Ever wondered what goes on inside your printer?

    Welcome back to this second in a series of articles looking at the inner workings of printers. Today's candidate is the inkjet printer, and we're going to look at the most common kind, the thermal DOD inkjet printer - let's get stuck in!

    Inkjet printers

    `Most consumer printers are inkjet printers - chances are, you'll have one or have used one at some point. They are fabulously complicated bits of kit - some even more so than colour laser printers - but most of the complexity exists within the ink cartridge. Ever think you pay way too much for ink? This article might make you think differently!`

    If you opened up an ink cartridge, it would look like the floor plan of a huge house filled with tiny square rooms. Inside each of these 'cells', there's a tiny resistor - a piece of material that's designed to get hot when current flows in to it.

    When the printer receives a signal to print, it heats up these tiny resistors. This causes the ink inside the little chambers to expand, like a bubble. At the 'nozzle' of the ink cartridge - where the ink comes out - this formation of bubbles pushes out a single drop. The process takes milliseconds, and different colours can be made by mixing different colours of ink.

    But there's a little more - most ink contains a little iron, which acts to increase the surface tension and give it a slight charge. It's this - like the xerographic effect we saw in laser printers - that helps the ink adhere to the page, and draw out varying amounts depending on the printer setting (or the desired colour).

    So, inkjet printers are pretty cool, and the cartridges are pretty complex. Now we know this, what can we say about pros and cons of owning a machine?

    Pros and Cons of Inkjet printers

    + They're less expensive than other kinds of printer. Because most of the magic happens in the ink cartridges, the printer itself is usually fairly cheap. Most printers come with ink cartridges too - but watch out, as these are usually 'sample' cartridges containing less ink than a regular one.
    + The ink cartridges don't actually cost that much. Compared to laser toner, they're fairly cost-effective. This is due to the effect of economies of scale - as we said earlier, inkjet printers are the most prolific consumer type, so a lot of ink gets made for them.
    - They cartridges aren't great for the environment. They're fairly complex bits of kit, and still (mostly) disposable. There do exist services that can 'refill' your ink cartridge, saving you money - but you have to think to send the cartridges to them in advance, possibly leaving you without printing capabilities for a while.
    - The ink dries out. If you don't use your printer for a while, the ink in the outermost chambers of the cartridge will dry up. We'll look at a good way to avoid this in the troubleshooting section.

    Troubleshooting Inkjet printers

    Because the innards of inkjet printers are a little simpler than laser printers, they can often be troubleshooted by hand. Here's my top three tips for dealing with common issues.
    1.  Nothing is printing, but the cartridges have ink in them. This is a sign that the ink is getting blocked before it can hit the paper - it's dried up somewhere. If you put a little alcohol (think white spirit, not beer) on a cotton bud and gently brush the printheads, that might loosen it up at bit. Print a 'test page' to make sure the ink starts flowing freely again before you print out your latest photographic masterpiece.
    2.  Printing is off-centre or misaligned. This indicates that the printheads are out of kilter, and most printers have a way of getting them back in line. It's typically found in the printer's settings menu, and termed 'align printheads'. It'll print a few pages, and might ask you to scan them back in (if you have an all-in-one printer). It does this to check that the image it actually printed is aligned with the one it wanted to print - if it's not, it'll manually adjust the printhead position to rectify any problems.
    3.  Unusual printing things are happening - such as constant printhead misalignment. This is a doozy, I'm afraid - if you use your inkjet cartridges right down to the last, or beyond the last, there's a danger that too little ink will be getting heated. That means the ink's hotter when it comes out, and it could damage the printhead as it passes through. Try with a new ink cartridge first, and if the problem still occurs, contact your printer manufacturer through the manual.

    Next time, we'll take a look at so-called 'inkless printers', and how they work their magic.

    Happy printing!

After discovering that a replacement ink cateridge was going to cost almost two-thirds of what I paid for the printer it ended up in the trash. Now I just take anything I need a hard copy of down to the local library or photo-print shop on a memory stick.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.