| Red Hat Linux 8.0: The Official Red Hat Linux System Administration Primer | ||
|---|---|---|
| Prev | Chapter 7. Printers and Printing | Next |
An older technology than inkjet, laser printers are another popular alternative to legacy impact printing. Laser printers are known for their high volume output and low cost-per-page. Laser printers are often deployed in enterprises as a workgroup or departmental print center, where performance, durability, and output requirements are a constant. Because laser printers service these needs so readily (and at a reasonable cost-per-page), the technology is widely regarded as the workhorse of enterprise printing.
Laser printers share much of the same (or similar) technologies as photocopiers. Mechanized rollers and gears pull a sheet of paper from a paper tray and through a charge roller, which infuses the paper with an electrostatic charge. The paper then passes through a printing drum, which is itself inversely charged and scanned by a laser that emits the print contents across the drum, discharging the drum at points corresponding to text and image points. The laser receives the print information from the laser printer's microprocessor, which in some cases can be a powerful RISC (Reduced Instruction Set Computer) architecture processor used for complex image rendering of print jobs. The processor rasterizes (or creates bitmap images from vector primitives and/or typographical/layout expressions) the print job and directs the laser to recreate a reproduction onto the drum. Then, as the paper passes through the drum, the charge of the paper reacts with the inversely charged drum. Toner (special powdered ink) is sprinkled on the drum and is pulled off of the drum as the paper passes through. Finally, the paper is passed through fusing rollers, which heat the paper and melts the toner (which would otherwise slide off the page as it exits the printer) onto the paper. The paper exits the printer literally hot off the press.
Color laser printers are an emerging technology created by printer manufacturers whose aim is to collect the features of laser and inkjet technology into a multi-purpose printer package. The technology is based on traditional monochrome laser printing, but uses additional technologies to create color images and documents. Instead of using black toner only, color laser printers use a CMYK toner combination. The print drum either rotates each color and lays the toner down one color at a time, or lays all four colors down onto a plate and then passes the paper through the drum, transferring the complete image onto the paper. Color laser printers also employ fuser oil along with the heated fusing rolls, which further bonds the color toner to the paper and can give varying degrees of gloss to the image finish.
Because of its increased features, color laser printers are typically twice (or several times) as expensive as a monochrome laser printer. In calculating the total cost of ownership with regards to printing resources, some administrators may wish to separate monochrome (text) and color (image) functionality to a dedicated monochrome laser printer and a dedicated inkjet printer, respectively.
Depending on the type of laser printer deployed, consumable costs usually are fixed and scale evenly with increased usage or print job volume over time. Toner comes in cartridges that are usually replaced outright; however, some models come with refillable cartridges. Color laser printers require one toner cartridge for each of the four colors. Additionally, color laser printers require fuser oils to bond toner onto paper and waste toner bottles to capture toner spillover. These added supplies raise the consumables cost of color laser printers; however, it is worth noting that such consumables, on average, last about 6000 pages, which is much greater than comparable inkjet or impact consumable lifespans. Paper type is less of an issue in laser printers, which means bulk purchases of regular xerographic or photocopy paper is acceptable for most print jobs; however, if you plan to print high-quality images, you should opt for glossy paper for a professional finish.