The printers that turn out correspondence, invoices and reports in your office contain hundreds of components that make up its functional parts. Though printers range widely in price, size and capability, they have many parts in common. All printers have paper storage, a feeder to get paper into the printer, a printing mechanism and electronics to control the whole process.
Printers have at least one tray — and sometimes several trays — that hold paper for printing. Simple desktop printers usually have a single tray you adjust for different sizes of paper, envelopes and other materials. A small printer tray generally 100 to 250 sheets. A larger printer, suitable for a group of users, has high-capacity cassette trays that hold thousands of sheets. In addition, it may have a separate manual feeder tray for envelopes and other special forms.
The printer’s feed mechanism draws a sheet of paper from the tray and carries it through the print mechanism. The feed mechanism has a set of rubber rollers designed to reliably pull single sheets from the top of the tray. The printer’s electronics send timing signals to the feed mechanism, so as the printer finishes with one sheet, it brings a new one into place.
Laser Print Mechanism
A laser printer has a print mechanism consisting of a metal drum, a laser, and optics to reflect the laser. The optics scan the laser beam across the surface of the drum, “drawing” text and graphics as a grid of tiny dots. The drum’s light-sensitive surface reacts to the laser by building up a charge of static electricity. Toner powder clings to the drum only where the static electricity holds it. The drum heats up, melting the powder, which the print mechanism presses onto a paper sheet.
Inkjet Print Mechanism
An inkjet printer precisely sprays ink from a cartridge or set of cartridges that moves back and forth across a sheet of paper. Because the cartridge itself contains many active components, an inkjet print mechanism is simple, consisting solely of a motor-driven belt that carries the cartridge.
A printer’s electronics consist of a microprocessor and memory, a control panel and other components. The microprocessor receives a document from the user’s computer and converts it into a series of tiny dots that form the image on the page. It also controls the timing of the feed and printing mechanisms and stops the printer if it detects a paper jam. The control panel lets you stop, start and test the printer, as well as change its configuration.
Printed sheets drop into one or more output bins. Most printers have a single bin that keeps the pages neatly stacked. More sophisticated printers have two or more bins to organize multiple print jobs or to collate the pages of a report. The output bin may have a switch that halts the printer when it becomes full. This prevents pages from slipping off the top of a stack and scattering onto the floor.