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35 Cards in this Set
- Front
- Back
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Three Cylinder System
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- widely used in sheetfed
- single sized impression |
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Five cylinder system
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- more compact
- two blanket cylinders print onto common impression -2 separate plate and blanket cylinders share 1 common impression cylinder. 2 colors per unit. |
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nip
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The line of contact between any two cylindrical objects, such as rollers, cylinders, drums, etc.
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bearers
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A metal ring attached to both ends of a plate cylinder, blanket cylinder and impression cylinder in the printing unit of an offset printing press.
True diameter of cylinder. |
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gutter
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space between cylinder body and bearer
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gap
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A break in the circumference of an offset press plate cylinder, blanket cylinder, impression cylinder, or transfer cylinder in which is typically housed the various clamps or reels that hold the plate or blanket to the cylinder or, in the case of an impression and transfer cylinder, the grippers that carry the paper (or other substrate) through the press.
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undercut
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On an offset lithographic printing press cylinder (in particular, the plate cylinder and the blanket cylinder), the difference between the radius of the cylinder's bearers (metal rings at each end of the cylinder) and that of the cylinder body itself.
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How to measure packing height
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- by packing gauge
- zero the gauge first |
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how to set form cylinder and plate cylinder
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use ink stripe or paper sandwich method
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how to set blanket and impression cylinder
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press knows thickness of paper so it adjusts itself accordingly
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consequences of inadequate packing
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not enough pressure, therefore bad impression/no image
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consequences of excessive packing
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dot gain or worn sheet
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packing materials
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kraft - water resistant
polyester - chemical resistant (not for packing blanket) |
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total squeeze
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pressure exerted between two offset press cylinders measured in inches.
packing height of blanket + packing height of plateanswer can be positive or negative! |
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calculate packing height of blanket cylinder:
blanket thickness is .006 packing sheets are .003 each, 2 pieces used undercut is .009 |
undercut - (blanket thickness + 2 pieces packing) = packing height of cylinder
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single-sheet feeder
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- used on duplicator or small presses
- top sheet is separated and lifted at front |
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stream feeders
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- high speed presses
- top sheet is separated and lifted at tail edge |
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register system
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- positions each sheet of paper
- detects double sheets - three point alignment |
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sheet transferring system
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- drum cylinder
- chain cylinder |
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work and turn
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switches the side guide to the opposite side
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work and tumble
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- front edge becomes rear edge
- gripper margins switch sides |
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perfecting
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- printing both sides of a sheet in one pass
- work and tumble |
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2/4 perfector
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- 6 color press which perfects after two color print
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delivery system
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- chute delivery
- chain delivery |
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chute delivery
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- must be emptied frequently
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chain delivery
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- automatically lowers
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delivery assist devices
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- sheet slow down
- decurlers |
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powder application
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- avoid smearing, offsetting and blocking
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negatives of powder application
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- soiling press
- reduces gloss - powder on blankets |
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IR drier
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accelerates drier
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roll-to-sheet feeder
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- larger amount of paper could be stored at feeder
- roll paper is less expensive |
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remote control system
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- presetting inking/dampening unit
- color registration - measure color density - color ink and dampening supply |
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make ready
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- should take less than 40 minutes and 300 sheets
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conventional blanket
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- requires packing
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compressible blanket
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- includes one layer (or more) of foam rubber, cork, or non-woven fabric fibers between plys of fabric backing.
- can be compressed without causing deformations or structural damage to either the rubber surface or the fabric backing. |
