Laser Printer Basics

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Laser Printers - Brief Outline

Laser printers currently lead the computer printer market. There are more inkjet printers in use because they are cheaper to buy, but they are slower and more troublesome.

The greater volume of printing comes from laser printers, which are very widely used in business.

 There is some sign that laser printer manufacturing costs can be reduced to compete with inkjets as well. Colour laser printers are rather more complicated than inkjets but the look and obustness of their print is often better.

Laser printers are based on the same process as the photocopier.

Chester Carlson invented the dry copying process in 1937. Carlson was then working as a patent agent and naturally patented every aspect of the technology. The first successful experiments used a sulphur on zinc electrostatic medium and lycopodium powder as a toner. Carlson initially had difficulty getting anyone to invest in the idea but eventually it was taken up by the Battelle Institute. Battelle interested Haloid, a maker of photographic films and the first public announcement of "xerography" was made in 1948. The term xerography is derived from the Greek for dry writing. Haloid sold the first printer in 1950. By 1960 the idea had become so successful that Haloid changed its name to "XeroX" Corporation. One of the many things Xerox did with the money was to found its Palo Alto Research Centre - PARC.

Gary Starkweather is generally credited with inventing the laser printer at Xerox PARC in 1971. (Starkweather went on to be Imaging Architect for Microsoft NT and to develop new forms of screen). The team modified a Xerox 9200 copier, replacing the lense assembly with a laser and the paper imaging with a character generator and "RIP" based on a DEC PDP11/34. The EARS printer (Ethernet, Alto Research) not only gave the world the first laser printer but to share it with others co-researcher Robert Metcalfe produced its network mechanism, Ethernet- which became the industry standard. By 1977 the Xerox 9700 based on EARS could produce 120 pages per minute.

Xerox was not alone. Burroughs apparently had an electrostatic printer in the early 1970s which induced an image using a pagewidth array of electrodes (How Things Work, 1972). However by the 1977 Hannover Messe they were apparently OEMing the Xerox design.

IBM developed its own xerographic printer. The IBM 3800 could print around 20,000 lines or 167 pages per minute on 28 cm forms. This early giant had an optical forms overlay station which meant the laser only needed to write variable information. (Hyman 1976).

The first practical laser printers widely marketed were the Apple LaserWriter and the Hewlett Packard LaserJet I. Both appeared in 1984. The LaserWriter was a natural complement to the Apple Macintosh's graphical capabilities.


Copiers and Printers Back to the Laser Printer Index

The basic imaging technology used in copiers and laser printers is much the same. The mechanism used in older copiers is in some ways a bit more complicated than that used in recent printers. Photocopiers need an optical / mechanical scanner to reduce the page image to a thin stripe that can be copied onto the drum.

The market has switched round completely. Today's multifunction copiers have a computer scanner mounted on the same chassis as a laser, phaser or inkjet printer.
 

Twenty years ago the market demand was for photocopiers, with a significant developing market for computer printers.

In today’s market the main demand is for printers. There is still a demand for copiers but almost all ecent models have computer printer innards.

The combined copier –fax-printer devices on the market today are generally computer CCD scanners sitting on top of a printer and combined in one neat, office-friendly unit. The innards of such a machine are purely a printer. It isn't even necessary for copiers to use xerography any more:
 

Low cost machines usually have an inkjet printer.

High speed copiers may well be laser printers - but could be solid ink "Phasers".

The electrophotography process used in today's laser printers is very different from Carlson's early experiments. Today's machines use silicon or OPC drum photoconductors and carefully engineered polymers as toner. Low cost computer power and memory allows printers to be used for photography as well as document copying.

Rather interestingly there are just a few machines that run much faster than the Xerox 9700. The record in 2005 is the IBM 4100 printer with 1,440 pages per minute but laser printers like this are still confined to data centres. Almost all the competition has been to make machines smaller, cheaper and easier for the average user to handle.


Electrophotography Process. Laser Printer Overview and Index

Despite its name the "laser" plays a small part in the overall printing process. The core process has more to do with photo-conductivity and static electricity. Photo-static imaging process or "electrophotography" are more accurate descriptions – but lack brevity and marketing punch. The term "xerography" is also used.

