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Inkjet Early History.
Inkjet printers have been the subject of thirty years research by some of the major printer manufacturers. The inkjet process has a simplicity and intellectual elegance sufficient to suggest that it might take over the whole future of printing.
The legend is that an engineer discovered the inkjet principle when a soldering iron accidentally touched the needle of a syringe full of ink, causing it to jet out over the desk. That might not be true. The first idea of an inkjet seems to have been patented by R. Elmqvist of Siemens Elema in Sweden. US patent 256643 awarded in 1951 is in Elmqvist's name.
Printing with droplets was used by Carl Hellmuth Hertz at University of Lund in instruments recorders like the Mingograph as early as the 1950s. An independent development of continuous inkjet technology started in the mid 1960s by Dr Sweet at Stanford. Sweet demonstrated that a stream of ink from a nozzle can be broken into droplets by sound waves and steered to a target. This developed into computer printers using continuous ink technology in the 1960's. 
According to some sources IBM licensed continuous inkjet technology and produced the IBM 4640 as a word processing output device in 1976. Internet search rather suggests one origin for this, and a search of IBMs site didn't find the product. Several teams were working on inkjets in the 1970s.
Siemens introduced the PT80 piezo-electric printer in 1977 (based on work by Zoltan, Kyser and Sears and Joachim Heinzl? ). This printer seems to be the ancestor of today's drop-on-demand inkjets. The Siemens printer was small and better than most of contemporary printers at producing graphics. The printhead had 12 jets and was capable of 120dpi - comparable with 9-pin dot matrix heads. Siemens also incorporated a head maintenance station, which other manufacturers took time to copy.
Siemens hit problems with a follow-up 32 jet design - they couldn't get uniformity between jets and nozzles would clog and be difficult to clear.
The Siemens printhead would have been expensive to make - piezoelectric heads have remained so to this day.
Thermal Inkjet History. 
Low cost inkjet printers generally use the thermal mechanism. Ink in a confined space is rapidly heated and a droplet ejects onto paper. Both Hewlett Packard and Canon claim the idea as their own.
Canon researchers Endo and Hara invented their own drop on demand method where a small heater blew bubbles out of a nozzle - hence their tradename "Bubblejet". The first working Bubblejet may have been demonstrated in 1981. Unfortunately there doesn't seem to be much information available on this - at least in English.
Turning drop on demand inkjet printing into a practical product was largely the work of a team led by Frank Cloutier at Hewlett Packard's Corvalis labs. HP decided it wanted to make printers in 1979, when it was mainly known as an instrument maker. (HP made all sorts of laboratory electronics and some rather innovative RISC computers). The main aim was to produce a printer for the little handheld scientific calculators which were then one of HP's strongest products.
Cloutier did the sensible thing, set some design goals and reviewed existing technology.
The design goals were quiet operation, ordinary paper, low power consumption to fit with the battery driven calculator and customers hands stay clean.
Calculator printers of the time typically used type bars and wheels which were heavy and clumsy. Thermal direct printers use special paper and too much power. Dot matrix was noisy and clumsy. The inkjets used in industrial applications (continuous inkjets) weren't practical because they needed pumps and pipes.
The Siemens design must have been attractive but HP wanted a disposable head for reliability and piezoelectric jets weren't going to provide that. To keep customers hands clean they wanted a throwaway all-in-one cartridge.
At HP's Palo Alto lab John Vaught demonstrated a thermal printhead. The prototype had a plate with a groove in it and a thin-film resistor aligned over the groove to make a tube. This made a one-jet pen. Cloutier realized that although scaling the idea up would be difficult the core idea was simple and would allow something that could be made in disposable form. Making a printhead with multiple elements something along the lines of an integrated circuit would reduce costs
Cloutier made his own lab model. This was a brass shim with a hole punched by a needle, held over a resistor covered in fountain pen ink. Cloutier examined what was happening using a strobe microscope and found it worked well. In fact, the device fired ink too well, covering him. This idea is still the basis of "roof-shooter" thermal heads.
