central impression flexo
Central impression flexo (CI flexo) is a press configuration where a single large cylinder serves as the impression surface for all color units. This unique arrangement provides exceptional print registration and is the industry standard for printing on thin, stretchable films used in food, beverage, and pharmaceutical packaging.
The central drum's large diameter (often over 1.5 meters) ensures that the substrate contacts the drum over a long arc, minimizing slip and tension variations. This design also allows for a compact footprint, as all decks are clustered around the drum, reducing the overall length of the press line.
High Speed Flexo Printing Machine - Stack Flexo Flexo Printing Machine
Compared to stack presses, CI presses offer better print quality on films but are more expensive and have limited accessibility for plate changes. They are typically used for runs longer than 50,000 meters, where the investment is justified by the consistency and low waste rate. For short runs, stack or inline presses may be more economical.
Substrate handling on a CI press requires careful tension control, especially for very thin films (12-20 microns). Advanced tension sensors and dancer rolls are used to maintain constant web tension from unwind to rewind. Additionally, the drum surface temperature can be regulated to prevent film distortion due to heat from drying.
Drying is achieved through a combination of hot air impingement and, in some cases, IR heating. Each printing deck has its own dryer that directs air onto the web immediately after printing, before the next color is applied. This interstation drying is essential for high-quality multi-color work, especially with solvent-based inks.
Productivity metrics for CI presses include setup time (often under 20 minutes with sleeve technology), waste percentage (typically 3-5% during start-up), and uptime (over 90% for well-maintained machines). Many modern CI presses feature remote diagnostics and predictive maintenance alerts, further enhancing operational efficiency.
