GRC 328: Quiz Flashcards

question

Components of a printing unit
answer

-Dampening system -Inking system -Plate cylinder -blanket cylinder -impression cylinder -Transfer drums
question

Three cylinder system
answer

-Most widely used in sheetfed printing -quick drying time -Double & single sized cylinder -Double is for cardboard , for thin paper -Impression cylinder in 3 cyl system can be Double or Triple sized
question

Five cylinder system
answer

-More compact design -Two blanket cylinders print onto a common impression cylinder.
question

Nip
answer

-When 2 plates make contact (highest pressure). -Contact line between plate and blanket cyl. -Nip width refers to the contact width between two rollers on the offset printing press, which is determined by roller pressure. -Nip width plays a major role in determining printing quality, so the ability to make period inspection and fine tuning of the nip width, based on factors such as ink characteristics, variations in roller condition (both rubber or metal), and even the printing environment.
question

Bearer ring
answer

the packing gauge is zeroed on the bearer ring
question

Gutter
answer

question

Cylinder body
answer

question

Undercut
answer

distance between cylinder body and bearer ring
question

Adjusting pressure between plate and blanket cylinder
answer

question

Adjusting pressure between blanket and impression cylinder
answer

impression pressure is adjusted by setting the thickness of paper.
question

Calculating packing height, thickness, undercut, etc.
answer

question

Problems caused by excessive packing & inadequate packing
answer

-Inadequate packing = too much pressure -Excessive packing = dot gain and worn heat -Hard roller to soft roller creates an ink stripe
question

Setting up roller pressure
answer

-Form rollers and plate cylinder -Plate and blanket cylinder -Blanket and impression cylinder
question

Packing materials
answer

-Kraft paper: water resistant with different thickness -Polyester: chemical resistant, not for packing blanket -Blanket packing should be cut 1/8 – 1/16 in narrower than the blanket
question

Proper packing:
answer

-Affected by the blanket, bearer compression, and print quality -HARD blanket generates more pressure -slightly overpack a blanket when the blanket is new.Raise up the surface a little more than usual.
question

How do you set up ink roller pressures?
answer

resistance method: \”paper sandwich\” -Wider strip of paper: HIGHER pressure -smaller strip of paper: LESS pressure
question

Conventional blanket
answer

prints mostly solids -at the printing nip
question

Compressible blanket
answer

more likely to use -soft blanket -high resolution prints
question

Blanket surface
answer

-The surface affects dot sharpness & paper release Transfers ink to plate with minimum distortion. -Printing Surface –>Fabric –>Compressible layer –>Fabric
question

Ink release
answer

-Tacking ink film break away from blanket surface -Poor release: cause dot distortion, excessive sheet curl or tail end hook
question

How to store the blanket
answer

-Store in dark, dry, cool plate -store in tubes -store flat
question

Single sheet feeder
answer

-Used on duplicator and some small presses -Top sheet is separated and lifted at the front -Sheet travels the same speed as press
question

Stream Feeder
answer

-High-speed presses with large formats -The top sheet is separated and lifted at the back edge -The front edge, floating on a layer of air, is forwarded on the feed board
question

Three-point alignment
answer

question

work & turn
answer

-The work-and-turn layout prints the same image on both sides of a sheet with one image carrier or plate. -The first side is printed; then, keeping the gripper edge constant, the side edges are reversed, turning the unprinted side toward the image carrier -The right edge becomes the left edge, the front edge remains the same -switch the side guide to the opposite side
question

Work & tumble
answer

-one side of the sheet of paper is printed, then the paper is turned upside down to print the other side from the same form, changing the gripper edge -The front edge becomes the rear edge, the side edges stay the same -Must include 2 gripper margins
question

Powder Application
answer

Pros: -Avoid smearing, offseting, and blocking Neg: -Soiling press -Reduce gloss -Finishing problems -Powder on blankets
question

Doubling
answer

second image appears alongside the first image
question

Slur
answer

dots appear elongated or smeared on a single unit
question

Ink Setoff & remedies
answer

-When ink transfers to the back side of the sheet Remedies: -less ink -more powder -need more drying time -less acid
question

