Initially Flexo printing used rubber (like a Stamp) which was then pressed to print the image. The first flexo printing machine was made in 1980 in England by Bibby Baron and Sons, at the same time the same machine was also made in Germany which is named Aniline because it uses Aniline ink.
In 1950 Franklin Moses proposed that the Aniline printing process be renamed be Flexo print.
For the next 30 years the flexo machine is still considered a printing technique for quality low so that it is generally used to print corrugated boxes. But with the discovery of UV ink and its drying, then flexo print using ink UV began to be used to print labels.
Basically the preparation for design and artwork for flexo printing is the same as artwork design work for other printing systems, but there are some differences fundamentals that we must understand. To print flexo what we see on the computer screen and what we see in the proof, may not be the same as the final flexo print.
Proof is made only to see the layout (position of the layout).
A. TERMS IN FLEXO
1. TYPOGRAPHY
Considerations for font size, object ex and line thickness
2. LINE REVERSE / KNOCKOUT
Line object, it is recommended to be limited to no more than 1 color for color
the arrangement.
3. DROP SHADOW
4. REGISTER
5. OVERPRINT
6. CONVERTING TYPE TO OUTLINE
7. TRAPPING
8. DIE LINE
B. HALFTONE SCREENS
Halftone is a collection of small dots that when viewed from a distance will appear
like a stream of gray or colored smelly shadows. The number of the dots must be
enough to be boxy. For color images, there is a stack of dots
consisting of dot colors cyan, magentha, yellow and black (CMYK). The higher the screen
frequency (the more lines per inch), the smoother the image will be. For flexo
quality can be used up to 175 lpi. The defaults are 100, 120, 133, 150 and 175 lpi.
Dot is a dot (circle) that is used to form halftone printing.
The shape of the dot also varies, including round, square, elliptical and octagonal.
In general, a round pacifier is widely used.
The things that cause dot enlargement:
. Excessive ink absorption
. The ink spreads to the material because the viscosity of the ink is too high, making it difficult
spread
. Over-pressed photopolymer (flexo must be with “kiss printing”
. Machine is not good
C. Ink
Flexo ink comparison:
1. Flexo Waterbased Ink
Excess :
- Does not require Exhaust
- Does not cause air pollution
- Excellent absorption, low energy cost for absorbent materials
- No need for explosion proof equipment
- Does not pose a problem for transportation (harmless)
Deficiency :
- If printed on plastic film, it can cause problems with sticking
as well as drying. But for modern machines this problem has been solved.
- Less shiny
- Sometimes foamy
- Cleaning is quite difficult
2. Solvent based flexo ink
Excess :
- Easy to use (set up, cleaning)
- Dries quickly
- Good adhesion to plastic film
- High mechanical resistance
- Stable surface tension
- Anilox is easy to clean (compared to using waterbased inks)
Deficiency :
- Evaporation of solvents causes pollution (harmful to health)
- Air exhaust equipment is required and must be explosion-proof
- There are regulations for the use and storage of solvents and inks
3. UV flexo ink
Excess :
- Does not require Exhaust
- The ink does not dry on the machine
- No need for explosion proof equipment
- Very glossy (glossy)
Deficiency :
- The price of ink is expensive
- Requires a high enough energy, especially if using a cooling roll
- If the temperature changes, the viscosity will also change and can
cause discoloration especially special colors.
- Some materials do not stick well.
by Su-harto
