Printer Faults - Misfeed in Cassette

Almost all modern printers use cut-sheet paper, trimmed to sizes that are easily handled. Paper sizes have increasingly been standardised in the machine age, so A4 is common in the UK, Europe and most of the rest of the world and "letter" or sometimes "legal" is widely used in the US.

continuous feed icon

Printers weren't always like this.   At one time the computer industry used 9.5 inch or 15 inch continuous forms as standard practice; without the sprocket holes this became 8 inch or 14 inches wide.   Continuous feed is highly reliable but sometimes a little complicated to set up. Laser printers were aimed at correspondence so they were equipped from the start with photocopier-like cut sheet trays.

Paper Feed Terminology

Multifunction printers have a scanner built on top.   Printer and scanner are separate subsystems, both have paper feed trays with rollers.   On the cheapest machines the scanner is usually flatbed with no document feeder. There is an Automatic Document Feeder (ADF) on office quality machines and a Reversing ADF (RADF) to scan both sides on more expensive devices. Top end printers have a double sided duplex ADF (DADF) with ultrasonic double-feed detection. A few older printers have letterbox or hopper feed units like old fax machine. Gravity feed from a hopper is possibly a bit more reliable and saved space but is not as flexible as flatbed devices. Automatic scanners have input trays and output trays. Incidentally large printers tend to be called multifunction or MFP whilst little ones are all-in-ones or AIOs.

Within the printer, paper travels from an input tray to an output tray. The print path can be straight-through, C shaped or S shaped. Most printers have an S shaped feed path from a cassette underneath to an output bin on top.

Most laser printers have a tray that folds down on the front. This is often called the "MultiPurpose" or MP tray because the path from it to the rear of the printer is more or less straight and it can handle envelopes and card. However printers look a bit ugly with the MP tray open so people commonly leave them closed and forget they are there.

Cheapskate models and many inkjets have a bypass slot on top of the cassette. Paper guides allow an envelope or a single sheet to be easily pushed onto the top of the existing paper stack and under the feed roller so that it will move first. The expense of an (often unused) MP tray mechanism is avoided.

We prefer to use the term cassette for input trays formed as "boxes" that can be slid into and removed from the body of the printer. The cassette is intended to be loaded with paper and swapped; in the US, where paper size might change with the job, having one loaded with letter and another loaded with legal paper allows them to be swapped around - its a bit cheaper than buying two full feeder units. In the UK people only buy cassettes when they break them. We stick with standard paper sizes.

In the UK and Europe we tend to use ISO 216 A series A4 for almost everything, so there is just the one tray and it isn't really treated as a pre-loaded cassette (although that gives faster reload in time-critical work). Architects, engineers and cartographers prefer A3 which is twice the size and can be folded to A4. Accommodating heavier paper makes A3 printers expensive - and A2 laser printers very rare.

Accessory or extra cassettes under or alongside the printer might best be called Feeder Units. People sometimes ask for another tray and are surprised to get just that, not the whole stackable unit. NOTE that Tray-2 on an HP printer is the built in cassette. Tray 2 on an OKI is usually an additional feeder unit.

Paper feed often involves a pickup roller, feed roller and a separation pad. The pickup roller starts paper moving. The feed roller pushes it out of the tray. The separation pad prevents more than one sheet moving into the printer at a time. Cheap printers make do with one roller for both pickup and feed; less reliable but less costly.

Separation pads always have some friction with paper so they inevitably wear out. More sophisticated printers use a retard or separation roller.   more below

Laser printers became standard office machinery around 1990 and were quickly followed by cheaper colour ink-jets which adopted the same standards.

Cut sheet feeding is pretty reliable these days thanks to soft rubber rollers with a textured surface. Once that soft rubber wears down the printer will start to misfeed.

Modern high quality laser printers are built with rollers that clip onto a shaft. They are easy to change. It will be much easier to change the roller than go to the trouble and expense of getting a new printer.

The rollers in inkjet printers are not usually designed to be changed.   Many inkjet printers are aimed at very light use, will not wear out the roller in their design life and so no design effort is put into making parts exchangeable. There are few spares - (often just the printhead and power brick).Manufacturers consider low cost printers to be disposable; not good, but that's how it is.   (Where rollers can't be replaced, try platen cleaner)

(Brother are an honourable exception. Service manuals and spares at reasonable prices are available for inkjets in 2015. They deserve credit for that. They do create a nuisance with secret reset codes. )

About This Page

This is a "generic" paper-jam page aimed at giving general help on a significant source of aggravation.

