1. Substrate compatibility and tolerance
Pressed cardboard edgeboards are a particularly demanding substrate: fibrous, irregular surfaces, high absorbency and non-planar profiles require a printing technology capable of adapting with precision.
- Surface topography: the surface, made of multiple layers of pressed board, is porous and non-homogeneous.
- Absorbency: the material is highly absorbent; the ink penetrates the fibers instead of remaining on the surface.
- Physical shape: the continuous L- or U-shaped profile does not allow the use of technologies that require perfectly flat surfaces.
How does flexography excel?
Flexography is inherently designed to operate on imperfect substrates, thanks to its fundamental characteristic: flexibility.
- Flexible photopolymer plates: the flexographic plate is made of soft, flexible photopolymer. Mounted on a cylinder, it conforms to the small irregularities of the edgeboard surface during contact, ensuring uniform ink transfer even on non-planar substrates.
- Kiss impression: printing is performed with minimal pressure; the plate merely touches the substrate, avoiding deformation or crushing of the profile.
- Low-viscosity inks: flexo inks are highly fluid and ideal for porous materials such as cardboard. Their characteristics offer two key advantages:
o Fast drying: natural absorption accelerates drying and reduces the need for additional curing (UV or IR), which is ideal for high-speed lines.
o Durability: the ink penetrates the fibers, becoming part of the substrate and ensuring resistance to rubbing, abrasion and peeling. This is essential for edgeboards subjected to continuous impact during strapping, handling and transport.
2. Seamless inline integration and production speed
Printing on edgeboards must integrate seamlessly into the continuous production process.
- Mechanical simplicity: a flexo station, composed of ink tray, anilox, plate cylinder and impression cylinder, is compact, robust and easy to integrate into the forming and cutting line.
- Rotary process: the rotary nature of the system enables continuous and consistent printing before the final cut.
- High speed: even basic units are engineered to operate at the high speeds typical of edgeboard manufacturing.
3. Cost-effectiveness for packaging applications
Since edgeboards are high-volume, low-margin products, cost efficiency is a critical factor.
- Ink cost: water-based flexo inks are extremely economical and suitable for simple, functional graphics.
- Plate cost: photopolymer plates are significantly cheaper than gravure cylinders while still offering excellent durability.
- Investment and operating costs: an inline flexo station requires a modest investment, is mechanically robust and demands minimal maintenance, qualities essential in cardboard-processing environments.
4. Perfect alignment with branding and customization needs
Communication on edgeboards must be clear, essential and consistently legible.
- Fit-for-purpose quality: flexography excels at printing solid areas, text, symbols and warnings (such as handling instructions “Fragile”, “Do not stack”), ensuring clarity and readability.
- Easy customization: quick plate changes allow efficient management of varied and customized production runs.
Why not other technologies?
Comparison with digital (industrial inkjet)
Inkjet represents the main alternative, but it carries significant limitations:
- Cost: inks are more expensive and the print cost per unit is higher.
- Durability: the print remains on the surface and often requires UV curing to achieve adequate resistance.
- Robustness: printheads are sensitive to dust, with risks of clogging and frequent maintenance needs.
- Speed: reaching edgeboard line speeds is possible, but entails high complexity and cost.
Comparison with gravure and offset
These technologies are unsuitable:
- Gravure: very high cylinder costs, suitable only for extremely long, non-variable runs.
- Offset: incompatible with irregular surfaces and not suitable for continuous inline processes.
Flexography is not only a suitable technology but the optimal solution for printing on pressed cardboard edgeboards. Its combination of flexibility, operational speed, robustness and cost-efficiency makes it perfectly aligned with both the material’s characteristics and the production demands of a high-volume sector.
Written by Marcello R. | Team Giugni®
