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Aug 1, 2008 12:00 AM


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Wide-format digital printing is a great example of technology bringing new solutions that add value and help commercial printers foster new business growth. Looking to the future, commercial printers will find it difficult to compete without some kind of digital imaging capability. Diversity will be the name of the game. Customers will increasingly value — and expect — the ability to provide a wide range of imaged products.

For those commercial printers who have implemented digital document printing, the addition of wide-format digital imaging is the next logical step toward becoming a total imaging solution provider.

Rolled or rigid?

Choosing digital equipment in today's marketplace — with more than 200 inkjet printing devices available and more added every day — can be a daunting challenge. With an understanding of the key concepts and technologies that go along with wide-format inkjet printers, you'll be in a better position to choose a device that best meets your company's needs.

Today's products span the advertising range. Whether products are indoor or outdoor, posters, banners or transit advertising, inkjet printers provide excellent results in print quality and have the ability to print on a wide variety of media.

The digital imaging market is segmented into several major machine types for wide-format inkjet. The dominant type is the roll-to-roll configuration. Roll-to-roll printers make use of flexible media to produce items that we see in our everyday world and include products that exist in the indoor and outdoor environments. This printer type ranges in widths from 0.9 m (36 inches) to more than 5 m (200 inches), with some units having the ability to run different jobs across multiple shorter width rolls.

Roll-to-roll printers easily handle rolled goods made of paper, vinyl film or other materials. Products created by roll-to-roll machines include posters, banners, backlit signs, fine art, displays and exhibits, billboards, and pressure-sensitive and static-cling products such as decals as well as vehicle wraps and transit/fleet advertising.

Flatbed printers are gaining popularity for rigid substrate printing. These machines are categorized as either “true flatbeds,” which have no capability to handle rolled materials, or “hybrid” flatbeds, which can be converted with tables and take up spools to run rigid substrates or roll-to-roll media, depending on the job requirements. Hybrids are advantageous if you need to alternate between flexible and rigid substrates without incurring the cost of a second machine.

The main advantage in using rigid substrates is the new markets this type of printer opens up to commercial print shops, which include signs, transit advertising, exhibits and displays. Acrylic, glass, tiles, doors, blinds, plastics, plywood, ceramic tile, corrugated plastic materials, lenticular sheets and many other rigid items are common printing substrates that previously were “out of the question.”

These inkjet printers can have one or more heads per color channel, with the ability to use four or more colors. Their ink systems range from water-based and low-solvent to true-solvent and UV-curable ink systems. Each of these ink types has distinct advantages and disadvantages, determined by the products you want to produce.

Think about your ink

Ink is one of the more important considerations when choosing an output device. The most commonly used digital inks are UV-curable, solvent-based and water-based (aqueous).

UV-curable inks are the most versatile in terms of the substrates they can be printed on, with high-quality printing achievable on rigid materials such as glass, wood, ceramic and metal. These inks can help achieve faster production, because they are cured using ultraviolet light and don't require drying time. However, UV systems tend to be more expensive than other wide-format inkjet systems and aren't fully capable of printing on soft, flexible substrates.

Solvent inks are regarded as more economical for wide-format digital printing operations when considering upfront equipment and maintenance costs. These inks — which can come in aggressive solvent formulations or milder ones (generally termed “eco-solvents”) — are compatible with numerous substrates and provide highly durable prints. Even though they dry quickly, solvent inks give off volatile organic compounds (VOCs), which are an environmental and worker safety concern.

Aqueous inks often are ideal for indoor prints and are a good entry point for indoor point-of-purchase (POP) applications. This ink, which is derived primarily from water with a small amount of milder solvent, has a relatively clean handling process. However, it does not resist outdoor elements as well as other digital inks and will require additional finishing processes for prints that are used outdoors or in challenging environments.

Vegetable-based “bio” inks are a growing option. The vegetable source — soy, linseed or corn to make ethanol — uses fewer nonrenewable sources such as petroleum. The inks adhere to a wide range of uncoated media and deliver nearly the same durability when compared with solvent inks. However, ethanol releases VOCs into the air. The amount might be less than regular solvent inks, but printers still have to be vigilant about proper ventilation and compliance with environmental regulations.

Piezo vs. thermal

The two major approaches to inkjet head construction are the “thermal” head and piezoelectric inkjet technology, generally called piezo. Piezo inkjet head technology — most commonly used in today's wide-format digital devices — uses a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element.

When voltage is applied, the piezoelectric material changes in shape and size and generates a pressure pulse in the fluid, forcing a droplet of ink from the nozzle. This is effectively the same as the thermal inkjet, but it generates the pressure pulse using a different physical principle.

Piezo head technology also allows the dispensing of more varied types of ink because of the heads' construction method and materials. Solvent, UV-curable, textile dyes and other inks are printed using this head technology.

Resolution in today's head technology is quite high and is read in the two directions of the print. The “X” direction, or the direction of head travel, is the first number; the second number refers to the resolution that is linked to the speed of the media feed. For example, 720 dpi by 1,440 dpi means the head has a true resolution of 720 dpi in the “X” direction, with an increased “Y” resolution of 1,440 dpi.

Finishing options

A range of finishing options are available to make wide-format digital imaging a profit center. This is more than just lamination, which is a quick and easy way to protect prints.

Post-print finishing procedures include grommeting, sewing, cutting, seaming and routing. The cutting of shapes with a flatbed router is one of the fastest growing revenue areas behind wide-format flatbed printing.

Several finished inkjet products consist of a substrate (what the print is mounted to), the print (printed on inkjet media or other material), and possibly an over-laminate or liquid laminate (additional protection against weather, fading, etc.).

These core components can be mixed and matched in many ways. Some solutions are best for economical short-term displays. Displays that must last for months have different considerations. At the upper end are more expensive systems that require specific construction of materials that will provide outdoor durability for several years. Other products that are not mounted can have additional protection added or other finishing procedures applied.

Workspace considerations

A new machine will need extra room, usually on all sides of the device. If you are looking at flatbeds, think about where you will store 1.2 m × 2.4 m (4 ft. × 8 ft.) or larger sheets of material that will be used later on your device.

Keep your workflow in mind if you plan to use large sheets or maneuver large media rolls. Make sure you have sufficient space surrounding the unit for maintenance, movement and safety. Some units require compressed air, and there are electrical specifications to consider.


Michael Robertson is president and CEO of The Specialty Graphic Imaging Association (SGIA). Contact him at miker@sgia.org.

Training tips

Your staff needs a good core set of computer graphic application skills, a good eye for color and familiarity with some inkjet production methods and devices. Production managers should be able to train new digital personnel and set up the necessary quality and workflow instruction methodologies.

SGIA offers hands-on workshops throughout the year that can teach you the wide scope of wide-format digital imaging possibilities. See http://sgia.org, keyword: Events.

CHOICE CHECKLIST

Consider these questions when talking with manufacturers and suppliers:

  • Which other machines have similar capabilities?
  • Is the machine's build quality sufficient for the work I require?
  • Does the machine accommodate the size of my materials?
  • How fast is the machine at my expected print quality?
  • Does the durability of the ink meet my products' requirements?
  • Is white ink an option?
  • What is the ink cost per unit? More importantly, what is the ink cost per sq. ft.?
  • How much is the service contract and warranty?
  • How is servicing handled? What are the typical response times for technicians?