You might be better off with a specific page for your printer. We do try to create specific pages but its an impossible task. We estimate that there are over 25,000 printer models from over 60 brands and manufacturers. For instance, we know that the LaserJet 2200dn has a tendency to jam on duplex print and we mention that on the page. Other than creating a forum, we haven't found a way to collect information systematically on the scale needed. The manufacturer's user guide is intended as your friend …

HP user guideThe HP LaserJet 4200 / 4300 user guide, a classic of its genre but 218 pages long

User guides have several problems;

  • they are written before products go on the market and don't reflect problems that emerge in use
  • corporate policy is probably to avoid mentioning problems in the user guide
  • people are reluctant to read user guides, expecting them to be minimal help.

Printers differ hugely in detail but paper feed mechanisms have so many common themes that a universal guide seems possible.


Short Summary

We can sum up this page:

Most paper feed problems are user error, overfilling the tray, not setting the guides, not telling the print-driver what paper is in use or using odd paper.

Using paper weakened by humidity is another problem. With a laser printer the signs are that the paper curls in the exit tray or develops mysterious creases in the fuser. Paper with serious curls is highly likely to jam in a duplexer.   Paper problems are more common than people realise.

When those points are eliminated, start suspecting the pickup pads and rollers. These are easily inspected and replaced in most of the bigger printers.

If it is utterly clear that the paper quality is good, correctly loaded and the pickup rollers are good then there may be an issue in the mechanics of the machine; usually a clutch or solenoid. That's an issue for technicians and engineers rather than users and it may need a specific service manual -  but we do look briefly at it below.

Identifying the Problem

Every printer will have a paper jam from time to time. It could just be a damaged sheet or something stranger like damp or static in the paper. One paper jam isn't a problem;   a succession of them is.

A fairly common problem is "jam first thing". The first time the printer is used after a break it develops a paper jam, then that clears up and it works fine. Try opening taking the cassette and taking the top few sheets off - does the problem go away? The first sheet in the tray is most weakened by exposure to atmospheric damp.

The first problem with changing rollers to cure misfeed problems in a commercial quality laser printer is to make sure it really is the printer, not the paper, or the person. - and then to get the right roller.


People rely on paper as a medium of thought and way to exchange ideas. Development of big screens, pocket screens, wrist screens and head -mounted displays may change that. Paper remains a clear, high contrast medium - that you can easily write notes on.

Printers are available at any price from £30 for a little colour inkjet sold in a supermarket to £5,730 for the A3 46ppm Color LaserJet Flow M880Z MFP. The 200 fold price difference reflects some different design assumptions.

Printer design sometimes works from small to large - as with inkjets. Other times it works large to small, as with laser printers. Ideas tried in fast industrial machines are scaled down to be affordable with a home computer. As the size shrinks, build quality and repairability declines. Revenue shifts from sale of the machine to the opportunity to sell a steady stream of cartridges.

Little printers get rid of niceties like plug-in fusers, exchangeable rollers, detectors that spot and recover from a paper jam, an error log, management reporting, and even a dust cover for the paper; things that help reliability.

Cheap printer often look as though they are very good value. The revenue stream from cartridges and the potential upgrade opportunities allow sophisticated OCR and photo-editing software to be bundled with cheap little printers. Achieving scale economies might sometimes give a brand hardware and feature quality advantages as well. Mostly, low cost printers are just a way to sell expensive ink.

Home and small businesses often underestimate how much they will print. In the UK it is thought the average worker prints about 8,500 pages per year (25 per day) and in the US about 10,000. It varies of course, authors, artists, script and copywriters tend to print more. Most home users just print a couple of pages a day, but they like photographs and that" magazine look" and that sucks up ink.

Printer brands don't mind if you buy a printer too small for your needs. You buy more expensive ink and since they break down more often people are forced to change printer and get yet another different type of cartridge.

Operator Error

We all develop habits, some of them good, others bad. Learning to use computers is gaining a set of habits. Buying a succession of cheap printers because the last one broke is probably a bad habit. Cheap printers have flimsy construction and expensive cartridges. Changing printers means pointless and annoying re-learning.   Printers are a massive cause of tech support calls; user mistakes and bad paper are major contributors. Field service engineers find users overfilling the printer cassette, don't set the guides properly and then slam the thing into the machine. People love the status symbol of iPhones and treat them carefully. Printers are treated as an unwanted cur; nobody even flips through its user guide - which generally has lots of pages about what paper to buy and how to fill the trays.

