Web offset
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Transcript of Web offset
The paper is in roll format not sheets. Rolls of paper come in several different widths.Web cutoff is set and determines one dimension of the size of paper you can run.½ web and full web
½ web cutoff around 17-3/4”Full web cutoff around 23”
Ink dries by solvent evaporation which is speeded up by heatMagazines, large quantity brochures, and periodicals all print on web presses.Web presses are perfecting pressesDo not run as many types of paper as sheet fed offset.
InfeedPrinting Units (CMYK + spot colors)Heater – must have to dry inksChillerFinishing
Die cut, fold, trim, perf, score
Plate Cylinder
Blanket Cylinder
Plate Cylinder
Blanket Cylinder
Ink Train
Ink Train
Water rollers
Water rollers
Used mainly for newspapers and advertising flyers with a short lifespanInk is dried by oxidation and absorption into the paper, not heat.The same process as heat set web except for the heater and chiller
What is it?Spoilage of materials & timeAutomation possibilities
Closed loopPress fountain set-up from electronic fileStore final press settings
A mixture of colorant, vehicle (varnish), and additives (modifiers).
Dry powder or Paste pigments give color (hue) to inks.Synthetic or organic colorantMost expensive component in ink
Composed of several different resinsUsed to wet the pigment.Vehicle bonds the pigment particles to paper.Allows ink to transfer through the press
Substances that give ink additional additional characteristics.Some additive functions:
DryingScuff resistanceDurabilityFade resistancePH Buffer
AbsorptionSheetfed offsetCold set web offset
OxidationSheetfed offset
EvaporationHeat set web
RadiationUV inks