Appendix D. Workflow

Digital

Digital printing for short-run production has been around for a while in the black-and-white category. Typical examples are technical documentation and in-plant short-run production of black-only communications, but in-roads to color laser and inkjet technology and applications allowing for customization of digital output have led to an explosion in this printing technology.

Applications for this technology include inplant short-run production, variable data publishing, direct mail, and just-in-time publishing including books on demand.

The equipment used for digital printing includes variable imaging digital presses (computer-to-paper), digital desktop printers, digital copiers, and direct imaging presses (computer-to-plate-on-press). For the purpose of this discussion, I am going to leave out copiers, desktop printers, and direct-to-press imaging and concentrate on laser and inkjet technology in the digital press category. These are the two most common forms of digital printing found on the commercial market and in-plant production today.

Computer-to-paper devices abound on the market as copier manufacturers have taken their imaging technology and applied it to the graphic arts market. Many commercial printers have added digital devices to service short-run requests. Technologies that characterize digital output include the use of electrophotography for imaging as well as duplex printing, or printers that can print on both sides of the paper in one pass.

Here's how it works: From the computer, the digital file or layout is sent to the RIP (the computer attached to the output device), which takes your PostScript data, interprets the math, and creates an image mapped out in machine pixels on a grid. From the RIP, the image is sent to the marking engine and then onto the drum, where toner is attracted to the laser-imaged areas of the drum, which is then deposited onto your paper. It is extremely important to follow the manufacturer's guidelines when it comes to using stock specifically designed for digital output because extreme heat is involved to bond the color to the substrate. The toners that create the color can be a dry mixture or liquid. Dry toner images are fixed onto the substrate with heat, whereas liquid toner images dry shortly after the liquid toner makes contact with the substrate. The paper passes through each set of drums and comes into contact with the toner; then it makes its final pass through a heating set of rollers and then a cooling set of rollers before the paper emerges.

Note

Digital devices can be sheetfed or web; rolls of paper can be attached to the front end with finishing options attached to the back end of these presses to cut, fold, and bind multipage documents.

Considerations when designing for digital include not only a working understanding of the process, but also differences in your manufacturing supplies. For example, the same machine that will produce your job will also proof your joba distinct advantage because your proof will match your production. But toner is not the same thing as ink and there is no spot color option with these devices. So, you must design for process color. I advise a good swatch reference specific to your device.

If you will be combining both offset and digital in a large campaign, understand that getting your digital pieces to match your offset pieces will be problematic. If the entire job can stay digital, you are better off using that option. As indicated earlier, paper for digital production is specific and you should have adequate references for stock choices for this type of production as well. For example, toner will not stick well to a coarse surface such as you would find on linen or recycled stock.

Spreading color over large areas is not advisable because it is difficult for toner to bond evenly over great distance. Take advantage of what these color devices do very well, and use photographic images instead and you will be very pleased.

Inkjet technology is another form of digital printing for production and, as mentioned earlier, it has found a home in wide-format devices. The two basic technologies in this category are continuous flow and drop on demand. Continuous flow uses a static charge to deliver the ink (made of dye, not pigment) to the substrate and uncharged droplets are collected and recycled. Drop on demand squeezes out drops as needed so inks have faster dry times.

Everything from posters to signs, from point-of-purchase merchandising to fine art can be produced from these devices. Because these devices use highly concentrated dyes, color reproduction is very good. Inks are also available in UV, which will resist fading. A variety of substrate choices are available, including bond and coated papers, proofing, backlit, self-adhesive (for mounting on rigid surfaces such as foam core), and synthetic banner material.

Note

For more information on digital printing, visit dpia.org, printondemand.com, and the Digital Printing Council at www.gain.net.