WHAT IS INKJET?
How does inkjet printing work?
WHAT IS INKJET?
Inkjet is a non-contact printing process in which very small drops of ink are sprayed (on demand) through nozzles.
There are two possible printing modes with inkjet: HIGH DEFINITION (used for fine print and text) and LOW DEFINITION (used for solid print and coarse text). Inkjet is often used for short/medium run, high quality printing.
WHERE DOES INKJET FIT IN?
OPERATION OF THE INKJET MACHINE :
To start the printing process, the machine operator assembles a reel of paper which passes between anti-static bars to remove any trace of electricity. The paper is then passed between anti-dust rollers to remove any impurities (wood, dust, cardboard) that may have remained on the substrate. Then, other rollers will stretch the paper to the maximum so that it is well stretched.
Once perfectly cleaned, the paper is fed into the machine where the 35 print heads are located. There are a total of 5 heads per colour (in order of application): white, violet, orange, blue, magenta, yellow and black. When the paper is fed, the print heads deposit the ink by means of a drop system. The drop can be larger or smaller depending on the precision required: larger for solid colours and finer for text. The superimposition of the inks makes it possible to obtain a natural opacity (more opaque than flexography, similar to silk-screen printing).
Once the print heads have deposited the different inks in turn, two UV lamps will dry the surface of the print to set it. Then two other UV lamps will dry the print thoroughly so that it does not move. Once the drying process is complete, the print goes back up to the operator's control table to check the quality of the print. All the calibrations are carried out with the help of a camera and manually, for extreme precision.
SPECIFICATIONS FOR INKJET PRINTING
- Unlike other printing systems, with inkjet there is no movement of the print heads. It is the paper that moves and picks up the colours one after the other.
- There is a constraint in the quality of the registration of the colours one on top of the other, especially if the texts are very fine. This is why it is compulsory to use a text size of at least 5 points. Please note that if you use white support, the text must be greased so that the white does not come out during printing.
PROS AND CONS
- UV and moisture resistance
- Ink durability (no need to add protection: varnish, laminate, etc.)
- Opacity of the print
- Leaves a glossy finish (similar to silk-screen printing)
- Stability of colours throughout the print run
- Possibility of printing in indichromy (6 colours) to get closer to Pantone colours
- The area where the printheads cross may cause a slight variation in the final rendering (especially on solids)
- Marking of delicate white under fine text
- The order in which the colours are applied cannot be changed
OVERVIEW OF INKJET PRINTING
- Inkjet is perfectly suited to a wide variety of sectors: food, cosmetics, industrial, etc.
- Inkjet printing is similar to screen printing thanks to its high ink deposit, which gives it relief and good resistance over time
- Some papers and substrates are not suitable, especially those that absorb a lot of ink (e.g. natural-looking, porous paper). It is essential to use materials specific to inkjet for optimal results
- The crossing zones of the print heads can, depending on the visuals, show lines or differences in colour in the final rendering
- The print files must be designed in accordance with the expectations of the inkjet process (width of the text, registration of the overprint).