Cloutier's co-developers of the inkjet pen had to solve problems like ink drooling out when the head wasn't in use - they initially used a rubber thimble as an inner container - and manufacturing the nozzles in the orifice plate which they did using electroforming.
Paper behavior can also be a problem, ink spreads along fibers and absorption is often too slow to allow several nearby droplets giving a grey-scale. Ordinary paper isn't perfect for inkjet print but it can be made to work.
HP's first working printer was the ThinkJet in 1984. Canon introduced the BJ-80 in 1985. Whoever actually invented the idea HP and Canon had by then formed a close partnership developing laser printer products. All of HP's early laser printers were based on Canon engines and although there is more distinction between the products now Canon are still the main maker of HP Laserjets. There is no such overlap on inkjet printers where Canon is a particularly strong competitor to HP but presumably there is cooperation on sharing technology and patents.
Thinkjet.
HP Corvallis team produced the "St Helens" 12 nozzle 96 dpi head (named for the Volcano). This was turned into the HP Thinkjet cartridge. Curiously the St Helens pen was first marketed in 1984 and is still in use today in cash registers and ATMs. The basic pen is a versatile device so it has found surprising applications - like printing a cell matrix for skin grafts. Micromanufacturing based on inkjets promises to become a big industry.
The first HP 2225 printer was only moderately successful in the calculator market. It turned out that the market for PC printers was larger (PCs were then a relatively new product). The basic problem was that dot-matrix printers were cheaper, whilst laser printers had higher quality.
Paintjet.
One breakthrough product was the HP PaintJet, introduced in 1987. The PaintJet used two cartridges, one black and the other a CMY tri-colour device with three ows of nozzles. The PaintJet was designed by HP's San Diego plotter division as an improvement on low cost X-Y plotters - but is was also the first practical desktop colour printer. The market for colour printing was just starting to emerge as big computer memories made graphics more common.
Deskjet.
The HP deskjet introduced in 1988 was the first inkjet to have a quality approaching laser printer abilities but a clear purchase price advantage. Deskjet printers had a 300 dpi output comparable with many laser printers but cost about the same as a dot matrix printer to buy. The cartridges with their disposable heads cost less than those for a laser printer as well - even if they did only last a tenth as long.
Deskjets and their successors were a marketing breakthrough. Graphical capabilities were growing in importance. Apple's success with its Macintosh machines impressed the industry and was widely imitated. For printing Apple favoured laser-printers (they were amongst the first on the market with the LaserWriter).
The big success in graphical systems was Microsoft Windows, which ran on relatively low-cost PCs. A graphical operating system with word-processors and spreadsheets can incorporate logos and charts. Graphical documents need a graphical printer. Dot matrix machines with their crude 200dpi output weren't going to meet needs. Thermal transfer printers had dreadful operating economies. Laser printers weren't affordable. With its DeskJet series HP had the right product at the right time.
Epson.
One of the big success stories in the computer market of the 1980s was Seiko Epson, who produced dot matrix printers (the "FX" and "LQ" anges). HP and Canon had extensive patents on thermal inkjets and Epson would have to license these. Epson chose instead to develop the piezoelectric inkjet idea first explored by Siemens. Epson's inkjet printers are therefore quite unlike the majority of inkjets in having a printhead that is expensive but ink tanks that can be cheap. In effect the Epson heads are designed to last the life of the printer.InkJet Types.
There are at least three types of inkjet printer:
Continuous inkjet developed by Elmqvist then Sweet fires a stream of droplets at a target and recirculates ink that isn't needed. Printing is potentially fast but mainly suits production lines and bulk printing. Hitachi is a noted maker of continuous inkjets.
Thermal inkjets create a drop on demand in a head with many nozzles. Printheads were intended from the start to be disposable, keeping the users hands clean and reducing any issues with blocked nozzles. HP, Canon and Lexmark generally use thermal printheads. HP has proselytized in favour of thermal heads so much that commentators were shocked when a couple of their high end Designjets used piezo heads.