Loading Paper

Paper usually comes in packs of a ream which is 500 sheets and with 80gsm office paper weighs 2.5 kilos. The reams are packed 5 to a box so it weighs fractionally over 12.5 kilos with the wrapping paper and the cardboard.


Most low end printers come with a cassette tray that takes 250 sheets, half a ream. Inkjet trays take even less. About half the paper goes in the printer and half stays in the pack. A pack with one end open or the side ripped goes on the shelf. That remaining paper isn't being treated very well - its sides get damaged and it will be picking up atmospheric damp. Our recommendation is to open packs carefully and re-fold them. If paper will not be used for some time put it in a plastic bag to keep out dust and damp.

Proper office-quality printers have 500 sheet cassette trays. Bigger trays cost more to make and suggest the need for a motorised paper lift, although some designs do without. Some user manuals say 500 sheets of 75gsm paper which is fractionally thinner. Office paper in the UK and Europe is 80gsm. Some printers (Lexmark) have slightly bigger trays that take 550 sheets and copes with that discrepancy - and lets you use a complete ream in one go. A little mark like this ∇ ∇ marking the maximum fill level is often moulded into the paper guides. Overfilling above the mark will cause problems; there is stress on the mechanism. Overfilling also brings the risk that paper will hit the paper sensor flag and pickup roller which usually drop down into the cassette when it is pushed home.

Loading paper is one of the risk-points in the life of a printer.   Users are frustrated, they wanted a printed sheet but now they have to find the paper, load the tray and see whether the printer, computer or both re-try the print job. (They may wish the printer had a bigger tray).

Overfull cassettes are at increased risk of breakage. People may be rough pushing a cassette into the printer; they need to make some effort because it is moderately heavy. A ream of A4 paper weighs 2.5 kilos so a fast-moving tray weighing that can do a bit of damage. Some printers have sensors that hang into the tray and overfilling can break them. Printers like the LaserJet 5100 and relatives have suffered end-stops getting broken; they use A3 paper and that weighs twice as much, people drop a big stack of paper in, ram the tray home and the plastic end stop snaps. The LJ-5200 strengthened the design.


Trays provide end stops and side guides to ensure the paper is held up against the pickup and feed point. If the endstop is set too long then paper may not be up against the pickup roller and will not move at all or stop short of the feed rollers.

If the guides are too lose then paper will be skewed as it goes into the printer. More expensive printers have a registration mechanism that aims to catch and correct this. Cheap printers just feed the paper anyway giving text skewed on the page. There is a risk that a corner will be curved over, or that the paper will jam when it hits the side of the fuser. It is possible to have a jam in the fuser caused by problems in the cassette.

As the cassette goes into the printer it presses a lever at the side that lowers the paper pickup assembly and the paper detector flag(s). The extra push often needed to get the tray home is as this clicks into place. There is usually some "detent" to make sure the tray stays closed despite some pressure on the paper from the pickup rollers and vibration from the machinery.


Things Drift

Field service engineers get used to the phrase "but it never gave trouble before".

It is that humid day when a thunderstorm is about to break. The packet of paper has been ripped open and lying on the storeroom shelf for a month since the last catalogues were made for a trade show. The paper guides are set a bit too slack, giving the paper some wriggle room (or too tight so the roller can't grip). The roller has been getting worn because there is excessive friction with the cheap paper. The paper is sticky because it is damp. Just when there is another urgent catalogue job on A3, the printer plays up!

But it never did that before.

User habits like overfilling the cassette eventually bite. The paper feed subsystem is built to be tolerant so it works with one thing a bit wrong. With too many parameters out, misfeeds start. They get worse because the paper keeps on wrinkling and jamming and ripping the texture off the roller - hence the scuff-mark on the spoiled paper.

Office quality printers keep an error log which can be printed from the control panel or examined through the printer's Web interface (or via its management reporting). If the roller is wearing out - or the paper quality has gone wrong - there will be a build-up of paper feed errors. HP printers report these as "13.wx.yz" where "13" is the code for a paper jam and wx is the sensor location where the mistiming was detected

Branded paper may have advantages. Companies like Xerox and HP take an interest in their products from manufacture to delivery. They give the paper mill a specification and check the product. They tell the supply chain how to treat goods. Our experience of HP is that they take an interest in things working for the customer. They might not give a free engineering service call because you complain about a packet of paper but someone will be working on the statistics, looking at what printers under management contract in the field are doing. They have procedures.

