On a roll: plotter technology keeps paper popular

CADalyst,  April, 2005  by Ron LaFon

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If you've seen the output from modern wide-format printers, you probably don't need much convincing as to the usefulness of the technology, whether the final output is used for presentations or display, input from a workgroup or for archival purposes. These often larger-than-life images have many applications and often become the deciding factor when a project is presented to a client. Desipte the rising popularily of electronic document exchange and storage, hard copies continue to serve vital functions in manufacturing, AEC and GIS organizations.

In-House or Service Provider?

For smaller firms, or those with limited needs, a service provider is usually the option of choice for obtaining large prints. At some point, however, firms may find that it makes sense to bring this work in-house. The most common reasons are to save money and to get the work done faster. In practice, it may work best to use a combination of in-house and service provider production--especially when a firm needs more prints than it can easily produce or requires finishing options not available with its current equipment.

Not only do today's reprographic companies offer a variety of printing options, many now provide quick delivery services that may prove more convenient and cost-effective than doing it all yourself. Plan Express (www.planexpress.com), for example, uses its location near the Federal Express hub in Memphis, Tennessee, to offer same-day fulfillment on print orders. Orders can be placed directly with Plan Express or through members of the Reprographic Services Association, which counts 170 providers across the nation.

To justify an in-house production facility, your company must have a regular need for wide-format prints. A wide-format printer that is used infrequently is prone to having dry ink clog its nozzles. This problem can be frustrating and time-consuming to remedy--not exactly what users want when they have pressing deadlines.

If you've determined that your office is ready for in-house production of large prints, the next step is to decide which technology is appropriate to your needs, and what output resolution you need.

Technology Options

Inkjet. In one variation or another, inkjet technology is the most common printing method found in wide-format printers. Most inkjets use thermal technology, in which heat is used to expel ink onto the paper. Typically the ink spray is initiated by heating the ink to create a bubble that bursts. The burst ink bubble collapses as the element cools, and the resulting vacuum pulls ink from the cartridge or reservoir to replace the ink that was expelled.

Such inkjets typically have between 300 and 600 nozzles, each about the diameter of a hair. Dye-based inks (usually cyan, magenta and yellow) work in combination with a separate black cartridge or reservoir to deliver a variable dot size. The nozzle density, though usually 300- to 600dpi, offers the possibility of enhanced resolutions as high as 1200dpi, usually with a second pass of the printhead.

Aside from the inherent nature of ink to dry and clog the nozzles, particularly when the printer is not used often, thermal inkjet technology also requires that the ink be heat resistant. The cooling process adds slightly to printing time.

Piezo crystal. Epson proprietary inkjet technology uses a Piezo crystal located near the ink reservoir. An electric current sent to the Piezo crystal causes it to flex and, in the process, expel a drop of ink from the printing nozzle.

The Piezo process permits greater control over the shape and size of the released ink drop. Slight fluctuations in the crystal allow smaller droplet size and greater nozzle density. The ink doesn't need to be heated, as it does in thermal inkjets, which saves time and enables a wider range of inks to be used.

Because the Piezo process delivers small dots with great accuracy, enhanced resolutions can be achieved by making two passes with the printhead, which slows the printing process somewhat. Inks for Piezo technology are solvent-based and dry fairly quickly, penetrating the paper rather than spreading out on the surface.

LED. Yet another technology, though one not used by any of the wide-format printers in this particular survey, is LED (light-emitting diode). LED printers are capable of printing at close to the same quality as the ubiquitous laser printer, and work in a similar manner. An LED panel recreates the image on a negatively charged drum. Where light hits the sensitive drum, it becomes less charged and attracts more toner. The printer then transfers the toner from the drum to the paper and applies intense heat to fuse the toner to the paper. Because it's basically a dry process, LED printers eliminate worries about clogged or dried-out printheads. The choice of pigment is, of course, limited to the toner cartridges available.

Ink and media. Typically, glossy and smooth-surface papers show more detail than matte and textured surfaces. Selecting paper stock depends first of all on what's available for the technology you plan to use, the size of the final output and how much detail you want to be able to see on close examination.