An inside look at laser printer technology

by Reads (6,046)

Laser printers have come a long way since the first mass-marketed models were introduced by HP in the 1980s.

Back then, the first laser printers were relatively slow and expensive, priced at about $4000. Today, you can buy an infinitely smaller but equally capable color printer for $300 or less from a choice of vendors, outfitted with the latest features including front side USB ports and built-in WiFi. Printing speeds for a product in this category can reach up to 20 ppm for both monochrome and color devices.HP Resource Center

Laser printers are also getting much easier to maintain, a productivity consideration for both small-to-medium businesses (SMBs) and consumers. Technological changes that have helped this to happen include: component miniaturization, cheaper CPUs and memory, new printer cartridges and elimination of outdated parts. Although progress has been gradual, the incremental improvements add up to some colossal gains.

Regardless of size, pricing or feature sets, laser printer technology still revolves around the same basic principles; precision lasers used to glue dry ink (toner) to an electrically charged drum, which heats the ink and applies it to the printing paper.

Depending on the specific needs of each customer, each laser printer can use very different technical approaches to carry out demands. The printers also come in various sizes and form factors geared to a vast range of user requirements.

Different laser printers for different purposes

Analyst group IDC divides laser printers and multi-function devices into two main categories: personal devices and shared workgroup devices.

Personal devices are desktop printers dedicated to a single computer user and connect directly to the user’s computer while shared workgroup devices are connected to a network and used by multiple employees, according to Keith Kmetz, Vice President, Hardcopy Peripherals, IDC.

Lyra Research, another analyst firm, is now moving to three classifications: workgroup printers, small workgroup printers and small office home office (SOHO) printers. Larry Jamieson, director, Hard Copy, in Lyra’s Industry Service explained that the workgroup printers typically serve six or more users and are typically priced at $500 or more while the small workgroup printers are shared by two to five users, typically in an small or medium business (SMB) setting. The third group, less costly SOHO printers, serve only one or two users.

The initial laser printer and its early successors were “heavy and built like tanks,” Jamieson noted. But over the years, desktop laser printers have consumed less and less space and many laser printers have a footprint not much larger than a piece of printer paper, he pointed out.

Vendors have tended to swap out metal materials for less weighty plastic. Meanwhile, printer components are not only smaller but fewer.

A high-end printer today might have an on-board controller chip to handle most imaging processing functions, along with separate chips for raster imaging processing (RIP) and memory. However, some lower-end monochrome printers – which might cost $100 or less – eliminate controller and RIP chips. Instead, the tasks performed by these chips are offloaded to the PC processor for host-based processing, said IDC’s Kmetz.

For applications demanding a heavy volume of large and complex documents, RIP tasks are sometimes done in software or firmware directly on the printer.

To save on both space and money, computer makers have also introduced disposable all-in-one cartridges with preloaded toner. These all-in-ones integrate the functionality of multiple earlier hardware components, observed Kmetz.

New heights in speed and resolution

HP’s first LaserJet and other members of the initial crop of laser printers ran at 8 ppm. The printer was limited in memory to a paltry 512K.

“Speeds of laser printers didn’t really start rising until the 1990s, when 12 ppm printers became available,” said Jamieson.

In comparison, printing speeds of 20 to 50 ppm are now prevalent on monochrome business printers, while come production laser printers can crank out pages at rates of 150 ppm or faster.

Why the big changes? For one thing, pricing for CPUs and memory chips has fallen over time.

For high-speed printing on workgroup laser printers, the minimum recommendation for a monochrome printer is a 400 MHz processor and 32 MB of memory. For a color printer, analysts recommend a 500Mhz processor and 64MB to 128MB of memory.

Also, for faster speeds and crisper output, many of today’s printers come with graphics compression software.

With the availability of cheaper CPUs and memory, resolution has also increased, although not quite as dramatically. Where the initial LaserJet printed out at only 300 dpi, it is commonplace to find a maximum resolution of 1200 dpi for many models on the market today.

Despite the high costs of older models, vendors still managed to produce new technologies that took important steps toward improving the image clarity of printed documents.

HP, for example, created Resolution Enhancement Technology (RET) for making lines look smoother by filling in “jaggies,” the jagged edges produced when larger dots make a diagonal line.

Only a couple of years ago, toner was difficult and messy to install in laser printers. But with the creation of all-in-one toner cartridges, manufacturers eliminated the need for hardware gizmos such as toner receptacles and keep users from getting their hands grubby with toner.

How else is maintenance getting easier? Contemporary laser printers use “charged drums” instead of earlier so-called “corona wires,” thin wires within the printer that were needed for charging the drums.

Not only were corona wires subject to easy breakage, but they also had to be cleaned with a special felt-tipped tool designed just for that purpose.


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