People who rely on a printer might like to develop their own procedures. Open packets of paper at the end and reclose them. Keep part-used packs in a dry cool place. But it can be difficult; one hospital we spoke to had the paper on shelves in the room with the autoclave - they had never thought steam might cause wrinkled pages!

HP CHP110 paper
HP CHP210 paper
HP CHP370 paper
HP CHP113 paper

Paper Quality

Paper looks simple but is not.   Paper is usually a cheap and cheerful commodity; in 2015 a ream of reliable, branded office paper can be had with no special discount for less than £2 and for not much more in a supermarket. Rather heavier paper intended to make an impression might cost £5, still just a penny per page. (Handmade paper is much more expensive.)

A sheet of paper is a mesh of billions of cellulose fibres about a hundredth of a millimetre across and between 0.1 and 2 mm long. The fibre mat of pulp is mainly held together by hydrogen bonds which are made between fibres as water in the pulp evaporates. Individual bonds are weak but each fibre has a great many so the net effect gives paper its strength. Some cationic starch improves the number of bonds. During manufacture the paper is pulled along a production line and this tensions fibres and gives paper its grain including a resistance to bending and wrinkling.

Pulps differ, longer fibres generally make stronger paper but preserving their length is difficult. As material is recycled fibres get shorter and have less opportunity to bond. These days most office papers have 60% recycled content mixed with fresh pulp and various chemicals to bring the average fibre length and number of bonds up.

Papers can look the same but differ hugely. Most paper wears a disguise; it is coated with fine kaolin, chalk or titanium dioxide. The coating itself can be made by grinding which is cheap or by recovery from a precipitate which is more expensive. This coat is the basis for the optical opalescence and the absorption of ink. There is also a coating binder and a fluorescing agent to shift the paper look from yellow to white.

Bonds in paper are hygroscopic and break if they can attract a water molecule, which can come from the atmosphere. Wet paper easily reverts to pulp. Exposed to the atmosphere paper loses its stiffness and ability to resist wrinkles which doesn't impair its human handling but might have an impact on simple machine processing. If paper wrinkles too easily then rollers will have more difficulty driving it out of the tray. If the coating materials aren't bound adequately then the rollers strip the chalk from the surface rather than move the body of the paper.

It is natural to assume that if you have dealt with a supplier for a decade and had no trouble then paper cannot be wrong. But paper shifts in huge quantity. The producing mills change, so do specifications. Paper stored in warehouses of varying standards. Sometimes the packing and storage may not be adequate. Sometimes paper just doesn't perform as it should.


Fanning the Paper

One of the things people often do with paper before putting it in a cassette is to "fan" it. Hold it in one hand and flip the other side so that each sheet separates but then the stack comes back together. With old photocopiers (and their dodgy paper) this was a standard trick.

Fanning the paper overcomes two things, damp and mechanical guillotining.

  • Slightly damp paper sheets tend to stick together
  • Guillotining bends the edge of sheets and sticks them together

This trick might not work well any more. It's a habit that needs to be further informed. Fanning the paper separates and then re-joins sheets by sliding them. One effect is the action of electrophorous, a device for making static electricity. If the paper is dry (as it should be) then fanning it generates static charges which could make the paper stack less inclined to move. In most recent user guides printer manufacturers recommend NOT fanning the paper. They may recommend picking up the stack and gently bending it each way to free up edges locked together.

Printer brochures often set out the paper handling capabilities of a printer. User guides usually go into further detail, and so will the service manual. Several manufacturers also have short books setting out their views on paper; for instance the HP LaserJet Printer Family Print Media Guide (eg 5851-1468 2002).

Testing for Paper Problems

In summary, if you are suffering misfeeds or wrinkling it might be a good idea to just spend a little on a pack of paper from a supermarket and see if the problem goes away. We don't like supermarket paper much because it gets bashed around on their shelves, but the issue here is to sort out a problem. It wont cost much and if it doesn't work you can move to the next stage with a plentiful supply of material for origami and paper aeroplanes.

Alternatively look at the rollers, unclip them and take them out to get a good look. (If they clip on there will be instructions in the user guide).

By this stage it should be pretty clear if the problem is user, paper or worn rollers.

If the rollers are removable (and most on the large laser printers are) it is worth taking them out and examining them - and a temporary fix might be possible while you wait for a new set.


