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Printers need a medium to print on - most often paper but transparencies and light card are common as well.
The paper feed mechanism on modern printers is based on an input tray, a set of feed rollers and an output tray. Paper feed can get very elaborate with multiple input and output trays, collators, saddle stitch units and bookbinders. These plug into the printer as accessories and aren't essential, so if they pose problems they can be diagnosed on their own.
The feed mechanism looks straight forward but it's the product of 30 years of development. Paper paths have changed substantially over time and some of the components behave in quite complicated ways.
When paper doesn't emerge from a printer as expected, when it jams or doesn't print in the right place then paper feed no longer seems so simple. It can be difficult to diagnose feed problems, particularly on fast duplex printers, because one page is emerging from a tray whilst another is in the duplexer and yet another is emerging from the fuser - so when the printer says "feed error" the problem might be anywhere. Many recent printers assist by suggesting where the problem is - sometimes in a diagram shown on the display or by a PC driver. That is helpful although it isn't always right.
There are half a dozen fixes:
Paper quality is a frequent cause of paper jams and feed errors. A ream of paper bashed against the side of supermarket trolley or stored on a cold, damp warehouse shelf is likely to give feed errors. Paper needs to be handled carefully. Before putting a stack of paper into a printer look for damage and fan the front and side to make sure the sheets separate. Bad paper usually causes intermittent faults but sometimes it is bad enough that the printer just can't cope. An indication of bad paper is that sheets that do pass through the printer curl noticeably; damp paper causes that.
Tray guides commonly give issues. The paper tray guides hold the stack of paper tidily and ensure that when sheets move they move they follow a straight path. If the tray guides are too lose the paper will not set off straight and may hit the sides of the print path crumpling on one edge. If the tray guides are too tight the pickup roller may have difficulty overcoming the friction and the paper either won't shift at all or it will move too slowly.
Paper debris frequently causes problems. If pages won't feed at all the problem is almost certainly a fragment of paper that has torn away from a previous misfeed and is lurking in the mechanism. Labels stuck in the feed path are worse, often glued to the printer feed path somewhere inconspicuous. A lot of printer problems are solved by taking the cartridges out and making sure that paper is actually free to move.
Paper movement sensors can give erroneous misfeeds. One style of sensor is a little plastic flag protruding into the paper path that moves when paper passes. Recent and more expensive printers use reflective sensors - a transparent window looking into the paper path. If the sensor is dirty, stuck or just plain missing, the printer will signal feed errors.
Dust is a problem. If the mechanism is dirty it needs cleaning both of lose paper, toner dust and other dust. Laser printers work using electrostatic fields and high voltages which are generated by a power supply board and by the triboelectric effect of toner particles on other plastic surfaces. Correct movement of the toner relies on those voltages being right and if a contact is dirty toner won't move properly. Missing screws in the paper path can have the same effect. Voltages that should attract toner in the right place can also attract dust and escaped toner to the wrong places. Many engineers use a compressor to blow toner and paper fragments away outdoors - it is more effective than using a vacuum. If a printer has to be cleaned in an office environment then there are special vacuum cleaners.
Fuser problems like a broken fuser foil may also give feed errors. Printers generally have no sensors to tell when the fuser foil or roller has lost part of its coating. A thorough cleaning of a printer means taking the fuser out so that's a good time to inspect it. Don't be tempted to touch the fuser roller or foil, it may be hot and contamination will spoil its performance.
Feed rollers wear out. Finally we get to the main topic of this section. If the print mechanism is clear but paper feeds erratically the likelihood is that one or more of the feed rollers is exhausted. Rollers lose their surface texture through wear and lose their plasticisers as they age. Normal life for a roller is something above 50,000 pages and possibly much more. Worn rollers can look quite good to people with nothing to compare them to. Changing a roller is often quite easy on recent printers. If none of the issues above seems true and paper still won't feed properly then you need new rollers or possible a paper feed repair kit.
The remainder of this section goes into much more detail on paper handling mechanisms. One of the first things to look at seems to be the context. Why pass individual cut sheets through a printer when that is a difficult thing to do?
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Paper Style. |
| Most printers cost too much to run. If a 300 page novel costs £10 to print and bind it's about twice the price of running the job through an offset litho press. Digital print is becoming practical - but at the moment its main appeal is for specialist books. |
| Most printers can only print the pages, and cheap printers just manage single sided. Just a few top-end machines can make anything like a finished document using a saddle-stitcher and binder. |
Continuous Feed
The simplest way for printer mechanisms to handle paper is by continuous feed - either on a roll or as fan-fold perforated sheets.