Piezoelectric inkjets also create a drop on demand. The head is more difficult and expensive to make but it can handle a wider variety of ink - including hot wax in the Xerox "Phaser" process.
Market.
Inkjets are the best selling print technology in today's market. Home users are attracted to inkjets by the low purchase price. Inkjets can also do some business tasks that laser printers can't manage economically - large format engineering and cartographic plotting, for instance. Inkjets should appeal in the wider business printing market as well, there are designs that claim to operate for two-thirds the cost of a laser printer. Hewlett Packard who established inkjet technology are the largest inkjet maker with half the market.
Inkjet printers are attractive because the mechanism is fairly simple, so they are cheap to buy. The carriage line scanning and paper feed mechanisms are a couple of light duty motors and a collection of plastic mouldings. The inkjet chassis is quite similar to a dot matrix printer as are the support electronics and drivers. The complex bit of an inkjet printer is its printhead but even here inkjets have an advantage. Thermal printheads are made using techniques similar to semiconductor chipmaking and packaging so if they are made in volume they can be cheap. Inkjet cartridges are light and suited to automated production techniques so they can be cheap and disposable. Inkjets are faster, cheaper, and give nicer print than dot matrix printers so they took market share from them.
Colour is one of the big advantages of inkjets. Making a colour inkjet just needs the addition of a colour cartridge and extra drive circuits - which aren't complex or expensive. Cartridges are relatively cheap so manufacturers can easily add them and giving the users the ability to print in colour creates a potential revenue stream. Inkjet printing has developed new markets such as home photographic printing.
Inkjet heads are moderately complex and need a production plant to electroform nozzle plates, supply rather unusual microchips and line them up on a plastic ink tank. The early experiments might have used a set of resistors under a brass shim but this has been refined into something mass produced to sub-micron precision. Once a design is established there will be a continual market for heads so mass production techniques drive production and distribution costs down.
The focus of innovation in inkjet printer making is the printhead. Should it be thermal and long life, thermal but disposable, piezoelectric, integrated with the cartridge and if so with how much ink? Above all, how many nozzles will it have delivering how much ink. In general the smaller the nozzles the better the image will look so we want droplets of just one or two picolitres. But very small droplets will be needed in huge numbers to make up a page, perhaps as many as 5000 dots per inch. The ideal printhead will have thousands of tiny nozzles that fire very rapidly and don't block. So far 30 years of innovation haven't quite delivered the ideal; so designs are still changing.
Inkjet printers weren't intended to give low cost printing. They are small and relatively quiet, simple to use and don't use much power. Inkjets give nice looking print including graphics and the technology has improved to the point where they can print photographs at lower cost than chemical photography. As it happens the printer mechanism is fairly simple, well understood and need not be very expensive.
Cartridges aren't cheap because designs are proprietary and manufacturers recoup their investment through cartridge sales.
Razor Sharp Practice.
Cartridge sales completely dominate the market to the point of irritating customers and perhaps disconcerting manufacturers. What has developed is sometimes described as "Gillette marketing". Razor blade makers often give razors away at below cost price, making the money by selling a unique design of blade. The user, committed to their shiny new toy, goes on buying rather expensive blades for it. The hope is that user loyalty repays the manufacturers initial generosity many times over.The low price of consumer oriented printers and high price of inks suggests the printer market has adopted this pattern. Printers are sold in supermarkets so cheaply as to be an impulse buy.
Odd effects arise;
It is not uncommon to find that a new printer with a set of ink cartridges costs less to buy than the cartridges on their own. Consumers following the logic of markets are encouraged to throw out perfectly good printers rather than buy a simple ink cartridge. Although this does happen the situation is usually temporary; retailers pull the price of printers right down to shift old products when new stock is due.
A significant part of the print industry is being run by lawsuits with brandname printer makers taking a succession of Asian manufacturers and their US and European importers to court for patent infringement.
