Stack type flexo printing machine presses are those where the printing units are stacked one a top another. The individual impression drums located at each station are called impression rolls, whereas the central impression drum (CI-Press) is referred to as the impression drum.
The main press frame consists of several individual colour stations (sometimes sections or decks). These stations are driven either by gear trains supported by the press frame or servo motors. The most common configuration for stack presses is a Six-color press; however, stack presses can have from one to eight colour stations.
It is possible to print on both sides of a substrate using a stack press. Small runs can also be printed on the stack press.
There are three primary advantages to stack type flexo printing machine presses :
Both side printing
Most operators can reverse the web so that both sides can be printed in one pass through the press. The web can be threaded in many different ways, allowing the reverse side to be published completely dry before the ink is applied, provided enough area is set aside for drying between stations.
Easy to access the colour station
The second benefit is that the colour stations are readily accessible, making changeover, washing up, etc.
Stack presses are the best choice for short-run live printing and fast delivery in small batches. They have many stations, using one machine for many purposes and special printing.
Limitations of Stack type flexography printing machines
It is difficult for the stack flexographic printing machine to achieve overprint accuracy when the substrate is malleable or very thin material, limiting colour prints when printing. However, the stack flexographic printing machine is easier to print and more economical when the substrate is thicker or can withstand relatively high tape tension, such as paper or multi-layered composite films.