Roll -feed is used for plotters and some industrial printers.
Until the 1990s most dot-matrix printers, bandprinters and even inkjets were designed to handle fan-fold paper usually in the 14 x11 inch form that somehow became a computer industry standard.
Fan- fold perforated sheets had their merits for users as well, they were self stacking, could easily be bound on one edge, and the wide pages suited spreadsheet work. However handling fanfold paper is a skill and a lot of people found it a nuisance to work with.
| Aim for this section:- Everything you (n)ever wanted to know about laser printer paper feed. Obviously this isn't a guide to changing rollers on every printer - there are hundreds of designs. Instead it's a general outline on how the printer feed path works. |
| Why it isn't tractor feed |  |
| Paper trays of many forms | |
| Paper quality | |
| Letterheads | |
| The up arrow on paper packs | |
| Pickup problems | |
| Peace and happiness using a paper feed kit | |
| The S Path Saves Space | |
| Paper Paths many Clutches | |
| Multiple Trays & Feed Options | |
| Collators & Staplers | |
Laser printers began a differentiation of the market. Dot matrix printers were bought because they were the only way to get printed information quickly and cheaply. Laser printers were bought for desk-top publishing and correspondence and they were expensive, several thousand pounds for a four page per minute A4 printer.
Laser quality print was originally aimed at the market for correspondence and report printing, where cut sheets of paper like those used in typewriters are expected. Rather than change cultural expectations and have letters on fan-fold paper (which might have been easier in engineering terms) the printer designers opted to make computer printers handle cut sheets.
Laser printers that handle continual feed paper are quite rare but they do exist. They are generally used in applications where high volume and low copy price are priorities. Laser printers give high print quality but cost significantly more to operate than dot matrix printers.
Cut Sheet
Most of the laser printers on the market allow for A4 in Europe and the US standards of "legal" and "letter". To meet these standards the paper path has to be:
| about 8.5 to 9" wide, just exceeding the 210 mm width of A4. |
| less critically the feed path has to handle sheets about 12" long ( 300 mm approx). Some laser (and many inkjet) printers can print much longer pages - 30 inches or more counting as "Banner". The only problem with banner print is that a long page might exhaust the printer memory. |
Many printers can cope with smaller paper - down to A5 (149x211mm). The paper tray guides will have to be adjusted to cope with small paper. Most laser printer feed mechanisms cannot deal with very small paper the size of individual labels because the distance between feed rollers is to great. To overcome this label makers assemble grids of product on A4 sheets.
A3
There are advantages to designing the paper path to be 11" wide. This allows A3 paper through the machine in "portrait" orientation, and A4 sheets to pass through quickly in landscape mode. Engineering diagrams commonly need a minimum of A3.
A3 colour printers with a duplex mechanism often have a clear aim, they can print four sided A4 brochures in one easy step. Print the two-sided document and then just fold the page. Just for information note that a double sided A3 brochure can need a lot of memory and whilst recent printers generally come with enough that isn't always guaranteed. Photographs with lots of detail and textured backgrounds potentially use a great deal of memory so finding out how much memory is needed can be a matter of trial and error.
The average laser printer is designed to hold A4 paper with its 8" side presented to the paper path. The printer can be set to print this as "portrait" or "landscape" because the laser mechanism is quite indifferent as to what pattern it creates in the raster image memory- the printer just needs to be given the correct instructions. If the printer has an A3 capability the 11" side will be turned to the paper path, and in this case A4 will pass through the same way round (sideways) so as to make better use of the OPC surface. Printers with an 11" path are inherently faster for A4 because they only need to roll 8" of paper through the paper path.
Achieving A2 print would need a 16" paper path and drum and only very exceptional laser printer designs allow this. A2 is good for maps, diagrams and display work but is too large for most offices and even for photography.
Cultural expectations demanded cut sheet paper and printer designers provided it. It isn't always a great decision. When the printer jams half way through printing a report, thank your culture! The main problem in most recent printers is reliable paper handling and the main obstacle is the cult of the cut sheet. (But I don't think we are going to see a roll-feed revolution)
Paper Trays.
Cut-sheet presents some handling difficulties, because it is difficult to control the way a sheet passes through the print mechanism. Paper is generally stored and initially guided from a spring loaded tray, its progress through the printer is then controlled by rollers in a feed station, registration station, then in the fuser and finally through a "redrive" or exit assembly. If the printer is capable of placing 1200 dots per inch then paper feed has to work reliably to less than a thousandth of an inch.
The simplest paper feed is single sheet - as with a typewriter the user inserts a page between some rollers and they just drive it through the print station. Some early computer printers of the dot-matrix and daisywheel type required this. It's irritating for the user because it wastes time.
