Offset Lithography plate first dampened w/ water-based fountain solution fountain solution adheres to non-image areas image areas repel fountain solution highest quality ink rollers apply ink to image area (which doesn’t adhere to water coated non-image area) imk image is transferred (offset) to a rubber blanket substrate plate: right reading blanket: wrong reading printed image: right reading used for magazine, books, flyers 3. INTAGLIO image is “etched” or embedded into metal printing cylinder as tiny as cells image can be made darker by etching “cell” deeper/larger than for lighter colours  Gravure printing cylinder rotates in an ink pan doctor blade – scrapes ink off surface impression cylinder pressespaper against printing cylinder long-term press runs that go for millions of impressions the only press that has ability to control amount of ink is layed down in a gravured area deep (dark cyan) / shallow (light cyan) not well suited for plastic/foil, suitable for paper substrate 4. POROUS PRINTING  Screen Printing image carrier: screen in a frame ink: thick , transferred through image carrier non-image areas are “masked off” image areas are porous non permeable (dark areas where ink doesn’t pass) squeegee used to draw ink across through porous image area most commonly used for fabrics/glass/ceramic Non-Impact Processes Advantages Disadvantages  variable data capable  limited quality/reso on some substrates  4-colour process in one pass  colour inks (dyes) fade quickly  low cost for small quantities (<1000)  no econoy of scale for larger quantities  economical make ready  slow print speed  cleaner operation Processes characteristics NIP Printing  no physical plate or image carrier Plateless Printing  no pressure applied to substrate Electronic/ Non-Conventional Printing  can be used for computer-2-print output Digital Printing  applications in variable-data printing 1. XEROGRAPHY  Electrophotography, Laser Printing, Photocopying tiny solid toner particles (+) charge photoconductor drum (-) charge toner is transferred to substrate of (+) charge – static electric toner particles (powder) are fused to paper by heat drum is cleaned, process repeats little round beads of plastic – small carbon particle (toner particles) white/black 2. INK JET PRINTING  Continuous uses highly-fluid water-based ink controlled stream of individual droplets print head moves across the page droplets are charged in charging system deflector uses opposite charge to direct droplets unneeded droplets are deflected into gutter/recycled  Drop on Demand (DOD) intermittent system discrete “bursts” of ink are directed by a moving print head drops are created by piezoelectric crystal effect/thermal technology (bubble jet) Definitions: Printing  the mass production of an original file/doc Printing Process Conventional Printing Process TOPIC 3: PAPER Paper Sizes BASIC Basic Size One sheet Paper Types (inches) area (sq. in) 17 x 22 374 Bond, ledger, onionskin, writing 20 x 26 520 Cover 22.5 x 28.5 641.25 Bristol 24 x 36 864 Newsprint, kraft, tag 25.5 x 30.5 777.75 Index Bristol 25 x 38 950 Offset, coated offset, uncoated book, coated book, C1S label, C2S offset *17x22 Bond (4 legal sizes) *25x38 Uncoated/Coated Offset Book *20x26 Cover METRIC (ISO) – US/Canada A Series Typical Applications B Series A0 841 x 1189 posters, tech drawings, maps 1000 x 1414 B0 A1 594 x 841 707 x 1000 B1 A2 420 x 594 diagrams, drawings, large tablets, tabloid newspapers 500 x 707 B2 A3 297 x 420 353 x 500 B3 A4 210 x 297 stationary, magazine, catalogues, forms, lazer/inkjet printer copyi250 x 353 B4 paper, business paper A5 148 x 210 notepads, books 176 x 250 B5 A6 105 x 148 postcards, books 125 x 176 B6 A7 74 x 105 88 x 125 B7 A8 52 x 74 62 x88 B8 A9 37 x 52 44 x 62 B9 A10 26 x 37 31 x 44 B10 *A0 Size (841 x 1189mm) = 0.841m x 1.189m = 1.0 m2 *B0 Size (1000 x 1414mm) = 1.000m x 1.414m = 1.414m 2  Bigger than A0  Design and proportion for esthetics  Always round down Paper Weights in (lbs. or gram) is a way of describing the heaviness, bulk of a sheet as paper weight increases, implications increase implications for:  opacity, ink show through  folding, rigidity and stiffness, softness  strength and feel  cost M WEIGHT (lbs.) BASIS WEIGHT GRAMMAGE 25 x 38 160 M Mead Gloss Offset
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