At the heart of the photocopier and laser printer process are two physical principles:

  • Photo-conductivity. Semiconductors and some plastics are photo-conductive, they act as insulators in the dark, but become conductive when exposed to light. A surface coated in photo-conductive material can be charged to a high voltage in the dark. A picture can then be painted in light on the surface, and this will discharge static electricity wherever the light hits. The image is now stored in static on the photo-conductor.
  • Electro-static attraction – materials can carry a static electric charge and be attracted or repelled from one another depending on the charges polarity and strength. In the laser printer a fine dust called "toner" is given a charge so that it is attracted to the areas of the photo-conductor that carry the image and repelled from others.

 

Drum Laser Printer Overview - Electrophotography Section

The printer is usually built around a metal drum, the outer layer of which is the photo-conductive surface. The material used in early machines was amorphous selenium. Photoconductors can be silicon, but in most ecent machines they are couple of layers of plastic - hence the name organic photo-conductor or "OPC" for short. Using a drum gives structural support to the photo-conductive material and the rotating surface of the drum acts as a temporary memory for the image as it is produced.

Drum Picks Up Charge, Discharged by Laser, Developed with Toner

When the drum is in darkness it’s surface acts as an insulator. The drum surface can therefore be made to pick up a strong charge of static electricity as it passes near a wire charged to several hundred volts. The surface charge is usually negative. Page on Photoconductors

 

Scanning Laser Printer Overview and Index - Electrophotography Section

The image to be printed is painted on the drum by scanning it with laser light. The laser scans from side to side as the drum turns forming a pattern called a raster (similar to that used in a TV). Other sources of light can be used – some printers use an array of tiny LEDs. Photocopiers often illuminate the document brightly and use a lense to focus a thin strip of document onto the drum.

Polygon Mirror Scans Laser Over Drum

Exposing the surface of the drum to light from the laser discharges it’s surface charge into the metal beneath. When it has been raster scanned the drum carries an invisible image in static electricity. Page on Optical Scanning Mechanisms

 

Developer Laser Printer Overview and Index - Electrophotography Section

The image in static electricity needs to be developed – made visible. The developer introduces small particles of toner (coloured plastic dust)onto the static-charged surface of the drum.

Developer introduces toner to drum surface

The developer is often a hopper filled with toner and mixed with iron filings. The developer roller faces the drum, with just a fractional separation. The developer roller

  • rotates carrying a thin layer of filings and toner out towards the drum
  • has an electrical charge equal to the charged area of the drum, so toner will only stick where the light has discharged the photoconductor.
  • contains a magnet which causes the filings coated in toner to stand on end as they pass the drum.
Actually some more recent developers, those used in colour printers for instance, use "resin" rollers and sheets to create a finer developer coating. The net effect is the same. The developer brushes the drum gently with plastic dust which is repelled from areas that still carry a charge – but sticks to those areas with no charge. Section on the Developer and Toner Mechanism

 

Toner Transfer Laser Printer Overview & Index - Electrophotography Section


The image is now sharply defined in toner powder, and the drum rotates further until it is over the paper. At this point, drum and paper are also over a charge-wire or roller sometimes called the "transfer station".
 

Paper kicked out of tray, fed through registration station and across transfer station to fuser

The transfer station carries a positive charge. This is picked up by the back of the paper and attracts the toner off the OPC and onto the paper sheet. Because the drum rotates at the same speed as the paper is moving the image is transferred between them with precision. The paper now carries the image outlined in plastic dust. The paper moves to the fuser.

The drum rotates on past eraser lights and a cleaning blade which emoves any surplus toner from the OPC. The drum is then ready to go through the print cycle again. Page on the Paper Transport Mechanism

 

Fuser Laser Printer Overview & Index - Electrophotography Section

The plastic dust on the paper will smear if it is touched. The printer carries the paper and the image into a device called the fuser. The fuser has two rollers, one of which is heated to a point where the plastic dust will melt. The other is usually a foam roller that is spring-loaded to apply pressure. The plastic melts onto the paper and so is "fused" to it.

Fuser melts and presses toner into the paper

The printed paper is now ready for use. The image is made of a very thin layer of plastic melted onto the top layer of the paper, so it will not easily come off even if the paper gets damp or left on a radiator. Some effort has been made to develop machines that can re-separate the image from pages so that they can be recycled but this idea has yet to catch on - it seems simpler to send the paper for recycling. Page on Laser Fuser Mechanisms

Electronics & RIP Laser Printer Overview & Index - Electrophotography Section


This simplified outline of the "electrophotography" process holds broadly true for copiers and printers of various kinds. Some machines use a belt ather than a drum. Colour machines may have four drums and an intermediate storage belt.