A bypass feed slot is similar - the printer has a "proper" paper tray but there is a slot above it or some guides on the tray lid that allow one piece of letterhead or one envelope to be fed into the machine. Again this requires the user to sit near the printer and be ready when the moment comes. Sitting next to a busy printer is not recommended. 
Next up in the hierarchy is the multiurpose tray (MP tray) which folds down on the front of many printers. This is usually rated to take something between 10 and 50 pages of 80gsm A4 or a few envelopes. The limitation on how much paper this tray can take is that it is either weakly spring loaded against its pickup roller or the roller is normally held a few millimetres up and is driven down on the top page when the printer uses the tray. The tray is "MultiPurpose" in the sense that it has guides adjustable to hold anything from around postcard sized to oversized paper. The MP tray is also multipurpose in the sense that media placed in it face straight into the print path and there is usually a fold down face-down exit path on the back of the printer to take output. This allows "heavy" media like envelopes, index cards, light card and banner media to pass straight through the printer. Most HP printers have an MP tray and it is almost always "Tray 1". Lexmark seem more inclined to treat a multipurpose tray as an optional extra; in fact people who don't handle correspondence rarely use it. The MP tray folded down makes the printer look ugly and there might be an issue with things like paper clips falling into it.
"Proper" Trays
There are lots of different paper tray designs, but there are common themes that emerged in the early 1990s.
Older and simpler printers often have a paper tray that inserts into the front of the printer. This keeps the feed path simple so the printer can feed paper reliably with a simple set of rollers. However the tray sticks part way out of the front and gives the printer a large footprint; it takes more space on a desk.
Most recent printers usually have a main tray that slides right under the printer. This means the paper feeds up from the tray, bends around into the print station and then bends around after the fuser so that paper emerges into a face-down stack on the top. The "S" shaped feed path greatly reduces the space a printer takes. A potential problem is that it will not take very heavy media; most printers have a limit somewhere around 110 to 120 gsm for this path - but that sort of paper weight is normally used for letterhead and might be put in the MP tray.
It is more or less standard on laser printers that the main tray holds more than 200 pages of 80gsm paper. Printers aimed at "workgroups" (shared on a network) often have a 500 sheet tray or two 250 sheet trays. A pair of 250 sheet trays is really handy in some kinds of office work because that allows letterhead in one, plain paper in the other and the MP tray for envelopes. If the printer doesn't come with an optional extra tray users very often add it anyway despite the extra expense. The sheer quantity of paper a printer can hold is actually quite important because a shared printer that holds very little paper disrupts people's work. They print, the paper runs out, they refill the printer and the printer fails to resume in the expected place. The whole office gets disrupted.
In simple trays holding up to 250 sheets the tray usually has a spring loaded plate at the bottom, this forces the paper up against the pickup rollers which are very often "D" shaped and between two idle rollers. When the printer turns the "D" roller it pushes paper out of the tray and into the feed roller.
500 sheet trays are more expensive, not because a little bit of extra plastic is involved but because they tend to need a motorised paper lift.
Pickup
Pickup looks simple but often is not. At pickup one sheet must move into the printer, where is will be held momentarily at the registration station.
The simplest approach is probably a "D" roller. The roller is on a shaft that is connected to the main printer gear chain via a clutch. The clutch is often a nylon wheel held by a solenoid. When the clutch operates the roller is connected to the motor. Turning the D roller pushes paper out of the tray and into the feed roller but as the D roller turns it disengages from the paper before the roller actually returns it to the parked position. So the paper is pushed forward a bit but not continually driven.
With a round pickup roller the printer usually has a cam follower mechanism that lowers the roller onto the paper as it turns. Rollers can also be spring loaded so that they engage the paper and rely entirely on the printer's control over a clutch or motor for the timing.
Sheets may stick together for several reasons - they may be damp, the cutting process may force edges together, or friction between sheets may cause several to move at once. The tray and printer have a "separator":
- on older printers a device that causes sheets to ruck as they leave the tray and breaks them away from their successors. A spring loaded roller from above pushes the paper and it distorts (rucks) slightly so that it breaks away from the stack.
- and / or a pad that grips the paper a bit and that grip will only be overcome when a sheet is being directly driven by a roller above.
There is often a cork pad at the bottom of the paper tray as well, this is to ensure the last sheet feeds freely and then the roller has something that will resist but not prevent turning if the printer tries to pick up a page.