Profits from print cartridges have significantly changed the dynamics of PC manufacture. For all their innovative image PCs have become commodity products with very small sales margins. It is often suggested that HP cross-subsidises its PC business from the profits on cartridges and Dell's development of a printer product line tends to suggest they are thinking the same way.
In the US (and presumably elsewhere) something like half of all printers are sold as part of a "bundle" with a PC and a monitor. The trick is to get the headline price of the bundle very low and this is typically done by the printer manufacturer offering a discount voucher - the customer pays say $399 at the till but gets a voucher to claim $50 from Lexmark. (Lexmark are masters of the technique). A lot of printers are being chosen on deals between manufacturers and large dealerships, with financial engineering being the main concern and the technical detail of the printer a minor consideration.From time to time people pick up on the price of ink and run critical stories in the press. In the UK Which? Magazine has claimed (July 2003) that some inks cost 7 times as much as vintage champaign per millilitre. Furthermore a lot of printers will warn that the printer is about to run out of ink when 20-30% actually remains, a margin that looks like a con-trick.
The printer market is odd, but there is a lot of competition.
Refills.
One obvious customer response is to refill cartridges using bulk ink. Refilling is often fairly easy to do with a syringe although it can prove a bit messy. To save people the trouble of refilling a whole industry of local shops, franchises and supplies has developed.
Manufacturers sometimes respond by making cartridges more difficult to refill. One method is to "chip" the cartridge. When the cartridge is in place the printer expects to read data from a microchip built into the cartridge. The chip might be partly justified - it can hold the date of manufacture and first use and it might be able to sense ink levels. Lexmark bought a case against Static Control Components for making a generic chip that could respond to their printers, claiming that it infringed the US Digital Millennium Copyright Act. The court ruled that reverse engineering the handshake and communication was not illegal (although copying the chips software is).
Refilling cartridges is never going to work really well. Thermal heads won't last through many refills as several nozzles will ultimately block either through obstruction of because an air-lock causes the heater to fail. Ink colour and consistency is unlikely to match the original so efills might not work well with photographs. There can also be ink esidues and leaks and these might just be annoying but they could also contaminate parts of the printer like the electronic contacts. Hewlett Packard were sufficiently annoyed by refurbs that they ran a campaign (2007) claiming that one cartridge in 7 didn't work properly. On the other hand the cost savings from 6 out of 7 cartridges working are substantial.
Generics
In the early days of the market it was conceivable that a de-facto standard might emerge around the HP DeskJet cartridge, but that didn't happen. Cartridge designs are proprietary, with both copyright and patent protection; other manufactuers don't have a right to simply copy them.Generic or "aftermarket" cartridges are new cartridges made to fit a printer, ideally without breaching the manufacturers copyright or patents. Which? recommended that people respond to high prices by buying generic cartridges, which are often half the price of manufacturer branded product.
Brandname and generic cartridge manufacturers are engaged in a legalistic war of attrition over what is and is not a legitimate product
HP won a case for patent infringement against International United Technology in 2000 and Microjet Technology of Taiwan and several US esellers in 2002
HP has had a bit of tussle with Pelikan of Germany, winning a patent infringement case against them in 2007 and then bringing another case in 2008 where Pelikan were selling new cartridges as remanufactured. Manufacturers selling new product as recycled should be funny. HP had previously brought a case against Rhinotek of California for falsely advertising its products as new.
