Lineaturation in flexography is the way to measure the print resolution of the packaging. It is a very important element, since the correct choice of the lineatura will allow the printing process to be the most optimal.
Let's start by defining what the weft line is in flexography, to understand its importance.
What is the screen ruling?
Lineaturation is a measurement used to determine the number of dots printed per linear inches or centimeters.
In other words, it is the number of points in an area. The more concentrated points there are, the greater the linearity.
The weft in flexographic printing
But it is important to know that flexo printing is given by the overlapping of screens or percentages of dots.
If you did not know, it is very easy to identify.
Take whatever packaging is close to you, and get as close as possible.
Can you see the small dots? That is the screen that is generated in flexo.
If you compare between several packages, you will see that in some it is more difficult to see them and in others it is easier.
The ones that are less noticeable, is because they have a high lineature in printing, and the most visible, on the contrary, it is lower.
Examples of guidelines
Through the following images, you can see the difference.
If we take an image as seen on any digital device like this,
And we apply different resolutions of lineatura, this would be the result
See how each one would look from closer
How is linearity measured?
There are two ways in which a linear measurement can be expressed. Lines per printed inch LPI or lines per printed centimeter.
This depends on which style of measurement you are most familiar with, inches or centimeters. But it is very important to know that there are 2 expressions.
It is usually expressed in LPI.
If you have a flexographic print that has a screen, you can measure the linearity with a tool called a lineometer.
It is made on a sheet of transparent material and can approximate the linearity of a printed form with an ordered pattern (not stochastic).
To use it is very easy.
The lineometer is placed on the form and it is rotated and moved until a moire effect appears due to the interaction of the screen of the form and the pattern formed by the lines.
A figure similar to a cross will be formed, which will indicate towards the edge the value of the linearity. This is not a precision tool, but it will help you quickly know the printed resolution.
How to define the lineatura?
To print in flexo, you must tell your pre-press supplier that the flexo plates are processed in the correct lineaturation, otherwise printing problems may occur.
Some considerations to have:
- Find out if the plate technology is capable of reproducing the desired lineaturation. Conventional technologies cannot reproduce high lineatures.
- The technical capabilities of the printer.
- According to the line of the Anilox rollers. The advisable ratio is 1/7
Example, if the anilox is 700 L / PI, the screen ruling should be 100 L / PI (700/7).
Some use it with a 1/6 ratio.