Chemical & mechanical ghosting remedies:
answer

Chemical Ghosting: -can see through the other side -glossier on one side -drying issue -back side printed firstCAUSES: 1) ink coverage on 2 sides are different 2) drying problems-dry fast enough *print heavy coverage first, not light coverage to eliminate this problem Mechanical Ghosting: -faint images -form rollers have hole, less ink -diameter is smaller than the plate CAUSES: 1) ink starvation-4 form rollers are better than 3 2)layout 3)form roller(oscillating=image becomes smaller)
question

Poor fit at tail edge
answer

question

Flood coating & Spot coating
answer

Flood coating: coats everything Spot coating: coats on certain area-waterbeads-sometimes spot coating is used to emphasize a picture
question

Pro’s and Con’s of Varnish
answer

PROS: .petroleum-based .same formulation as ink formulation but without .pigment, therefore, no color .5 or 6 = for non typical color press .the most economical coating .can apply flood or spot coating .can be applied on any unit .different gloss level-matte, dull, gloss CONS: .can yellow overtime *always put on last unit
question

Pro’s and Con’s of Aqueous Coating
answer

.for flood coating, easy to control and does not yellow overtime. .Requires heavier paper-80 lb or over text stock or will curl -certain pigments may bleed (rhodamine red, reflux blue, purple, violet)
question

Tower coater
answer

-the one after the last printing unit -has anilox roll and blanket
question

Color shift in aqueous coating and UV coating
answer

-color will change for certain pigments-reflex blue etc. because alkaline will shift color
question

Substrates requirements of aqueous coating and UV coating
answer

-coating on 2 sides: work n turn formula, apply least amount of coating as possible
question

UV primer
answer

aqueous coating, if want on uncoated paper cant apply uv coating first so you have to apply aqueous coating(primer) before UV
question

Coating quality difference (aqueous coating, varnish, and UV coating)
answer

-aqueous: -used to flood coat -used on 80 lb or over text -certain pigments may bleed: rhodamine, reflux blue, purple, violet -varnish: petrolium based -same formulation as ink formulation but w/o pigment, no color -most economical -can apply flood or spot coating -can be applied on any unit -different gloss level- matte, dull, gloss -can yellow ovetime *5/6 is typical for color press) *always put on last unit uv coating: -highest gloss and rub resistance -low vocs -immediately drying -no fda approval for food contact -3-10 times more expensive than aqeuous coating -can be inline or offline
question

Pressure settings on coater
answer

the \”kiss\” method applies just enough pressure
question

Requirements of coating on both sides
answer

special formulation: work and turn formula apply least amount of coating as possible
question

Coating problems ( sheet curl, backtrapping, color shift)
answer

backtrapping-ink on the coating blanket =by excessive pressure, too little coating applied, ink is pulled from sheet, ink is overemlusified, coating does not wet ink properlycolor shift- problem pigments (red, reflex blue etc.), ph (aqueous coating 8-9), ink contains dyes. sheet curl-low weight paper, excessive heat
question

Materials used in testing a press
answer

plates: determine the resolution (need to have high resolution), fine screen needs high, not low resolution. blankets: quick-release blankets for sharp dots. sponging= temperapedic=not quick at all paper- 80# or 100# C2S gloss. Grade 1 or 2 inks-acceptable dot gain and overprint traps at reasonable ink film thickness fountain solution-compatible with inks and plates, controlled pH and conductivity.
question

Dry Solid & Wet Solid
answer

dry solid: run on each unit and check impression turn off f.s. therefore, ink gets onto platewet solid: run on each unit and check dampening system. burn plate from image
question

Check the ink density variation through the press run
answer

50 consecutive sheets-determine if ink ductor and oscillator are mechanically operating correctly 50 random sheets-determine if ink and water balance, less than 0.05.
question

Neutral color defined in GRACoL 7
answer

neutral definition: a*0, b* -2 tvi-tone value increase or dot gain- CMY 12-16%, K 14-20% Grey balance %-50-40-40
question

Linear CTP plate
answer

make a calibration run using a linear CTP plate= first step -dots on plate= dot % in digital file * the info that is out in digital file, software interprets face tone area
question

Hybrid ink
answer

seen in conventional offset UV, oil based combined use regular rollers to blanket dries by radiation
question

Pre-set the ink keys on press for makeready
answer

Get instant access to
all materials

Become a Member