Epson won a court case in Oregon, US against Multi-Union Trading, a Hong Kong company that operates under the PrintRite and Dynamic brands and also makes cartridges for supermarkets, In the settlement 75 of Multi-Union's cartridge models were found to infringe 30 Epson patents. (Arcor )
The US International Trade Commission (ITC) has been enforcing a General Exclusion Order against a variety of cartridges that infringe Epson patents from January 2008. China's NineStar Technology, Town Sky Inc and Mipo International. This case raised some interesting issues, for instance the idea that legitimate refills must only be of cartridges sold by Epson in the US - not imports - and that cartridges can only be repaired, not completely reconstructed. Epson also took court action against several online retailers
HP had issues with NineStar as well, filing complaints in the US ITC in 2006 and resolving them in March 2007 and further in March 2009 when NineStar admitted the infringement and withdrew the products.Being a bit innovative is no protection. Seiko Epson were successful in a case in Taiwan against U-Bar International. U-Bar made a Continuous Ink Supply System which could be retrofitted to Epson printers allowing the heads to be fed from external bottles of ink. The court ruled that U-Bar's device infringed Epson's patents.
It might seem that Epson are particularly litigious, that might be the case but their reliable piezoelectric technology gives them a problem. Epson printheads will put up with things other printer models would have a problem with so they might rather suit generic cartridges.
The inkjet market inspires a lot of patent infringement cases; Google finds 34,000 pages on the subject "patent infringement" + lawsuit + inkjet In April 2009. (but only 13,000 in January 2010 so perhaps the flurry of litigation is dying down)
Intellectual Property
Print cartridges pose some interesting problems in intellectual property and technology.
The fundamental technology underlying modern printers is quite old and has limited patent or copyright protection.
The history of inkjet printers outlined at the start of this page suggests that the idea is quite old and recurred several times. Many of the early inkjet patents are at or over 20 years old and expiring.
Chester Carlson's "electrophotography" inventions which created Xerox's business and allowed the invention of the laser printer had largely expired in by the early 1980s just as laser printer became popular.
The key invention that makes the modern printing industry profitable is the cartridge; wrapping the print mechanism in a box. There can be innovation in how this wrapping works, how the shutters move out of the way and the seals are removed without the user getting ink on their fingers. Inventions in packaging seem an order of magnitude less important than those for the fundamental technology.
A problem with cartridges is that the prices charged for replacements sometimes seem to bear little elationship to their value. Quite a lot of people buy a printer, use the demonstration cartridges that come with it and are then utterly horrified by the replacement costs.Politicians grant patents because societies value creativity and invention. If the songwriter makes no money that seems unfair. Likewise people are unlikely to begrudge Chester Carlson the fortune he made late in life. Giving legal protection to creativity has generally proved positive. The price of printer cartridges is one of those places where people question just how equitable the law is.
Competition
Hewlett Packard have half the computer printing market but they are scarcely without competition. Products from Canon, Epson and Lexmark compete on purchase price, performance and consumable price. The buyer might balance these things - but often just goes for the gratification with a new cheap printer with all the latest features from a trusted brand.
The market for inkjets is huge and now driven by photography - a market einforced by low cost digital cameras and mobile phones. In the 1970s the printer market was government, commerce and industry. In the 1980s hobbyists, gamers, typists and authors joined in. Windows programs began a massive expansion in home computer ownership - and a growing need for printers to handle graphics. Now everyone wants a printer for their colour snaps. Kodak have taken an interesting position marketing printers with a promise of more reasonably priced inks - half that of competitors in many cases.
Mass production changes the market. Inkjet technology might deliver low cost flexible printing competing directly with laser printing which has been the commercial favourite since the early 1980s (and another HP success story)
It is possible to question just how competitive the market is. It was suggested above that Epson chose piezoelectric inkjet because Canon and HP had so many patents on thermal inkjets. But many of the patents on the core technology will be expiring. There could be room for new entrants to the inkjet printer market.
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Technology.