Tray Guides
Paper trays look simple - a plastic box with a metal plate and a few springs. Adjustment of the parts in the paper tray is one of the most common causes of trouble with printing.
| Lose Guides. If the paper guides are too lose the sheets of paper will go out of alignment as they enter the printer and hit the sides of the feed path. This will cause a rather unpredictable jam, probably somewhere near the registration station as the paper is skewed off course by any slight unevenness in the pickup and feed rollers. |
| Tight Guides. If the guides are too tight the pickup roller won't always be able to pull sheets off the stack of paper and will give a feed error when it fails to do so after a second or so. There will probably be a grinding noise as the rubber of the roller skips and jumps on the page. There is something called a torque limiter that is supposed to prevent the paper actually getting torn or concertinered in the tray. The torque limiter can get weak and then paper that should have fed with correctly set guides won't do so. |
Some printer makers have a letter sized tray for the US and a "Universal" tray for other markets but available in the US as well. Having a tray fixed at letter size looks strange from a UK perspective but presumably it cuts down the calls to technical support.
Powered Trays
Small printers like home inkjets and lasers may just have a simple spring loaded tray. This will typically hold somewhere between 50 and 100 sheets without giving trouble.
There is a problem with handling more than about 250 sheets; the printer needs a paper lift mechanism instead of a spring.
Larger trays could use larger springs. The problem is that the spring will be too weak to hold the paper up when the tray is fully loaded but press too hard toward the pickup and feed rollers when it is almost empty possibly causing multiple sheet feeds.
Larger printers often have a motor lift for the tray, allowing them to cope with a whole ream of paper (500 sheets) or more at one go. When the paper tray is inserted the printer will whine a bit as a lift motor brings the paper up against the pickup roller. A sensor in the roller mounting cuts the motor when the paper is at the right height then lifts it further from time to time as it works.
Printers providing a central service to a fairly large workgroup often have fully motorised trays that may cope with 2000 or more sheets before they need a refill. Clearly this kind of printer often has multiple trays as well.
Paper Grades and Trays
Not all paper feeds well from all trays.
| Thick card may not behave properly in the paper separator. It probably can't feed from a tray anyway if it has to enter the S shaped path on most modern printers. Quite commonly material up to 200gsm will feed from the multipurpose to the rear face-up tray - the straight through path. |
Thinner grade envelopes give trouble because the material distorts under pressure from the feed roller and causes a jam. Thin grades can be attracted into the printer's electrostatic field as well.  |
| Thick grade envelopes give trouble like card - they can't get past the paper separator. The glue on envelope flaps also needs to resist melting in the fuser. |
| Shiny paper can give trouble because the pickup rollers miss their grip. Because shiny paper has become popular some recent printers specify that they can handle it. |
The user manuals for printers often devote several pages to detailing what the machine should and and should not be able to handle. Printer manufacturers are increasingly keen to sell their own brands of paper so if your own favourite and perhaps cheaper brand won't feed you can guess what the tech support helpline is going to say!
Rollers, Feed Repair Kits and Maintenance Kits.
Pickup and feed rollers are made from soft rubber to give some grip on the paper. As the rubber ages it loses any textured surface it had, loses its plasticiser and picks up paper dust. The result is that the roller becomes harder and inclined to slide on the paper. Paper feed problems generally start as a few months of intermittent feed errors with difficult paper types getting progressively worse until the printer will scarcely work at all.On recent printers the rollers are often really easy to change. Designers have exercised some thought and rollers are held in place by locking tabs so that replacements just pop onto the shaft. These kits can usually be fitted by users.
Unfortunately easy roller replacement was not considered an issue with older printers. It is true that they often had harder wearing rollers - but less flexibility in the paper they would handle. The result can be that changing one seemingly inoffensive pad or roller means completely stripping the printer so the job really needs someone with a technical mindset.
If one roller is worn it is usually reasonable to suppose that some others are as well, together with the separator pads they engage with. Many manufacturers provide feed repair kits - a set of all the rollers in the feed path.
Maintenance Kits provide a fuser together with a feed repair kit. Fusers tend to last quite a long time and when they do fail it's usually a good time to change the rollers in order to save the users trouble.
Colour printers sometimes don't have manufacturer specified maintenance kits. The argument might be that the rate of wear for fusers in colour printers differs depending on page cover whilst the wear on the rollers does not. Several spares suppliers make up maintenance kits anyway. Given the trouble and expense a service call involves, the extra cost of changing the feed rollers may be worthwhile.
Registration
The pickup roller pushes the paper forward to the first feed rollers if there are any and then to the position called the registration station.
Inside the printer there will be a pickup roller and a paper detector - a device called a "dog" which is a small plastic flag that is held up when paper is present so that the printer can detect and signal when paper runs out.
