The Print Head – Demystified

One of the better disguised modern marvels of our day is the ink jet printer. Without giving it much thought, we spit out words and graphics in a glorious display of color and black. Considering the fact that each bit of ink is deposited as a drop smaller than the width of a human hair, it becomes a little more understandable that occasionally they don't perform as we would like.

How the printhead actually works depends on your technology choice. Cannon likes the idea known as bubble jet technology. This uses a small resistor to heat up the ink creating thermal expansion so that a 'bubble' of ink is displaced. The Hewlett-Packard concept is to expand a piezo-electric crystal to pump a small amount of ink through the printhead nozzle, then pulling more ink from the reservoir when the piezo contracts.

Of the two technologies, the Hewlett-Packard approach is more common due to the fact a wider variety of ink types can be used. This can range from what you're probably used to using or specialty inks for dye sublimation to food. Yes, there are printers for decorating cakes with icing!

Depending on design requirements the printhead may be integrated with the tank of ink or may be either a permanent or semi permanent part of the printer body. The former option carries with it a higher cost since the printhead is disposed of when the ink reservoir is empty. The latter option can be expensive if the printhead is accidentally damaged. Some high-volume HP printers use a hybrid model of the two choices.


The most common issue with inkjet printheads is clogging. This is because the liquid carrying the pigment evaporates leaving behind the solid pigment, much like a clogged drain. There are several steps you can take to minimize a clogging issue. It is considered best practice to allow a printer to shut down using the power off button. This cycles the printer so that the print head(s) are parked on rubber seals to minimize evaporation of the carrier. Infrequently used ink based printers should be cycled with a test page. Sooner or later you'll experience a clogged printhead. The quickest attempted fix is to run a cleaning cycle. Should that fail, a solvent appropriate to your ink may be required. If you printhead is of the integrated (disposable) variety, it may be less hassle to simply replace the assembly.


Today is the rare inkjet printer that is mono color. Photo printers are equipped with four or more different colored pigments, each with the printhead containing dozens or even hundreds of micro-nozzles arranged in a horizontal and vertical axis. Large changes in temperature may impact nozzle alignment. Follow your manufacturers instructions if you are experiencing registration errors. Typically, this means printing out a test page with alignment patterns. Via the printers menu settings you select by the numbered output the most accurate alignment.


Ink should be stored at a temperature of approximately 70°F/20°C. Ink cartridges with integrated printheads should be stored in an upright position, never on their side. Following these two instructions, it is possible to attain a shelflife of upwards of two years. Storage of an inkjet printer requires that the ink cartridges be removed. Failure to do so typically renders the printer permanently nonfunctional. When storing an ink cartridge that has already been used, place it in a small plastic bag, squeezing out as much air as you can. Unless you're using a specialty ink, some folks put a small piece of wet sponge inside the plastic bag. Again, follow the procedure of storing upright.

The Printhead of Tomorrow

Ink-based printing is poised for a glorious future. Hewlett-Packard engineers have determined a laser printer cannot go faster than 60 pages a minute or about one page second. The challenge lies in the physics. In the last stage of the circular laser print process, the tiny pieces of iron coated like a M&M candy with plastic is transferred to the paper and squished using heat and pressure with two silicon rollers. This process is called fusing. The iconic engineering firm has determined an 8/2x11/A4 piece of paper cannot complete the fusing process faster than a page a second. The New York Times was HP's first 'guinea pig' for a new type of high-speed printing process. The printhead looks more like a precision water sprinkling hose as you might use in the garden. Unlike ink-based printing of today, which relies on evaporation, the new full-color print technology has a second printhead. The process is not unlike a two-part epoxy process. Part A is sprayed down, followed by a Part B chemical from a separate printhead. This causes a chemical reaction, and voilà, instant drying. In fact some of the self-serve photo kiosks you find in the store are using this technology.

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