There are two broad classes of inkjet named according to how the ink moves:
 | Continous ink is the process used in industrial printing. This is actually an old technology. Things coming off a production line - bottles and packets, polythene wrappers on magazines and suchlike are printed by the continuous inkjet process. The equipment is expensive but the process is cheap to operate - fractions of a penny per object. Continual ink processes are not usually very accurate - they produce readable text, they don't generally achieve good looking correspondence or reproduce a photograph convincingly. The continuous process can also be very messy - it wouldn't fit into a home or office environment. |
| Drop on demand is the familiar office inkjet. Student essays, colour pictures of photographic quality - things like this are printed by drop on demand inkjet. Although it uses similar material drop on demand is much more expensive than continuous ink because it tends to need a stream of new printheads and ink cartridges. The price also reflects the current generation of manufacturers liking for cartridge sales. The basis of drop on demand inkjet printing is very similar to that used by dot-matrix machines - a print-head is swept back and forth across the page making a pattern of dots. Everything about an inkjet machine can be very similar to a dot matrix printer except the print-head. The Epson SQ series served to emphasise this – they were inkjets, but looked very similar to the dot-matrix LQ Series. |
Printheads are the heart of the drop on demand process. The printer assembles a bitmap in memory then translates that to pixels on the page much as a dot-matrix printer would. A dot matrix printer uses pins to push ink out of a ribbon. The inkjet makes picolitre sized droplets by forcing ink out of tiny capillary tubes - either using:
| heat to make a steam bubble - thermal printheads |
| crystals changing shape to give mechanical force - piezoelectric heads. |
Other ways of forming droplets are possible - pressurized ink held in check by valves, ionic control of membranes, electro or magneto rheological inks, liquid sparks, electrohydrodynamics and focussed acoustic beams. All sorts of inventions haven't made it out of the laboratory - or are "industrial use only" products.
Thermal printheads are essentially an array of resistors so they are relatively cheap to make. Unfortunately the chemical reactions, salt accumulation and pressure waves within the ink and the possibility of sucking contamination back from the paper as bubbles collapse make thermal heads prone to failure - so they usually have to be designed to be disposable, either by:
| incorporating them in the cartridge and keeping users hands clean or by |
| having cartridge and head separate -allowing the heads to see out their life but with the prospect of users making a mess |
Piezoelectric heads are a crystal of material that changes shape when a voltage is applied. The material used is often PZT. The piezo effect is rather small, so the inkjet chambers have to be relatively large, which means a head with lots of jets must be quite big. However the piezo effect is very reliable and tolerant - inks can even be the hot melted wax used by phasers. Piezoelectric heads are more expensive to make; industry estimates seem to suggest that the price is greater by a factor of ten. The piezo printhead is not going to be disposable, so it will be a separate unit from the cartridge.
The only thing an inkjet printer must necessarily consume is ink. Ink production is a well-researched practical art. The basis of printing since the invention of the process by the Chinese and its importation into Europe by Gutenberg and Caxton has been the application of ink to paper.
Ink is usually a suspension of tiny particles in a liquid. Many possible formulations for ink exist, but a common characteristic is that there is a carrier or "vector" that evaporates and a dye or pigment that remains behind. Since the liquid can be as common as water, and the pigment particles can largely be soot or "carbon black" ink might be cheap. There are problems, though. As anyone who tries it finds out, soot doesn't want to mix with water unless there are surfactants. Soot grains are irregular and don't flow well or stick to paper effectively. Dyes are coloured liquids or solutions and should flow well but they may dry out. Intense, lasting colour is difficult to achieve with a dye. Ink manufacture started to use modern chemistry about a century ago and pigment or dye inks are often complex materials - particularly to avoid chemical reactions in the pen, printhead or on the paper.
Specially formulated inks like "Quink" have been standard products for a century or more, usually sold in small bottles that would last the average user of a fountain pen for years.
Within a thermal head the ink tends to deposit a "biscuit" of salt on the resistors. This process, known as kogation, is reduced by eliminating impurities from the ink.
On the page inks tend to fade. Early inks were very prone to fading - and many pens still have the same problem but it isn't usually critical in handwriting. Fade-proof inks are important in inkjets because users want to produce posters, artwork and even photographs. People take photographs to preserve their memories, so a photo that fades isn't much use.
Piezoelectric heads don't heat the ink as a propellant so there is generally more latitude for different chemical formulations.