Detecting Misfeeds

typical laser printer

Printers detect a paper jam using a series of sensors along the paper path. Each sensor acts as a little switch which is closed by the pressure of the paper. In a few cheap inkjet and dot-matrix designs the sensor was literally a switch. In laser printers the paper sense flags are usually little spring-loaded plastic levers that protrude into the paper path. Under them are opto-detectors, little "U" shaped devices with an infra-red LED on one side and a photo-transistor on the other. The paper sense flag is a sensitive switch with a very long life. There is more on photo-interrupters here.

Detecting a jam needs just one switch; an exit sensor on the output. Paper takes time to travel, from the pickup roller to the switch might be allowed four seconds. If the switch doesn't operate in that time the printer signals an error. If a sheet is stuck the paper feed must stop or it will be crashing another sheet in, limited only by the power of the motors. If it didn't stop when paper jammed a printer could wreck itself.

An exit sensor may be adequate in a slow little printer but a large printer might have two or three sheets travelling the paper path at a time. It achieves that using several sensors and timing the arrival of pages.

Extra sensors cost more but they also allow the printer to report where the paper is jammed, such as invisibly in a duplex unit or wrapped round the fuser. Getting a big printer going after a problem is easier because the error report log can be more specific. If there are lots of misfeeds at the pickup and feed rollers in the cassette that is a clear indication new rollers are needed.

Office quality printers have firmware that can be put into a test mode and report what each sensor is doing, allowing engineers to eliminate them as problems.

Paper Pickup

Paper pickup works along the following lines.

A stack of paper is held in a tray. The pickup mechanism has to get just one sheet from the top of that stack reliably. Paper sheets have a tendency to stick together because of their shape, surface texture, damp or static charges.

A laser printer usually has both pickup and feed rollers.

The pickup roller starts the paper moving, pushing it off the stack by a combination of friction and some downward pressure. Actually the pressure may be mostly upwards, the tray lifting the paper up towards the roller, limited by an end stop. Having done the pickup action the roller disengages and no longer contacts the paper. The disengagement can be by the roller being "D" shaped so that it normally has the flat side towards the paper - this is common in older and cheaper designs. It can also be by a cam-follower triggering as the roller turns and carrying the pickup mechanism down, placing a controlled pressure on and the roller turning at the same time. Either way, the paper has now moved under the feed roller.

Feed rollers push paper into the body of the printer, usually against some kind of separation mechanism. The two common separators are pads and rollers.

There is normally just one feed roller to each cassette, usually about an inch across, generally textured and quite often with accompanying idle rollers at either side.


The roller and pad combination will last thousands of pages, usually upwards of ten thousand. Designs vary greatly. Circumstances vary a bit as well, whilst most people print ordinary A4 office paper others might print postcards or labels which are smaller but sometimes more difficult to move.

Separation roller designs should last longer with lives up to 250,000 pages suggested in the service manuals. It is difficult to be sure because changing the rollers is often trivial and not noticed or reported. Field service engineers will change rollers on bigger printers and copiers as a matter of course if anyone says "misfeed".

Roller and pad life depend heavily on the material of the roller and the paper and its coatings.

  • The white, smooth, surface of the paper is often a thin coat of chalk, kaolin or titanium dioxide with a binder. Cheap paper may use ground material which is mildly abrasive. Sometimes deposits of coating material build up on the rollers.
  • Pickup and feed rollers are a soft rubber-like material. They could be natural latex, styrene-butadiene, polybutadiene, polychloroprene, nitrile rubber, silicone or a combination with a surface of one on a foam core of another. Rollers are small and not marked with the plastic type.

How long rollers would last is indeterminate; hence the engineer approach of changing them at a sign of trouble. Things may differ by user as well. Small offices with a printer shared between two people might tolerate the odd paper jam if both can reach the printer and put things right. Attitudes may differ in a workgroup if people get up from their desk only to find the printer with a flashing light and a paper jam. People packing parcels and producing despatch notes have no time for trouble and distraction from the printer; they want a solid industrial product.

Since feed rollers cause tech support calls, manufacturers increasingly program printer firmware to prompt for new ones.

Brother printers prompt for a "PF KIT"; in the MFC8480 case at 100,000 pages. They commonly use a little bogey with two rollers on it driven by a shaft. The printer prompts for a new one at the control panel presumably to avoid users being flumoxed by feed errors.

Some Samsung printers prompt for new rollers at 70,000 pages.

HPs large office printers like the M601 that use separation rollers prompt for a maintenance kit (fuser and rollers) at 225,000 pages.

Firmware prompt to change rollers are presumably based on page count. The prompt will happen somewhat before the rollers really need changing, rather than generate tech support calls.

