Wide-Format Injet Printing - Part 1: Roll-to-Roll Printers

Wide-format inkjet printing is an extremely versatile, computer-driven printing technology that means different things to different people.

To professionals working in offices, design firms, photography studios, and fine-art printmaking bureaus. and schools, a wide-format printer is a 24 to a 60-inch printer that uses water-based inks to print posters, engineering drawings, architectural renderings, photos, simple signs, and banners.

This post focuses on the 63- to100-inch production-grade wide-format inkjet printers used by print-service providers. Most of these printers use durable latex, eco-solvent, and UV-curable inks to eliminate the need to use traditional screen-printing presses for small runs of outdoor signs and retail point-of-purchase graphics. Wide-format printers have also replaced darkroom methods of enlarging photo prints for museum exhibits and trade-show displays.

While large-format printing has replicated what was possible with screen printing or photo processing, it has also opened new markets for products such as vehicle wraps, personalized photo posters and gifts, and custom packaging, wallcoverings, and window graphics.  

How Wide-Format Inkjet Printers Work?

High-precision microscopic nozzles mounted on printhead eject tiny droplets on the paper. Each printhead may contain thousands of nozzles, with hundreds of nozzles dedicated to each color ink. A pulse of pressure is applied to the fluid in the nozzle to eject the ink.

Thermal inkjet printheads use small heaters to boil the ink and create vapor bubbles that expand in volume to eject ink from the nozzles. After several microseconds, the vapor bubble cools and collapses and the nozzle pulls in more ink to be ejected. HP and Canon used thermal inkjet printheads in their first wide-format inkjet printers.

Piezoelectric inkjet printheads use crystalline materials that deform when high electric fields are formed across them. This deformation squeezes the ink channel, creating the pressure needed to eject the ink from the nozzle. Epson, Roland, Mimaki, and Mutoh were among the first printer manufacturers to use piezo inkjet printheads.

On most wide-format inkjet printers, the printheads move at high speeds back and forth across the with of the paper and eject ink droplets in computer-controlled patterns onto the page.

To improve print quality, the printhead makes multiple passes over the same swath of paper. This makes it possible to achieve the higher ink densities needed for a wider range of color tones and details. Many printers can vary the size of the ink droplets being ejected to improve the appearance of the full-color photographic print.

Multi-pass inkjet printers have sophisticated paper advance mechanisms to control the speed at which the paper moves through the press. In high-quality print modes that require multiple passes of the printheads, the paper moves more slowly through the printer.

Types of Wide-Format Inkjet Printers

Roll-feed Printers start with rolls of flexible materials that will be fed either in roll or sheet form to cutters, clearcoaters, laminators or other finishing devices.

This video shows how to use the RIP software to make stickers that will be printed on pressure-sensitive materials on an HP Latex roll-to-roll printer and automatically cut on a HP Latex Cutter. (Video: HP Latex Print and Cut Solution)

Flatbed Printers can print directly on rigid sheets of sign materials up to 5 ft. x 10 ft. Some wide-format flatbed printers enable users to load several smaller sheets across the width of the printing table.

The Agfa Anapurna M2540i flatbed is available with as Asanti automated workflow for sign and display graphics. (Video: Anapurna M2540i FB)

Hybrid Printers enable smaller print shops to print on either rolls or rigid sheets.

The EFI H1625 LED UV hybrid wide-format printer uses Konica Minolta printheads and is available from Konica Minolta. (Video: Konica Minolta EFI H1625 LED Wide Format Printer)

In future posts, we will discuss how the inkjet printing process has been adapted to use different types of inks and media-handling mechanisms for other types of printers. Other types of inkjet printers include grand-format, textile, dye-sublimation, direct-to-garment, direct-to-object; functional; and compact flatbeds.

Types of Inks

An extensive range of wide-format inks have been developed to meet the vastly different durability, gamut, and productivity requirements of photo and art printing, indoor and outdoor signage, prepress proofing, posters, vehicle graphics, and wallcovering and decor products

Aqueous Inks use water to carry different types of colorants to the surface of the printing material. Aqueous dye inks use colored dyes that dissolve into the water.
Substrates for printing photographs or display graphics with aqueous dye inks are specially coated to keep the inks from soaking into the substrate, causing ripples in the paper, or running off the smooth surface of the film or vinyl. UV-blocking laminating films were applied to the first display graphics, posters, and signs printed with aqueous dye inks so the ink colors wouldn’t shift when exposed to sunlight, airborne pollutants, water, or humidity.

Aqueous pigment inks use tiny particles of color pigments that remain suspended in the water. Pigment inks are more resistant to UV-light and humidity. They can be archival photo and art prints, color-stable prepress proofs, and unlaminated temporary outdoor signs.