The registration station is often a pair of thin rollers the width of the paper path - often one in hard rubber and the other metal, or a whole series of hard plastic idle rollers. The paper hits this position and is supposed to be square on to the print path and "registered" in precisely the right place. The paper may really halt at the registration station for a moment because from this point onwards it is meant to travel at exactly the same speed as the OPC drum and the fuser rollers so the image can transfer accurately. A pickup then a momentary halt whilst the printer registers that the expected sheet did in fact arrive allows the printer to hold off drum action if there's a problem. If the drum acted when there was no paper the transfer station would get dosed in toner which would then spoil future prints until the mess is cleaned up.
If there is an issue with pages printed too high, low or skewed it is probably related to registration. Quite often the issue is a clutch used to engage the registration rollers when the main motor chain starts turning the drum and the fuser.
Paper Quality.
A laser printer will generally take paper to a maximum thickness of 150 gram per square meter (gsm) – a thin card. The maximum thickness is usually set by the
| pickup rollers ability to kick sheets out of the tray |
| feed rollers ability to bend the paper through the feed path – there may also be an issue as to how large the transfer station gap is. |
Minimum paper thickness is usually about 70gsm - just a bit thicker than "bank paper". The minimum paper thickness is partly set by what the feed rollers would be likely to tear, and partly by the likelihood of paper being deflected from its proper path by the fairly powerful electrostatic fields inside the printer. Very thin papers can get attracted up into the photoconductive drums housing and once they get in there and stuck under the waste scraper blade it can be impossible to get them back out of a sealed cartridge.
Printers with a fairly straight path will often take 150 gsm or even heavier material from the "hand feed", "multipurpose" or "envelope" tray. The pickup roller for this tray doesn't usually have to deal with a separator.
As already suggested newer printers have softer and more textured rollers that will feed a greater variety of materials.
Bank Paper Copies.
Some organisations have office practices that require copies to be made on coloured paper. The typing pool practice of using 60gsm bank paper developed in the days of carbon-paper copies is carried through. Bank paper often seems to work OK in a laser printer for several weeks, but it can create disasters. On the odd occasion bank paper will disappear up into the drum assembly of a printer, jamming it severely.
Paper is attracted to static fields and laser printers work precisely by using strong electrostatic fields to move toner powder. Flimsy paper bends in the printer and sticks to surfaces it should not touch.
Keeping two or three copies on different coloured paper also usually implies having a complicated feed path for the printer, with multiple input trays. The word-processor or printer controller can then be set up to triplicate each document from a different tray. The obvious problem is that there will now be four trays - one for letterhead, one plain paper, a yellow and a green copy. If one tray has a finite probability of error then four trays could well be at least four times the trouble.
Support technicians vary in their patience with paper trays - usually in proportion to whether they are getting paid for the job or not. However it can be said that making multiple paper copies seems rather sad in an age of big disks, e-mail and tape archives and it might be better to look at those ways of distributing and archiving, rather than paper files.
Sadly people adopting precisely this attitude seems to have led to the demise of manufacturing by Rutishuaser, makers of truly wonderful paper feed stacks (and naturally one of my favourites). They now manage real-estate and license some of their intellectual property. 
Letterhead.
Organisations often like to stress their social standing with good quality correspondence paper, most of us fall for the trick. A good thick vellum with an embossed colour letterhead seems to suggest importance; the content doesn't seem like a mail-merge sent identically to a thousand others.
Most laser printers will take a maximum of 120 gsm paper from the main tray. A printer with a flat feed path will take higher weights. No laser printer will take very heavy papers because it won't be able to establish the electrostatic field needed for toner transfer from the drum.
Embossing will cause problems because the printer now has to overcome the friction it causes in the feed tray and paper station. The fuser will try to squash the raised portion out - users probably don't want toner to stick near the embossing, but it won't be practical if they do.
Coloured inks on letterhead needs to be stable as they pass through a fuser at 150 centigrade plus. Commercial printing firms normally use inks applied as liquids with a pigment or binder that can melt at this sort of temperature, spoiling the paper - and possibly damaging the fuser.
Heavier letterhead paper will often go through the paper path from the multifunction tray to the rear face-up tray. The kind of printer that will stand on a shelf usually has a complicated "S" shaped feed path, so check this before trying to feed high quality letterhead through its main tray.
Paper Up Arrow.
Older papers often had an arrow on the pack to show which way up it should be placed. The arrow points to the print surface, which is sometimes more polished than the other side. Having an intended print surface isn't much use with a duplexer of course but there rarely seems to be much difference between surfaces.
