Before Servo: The Mechanical Gear Era
For most of flexographic printing's history, print cylinder synchronization was achieved mechanically through a central gear train. All cylinders rotated in mechanical synchrony. This approach worked — but imposed fundamental limitations as brand owners demanded tighter registration and more frequent job changeovers.
The Fundamental Problem With Gear-Driven Flexo
In a mechanical gear system, every gear has a pitch tolerance. When gears mesh, their respective pitch errors interact, producing small but real positional variations that appear as registration "beating" — a cyclical pattern visible in long print runs. Additional limitations include:
- Fixed repeat length: Changing repeat length requires physically swapping gears
- Speed-dependent performance: Registration degrades at higher speeds due to gear-tooth dynamics
- Cumulative wear: Gear and bearing degradation gradually increases the registration error floor
The Servo Revolution: Electronic Shaft Architecture
Servo-driven presses replace the mechanical gear shaft with an "electronic shaft" — each print unit has its own servo motor, controlled by a master digital system that maintains precise phase relationships electronically. There are no mechanical gears connecting print units to each other.
The control system continuously monitors each cylinder's angular position at microsecond resolution, correcting any deviation thousands of times per second.
What Servo Drive Delivers
Registration Accuracy
Modern servo CI flexo presses achieve ±0.05 mm registration — rivaling rotogravure and satisfying the most demanding brand owner requirements. This accuracy is maintained at all production speeds, unlike gear-driven presses which degrade at higher speeds.
Repeat Length Flexibility
Servo presses support variable repeat lengths through software parameter changes, not physical gear swaps. A 300 mm repeat job in the morning and a 500 mm repeat job in the afternoon require no hardware changes.
Waste Reduction
Electronic registration reaches steady-state in 20–50 meters versus 100–300 meters for manual mechanical adjustment. Combined with stored digital job recipes, returning to a previously run job takes minutes. Typical result: 50–150 m startup waste on servo presses versus 200–500 m on gear-driven equivalents.
LISHG Servo Architecture
The King Series uses full servo-gear architecture — servo motors with precision gearboxes, combining positioning accuracy with mechanical robustness for high-torque applications. The Master Series uses gearless servo design — no intermediate gear transmission — for the highest registration accuracy and fastest job changeovers available in CI flexo. Both series use closed-loop tension control maintaining substrate tension within ±1 N throughout the press.
