The stack press is characterized by one or more stacks of printing stations arranged vertically on either side of the press frame. Each stack has its own plate cylinder which prints one color of a multicolor impression. All stations are driven from a common gear train. Stack presses are easy to set up and can print both sides of the web in one pass. They can be integrated with winders, unwinders, cutters, creasers, and coating equipment. They are very popular for milk carton printing. A drawback of stack presses is their poor registration; the image position on every printed sheet is not as consistent as in many other printing processes.
Central impression cylinder (CIC)
Central impression cylinder (CIC), like the common impression rotary letterpress, use a single impression cylinder mounted in the press frame. Two to eight color printing stations surround the central impression cylinder. Each station consists of an ink pan, fountain roller, anilox roll, doctor blade, and plate cylinder. As the web enters the press it comes into contact with the impression cylinder and remains in contact until it leaves the press. The result is precise registration which allows CIC presses to produce very good color impressions. CIC presses are used extensively for printing flexible films.
In Line flexo printing is similar to a unit type rotary press or the stacked press except the printing stations are arranged in a horizontal line. They are all driven by a common line shaft and may be coupled to folders, cutters, and other postpress equipment. These presses are used for printing bags, corrugated board, folding boxes, and similar products.
Commercial Publication Flexographic Presses
Commercial publication flexographic presses are compact high-speed presses with wide web capability that utilize dedicated 4-, 5-, or 6-color units. Typically, two four-color units are paired in one press to allow printing on both sides of the web. Publication flexographic presses generally incorporate infrared dryers to ensure drying of the waterborne ink after each side of the web is printed (Buonicore).