Graphic Imagers : Wide Format Technology

The end products that you wish to manufacture will drive the equipment choice for the printer you purchase. Having said that, there are distinct advantages to understanding the pluses and minuses of each imaging technology and the end products it was designed to produce. Let’s explore some of the common characteristics to better understand the variations inherent within these products.

In general terms, each piece of equipment used to output digitally imaged graphics could be classified into one of three format designations:

• Narrow format (less than 36” in width)
• Wide format (36” to 96”)
• Grand format (greater than 96”).

Speed
The print speed of any given device is dictated by its printing technology and the output resolution printed at. For inkjet printing systems, lowering a printer’s output resolution will increase print speed. Increases in printing speed can also be achieved by using a printer that has multiple print heads for each ink color.

Resolution
Image resolution is the number of pixels displayed per unit of length in an image, usually measured in “pixels per inch” or “pixels per centimeter.” Dots per inch, for example, typically refers to the number of dots printed along a linear inch or centimeter.

Number of Colors
The first color inkjet devices had four heads, one for each color: cyan, magenta, yellow and black, or CMYK. The limitations of this four head, four-color set appeared as banding in gradient fills and a somewhat compressed tonal scale. The next logical step was to introduce a light cyan (Lc) and a light magenta (Lm), with an additional head for each new color. While color choices range from four to twelve, six colors could be considered a realistic minimum for viewing close up POP display work. More colors expand the color gamut dramatically; while light or multi-density inks improve resolution, color vibrancy, blends and gradients.

Output Technologies

Roll-to-Roll Output Devices
Roll-based digital output devices use a substrate delivered on a roll and printed after it is fed into the machine. Roll-based devices allow printing on flexible surfaces including paper, vinyl, fabrics and thin plastics, and on papers used in thermal image transfer processes such as dye sublimation.

Flatbed Inkjet Output Devices
Flatbed devices allow direct printing on rigid substrates, which can range from the common, such as poster board, foam board or rigid plastics; to the uncommon, including metal, glass, wood and other substrates. Printing directly on these rigid substrates may eliminate the mounting processes required of many images printed on roll-to-roll units.

Direct Photographic Imaging Exposure Technology
Direct photographic imaging consists of two primary technologies. The first uses three colored lasers (red, green and blue), controlled by sensors with an optical system. The exposure of the digitized images is made one line at a time, pixel by pixel, at the selected resolution of either 200 ppi or 400 ppi, on photosensitive roll materials. Another solution involves a solid state LED (light emitting diode) head that is coupled with an optical system providing resolutions of either 300 ppi or 425 ppi. Either system requires an RA4 photographic material processor for processing of the photographic media.

Ink Technologies

Inkjet & Ink Types
Manufacturers assure ink/ equipment compatibility through a total system approach to ink formulation, determining ink performance in the printer head, on the machine, and on the media. Head parameters affect colorant strengths and solution levels, which in turn affect dry time, color strength, color balance, and dot shape as the ink collides with the substrate. As in all types of printing, ink is distinctly important to the creation of a print with reliable and accurate color, durability and longevity. In today’s digital inkjet markets, the following types of ink systems have gained prominence, and represent nearly 100 percent of inkjet graphics created worldwide.

Water-Based Dyes and Pigments
Dye-based and pigment-based ink systems are aqueous, meaning they are water based. Unprotected, these ink systems can be used to print for indoor use. For outdoor uses, or to increase the durability of the print, the print should be laminated. This type of printer is still a good entry point for indoor POP printing, but is being overtaken by solvent based printing solutions that have the added benefit of outdoor longevity with or without lamination.

Solvent Inks
A solvent is a liquid that has the ability to dissolve, suspend, or extract other materials without causing a chemical change to the material or solvent.
Solvent-based ink also offers high durability. However, when purchasing a printer that uses a solvent-based ink system, it is important to consider that the use of solvents can lead to significant air emissions, triggering the need to comply with air quality regulations. Without proper ventilation, the fumes from these systems may also be a concern for worker safety and health. Solvent inks for inkjet printing come in two types currently. These inks that contain a more aggressive solvent tend to have a wider range of substrate compatibility. Eco-solvent inks, which contain a less aggressive solvent, require a compatible media.

Dye-Sublimation
In the dye-sublimation process, solid dye particles are changed into gas using heat and pressure, then bond with any polymers present, and change back into a solid. Digitally printing dye-sublimation inks onto paper is only an initial step. A final step involves using a heat press to transfer the inks from the paper onto an acrylic or polyester-based substrate such as ceramic, wood, glass, metal, fabric or plastic.

Ultra Violet Curable Inks
Once cured, the finished UV print offers high durability, even outdoors, without the need for lamination or other protective measures. Currently, UV ink is also the ink system that allows for printing on the widest variety of substrates.

Ink & Media Compatibility
Not all ink types are compatible with all types of media. As stated, when selecting equipment or ink type, it is imperative that these choices compliment the printing of your intended end product. The following table is a reference to the compatibility of ink and media.