Solvent and Eco-Solvent inks use solvents with volatile organic compounds (VOCs) instead of water to carry the pigments.

The first solvent Inks were developed to print unlaminated outdoor-durable signage on the lower-cost, uncoated vinyls that screen-printing firms used to make outdoor durable banners and billboards, traffic signs, decals, and fleet marketings. These “hard solvent” inks require special handling and the print room must be ventilated to protect employees from harmful fumes.

Eco-solvent inks use milder solvents that don’t require extra ventilation. Some eco-solvent inks have received GREENGUARD certification for safe use in building interiors. Eco-solvent inks are used for shorter-term vehicle advertising, indoor and outdoor signs, durable wall murals, and indoor and outdoor art. Graphics that will be exposed to harsh environmental conditions or car washes must be laminated.

Latex inks are sometimes referred to as “durable aqueous” inks. In these water-based inks, the pigments are carried by latex or resin-based polymers that bond to the substrate after passing beneath radiant heaters.

HP developed latex inks as an environmentally friendly alternative to solvent and eco-solvent inks for unlaminated signs that need to last three years or less outdoors. Ricoh and Mimaki also make wide-format inkjet printers that use latex inks.

Latex inks are used to print indoor and outdoor signs, wallcoverings, durable fabrics for signage and home furnishings, backlit signs, and canvas prints. HP recently introduced latex inks that can be used with a rigid sign and decor substrates.

UV-Curable inks have chemistries that “cure” to form a rigid film when exposed to controlled intensities of specific wavelengths of UV light. The ink doesn’t evaporate when exposed to heat. Nor does it sink into the substrate. The newest generation of printers used energy-efficient LED lighting to cure the inks.

UV-curable inks were introduced to enable wide-format inkjet printers to print directly to rigid substrates. This eliminated the need to mount graphics printed on self-adhesive substrates onto signboards. With advances in UV curing technologies and ink chemistries, UV-curable inks are now used for specialized printing requirements, such as printing on ceramics, glass, acrylics, wood, and three-dimensional objects.

UV-curable inks and clearcoats can be applied in layers to create special effects such as textured surfaces or Braille lettering.

Color Gamuts: Wide-format inkjet printers don’t use spot colors like offset, screen, and flexo presses can. So, “wide-gamut” inksets have been developed to match as many Pantone spot colors as possible. Some Epson eco-solvent printers for vehicle graphics and signage use up to 10 colors of ink, including red, white, and metallic silver.

The Epson SureColor S series of eco-solvent printers includes a model that can print with red inks and silver-metallic inks.(Video: Epson SureColor S- Series)

The Canon imagePROGRAF PRO series of photo printers can run 11 colors of inks. The ink set includes red, green, and blue as well as different densities of cyan, magenta, black, and gray ink. Together, these inks can print the range of tones and colors reproduce subtle tonal variations and fine details on different types of photo and art papers.

Types of Substrates

The range of substrates a wide-format printer can use depends on the types of ink the printer uses, the adjustable-height of the printhead, and its media-handling capabilities.

The first materials developed for wide-format printing were flexible substrates developed for photographic darkroom processing or screen printing. UV-curable inks made it possible to print on a huge range of rigid and semi-rigid materials used in signage, packaging, labels, and decor.    

Flexible materials include:

  • Uncoated, coated, and tearproof synthetic papers in different weights;
  • Clear films for overlays, and prepress film positives for negatives
  • Translucent backlit films for lightbox graphics;
  • White polypropylene and polyester display films for banner-stand graphics;
  • Different weights and types of vinyls for indoor and outdoor banners
  • Photo papers with gloss, matte, semi-gloss, and metallic finishes;
  • Fine art papers with smooth and textured papers;
  • Canvases with gloss or matte coatings and different weights and textures;
  • Magnetic materials for fast-change displays and vehicle signage
  • Durable fabrics for indoor and outdoor signs and displays.

Self-adhesive papers, films, vinyls, and fabrics have different types of pressure-sensitive adhesives on the back. This enables prints to be applied to rigid substrates and paperboards, as well as vehicles, walls, windows, doors, floors, and 3D printed objects.

Rigid substrates for printing signs and graphics include acrylic, aluminum panels, corrugated plastic sheets, painted MDO wood panels, and foamboards. Some flatbed printers can print materials up to 5 inches thick, including pre-stretched art canvas, bricks, and doors.  

Follow Us on Social Media

This post is part of a series we are publishing to help you understand the many types of analog and digital printing processes now in use.

Follow Ordant on LinkedIn, Facebook, or Twitter to learn when the next post in this series has been published. Our next post will discuss grand-format inkjet printers.

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