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111 Cards in this Set
- Front
- Back
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press approval
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when the client attends the start of the press run, for the purpose of approving the first good sheet
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what to bring to press approval
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loupe, samples, pms book, good attitude
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what to look for in a press run
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registration, colour, flaws/typos, completeness, density
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what is considered proper lighting
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D50 (5000 Kelvin) - sunlight @noon
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hickey
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donut shaped marks
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ghosting
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faint patterns
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slur
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elongated halftones
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excessive dot gain
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halftone dots grow in size
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scumming
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ink in non-image areas
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mottle
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uneven appearance in heavy solids
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Press Run must have consistency - 3 things
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1. postion of image (registration from and side guides)
2. registration between colours (no shift) 3. colour and density |
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press approval consistency (pulls)
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pull every 100-500 sheets, then every 1000 sheets
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4 components of printing ink
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1. pigments
2. vehicle 3. dryers 4. additives |
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pigments
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gives ink its colour, must be consistent and non-abrasive
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vehicle
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liquid mix of varnishes and students which holds and disperses the pigment (disperses pigment like glue)
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dryers
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salts that promote drying and harden the ink surface, too much slows it down
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additives
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substances that improve ink quality- slip compounds, wetting agents
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ink mixing (device)
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twin shaft diserpser
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ink milling (device)
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three roll mill
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ink setting
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occurs right after printing
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drying
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occurs after ink setting down by several processes - absorption, evaporation, IR (infared radiation), UV, Oxidative Polymerization (chemical with H20)
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Uncoated
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pigments lay on top, ink vehicle below it
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coated
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has capillary pores (strings) - taller
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ink film thickness (microns) 1/1000
sheetfed offset |
5.0
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web offset
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7. 5
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lettterpress
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10.0
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gravure
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30
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screen
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25-125
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halftone dots affect the appearance of the printed colour image (3)
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- size
-frequency - colour |
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density
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how light/dark a printed colour is
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snap specifications
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specifications newsprint advertising product
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dryback
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ink film dries, density goes lower
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GATF Star target shows printing problems...
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slurring
doubling dot gain |
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cause of excessive dot gain
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improper in/water balance
too much ink and type of paper |
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slurring
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paper moves slightly while being printed
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doubling
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static electricity or paper deformation
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3 principles of inkling system
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ink metering system
distributor section form rollers |
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ink metering system
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contains and control ink supply
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distributor section
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evens and distributes the ink
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form rollers
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provides ink to the image carrier
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ink fountain
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controls the flow of ink
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rollers
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distributes ink
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conventional blankets
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sensitive to packing, meant for long runs with same thickness, harder, deforms at the nip
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compressible blankets
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allows for changes in thickness of paper, softer, better registration, wider packing altitude, has extra layer of thickness
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store blankets in..
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cool, dark place, rolled loosely in tubes
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blanket bars
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mount blankets to press
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3 reasons for packing
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compensate for diff. thickness
adjust pressure compensate for paper stretch |
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plate to blanket squeeze
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"0.002 - 0.006"
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true rolling
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identical in diamete, proper P-B squeeze
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bearers
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come up on each side
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body setting equation
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PUC + BUC = BS
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BS AND PB Squeeze equation
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BS + PB squeeze = Plate Cylinder + plate packing + blanket caliper + blanket packing
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fountain solution components
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water, gum, acid, buffer, wetting agent, fungicide, antifoaming agent
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gum
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desensitizes non-image areas
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buffer
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maintains constant pH
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Wetting agent
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reduces surface tension, makes water wet
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IPA
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Isopropyl Alcohol - add last to FS, makes water fluid
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advantages of IPA
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fast drying, increases viscosity , easier control
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disadvantages
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flammable toxic, irritating vapours, decreases ink density
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ideal pH of FS
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4.5-5
