Printers

A basic guide to inkjet printers

Just because you can replace a spent inkjet cartridge and clear a paper jam doesn't mean that you can pass an Inkjet Printers 101 class. Take a minute to learn how inkjet printers function so that you'll be ready for a bona fide inkjet problem.


With their low cost, high-image quality, and ease of use, inkjet printers have become the standard for many small and home offices. Indeed, when color printing is needed, there is no real alternative to the inkjet except for those with deep enough pockets to afford a color laser printer. If you’ve been putting off learning the nuts and bolts of inkjet printers, delay no more. This detailed overview of the anatomy of inkjet printers and the basics behind the inkjet printing process will give you the foundation you need to begin troubleshooting inkjet printer problems.

A word to the wise
Before I get started, I’d like to point out that this article is intended only to assist with basic printer repair and maintenance. If you’re unsure of your ability to perform any sort of printer repair or if performing such repairs will void the printer's warranty, you should contact a qualified service professional or the manufacturer.

The inkjet printing process
So how does the printing process work? Inkjet printers have many of the same components as laser printers, but they function completely differently. Like a laser printer, an inkjet printer contains a system board that controls the printing process by translating instructions from the computer into a rendering. However, unlike a laser printer, an inkjet printer isn’t nearly as dependent on memory.

As you may recall from my earlier article "Learn the basics of laser printing," a laser printer requires that an entire page be spooled to memory before the printing process can begin. Inkjet printers contain memory, but the memory is provided primarily as a timesaving feature. Once the computer has spooled an entire document to a printer, it’s free to work on something else. Therefore, because the spooling process is faster than the printing process, most inkjet printers have a print buffer that allows a computer to spool at least a page or two to the printer. Unlike laser printers, inkjet printers don’t have to wait for a page to be completely spooled before they can begin printing it.

It's all in the jets
The biggest difference between inkjet printers and laser printers is the inkjet's print head. An inkjet printer's print head, shown in Figure A, contains nozzles that squirt ink onto the paper. These nozzles are thinner than a human hair, allowing very small dots to be printed. Placing these dots extremely close together produces very sharp images.

Figure A
This print head contains both color and black ink cartridges.


Another advantage to having such small dots is that it allows for great color reproduction. As you may know, inkjet printers typically contain a black ink cartridge and a color ink cartridge with three colors of ink. By using these four different inks in the right combinations, any color can be created. For example, placing a series of yellow and blue dots extremely close together gives the illusion of printing in green. However, if you look at a page from an inkjet printer under a magnifying glass, you can see that the majority of the colors are artificially produced.

Connect the dots
The actual printing process works by using stepper motors to control the print head’s position along a stabilizer bar. As the print head slides back and forth along this bar, dots of ink are placed on the paper below. When the printer produces a line of dots, the printer uses rollers to slightly advance the paper to make room for the next roll of dots. So how does the printer create these dots? There are two basic printing methods used by inkjet printers, thermal bubble and piezo electric.

1. Thermal bubble printers
The thermal bubble method is frequently used by Hewlett-Packard and Canon printers. The idea behind this method is that the printer runs an electrical current through tiny resistors to produce heat. The on and off pattern of this current is controlled by the printer’s system board in response to the instructions that the computer sends to the printer. The heat vaporizes just enough ink to create a bubble. As the ink bubble expands, it pushes a small amount of ink out of one of the printer’s nozzles. When the bubble eventually pops, the popping creates a vacuum, which causes more ink to be sucked from the print cartridge. While this method may sound slow, a typical inkjet printer can produce 300 to 600 of these tiny bubbles at the same time.

2. Piezo electric printers
The other method for inkjet printing is called piezo electric and is used primarily in Epson printers. This method works similarly to the thermal bubble method except that piezo crystals are used in place of resistors. The printer passes an electric current through a crystal and causes the crystal to vibrate. As the crystal vibrates, the vibration pushes some ink out of the nozzle. After the ink has been expelled, the crystal returns to a calm state. The absence of the expelled ink creates a vacuum that then causes more ink to be released from the ink cartridge.

Calling all inkjet printer gurus
Are you an inkjet printer expert? Can you spot a paper jam or sense an empty ink cartridge from three offices away? If so, we want to know your secrets. Post a comment to this article and share your inkjet printer tips.

 

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