In laser printers the image is scanned by the laser and polygon mirror but obviously it has to come from somewhere. The Raster Image Processor or "RIP" is a key part of the process, accepting a stream of commands, text and bitmaps and assembling in memory a version of what will be on the page.

There are a lot of pixels on a page -

  • around 8 million for an A4 page with margins and a low 300 dpi esolution.
  • 35 million pixels for full cover of A4 at 600 dpi
  • 280 million for A3 colour at 600 dpi
Memory needed quadruples with each doubling of dpi so printers can need quite a lot of memory.

Most computer print technologies like inkjets don't need to assemble the whole page before they can print - the print engine can stop and wait for the computer. Laser printers can't normally do this. Once the drum, developer, paper and fuser are moving they can't stop. The printer has to have the whole image ready in memory. Historically the memory and processor power to do this was expensive. Since computer power gets cheaper with each generation of machines this is a diminishing issue - though still significant for big, fast high resolution colour printers. About Laser RIPs


 

Costs Laser Printer Overview & Index - Costs

Machinery for laser printing is obviously quite elaborate, but mass production has brought costs down. Furthermore most of the parts can be made as user-changeable consumable cartridges.

The only materials that must inescapably be consumed by the laser printer process are paper and toner. (Yes most printers do wear through the  drum, developer and fuser but those parts could be made with very long lives)

Printers have several costs - purchase, consumable, maintenance, etc

Laser Printer Overview & Index - Costs
Paper has to be ight for the process. Paper itself is attracted to static charges so it mustn't be too flimsy or it will dissapear into the mechanism. If the paper is too thick or damp or already electrically charged it might also misbehave. Reputedly paper is Xerox corporation's biggest earner.

People often think that printers should work with any paper - that isn't the case. What has actually happened is that modern office copying papers have been specifically made to work with laser and inkjet printers.

A big advantage of laser printers offer over inkjets is that they produce good looking print including photography on ordinary copier paper - they don't need very special material.

Laser Printers have Low Paper Costs

Laser Printer Overview & Index - Costs
Toner is essentially plastic powder but that rather understates its chemical complexity. Toner has to accept and carry a charge. The grains have to be fine and even enough to give the resolution wanted. The colouration might be carbon-black for most toner, but cyan, magenta and yellow toners will be more complicated. Toner grains have to melt in the fuser and adhere to the paper, not the ollers. To do the job some toners are resin outers with encapsulated wax cores.Laser Printer Toner is the Core Consumable


Wear Laser Printer Overview & Index - Costs

Other parts of the printer wear out. The OPC is being exposed to light and brushed by the developer so it may lose part of it's surface composition and sensitivity. The developer material is being churned which will gradually wear it down. The developer roller is undergoing continual frictional wear. Furthermore the whole process is working using static electricity - and dust from the air and from paper is attracted to static and will interfere with operation if it builds up.

Rather than expect users to deal with all the components Xerox used to put it's copiers on lease. The whole process was dealt with by their specialist technicians.

Laser printer makers have generally turned a problem into an opportunity. The components that wear out have been wrapped up in one or two user changeable cartridges. The printer's internal computer demands a new cartridge every so often. This is the same approach used with most inkjets; critical parts that wear out are kept in order by replacing the cartridge.


Ownership and Operating Costs Laser Printer Overview & Index - Costs

In the 1970s printers often took ribbons that were more or less the same as those used on typewriters. A manufacturer might have a proprietary design, but if they pushed prices high then someone else would start making compatible ribbons - manufacturing wasn't really difficult.

As printer design evolved consumables became more complicated. Manufacturers could push the price of consumables higher because compatibles cartridges were more difficult to make.

Printers used to be expensive machines but as the market grew mass production has allowed them to be made more cheaply. There are quite a few designs and several large manufacturers so it might seem that the printer market would be highly competitive both on purchase price and operating cost.

Most printer manufacturers have the opportunity to make very much more from consumables than they ever could from selling the printer. There is a strong incentive for them to do so because users are price sensitive about purchase price but seem to be rather indifferent to the value of consumables (in industry, its often a different budget).