Putting paper the correct way up can also help correct paper feed problems, presumably because the way sheets are cut can cause a slight convexity / concavity depending on which way up they are.
In printers with trays underneath and an S shaped feed path the print-surface can be the underside of the paper in the input tray. The rollers in the feed path turn the paper through a bend before it reaches the print-station.
When printing from the multifunction tray the print surface is uppermost in the tray.
Print Jam Epidemic.
Five years ago paper quality often gave serious reliability problems. Some paper manufacturers sold "laser printer paper" as a product quite distinct from photo-copier paper – even though the two processes are much the same. Most people now just use photocopier paper. So much bland and uninteresting copier paper is in circulation that people tend to forget that different paper qualities can look and feel quite distinctive. Unfortunately high quality stiff paper can give trouble in laser printers, particularly if they have an "S" shaped feed path.
Large organisations sometimes have epidemics of print jams when a new shipment of paper arrives. A large organisation buys paper by the lorry load, and the main decision making criterion is often price per ream. Over a few weeks the new paper penetrates to every department, and the photo-copiers and laser printers start giving trouble.
The problem is usually caused by poor paper storage. Paper is hygroscopic and takes up some water from the air. Slightly damp paper is more inclined to stick as the printer attempts to free sheets from the input tray. Damp paper will also curl very noticeably when it leaves the printer because it has been heated in the fuser and damp that had penetrated the edges has now been driven off and from the printed surface more than the other.
Duplex printing will be particularly difficult with damp paper, the curling of the page after the first side has been printed makes it very difficult for it to pass through the duplex unit. The test is to print a short document single sided and see if the paper is curling excessively.
Paper is stacked in pallet loads in a warehouse. Damp tends to be bad on some packs that were on the outer surfaces so the faults come and go as the paper is used. Engineers are called out and find no fault; the next morning it happens again.This problem may be less common than it used to be. Paper manufacturers and distributors seem to have improved the quality of ordinary photo-copier paper and it now rarely gives trouble - at least with fresh material. Paper that has been kept around in a warehouse for months will never work well.
Recommendations on holding paper are to keep it in pallet-loads until they need to be broken up. Pallet loads tend to be cling-wrapped anyway. Keep the paper well away from warehouse doors and preferably somewhere where the temperature is a bit above ambient so there is little likelihood of condensation. Keep paper off the floor level; warehouses naturally tend to put paper at floor level because a pallet is heavy. Avoid shipping paper even in cling wrap if that will mean loading or unloading it in damp conditions.
Manufacturers could put a hydrophilic strip that changes colour on the packaging to show whether paper has remained good in its journey from factory to customer.
National Preferences.
At the start of this section cultural expectations were mentioned. People like a printed document to look right, a preference that often owes more to history than logic.
There are national preferences in paper. For some reason the US, Canada and Mexico have never managed to break away from their habit of using "legal" and "letter" sizes. The UK has a general dislike of the metre and the gram but does seem to have escaped from quarto and foolscap and standardised on the ISO "A" paper sizes. 
Once you have a paper archive it gets very difficult to change of course. The whole filing system is built around the preferred paper size. A different paper size won't fit in binders or shelves or cabinets properly. We are probably never going to achieve a world standard paper size whilst paper remains important because so many people have irreversible investments in their current system. Once the documents are electronic their layout can often be changed or the image adjusted to fit the page - so standardisation may become easier in future.
UK paper users are said to like a highly polished very smooth paper. This finish is achieved by coating the paper with kaolin (china clay) which is absorbed into the paper structure. The kaolin can cause problems – for instance there can be an excessive dust build-up in the drum cleaner. This may be worsened because inkjet printers also tend to have polished surfaces. The kaolin soaks up the ink preventing it feathering along the fibres. A lot of paper now tries to match the needs of both worlds.
Personal Preferences.
Most people think photographs should be shiny, gloss finished. Presumably this is because that is what photographic bureaux deliver as standard. (Although you can ask for a matte finish). Shiny paper is often a nuisance because glare interferes with the view of the image. Laser printers tend to deliver a moderately shiny finish on ordinary paper simply because that is the result of passing toner through the fuser.Magazines and coffee table books tend to be on gloss paper as well. Non gloss paper used in bulk printing doesn't feel or smell quite so nice so perhaps that is where the preference for gloss comes from. Office grade copy paper has little smell and isn't unpleasant to handle.
Laser printer paper has tended to take some of the joy out of paper partly because the printers could not easily handle anything else and partly because the emergence of a standard made mass produced boring paper so cheap.