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if pH is too alkaline... 7-14
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plate scumming
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if pH is too acidic 0-7
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image loss, ink stripping, poor ink drying
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dampening system components
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water pan, pan roller, doctor roller, oscillating roller, form roller,
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continuous dampening system
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no ductor roller, constant FS film thickness,
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intermittent dampening system
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adjustable speed, roller goes back and forth,
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example of intermittent system
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Dampen-orr system
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example of continuous system
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Miller-meter,
miehle-matic, harris-cottrel |
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integrated system example
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dahlgren system
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flexo advantages
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lower cost, speed, wide variety,
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anilox roller
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controls amount of ink brought to plate by thousands of cells
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doctor blade
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shears excess ink from anilox roller (plastic/metal)
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plate cylinder
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accepts ink from anilox roller, prints directly to substrate (wrong reading, raised image area) can be reused (either rubber or photopolymer)
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anilox settings
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land area- area between cells
cell opening- w of top cell cell depth- depth cell volume- ink capacity, BCM Billion cubic microns |
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low LPI
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loss of detail, more ink
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high LPI
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more detail, less ink
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Dr. Blade
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plastic- short life, poor quality
steel- high quality, expensive |
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in-line flexo
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printing units are in-line w each other
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common-impression flex
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printing units are around one cylinder
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sheetfed flexo
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one big unit good for corrupted boxes
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anilox settings
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laser engraved- great, expensive
chrome/ceramic- sucks, cheap |
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stickyback tape
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variable flexibilty for diff. print jobs
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flexo inks
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water-based
solvent-based UV Inks |
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water based inks
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least harmful to enviro.
most common dries by evaporation, difficult to clean |
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solvent-based
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for difficulties substrates ex foil
harmful to enviro. dries by evaporation |
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UV inks
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fires by UV, high cost, easy wash-up, allows thick ink density
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kiss cutting
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allows cut through of top surface, not the back
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Ink Film Thickness
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-correlation between ink film thickness and optical density
-prufbau, densitometer, ink film thickness gauge -higher ink film, higher density - |
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Opacity of Ink
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-visually compare opacity/transparencies of two ink (yellow pantone, process)
-draw down blade -spot colours are more opaque than process colours |
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rubber and plastic hardness test
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hardness of compressible vs. conventional blankets and two form rollers
- two blankets -dampening/form roller - conventional blanket should be harder than a compressible blanket |
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Colour Strength and Ink mileage Correlation
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correlation between standard and sample cyan (strength and ink mileage)
-densitometer, drawdown blade, digital scale -standard has more pigment than sample - better density, stronger colour |
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abrasion resistance rub-proof test
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-affect of linseed oil on formulation of ink
-little joe, ink rub tester -coated has less rub resistance than uncoated (more absorption), oil should mean ore rub resistance |
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sheetfed offset training stimulation (SHOTS)
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-determine how changes in the press can affect output (ink level, FS,
-PC monitor, software |
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pH and conductivity of FS
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-determine pH and conductivity with increasing increments of FS
-digital ph and conductivty meter, ph strips -ph should eventually even out |
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Flexo ink Evaluation
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-capabilities of water-based ink on different substrates
-flexo hand proofer -coated- maintained colour and strength -uncoated- lost colour, absorbed darker -acetate- maintained its colour, most dense, |
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unwind diameter
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36"
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print width
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7"
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press speed
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300 ft/min
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main drive
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3 HP
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a loupe is used at a press for...
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identify printing flaws and check colour to colour registration
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What is the purpose of punching the lead edge of the plates before mounting them to the press?
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It helps to achieve registration between colours more quickly
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antiskinning
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prevents skin on ink can
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anti-set off
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stops ink on paper from rubbing off onto other paper
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what is the density tolerance that was used for the digest ad press run?
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+/- 0.2
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What is the paper stock that was used for the digest print ad?
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100 lb. gloss text
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The print control strip is printed at the tail edge of the press because:
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The lead edge is reserved for the press grippers
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what type of print control strip was used?
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Heidelberg 4GS
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exact places a 3 pt registration would be on a press?
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THERES ONE ON THE OPERATOR SIDE AND TWO ON THE LEAD EDGE
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paper feeding issues are caused by:
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1) static electricity, damaged paper, humidity and temperature issues
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what should be checked for proper registration when printing 4/4?
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a &c
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Which of the following accurately describes the plate mounting system on the Heidelberg pm74-4p?
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semi automatic
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brand and model of the flexo machine in the lab ?
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cadet model 700
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