At the low cost end of the market manufacturers are almost certainly selling printers at production cost or less as a way to get consumable evenues. This trend is less noticeable for larger printers because the buyers are more likely to ask about consumable price and life. There is more on consumables below but its worth noting that some office printers costing £500 will work through a thousand pounds worth of cartridges in the first year of ownership.

Maintenance can cost nothing or be rather notably expensive. Again things are not straightforward.  Manufacturers like customers to have a long warranty not just because it gives an aura of quality and reliability but also because quite a few likely faults are not covered - consumable faults are usually not. Warranty terms sometimes exclude the use of any ecycled consumables from a source other than themselves entirely, other manufacturers will allow recycled cartridges but the call will be chargeable if the fault proves to be the consumable. Long warranty helps guarantee consumable sales even if there are compatible makers in the market. 

A long warranty free from the manufacturer does give users some confidence that faults that happen through no fault of their own. Extended warranties from manufacturers and retailers vary in the value they offer but in the UK the Consumer's Association has warned that they are generally poor value.

Parts for printers are like car-engine parts - not necessarily unique to the manufacturer and model, but not commonplace. If a motor or control board fails out of warranty the manufacturer's price is likely to be quite spectacularly high - they'd rather the service engineer sold a new printer ather than fix the old one.

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Manufacturers Laser Printer Overview & Index - Costs

Obviously the description of the photo-static imaging process given here is very broad. There are a great variety of photo-conductive materials, developer mechanisms, transfer voltages and fusers in use.

More than 20 laser-printer manufacturers are competing to produce machines that print faster, give higher resolution images, better grey-scale handling for photographs, colour, lower copy prices, and easier handling for users. Laser-print technology has advanced rapidly in the last thirty years– one esult is that printer prices have fallen significantly from many thousands of pounds to the point where some home laser printers are sold for less than £100. There have even been colour models for £100!

For low cost printers the main thrust of the market is not really technical at all; its to lower the printer sale price as far as possible then get users to repeatedly purchase manufacturer original consumables.


OEM Mechanisms & Engines Laser Printer Overview & Index - Costs

Laser printer mechanisms are both complicated and mechanical. Electronic devices can theoretically double in complexity and half in price every couple of years - this observation is called Moore's Law. Mechanical things should not be able to do this but laser printers have sometimes seemed to do so. 

One way to get the cost of components right down is to manufacture to a very large scale. In the printer industry this is done by using "engines". The mechanics of a laser printer are usually designed by one manufacturer, made by many subcontractors and maybe assembled in a contract plant. Perhaps surprisingly they are then sold under several different manufacturers brands, perhaps with different electronics.

The manufacturer label on the front of the printer and the maker of the actual print-mechanism are often very different.

Some companies have a historic strength producing photo-copiers but initially missed the potential of the laser printer market. Canon, Ricoh, Minolta and Fuji-Xerox seem to have been examples. These companies have developed their strength in the printer market, but as well as selling their own brand they tend to make "print engines" - the metalwork, plastic and perhaps consumables of the printer.

Hewlett Packard, Apple and QMS led the move to using Engines in 1984 when they launched machines built on Canon's LBP-IV engine.Brother and Epson, two of the giants of the dot-matrix printer market in the 1980s, chose to use other manufacturers engines in their laser printers.

Use of engines gives huge scale economies. The developer of an engine will invest a great deal on research, defining the parts and setting up the contracts to manufacture them. They may find that their own software , consumables pricing, support package and marketing efforts are hugely successful. If they also sell the "engine" to a half-dozen other makers they get six shots at market success. If things work really well there are huge scale economies.

Manufacturer use of engines obviously has great significance for field support and spares. It is highly likely that a paper feed problem with printer A will also be found with lookalike printer B. It is probable that  a pickup roller for printer A is also the roller for lookalike printer B - but not certain, that manufacturer could have varied the specification. If you are minded to substitute HP with Canon parts it will generally but not invariably work.

Rollers don't vary frequently; software is often very different. 

Software determines a large part of laser-printer performance. There are at least two elements to the software controlling a printer.Two printers with the same engine can behave very differently. Hewlett – Packard have used Canon Laser print engines to achieve a strong market position in laser printers. In principle the Canon engines do the same as their HP equivalents – but historically HP had an advantage in software. the curious position emerges that HP are the best selling laser printers with half the market - but they don't actually make the bulk of the metalwork and plastics. Those are made for them by Canon. Nevertheless HP machines remain an excellent choice, because the HP / Canon team produces machines that are flexible, powerful and easy to use.

