For all those curious how an inkjet printer works, keep reading. This is a practical explanation of what’s actually going on inside an inkjet printer. An inkjet printer may have more than 4 colors or print on 36 inch wide paper but the inkjet process is basically the same. The printhead will pass over the paper several times spraying tiny amounts of ink, advance the paper a little and repeat the process until the image is printed. The ink is designed to dry fast, otherwise it would smear from handling it or the next page coming out of the inkjet printer. Of course, this also means ink can dry on the printhead from inactivity. Which is why it’s a good idea to print a small test pattern using all 4 colors once a week.
The ink cartridge is the heart of the inkjet printer works, so deserves a slightly expanded explanation. It is comprised of the ‘tank’ and the ‘printhead’. The printhead is basically a ribbon cable attached to the bottom of the cartridge with tiny holes in it. It continues up the front or side of the cartridge and has contacts for the electrical connection. Molded in the plastic are small channels for the ink to flow from the tank to the printhead. Inside the printhead are anywhere from hundreds to thousands of holes depending on the printer. The more holes better and faster the output.
Surrounding each hole there is a tiny resistor which produces heat. Ink is channeled to each hole. When the resistor heats up the ink boils. The expansion causes ink to spray out the hole (aka nozzle) and onto the paper. This happens very fast since it is a tiny amount of ink heated rapidly. Since it is a small amount of ink it takes several passes of spraying ink on the paper to get the desired density.
When a nozzle clogs it can leave light streaks in the image. Sometimes they can unclog and the streak will go away. Other times the resistor has burned out, causing a dead nozzle. If there isn’t any ink touching the resistor they will easily burn out. Which is why it’s important, if you refill ink cartridges, to refill them before they are completely empty and prime them before use. Some inkjet printers will have a nozzle substitution utility which can eliminate the streaks by having other parallel nozzles do double duty.
Noises and Nozzles
Some printers you can actually see the spray coming out the printhead as it passes back and forth over the paper. This back and forth motion is the classic zip, zip, zip sound you hear as paper steps forward through the printer. The cracking and popping noises you hear when the printing starts is the printhead leaves the service station and goes to the cleaning station. The service or docking station is where the inkjet printer keeps the printhead when not in use. The service station will lock the printhead in place when not in use and typically have a rubber seal to keep it from drying out.
The cleaning station, sometimes called a purging station or spittoon, is typically comprised of a white or yellow sponge to absorb excess ink and sometimes a wiper blade to clean the printhead. During a cleaning cycle the printhead will move above this sponge and spray some ink to get rid of any dried ink to clear the nozzles. If it has one, the wiper blade will wipe the prinhead clean as it passes by, which works the same as a windshield wiper for a car. The service and cleaning stations can be at opposite ends of the carriage assembly (the metal rod the printhead moves on). Some cleaning and docking stations are combined into one unit at one end. Either way, it makes a lot of noise as the printhead engages and disengages with these stations.
Paper feed is accomplished by a set of small rubber rollers. Some printers substitute a pad instead of a roller to separate the paper. Their function is to take up one, and only one, sheet of paper from the stack, and feed it into the printer. Just like tires on a car the tread will wear down over time and they will loose traction, which means jams. Even new tires on a car they can slip when there is excess gravel, or paper dust in the case of the printer.
The printer expects paper to activate a sensor after a certain amount of time of activating the rollers. If it seems the paper inexplicably just stopped, it’s probably because it took more than the allotted time to activate or deactivate a sensor. It might only be a slight loss of traction on the paper but it’s enough to trigger a jam. If you do get a jam that’s hard to clear check out our guides to clearing printer jams.
Timing is critical to align the paper with the print. The inkjet printer uses a thin strip of mylar to synchronize the printhead with the paper. That encoder strip can get dirty over time from the ink overspray. If that happens the printhead can become lost and make some very distorted prints. Or in rare cases crash into the endcap of the carriage unit.
Overall there are few moving parts inside an inkjet printer. Also, the critical part related to print quality is replaced fairly often. This keeps the cost to produce an inkjet printer low, while able to produce a high quality output. I hope this helps understand how the inkjet printer process works, what the normal noises are, and typical points of failure for an ink printer.