Issue #0317/1 - It always seems incredible to me that ink can be spat from holes in a piece of metal with such delicacy and precision as to create legible black text down a piece of paper that is being moved through the printer under the print head that is moving from side to side, let alone produce stunningly beautiful photographic images using 4, 6 or even 7 different coloured inks! Yet this is achieved with ever increasing speed, accuracy, smoothness and depth of colour such that black text pages can be produced at up to 22 pages in a minute and a better-than-traditional full colour 10×15 (4×6) photograph in around one minute.
Although Hewlett-Packard claims to have invented thermal ink jet technology in 1979, the principles of ink jet is believed to be able to trace its origins back to something more than 150 years ago when it is reputed that a technician with a syringe and a hot iron accidentally touched the two together and was rewarded with a spurt of liquid from the needle. Between that time and 1979, ink jet printing was used in a variety of applications (including recorders and typewriters in the 1950s and ‘60s) and the printer industry worked hard during the 1970’s to develop a workable technology for computer printing. This included the development of the piezoelectric drop-on-demand technology used by Epson. Now, whether the time-line for Moore’s Law could be considered to begin at that point more than 150 years ago I rather doubt but, since 1984, Hewlett-Packard has been designing and building ink jet print heads with consistently increasing numbers of nozzles and firing speeds.
With a firing frequency of 1.2 KHz, the original print head used in the HP ThinkJet was capable of firing a total of 14,400 drops of ink per second (number of nozzles multiplied by firing frequency). This mono print head was one-eighth inch (0.125 inch) in length, had only 12 nozzles and produced drops of 180 picolitres (trillionths of a litre). The ThinkJet printer had only one print head (mono printer) and so the total drop per second capability of the ThinkJet was 14,400.
In 1987, Hewlett-Packard introduced the DeskJet. This mono print head had 50 nozzles and a firing frequency of 5 KHz, giving it a total drop per second capability of 250,000. Drop size was greatly improved at 85 picolitres.
Colour ink jet heads in 1995 had 192 nozzles (64 of each colour) firing 30 picolitre drops at 8 KHz frequency, meaning that just over 1.5 million drops could be fired each second. Add to this the black print head with its 300 nozzles firing at the same 8 KHz (giving 2.4 million drops per second) and we have a total capability for the printer of more than 3.9 million drops per second.
By 1999, with the print head used in the DesignJet 1000 printers, the firing frequency had increased to 12 KHz (although some HP sources indicate 15 KHz for the same print head), the size of the print head to 0.85 inch and the number of nozzles to 512. Therefore [at 12 KHz frequency] this head is capable of producing more than 6 million 12 picolitre drops per second and there are four heads in each printer. So, the total drop per second capability for the printer is almost 25 million. Furthermore, this head size and number of nozzles means that the nozzle density of this type of head is 600 per inch, meaning in turn that the print head can print a swath that is a full 0.85 inch wide in a single pass at 600dpi – a factor that greatly enhances print speed.
With the current state of the technology, some desktop printers are using seven inks and the some DesignJet printers use six print heads. Firing frequencies are as high as 36 KHz and drop sizes to 2 picolitre and below. Unfortunately, information is not available to be able to do a total drop per second calculation for the printers concerned. Hewlett-Packard does, of course, have further products in development that will push these boundaries higher and higher.
Source: Hewlett-PackardPlotting the technological advance from 1985 to the present day, Hewlett-Packard discovered that the progression actually fits Moore’s Law – incredible! Hewlett-Packard has approved the use of the chart below to illustrate the progression.
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