This distinction between what the print-engine does by virtue of it's mechanics and what the printer can do using clever electronics and software is continually shifting as the way PCs are used changes. At one time a laser printer sold if it could produce a nice clean page of typing. Today's buyers are looking at the machines ability to handle colour production printing to compete with offset litho work, office printing and home photography. Similar print engines can be used in very different ways.

Very large economies of scale can be achieved by a group of manufacturers sharing engines. Whether these economies can keep pace with Moore's Law and deliver a colour laser printer for £50 sometime in the next couple of years remains to be seen.



Cartridges Laser Printer Overview & Index - Costs

The key element in modern printer design is the cartridge. It isn't clear what the cost of manufacturing printers is because  it can be financed through the profit on cartridges.

The main driving factor in the printer market stems from the development of the cartridge. Perhaps inspired by the inkjet market, laser printer makers discovered that the real earnings were not from selling reliable printers that mainly used toner and sometimes used drums, developers and waste bottles. The real money comes  from selling cartridges.

Older photocopiers did not have cartridges and some still do not. Toner comes in a bottle and is poured into a hopper. Drums are large, long lasting and when they are changed it is done by an engineer, so they don't need special protection - the engineer knows not to touch the shiny surface. Likewise fusers are large and changed by an engineer. The reason for this is that photocopiers are commonly leased and then serviced on a price per copy; the rental firms are under pressure to get their material costs right down and they have sales and service eps on the road so the marginal cost of visiting a customer to change components is not that great.

Printers are most usually sold outright, alongside PCs. Manufacturers don't want to suggest users might need some knowledge to own one, and they don't want too many support calls. They do have some sort of warranty service cover but given the low price the machines are selling for those calls are relatively expensive.

Manufacturers have turned a problem into a solution in classic fashion. Instead of selling lose toner and components the manufacturer sells cartridges.

A cartridge wraps basic elements of the print process such as toner, developer or drum in an easily handled plug-in component. Drums come in a plastic assembly with a handle. The toner in a hopper that mates with the developer and protects the user from contact with toner stains.

Cartridges come in two broad types:

- one type puts the consumables  toner, drum, developer and waste handling in separate units. Each consumable has a different life so having them as separate elements should make sense. There are two problems: there are more bits to stock and whilst individually they may not be expensive the cost of all those parts does add up. Another issue is that if there is a fault such as faded or dirty print the user has to decide which component is wrong.

- another type puts several or all of these units into one print cartridge. To keep the cartridge small the toner may have a life of 5,000 pages or less although "workgroup" printers often have big cartridges with a life of 15,000 pages or more. A problem is that the developer and drum are partly wasted and could last a lot longer. Benefits are that there is just one thing to buy and stock, and one thing to change to fix most faults. HP suggest that changing a cartridge changes 70% of the print path components and experience validates that - more than half of print problems are cleared by changing the cartridge.

HP and Canon have nearly always used the one-piece print cartridge approach. Experience suggests it gives fewer support issues, and in confirmation of this other manufacturers like Lexmark have taken to using single piece cartridges on machines likely to be used as personal printers.  Incidentally HP do use separate components on big, fast toner hungry colour printers like the CP6015.

Cartridges And Cost

Whichever way it's done making a cartridge is the printer manufacturers license to print money.

Users have just one source of good reliable cartridges - the printer manufacturer. The manufacturer owns the copyright on the parts and in many cases has patents that may be technically trivial but are essential to making the cartridge work.
 
Even if the print engines are the same all the manufacturer has to do to limit the user to their own cartridges is to change a couple of points in the plastic mouldings. In some cases they are not being devious - the toner may well differ from that used in a competitors machine so that using it wrongly would wreck the fuser. In the past parsimonious users and incautious engineers were often caught out like this. The mess made by a low melting point toner in a hot fuser is unbelievable.

When the user buys a printer they also engage in a long term relationship with the manufacturer on consumables. One analogy that has been suggested is that it is like buying a car and agreeing only to fill up with petrol from Ford garages.
There are two alternative ways to get cartridges: recycling and clone cartridges.

Recycling

Recycling is one possibility. Each toner cartridge used brings the possibility of refilling it.