A potential problem with this, as we shall see, is that you might not be able to fix your own printer. If the printer demands a maintenance kit and will not continue without, and only dealers know the reset code then you either pay the dealers call out fee or do a bit of web research to get the reset code or software.

Rollers and Pads

Mechanisms aimed at low cost use a separation pad. A separation pad is a rubber strip of a particular area and consistency matching the roller and the expected types of paper. The roller contact area on the top is greater than the pad contact area underneath. The feed roller takes over from the pickup roller and pushes the paper over the separation pad onwards into the body of the printer.

It is quite likely that the pickup roller will have pushed more than one sheet into the nip-point between the feed-roller and pad. If that has happened the frictional contact between the feed roller and the paper above should be greater than the adhesion between the two sheets. The frictional contact between the bottom sheet and the separation pad should also be greater than that between the sheets. The top sheet breaks away and goes into the printer. The next sheet down, which was held on the pad is now also in contact with the roller so it will follow when the rollers turn again.

The mechanism isn't entirely satisfactory. One or more follow on sheets might be on the stack or the separation pad so their exact position isn't predictable. There will be a slight jitter in timing depending on where they were but this will be corrected in the registration station. There is also quite a lot of frictional wear between the feed roller and the paper, and between the paper and the pad. Both will wear out; they have a life of thousands and perhaps tens of thousands of pages but ultimately when the rollers wear out the printer will not feed; or if the pad wears out it will double feed.

There is usually a paper sensor just before the registration sensor. If paper does not trigger that sensor in a reasonable time the printer stops and gives a paper jam. If there were no sensor the print process would run and the OPC drum in the cartridge would make a mess of the transfer roller.

Double-feeds sometimes get through a printer intact but usually one is offset behind the other making the apparent length of the page too long. The printer's firmware monitors the paper sensors; detects that the paper has not cleared the sensors and signals a paper jam.

Print designers strike a balance between cost and reliability. The lowest cost feed mechanism has a pickup roller on an axle. The axle is driven through an eccentric cam which comes to set when it is trapped by a solenoid. The axle and roller are one thing and the rollers and pads aren't intended to be replaced. One roller can serve both the pickup and feed purposes. A bit more reliability is gained by having a "D" shaped pickup roller that initiates things.


On the Variety of Rollers & Pads

Few spheres of human endeavour have given rise to more unnecessary variations on a theme than printer paper feed mechanisms. There are hundreds of different kinds of roller in all kinds of size.

Converging on the mechanism we use today took some time. In the early days designers of cut-sheet feeders for typewriters and daisy-wheel printers favoured almost vertical hoppers where gravity did the job of stacking paper neatly ready to fall into the platen. Then the straight through trays took over, inherited from photocopiers. Straight through is logical and can handle heavy card, but it also takes about three times as much space because there is an input stack, process and output stack alongside one another. The "C" and "S" shaped feed patch stack the input under the printer and output on top.

Ordinary office paper is thin so that people can store a lot of it.   It is not very thin because otherwise it falls to bits too easily. Providing it is reasonably rigid rollers can push it around a series of bends.

The pickup and feed rollers are soft rubber but there can be quite a variation in formula (natural latex, styrene-butadiene, polybutadiene rubber polychloroprene (Neoprene), nitrile rubber (NR) and so forth)

Separation Rollers

Separation rollers cost more to implement but do a better job, are more reliable and last longer. The separation roller replaces the pad.

The feed and separation rollers are almost always a set of three - and some manufacturers use three identical rollers. There is a pickup roller and it pushes paper to the nip point between the feed and separation rollers.

The separation roller is often driven, normally through a torque limiter. Left to itself it would turn in the same direction as the feed roller so the top roller pulls material into the nip point whilst the bottom roller chucks it out.

The torque limiter makes all the difference. If the two rollers are engaged without paper the torque limiter on the separation roller weakens its drive so friction from the feed roller overcomes it.

When a single sheet of paper enters the nip point the frictional contact remains the same; the feed roller still overcomes the separation roller and the paper passes through.

If a double-feed arrives the frictional contact is broken, the feed roller drives the top sheet forward but the separation roller keeps driving any subsequent sheets back until it is clear. Only when the top sheet has departed can another follow on.

The separation roller mechanism costs more to make. Instead of a spring and a pad there is a roller, a torque limiter and a drive shaft connecting to the body of the printer through a cog. Separation rollers are more reliable and long lasting, so most larger printers use this mechanism. It will wear out in the end as there is some frictional contact as paper arrives and departs. That needn't be a problem as replacement rollers almost invariably just clip onto their shafts.

