HP Inkjet Printers - How do they work? February 02, 2010 12:35 by Matt Bird

After releasing information-rich articles on Epson Inkand Canon Inks... it is only natural I expand my wisdom sharing to the realms of HP Inks. Indeed, logically I would have started here – HP are thought to control close to 50% of the Inkjet printing market. Considering Inkjets are the tool of choice for the average home user – that is an awful lot of printers. Though to be fair, my Dad owns one, if it’s good enough for him, it is good enough for the rest of the world.

Why HP Ink Printers?

So.... what is special about HP and their inks? Bluntly put, it is in science, this article will go into the technology of the printers, and a following article will be on the Ink. I will be completely honest here – I started writing my HP ink article, and got so enthralled with the technology in the print heads, I ACCIDENTALLY wrote an article on it. Before I knew it, I had covered 800 words, and will need to make a separate posting for the Ink stage.... But away from my apparent long winded drawl method of writing (sometimes, I even bore myself), and onto the inkjet printing lesson.

HP invest an incredible amount of resources to their print technology, with advances in print head and ink technology heavily patented and protected. They vehemently guard the chemical makeup of their inks, with numerous lawsuits in the past against suppliers of 3rd party ink in breach of their protection. What is specifically important for consumers to remember is the science flows through the whole hp system – From the print heads -> nozzles -> Ink -> paper. The dedication for optimising every stage has meant the base output from HP’s, though incredibly expensive for constant use, gives a very high standard of search for the home environment.

The Beginning:  how did the technology for their printing come about?

I bring this up as it has a humorous urban myth behind it. Ever hear how post-it notes stemmed from research into the world’s strongest glue which went wrong? Well, apparently accidental discoveries span to HP too:

‘In 1978, a coffee-loving HP scientist noticed that his percolator had no moving parts—just a bottom heater that moved the water up and over the coffee grounds. Eureka!’

And thus HPs inkjet printing method was born. Contrary to this method is the piezoelectric technique which will be shortly writing an article on due to popular demand!

Utilising tiny heated chambers within the print head, a series of electrical currents is sent through, generating heat pulses within the nozzle (claimed to be up to 1000 times a second). This heat creates a miniscule vapour bubble of ink just above the heat chamber. The quick expansion of steam propels Ink out of the nozzle onto the page, and when coupled with the sudden contraction of this vapour bubble when the heat stops – due to the ceasing of the electrical current – the ink stops being pushed out of the nozzle, whilst the ink that was distributed is replenished from a reservoir. Now imagine this hundreds of times a second in one nozzle – with up to 300 nozzles per print head - whilst the print head is moving back and forth.

Impressed so far? Well then consider the technology behind aiming!

This ink of drop expelled from the nozzle is 1/3 of a human hair – or a picoliter.

HP Ink Is Mighty Small:

A millionth – of a millionth – of a litre. To fully put it into perspective... a 6x4 photo, you know those little things with all the happy memories you keep printing on, has 40 million drops of ink. So if you took everyone who lived in London – gave them all 5 ink drops from a nozzle and told them to share – they would combine to make one single photo. Though to be honest I doubt they would combine it with the accuracy the printer does, or if they did it would take a while – go go City-wide printing, a photo a year.

I figure I have space for 1 more figure to plump up HPs technology, as this is now its own stand-alone article. The ink drops are  small, and for image clarity you obviously have to have the drops next to each other in the correct sequence to create the colours..... roughly maintaining the ratio of distance to page and size of nozzle/drops, it is akin to one of us standing on top of a skyscraper, and attempting to drop a 5p piece into a paper cup on the ground. (The bottom floor ground, not the floor of the roof... I didn’t just pick a skyscraper for scenery). I have not tried this in my spare time, but judging from the difficulty I have to find my mouth with a spoonful of soup, I am guessing I would struggle to hit the cup. Let alone hit it 40 million times in a row for 1 image.

Yet HP manage this consistently across all their printers, winning awards year after year for quality of print, image consistency, printer reliability... the list goes on. Well my unintended article must draw to a close here, before my manager realises I have spent an hour writing something completely different to requested, which people probably won’t want to know anyway.... If I get fired because I found HP printing technology interesting, it may be a new low for me :-)

Hope you found it interesting, and don’t feel too compelled to go drop currency off varying building sizes – just remember. You Are Not A Printer.... yet....