A refill just inserts more  toner because the other components of an all in one cartridge last longer than it does.  Even if a cartridge has a large rubber bung just begging for refilling it is not necessarily a simple matter - there are two broad classes of toner - one with and one without a magnetic component depending on how the developer works. There are also many different melting points depending on the wax and resin components used. Using the wrong toner will destroy the cartridge and damage the fuser.

Remanufacturing might change all the wearable components as well as the toner, drum, doctor blade and scraper. The re-manufacturing cost of doing this is inevitably greater and might be more than the printer manufacturers cost in making a new cartridge because of the labour costs dismantling and rebuilding what was a sealed unit.

Recycling is another approach.  A factory can re-use the plastic and metals but as conventional scrap ground up and used as raw material. Some of the manufacturers do this. A problem is that ecycling in this way is not very distinct from what a conventional scrapyard would do in terms of separating components and producing industrial feedstock. There is also a significant logistics cost of eturning material to the global plants that make cartridges. The merit is that it does recycle material whilst giving the reliability of new manufacture.

Reliability is an issue with refilled and remanufactured cartridges. Manufacturers aren't inclined to help recyclers by publishing detailed specifications for the components used in their cartridges or to provide the components needed to fix them. A used cartridge split in two and refilled will naturally sometimes have issues - changes of shape, plastic debris in the mechanism and so forth. From time to time people will misjudge the type of toner used or fail to replace a component that turns out to be worn out. There are very distinct differences between recyclers and batches as well.

To keep the logistic costs low these activities really need to be done locally at neighbourhood or city level. It is not easy to determine things like toner type and grade or the right consistency of scraper blade in an individual shop. This kind of recycling tends to be done on a franchise basis with a head office running a lab and sourcing the components in bulk and franchisees buying approved parts.

Any manufacturing effort tends to be more economical the larger the plant is. Recycling itself seems to be moving to continental and global scale factories in low labour cost countries. This might reduce the environmental benefit of recycling but an alternative view is that a very large factory will better able to recycle components that aren't suitable  for remanufacturing.
 
There is a global industry sourcing parts for recyclers - notable names are Summit and Uninet, Future Graphics and Static Control.  And of course there are the component manufacturers of rollers, foils, toner powder, mouldings, heaters, bearings, thermocouples and so forth who make things under subcontract and would like to sell parts on their own account.

Compatible Cartridges

Compatible cartridges are sometimes possible for laser printers although the job is more complicated than for inkjets. Section on inkjet cartridges  The cartridges themselves are larger and generally more complicated - although they don't have anything quite so complicated to deal with as an inkjet printhead. A prospective manufacturer also has to consider the legal threat from the printer manufacturer.

Gearing up to make compatible cartridges is expensive and any infringement of the manufacturers intellectual property rights is likely to bring a ruinous legal action. Epson took action against several Asian manufacturers in the US.

UK Manufacturer DCI stress their care not to infringe others property rights - and they have a patent portfolio of their own.

One of the reasons the cartridge industry is keen on patents is that they can be used as a negotiating ploy. A suit from one manufacturer for a set of patent infringements often brings a countersuit.

Compatible cartridges have significant advantages over recycled items because they can be made to the same tight tolerances manufacturers apply to their branded new products. However there are not many compatible cartridges for modern laser printers because the manufacturers originals are so well protected by intellectual property law

User Choice


When you buy a printer you have to take into account its running cost, just as you would with a car where fuel is the main cost but servicing, tyres and so forth are surprisingly costly. Printers use toner cartridges but with some colour designs there can be as many as 14  items that will be consumed - toner, developer, drum for each colour, a transfer belt and a fuser

User behaviour with cartridges need not be a matter of buying for best value in the long term. Most users don't really grasp that a page of text contains very little ink but a photograph can easily contain more than 20 times as much. A laser printer that costs 2p per page for text might cost 20 times that or more for photography. Inkjets are usually more expensive still.

Nevertheless the cartridges in a colour machine to tend to be gradually used up - even if users almost never use colour. This gradual depletion by the purge process  is not often appreciated but can exhaust colours in a year or so if the printer is continually turned on and off.

Of course the worst cost is to buy the printer, then be so frightened of its operating costs that its  abilities are rarely used. Laser cartridges usually have a longer shelf life than those in an inkjet so occasional use is less of a problem.

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© Graham Huskinson 2010

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