Many recent printers have soft, textured rollers that can handle a greater variety of papers. The rollers will wear out more quickly but since they are usually quite cheap and easy to change that shouldn't be a problem.
Premature Pickup Problems.
Pickup rollers on most printers will eventually give trouble. In the UK this too may be connected with the fondness for kaolin smoothed paper. The rubber on the rollers contains a softener agent, and it is important that the rollers are the right composition or they don’t make enough frictional contact with the page. Some rubbers age – they can be seen to have a cracked surface. If kaolin powder builds up on the rollers they may build up a coating of kaolin mixed with the softener agent, and this is then polished as the slippage in the rollers gets progressively worse. As the number of misfeeds increases and the rubber gets polished the printer reaches a point when it will scarcely feed at all.
Rejuvenation & Feed Kits.
There are commercial "rejuvenators" for rubber rollers and these are recommended when no replacement rollers are to hand, or where removing rollers would require a complete stripdown of the printer that can't be justified on other grounds.
The best solution is usually just to replace the rollers. There is a paper feed kit available for most popular brands of printer. On many recent designs the rollers are easily accessible and often just clipped into place. Unfortunately there are still a few designs of printer where a complete stripdown is needed to get at some internal rollers.
There may be several sets of rollers depending on the shape of the paper path. The most significant is the paper registration station.
The registration station is usually located just before the transfer station. The purpose is to set the paper off through the transfer station held as straight as possible and as tightly as possible. If the paper is not straight or feeds unevenly then there will be distortion in the print.
The registration station often uses a page width metal and rubber roller pair. The kicker-roller in the feed tray would feed the paper slightly too far for these rollers, but when it hits them they are stopped so the paper recoils a bit and settles with its edge aligned straight in the rollers. The presence of the paper pushes a sensor–dog down and this notifies the print engine that it should start the polygon mirror scanner motor and the print engine.
The metal roller and other metalwork near the registration station helps ensure there is no electrostatic charge on the paper before it gets to the transfer station. Some printers have a short metal slot for the paper to pass through as well.
Some laser printers try to economize on desk space and this is done by having an "S" shaped paper path. The paper is taken from a tray on the underside of the printer, doubles back on itself, then doubles back again to feed out of the top. This design is popular because the paper input tray fits under the printer and the output collects on top. The printer therefore takes up a minimum amount of desk space, and can even stand on a large shelf. There is a disadvantage - it is difficult to bend heavy grades of paper through such a path so high quality letterhead paper might well misfeed a lot.
A common design feature is to have a front-loading tray that can handle heavier paper like letterhead because the feed-path is flatter. Of course this tray is normally only able to take a few sheets - but in a lot of offices this is all that is needed for correspondence.
If the printer has to handle lots of high-quality paper then it will generally need at least two front-mounted trays (letterhead and plain paper) feeding through a straight path to a rear mounted face output tray or a mail-box sorter. A machine offering these capabilities will begin to look more like a photocopier than a printer, and may need the same sort of space.
The rollers in a printer's paper feed path are generally connected together by a cog chain driven by a main motor that also drives the fuser, OPC and developer. The relative movement of all these parts is determined by the ratio of the cogs. The general idea is that all these things have precisely the same surface speed so that the image drops onto the paper and retains its form.
If the cog chain feeds paper unevenly there will be horizontal smudging of the print, usually particularly discernible at the top and bottom of pages where the rollers grip the paper rather weakly.
Individual pickup rollers are often connected to this chain by clutches which allow the roller action to be turned on and off. Low cost printers have a couple of paths - one from the main paper tray and another from an envelope tray. Higher quality machines have:
| two paper in trays, and an envelope tray |
| and can feed to a "face down" tray on top or a "face up" tray at the rear. Which path is used is selected by a solenoid. |
| and a duplex path; printed paper is turned over and the other side printed. |
The progress of the paper is normally monitored by sensor-dogs. If the printer control system releases a clutch and the expected sensor-dog is not triggered within a given time then the printer reports a paper jam. Some recent printers come with Windows graphical driver programs that can show a diagram of the printer and indicate where the jam has occurred. Sometimes the print driver even manages to get its diagnosis of what has happened right.
There are several limits on what kinds of material can be laser printed. The limit for a normal printer is:
| material has to bend through the paper path - which isn't easy if it's S shaped |
| the electrostatic properties of the material - if it can't attract toner it won't work |
| what can pass through the high temperature of the fuser. |
Ordinary envelopes often have glue on the flap that will stick to the fuser rollers - nothing will go wrong at first but print quality may be degraded and ultimately the machine will jam. Users are often surprised at the thought that they should use special envelopes and labels that withstand the heat. Just because something has been used a hundred times without a problem doesn't mean that this time it hasn't jammed and baked solid onto the fuser roller. A lot of the problems in computer engineering are matters of probability not certainty. Ninety Nine times out of a hundred the wrong material may work - it's that one time when it doesn't that causes all the trouble.
