Shah: Optimal ink and impression pressure is crucial in flexo

When did you first hear about flexo?
I used to visit Flexure Print N Pack’s manufacturing facility when I was pursuing engineering course and that is when I had heard the term “flexo”, in the year 2006. However, we have been in business much before I was introduced to the term in 2006.

What's the difference between flexo then and flexo now?
There's a huge difference in terms of everything as the technology has evolved over the years. In terms of process configuration, flexo then was a three-roller, open chambered system where ink would travel from ink pan to rubber fountain roller, then to metering roller, then to printing cylinder and finally onto the substrate. However, the flexo now is a sophisticated close-chambered doctor blade system, wherein ink would travel from ink tank to doctor blade closed chamber to anilox roller to printing cylinder, and finally onto the substrate.

150 LPI is enough? Or should one aim for higher?
Yes and no. It depends on many parameters such as type of substrate, artwork, anilox library and inks. Every process has its own advantages and limitations likewise in flexo, some artworks can be printed with higher screen ruling and some should be with lower screen ruling. Every print job should be engineered as per the design and requirements of a client.

One measurement equipment which is a must on the shopfloor?
Spectrophotometer.

One tech-insight about ink transfer or process control that you think everyone should know.
Optimal ink and impression pressure.

Where should one focus most on: densities, dot gains, plates, or anilox performance?
Densities are important for consistent print results every time the job is repeated. Dot gains are similarly essential to produce flawless and superior quality prints. Plate handling on the press, cleaning when infinitesimal dots are exposed, and appropriate storage are of the essence for its long lifecycle. Relevant anilox library and periodical cleaning of anilox is also equally important.

Which methods do you use to validate your flexo data?
On the shop floor during the production job, our press room engineers fundamentally measure ink viscosities, L*a*b values of spot inks, ink densities, GSM values, dot gains, ink drying performance and surface energies of the films.

The need of the hour is skilled pre-press talent. What is your take?
This is correct. We need pre-media and pre-press companies which understand the flexo-friendly artworks and provide separations which are suitable to print on a flexo press. Plate making process also plays a vital role. Holistic knowledge of base photopolymers, screening technologies, plate making process variables and impact of printing plate during printing on the press are the areas where pre-press and press people should work together to make the flexo process as standardised as possible.