Dryers

Flexo presses have integrated drying systems.

Generally there are individual dryers after each print station. These dryers are known as between color or interstation dryers.

The dryer after the last print station is called the main tunnel or overhead dryer.

The interstation dryers remove a sufficient amount of volatile liquids from the ink so that the next station can apply another color without altering the previous one.

The main tunnel dryer removes the final traces of volatiles from the substrate.

These systems generally consist of gas fired burners along with both supply and exhaust fans. The burners raise the temperature, which evaporates the solvents from the inks.

The fans maintain the air flow, which helps remove the evaporated solvents. The length of the dryer provides enough residence time for the drying process to occur.

UV inks don't dry like conventional liquid based flexo inks. Instead they cure by an acrylic polymerization similar to that employed in photopolymer plates.

The reaction is similar to that of the discussed earlier for flexo plates.

To cure these inks UV units are attached to the press between printing units.

We'll return to UV inks later when we discuss inks.