Transparencies for overhead projectors need to be rated for laser printer use - those that are not can melt into a mess in the fuser and write it off. Since fusers are expensive a single transparency sheet may be the end of the printer.
The electrostatic print process could be used quite widely. There are laser print based label printers. The same mechanism could be used to place patterns on cloth - or even metals and printed circuit boards with adjustments for the electrostatic properties. Most laser printers are aimed at 80gsm to 120 gsm A4 or letter paper and anything else needs to be checked first in the makers manual or with the supplier.
Multiple Trays and Paper Handling Options:
Very basic printers provide one paper input tray, usually with a capacity of about 150 sheets because this can be reliably fed from a simple spring-loaded tray and roller.
A slight advance on this design adds a "priority feed slot". A piece of paper in the priority feed slot will move into the printer first. When the user knows they want letterhead as the first sheet in a printout they add it (usually face up) in the priority feed.
Slightly more complicated devices have a lower tray capable of holding 200 – 250 sheets and a front-feed multi-purpose tray that can hold perhaps a dozen sheets of paper or one or two envelopes. The printer will take paper from the multi-purpose tray when specifically told to do so from the MS-Windows printer control panel.
Network printers intended for a workgroup need to hold more paper – nobody is specifically looking after them. It is also safe to assume that nobody will be near-by to load letterhead into the front tray when it is needed, so a network printer needs two or more large trays and to be able to select letterhead for the first page. In a correspondence oriented environment being able to select envelopes would be helpful as well.
Some printers such as the HP4Si come with dual trays built in. Others such as the Kyocera FS series can have a stack of trays built alongside or underneath.
Some printers can have a special envelope feeder added
Special trays and an envelope feeder tend to add very substantially to the cost of a printer. Most printer makers produce a model with an extra tray and a network card, commonly calling the printer the "TN" model.
Duplexing is just "double sided print" - the standard for books and a sensible option for any report more than a page long. Printers did not have any sort of duplex capability built in until quite recently. On mass market printers it was not even an option. In a world where people are trying to produce material that looks "professional" double sided print is an obvious requirement. Most people would also prefer to cut costs by using less paper, so it might be a surprise that duplexing hasn't been more widely used.
The problem with duplexing is that it means paper passing through the printer twice, two different ways up. That in turn means a much more complicated paper path with more probability of a jam occurring. The paper has already passed through the fuser once and that tends to dry one side of it out, making it inclined to curl. Passing through the printer also leaves residual static charges that may have odd effects on the print quality of the second side if they are not removed.
The net impact of all this used to be that duplexing was an expensive option and people who tried it were often disappointed by frequent paper jams.
Manufacturers do now seem to be trying to popularise duplex as standard on the more expensive printers. Duplex does seem to be less trouble on recent machines, perhaps because printers are benefiting from straighter paper paths and cooler running fusers.
Collators and staplers.
A basic laser printer is capable of single sided printing on a limited range of paper - it is up to the users to gather the output, put it in order and staple or bind it together. Of course what is really wanted for anything more than correspondence is for the printer to produce a ready prepared book. Some laser printers are like photocopiers and can be equipped with multiple input trays, duplex units that allow printing on both sides of the paper, output collators and staplers.
If a printer is typically used to produce six to ten copies of a report then a collator is a real time-saver, saving all that shuffling of paper to make sure each of forty pages is present in every copy.
Actually getting the stapler option to work correctly in the long term seems to be more problematic - or perhaps it's just the designs I've dealt with? Perhaps that is why machines with any sort of binding capability are still rare and expensive. They really need someone to care for them.
Large printers that can support binding options tend to be leased to corporations and meant as central facilities. This produces the problem that department X is sending its budget to a printer shared with department Y that is supposed to be separate. One answer to this is to equip the printer not just with a collator but with mail-box mechanisms - even mail-boxes that can be password locked so that only the correct user can collect the contents. Options like this cost far more than a basic printer. Administering the permissions and passwords can also be an issue. Then there are all the drive belts and solenoids that actuate paper paths from the collators to the mail boxes - all just asking for a paper jam.
The problem with things like the mailbox printer is that the big, central secure machine winds up costing a fortune in maintenance. It may be easier to give users their own printers.
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© Graham Huskinson 2010
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