Once an ink formulation is made then repeating it shouldn't be too much trouble. On the other hand the days are gone where a quick dose of Parker Quink would restore life to a cartridge - these days it will probably just clog the printhead.
Traditional ink is viscous and applied by a "plate" in a printing press. The ink adheres to the plate and is then transferred onto the paper – children imitate the process with potato cut-outs. In older "impact" computer printers a similar viscous ink is carried by a ribbon which is pressed against the paper by a matrix head, golfball or print-band. The print-head is a surrogate for printing plates, it presses the image onto the paper. The fabric ribbon aises the cost of the printing process a bit.
Pens are more like inkjets but they use capillary action to control flow rather than pressure. Fountain pens suffer from many of the same defects that hit the inkjet - ink dries in the pipes or blots on the page.
Inkjet printheads are unique because they aren't intended to actually touch the page and a little jet element has to propel tiny drops across the space onto the paper.
| Inkjet printheads with their mixture of electronics and plumbing aren't very like any product that has gone before. The ideas have all sorts of applications in microdosing and manufacturing so its a product area with huge potential. |
| Inkjet inks need to meet special demands for flow and propellant qualities as well as to colour the page correctly. |
Ink may look like a well researched and ancient product - but in it's modern formulation as inkjet material it's rather new.
Inkjets In Practice. -
Recent inkjet printers can do a fantastic job producing material that looks at least as good as magazine pages. Inkjet operating prices for full page cover are currently very much higher than ordinary printing made up partly of:
- expensive ink
- eplacement printheads
- sometimes - expensive special paper.
There are some signs that the market has become large and complex enough to split several ways:
Low purchase-price printers normally use "tricolor" cartridges. The tricolor cartridge has one head shared by three ink reservoirs, the idea being that it is cheap to make and buy. At one time there used to be a choice of mono and colour - but these days the ability to print colour photographs is just about compulsory. Performance usually isn't much of an issue so the printers have small motors and work slowly. Some (not all) of these printers still manage to produce good looking photographs. Almost all produce text well enough.
Home photography printers are obviously colour. Some printers have as many as seven cartridges to give a wider colour gamut. This can be achieved at low cost by having two tricolour cartridges, one for ordinary colour and another with a light magenta and cyan together with grey for instance. High resolution cartridges are needed to give the dither patterns which give colour shades. A little LCD colour preview screen is a popular addition as well. Camera and printer manufacturers agreed the "Pictbridge" standard which allows cameras to transfer straight to printers without involving a separate PC. WiFi networks are popular with home users and an increasing number of printers include WiFi so the user should be able to turn the printer on, give it an SSID and key and have it join the home network.
Wide-format printers in A3 or even A0 styles for workplaces - mainly aimed at engineering diagrams with some use for spreadsheets, artwork and posters. Ink cost might not matter because there is usually no alternative way to produce this kind of printout - however recent machines often use big cartridges to bring costs down.
Office workgroup printers - there are signs that inkjets with larger cartridges can compete on equal terms with laser printers. Inkjets with two trays (paper and envelope or letterhead and plain) and even with duplex (double sided print). Both HP and Epson have inkjet printers they claim cost less to operate then laser printers.
Despite their low price many inkjet printers now incorporate networking. WiFi networking tends to be aimed at home users, wired 10/100 ports are beginning to appear on workplace inkjets. These printers are more expensive than home printers, but usually have higher performance - as well as avoiding the potential security issues.
Printer makers might not make it self evident what group they are aiming their product at. Buy a cheap little printer and use it to share for office use and it will work (using MS-Windows printer sharing) but it will probably:
- slow down the machine that is sharing it when anyone else uses it. (the drivers installed on the computer do all the work)
- need rather a lot of small cartridges - and spoil printouts by running out of ink halfway through without telling anyone.
- be inconvenient to use for envelopes and suchlike
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The Forgery Problem "Digifeiting". 