The pickup roller only rotates momentarily against the paper so it generally seems to do less work, and that might explain why in some printers it isn't automatically listed as a spare or necessarily part of a maintenance or feed kit.

In principle the torque limiter could get too strong and cause feeds that are missed and excessive wear. If it were too weak the odd double-feed would appear. In practice torque limiters seem pretty reliable but if they do need replacing they are often held on the shaft with the roller and just slide on and off.

Printers with automatic recovery from a paper jam can be a nuisance to work on because the cause of the jam is obfuscated by the machine correcting itself. Look in the error log (print version or via the web server) to see what is triggering problems. Print the menus to find out where to turn the auto recovery option off whilst checking the printer for problems.

Automatic Recovery

On detecting a paper jam some recent printers with multiple motors and sensors will attempt to recover. Depending on the jam location the motors will slow down and try to pass the paper forwards to the exit, then repeat any pages that were incomplete. The exact recovery process will depend on circumstances and printer firmware. The operator has to be told there was a jam; but again its a matter of policy. A reasonable strategy might be to warn of the jam on the control panel or in the print-driver window of the computer that sent the job, but also notify technical support of the event.

About Maintenance Kits

Parts of a mono laser printer that will run out or wear out go roughly as follows:

  • toner (quantity set by manufacturer) 1,500 to 45,000 pages
  • photoconductor 10,000 to 100,000 pages for an OPC depending on manufacture. Amorphous silicon can last much longer.
  • wiper blade probably beyond 100,000 pages. The doctor blade is only in direct contact with developer or toner so it may have a longer life.
  • Primary Charge Roller (PCR) - probably in excess of 200,000 pages

HP and Canon generally wrap the parts above into an exchangeable print cartridge with a stated life that matches the quantity of toner. A kilo of toner will provide 5% cover on around 25,000 pages.

Of course, other parts are wearing out.

  • pickup roller - in excess of 10,000 pages and possibly over 100,000 but heavily dependent on design
  • feed roller and pad - likewise. Feed and separation roller - possibly to 250,000 pages depending on materials used and your tolerance for misfeeds.
  • transfer rollers are functionally the same as the PCR but more exposed to chipping and abrasion by paper. Lifetimes in excess of 225,000 pages are common in the HP LaserJet series.
  • Fuser thin-walled heated films, sleeves or belts last from 50,000 to 200,000 pages depending on size. Large ones have less contact with toner and paper per unit area so last longer. Thick walled heated rollers have a similar life in printers, but matched with an oiler in copiers sometimes last half a million pages.
  • Other rollers have indeterminate lives. For instance the registration station is often a mix of hard steel and hard rubber rollers. The clutch is more likely to be suspect than the roller themselves. You can attempt to treat rubber rollers with platen cleaner.
  • Fuser exit rollers are handling hot paper and that may denature them. Again, if they seem intended to be rubbery then some platen cleaner may work.

Some printer manufacturers bundle the fuser, transfer roller and feed-roller set into a maintenance kit - and may or may not prompt the user when it is to be fitted. Some take the attitude that kits can only be fitted by dealer technicians. HP has recently decided that kits are definitely end-user fixable on the LaserJet M601 etc.

The Right Roller

People are sometimes surprised that printers can be fixed at all; when one goes wrong, they buy another. This expectation, based on inkjets, has generally suited manufacturers because:

  • the logistics of mass market sales are simple; much easier than the logistical and support nightmare of spares.
  • they need market churn. New printers mean new cartridge designs that are smaller and less easy to copy.

At the bottom end of the market some manufacturers don't send an engineer anymore; they send a courier with another printer. Returned printers go to a contract repair centre for "triage" - easy faults are fixed and the machine put on the shelf to meet warranty calls - or sold through a so called "factory outlet". This trend has been growing for 20 years and is now almost universal in consumer oriented electronics.

In the business-oriented market HP has been moving to make printers user-repairable. Almost everything likely to go wrong is available in a kit, with a sheet of user instructions.

This reinforces what the service industry has been doing for a while anyway, packaging the parts as "feed repair kits".

For printers not covered by warranty or where this approach hasn't yet been adopted there is a problem getting the right part.

As we point out elsewhere there seem to be of the order 25,000 models of printer; more if we include minor variations of inkjet. (The EU Energy Star list has over 1,700 on 25 pages, and that is just the current list, printers can last 20 years). Nobody has knowledge of them all.

