Color Registration and Moire Pattern Elimination Technology for Multi-color Flexo Flexible Packaging
This technical paper explores multi-color overprint registration deviation mechanism of wide-web flexible packaging flexo presses, analyzes moire pattern generation root cause, and provides screen angle optimization solutions for high-gradient packaging patterns.
Wide-web flexible packaging flexo presses usually adopt 6 to 8 color groups for full-color packaging pattern overprinting. Compared with narrow-web label presses, wide-web equipment has longer web transmission path, more obvious tension fluctuation and larger cumulative register error, which is easy to produce macroscopic color ghosting and periodic moire interference patterns affecting packaging appearance.
Long-distance web transmission brings asynchronous vibration among different color printing units. Each color group has subtle mechanical phase difference during high-speed operation, resulting in progressive transverse and longitudinal register deviation. Conventional single-point register correction cannot eliminate long-distance accumulated phase error, so full-web multi-point visual register detection system is required.
High Speed Flexo Printing Machine - Stack Flexo Flexo Printing Machine
Halftone screen angle optimization to eliminate moire interference patterns. Moire pattern is formed by angle superposition interference of halftone dots of different color channels. Standard screen angle setting for
flexo flexible packaging: cyan 15 degrees, magenta 75 degrees, yellow 0 degrees, black 45 degrees. This fixed angle collocation avoids dot overlapping interference fundamentally and removes visible moire stripes on full-color packaging films.
Servo motor phase locking synchronous control for all printing units. All plate cylinders and impression cylinders adopt full independent servo drive, realizing phase locking synchronization of all color groups. The phase error among multiple color units is controlled within 0.005ms, greatly reducing multi-color overprint ghosting and improving gradient color transition smoothness.
Humidity interference elimination for flexible packaging printing workshop. Plastic film is sensitive to static electricity generated by low humidity environment, causing web adsorption deviation and random register error. Constant humidity control above 55% plus static elimination bars installed on each printing unit can remove surface static electricity stably.
Finished product color consistency control for large-batch flexible packaging. Long-time continuous operation leads to slight servo motor drift and ink viscosity fluctuation. The online color density detection system feeds back data to adjust ink metering and servo phase automatically, ensuring consistent color tone from initial test product to final finished packaging roll without manual intervention.
