Printing technics. Flexo printing. Gravure printing. Offset printing

Transcription

1 Printing technics Flexo printing Gravure printing Offset printing

2 Flexographic Rubber roll technics Anilox roller

3 Negative and positive doctor blades Advantage Better control over the ink transport Flexographic 3-Cylinder system negative doctor blade 2-Cylinder system negative doctor blade

4 Flexographic Chamber doctor blade technics Advantage Closed system for the ink Less evaporation Less contact with the air

5 Flexographic Anilox roller Doses the ink to the cliché; Number of lines - With what resolution the anilox roller can print. Is defined with Lines/cm or Lines/inch Volume - How much ink the roller theoretically can transport. Is defined with cm 3 /m 2. Approximately 75% of the ink is transported over to the cliché.

6 Flexographic Anilox roller Gravure angle - How the cells in the anilox roller are oriented

7 Flexographic Anilox roller Two different types - The classical; A steel core covered with a layer of copper and chromium - The new; A steel core covered with a ceramic layer The ceramic roller has a longer lifespan than the steel roller

8 Flexographic Printing machines CI (Central Impression) - Easy to maintain focus - Difficult to dry the ink between the printing units

9 Flexographic Line - Hard to maintain focus with flexible materials - Good drying capacity between the printing units

10 Flexographic Typical products made in flexographic printing machines - Corrugated board - Plastic bag - Flexible packages - Labels - Napkins - Envelopes - Gift wrappings - Wallpapers

11 Flexographic Advantages and disadvantages with flexographics; - High production rate with fast order changes - Simple and inexpensive method - Hard to achieve an even result - The printing result can change during an order

12 Gravure printing Techniques

13 Gravure printing Advantages and disadvantages with gravure printing; - High quality on the result - Easy to control the print in the machine - Even quality during printing - High production rate - Long durability of the rolls - The rolls are expensive to manufacture and buy - More suitable for long orders - Requires a smooth surface on the material

14 Gravure printing Typical gravure printing products - Flexible packaging - High quality paper products - Wallpapers - Aluminium foil - Exclusive magazines

15 Process Printing The relation between the number of lines Anilox : Cliché Gravure angle for the different processes colours Density Dot increasing Cyfus test

16 Number of lines The relation between Anilox : Cliché 20 LINES 34 LINES A higher number of lines gives a more detailed picture. It is more difficult to keep a clean print.

17 The relation between Anilox : Cliché Number of lines -The number of lines on the anilox should be at least four times higher than on the cliché

18 Why Anilox roller?

19 Gravure angle - The gravure angles is how the different process colours are oriented on the cliché. To avoid getting the Moire effect it is important that the colours are separated - Normally the colours are oriented accordingly; Cyan 7 Black 37 Magenta 67 Yellow 82

20 Density Shows what colour strength the current colour has Is measured with a Densitometer The density is measured at a given viscosity. The density is adjusted with varnish and colour concentrate not with solvent. Cyan 1,3-1,5 Magenta 1,3-1,5 Yellow 0,95-1,1 Black 1,4 2,0

21 Dot increasing The impression of a dot from the cliché will always be bigger than the equivalent dot on the cliché The dot increase is measured with a Densitometer IDEAL REAL

22 Dot increasing Factors that affect dot increase - The pressure between the material and the cliché - Transfer between anilox and cliché -The relation between anilox and cliché -The viscosity on the ink -Type of cliché

23 To much pressure between the cliché and the roll -Right pressure -To muck pressure between the anilox and the cliché -To much pressure between the cliché and the material

24 Cyfus test A Cyfus test is made to characterize the printing machine. The test is made together with the repro firm and the ink supplier. During the printing it's decided witch standard values that are accurate for the machine. - What density the colours should have - Witch printing viscosity that is correct - Dot increase - Witch type of cliché that should be used The values that the test gives are used by the repro firm when they manufacture the clichés for the current machine. When a new order arrives the printers use standard recepies then the images should be correct.

25 Factors that affect the printing result - Viscosity - Anilox roller - The pressure between the anilox roller and the cliché - Hardness of the cliché - The pressure between the cliché and the material - What type of material being used