Inkjets work so well they are creating problems - all in one copier printers costing £100 replicate things so well that they are increasingly used for forgery of things like banknotes. Printing firm De La Rue has traditionally believed silence is the best policy but in 2003 spokesman John Winchcombe said the company had to speak out.
Colour photocopiers created a problem with forgery in the mid 1980s. Manufacturers voluntarily built algorithms into their machines to detect the fine detail so that the machines refused to print good banknotes. De La Rue has worked with Software 2000 to produce an anti-digifeiting system that can modify printer driver software to recognise banknotes - but printer makers are reluctant to adopt the idea. Hewlett Packard, Epson and Lexmark say they don't have home grown technology to do this but would incorporate it if they did.
Incorporating anti-copy technology into all-in-one printer copiers wouldn't prevent people using separate devices. Secret driver code isn't likely to be feasible with open source software either. And since it is actually possible to build a printer from parts there isn't a chance that trying to incorporate traps into printer software will do anything to stop anyone determined enough forging money - it will deter amateurs and jokers.
Perhaps the best thing is to be aware that paper money is increasingly copyable. If it doesn't have the metal stripe, hologram and the right look to the paper then don't accept it. Very much the same problem applies to tickets. .
Paper documents like tickets, certificates and cash probably don't have much future. Governments and printer manufacturers can try to make printers that reject or report attempts to copy money but that just means there will be a premium on circumventing their measures. It might be better to accept that things move on and trash the idea of cash?
The inkjet printer applies ink to paper in a very controlled manner, without the intervention of any sort of mechanical plate or needle. The process is nearly silent and ought to be very reliable because it involves no great mechanical action. In principle with an inkjet there is nothing to wear out, the printhead doesn't touch the page. There is nothing consumable except liquid ink.
The problem is to make print-heads reliable and ink cheap without involving users in messy procedures.
Laser printers require complex actions by contrast. The laser printer first paints an image in static, then develops the image in toner, then finally drops one colour of toner on the page - or on an intermediate belt.
Because the laser printer involves a series of actions it looks superficially as though ink-based processes should give a lower cost per page. If inkjet printers could produce reliable high quality output with no more than the cost of ink then they would dominate the market.
Inkjet ink production probably has to be more expensive than commercial printing ink - the material has to be carried down fine channels so there must be no large particles. Most chemical production processes aim at purity and consistency so perhaps inks don't absolutely have to be expensive.
It seems plausible that inkjet printers could even match the operating speed of letterpress or offset lithographic machines whilst giving page-by-page flexibility. The inkjet mechanism is more complicated, involving a complex head and a pure ink. Inkjet printing also requires a significant amount of computer processing and memory - but these are no longer expensive if they are mass produced. On the other hand there is no plate-making or typesetting process and inkjet heads are mass produced so the inkjet mechanism might conceivably match the costs of large commercial printing presses.
For the present, however, the operating costs of inkjet printers are generally higher than those for laser printers and the laser engine makers seem confident of retaining their lead.
What inkjet printers currently achieve is a machine that is inexpensive to buy, but often costly to run. A colour inkjet typically costs between £30 and 300 compared with £150 - £1500 for a laser machine. The inkjet price per black and white page is 3-6p against 1-3p for laser printers.
A colour workgroup inkjet typically costs between £100 and £300 - but an equivalent laser would cost around £1000. Inkjet price per colour page is between 6p and 150p. The figures given are drawn from engineering experience across a range of machines - individual models may give quite distinct figures.
All the manufacturers are loath to admit it, but the current generation of inkjet machines are rather expensive to maintain and run. There are two interconnected reasons – print-heads are unreliable, and manufacturers are making a healthy profit on the price of ink.
Print manufacturers might argue that the cost of ink is ploughed back into R&D and building new production lines so it benefits their customers. There are four big printer makers (HP, Canon, Lexmark and Epson) so there must be competition between them. Whether the market truly is very competitive is more doubtful. It costs a lot to establish a factory and at present the technology is all locked up in patents so there seem to be few new entrants that might shake things up.
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