HIGH-SPEED ROTOGRAVURE & PACKAGING PREPRESS

Rotogravure Cylinder Engraving & Prepress Guide

Rotogravure is the premier printing process for high-run flexible packaging (snack wrappers, retort pouches, shrink sleeves), decorative laminates, and security banknotes. Unlike flexo or offset, gravure is an intaglio process: the image is engraved as millions of microscopic inverted pyramid or hexagonal cells directly into a copper-plated steel cylinder, which is later electroplated with a thin, ultra-hard chrome layer ($6 - 10\,\mu ext{m}$) for wear resistance against the steel doctor blade.

1. Engraving Methods: Diamond Stylus vs Direct Laser

2. Screen Angles & Moiré Elimination

In gravure printing, both line art, text, and process CMYK images are screened to provide supporting channel walls (lands) for the doctor blade. Typical cylinder screen angles:

• Yellow: 60° (elongated compressed cells)
• Cyan: 30° / 37°
• Magenta: 45°
• Black & Line Art: 45° or 90° (square cells for highest edge sharpness)

3. Vector Prepress Guidelines for Gravure

• Jagged Edge Compensation (Serration): Because all lines in gravure are broken up into screened cells, high-contrast vector lines should use dedicated "text edge optimization" algorithms in the RIP to place half-cells along outer vector contours.
• Minimum Positive Text: Minimum 4 pt ($1.4\, ext{mm}$ height) for positive sans-serif vector type; minimum 6 pt with bold weight for reverse white-out text to prevent ink bleed fill-in.
• Trapping: Apply $0.10\, ext{mm} - 0.20\, ext{mm}$ vector spread traps to account for high-speed press cylinder vibration and film stretch.