We research printers continually but it isn't always easy. If we had to award a prize for obscurity in service manuals it would probably go to OKI who typically have one document with the drawings and another with the parts lists - or perhaps Samsung who have been know to miss rollers out of the service manual diagrams. (Why should life be easy?)

User-oriented maintenance kit are a very good idea - providing they aren't overpriced.


Dealer Only Codes

Printers that give firmware prompts for maintenance kits generate a problem: obscure codes or even special maintenance software to tell the printer the reset has been done.

Manufacturer attitudes to obscure codes and "dealer only" software vary. Epson seem to love the idea. Brother use it but then brother.com sometimes has "how to replace the PF Kit" instructions. Sometimes you need the service manual. Too often you need a secret code or even special dealer-only software.

HP have moved to making maintenance kits and fuser mandatory self-repair part With the M601 models. The maintenance kit error codes are in the "10" range with consumables and the Reset Supplies menu easily available by default (Home > Administration > Manage Supplies > Reset Supplies > New Maintenace Kit > Yes).

Back in the days when laser printers cost over thousand pounds and dealers charged £50 for a callout it was natural to get the service guy in to fix the printer. Now a good printer costs £500, many of the Epson, Brother and Samsung models are sub £300 and call-outs are rarely less than £75.

Obscure maintenance codes turn good printers into scrap.

Everything Tried, Everything Failed

When all else has been tried with paper pickup it seems the print mechanism is truly to blame.   Each manufacturer has their own style. Lexmark likes an articulated arm with a pair of rollers each with a tyre. HP's office printers use the RM1-0036 /RM1-0037 separation and feed roller technique. Models all differ, but mechanisms share a theme that a pickup roller starts the paper moving then disengages, either through being "D" shaped or because a lift-arm takes it off the page. Paper moves a few inches to the registration station where another set of rollers takes over - so at that point the feed rollers must stop and disengage. There are two ways of doing that: clutch or solenoid.

HP (and Canon) use a combination but favour solenoids, particularly as a way to lower the pickup roller or activate it for one turn. A solenoid is a cylindrical electromagnet usually with several hundred turns of wire round an iron core. When the solenoid comes on the contribution of all those individual windings adds up to a powerful magnetic field, sufficient to pull hard on an armature. When the power goes off the armature is released and pulled back by a spring. Solenoids are a good way to get rapid mechanical action. The release action does have a problem, often the core has some residual magnetism and won't let go of the armature. To counter this the core has a mylar or foam anti-residual strip, but this ages and thins and timing goes wrong - you get multiple page feeds on the LaserJet 4200 series and relatives, or jams in the duplexer with the LaserJet 2200. On the LJ-4200 the pickup roller stays down when it shouldn't and that can be seen from the back with the duplexer out.   The printer will give lots of 13.02 errors and changing the rollers won't help.

the professional answer is a new solenoid. If its your own old printer then the answer might be to scrape of the old foam and replace it with a couple of layers of gaffer-tape.

solenoid feed mechanism

Fixing Rollers

Feed Rollers made from soft rubbers and naturally wear out due to friction between themselves or with a pad or the paper itself.   Once misfeeds start the problem will escalate because misfeeds tend to trigger a prolonged run of the feed motor and several retries. If paper is stuck the roller is getting frictional wear like skidding car tyres.

The obvious answer is to replace the rollers which can be done by buying

  • the suspect roller - cheapest, but possibly error prone.
  • a feedroller kit - not very expensive and changes all the suspects.
  • a maintenance kit - rather more expensive because it includes the fuser. You may need a fuser shortly, of course.

People who rely on a printer usually have a spare set of cartridges on the grounds they wouldn't like to run out in the middle of a critical job.   Most people don't have a maintenance kit and unless there is a "fleet" of printers to look after we don't always recommend it, as it is an expensive item.

Back in the logistics chain, of course things look very different. Ten or twenty cartridges are sold for every fuser and the manufacturers really care that cartridges are available; that is where they make their money. They don't sell nearly so many fusers. They may not even really want to sell fusers; they might prefer to sell new printers!  So when you are desperate for a fuser or a maintenance kit only the common ones are likely to be stocked for next day delivery.

Rollers are easier and cheaper stock to hold but once again demand is quite low. That could mean waiting a few days whilst less popular stock comes from Germany or Japan (a lot of printer makers have their stock in those places).


Test Modes

One way some recent printers offer advantages over their predecessors is by offering a set of test modes through the control panel or perhaps through the printer driver or special maintenance software.

In test or service mode an engineer can trigger specific events one at a time or in sequence to find out what does happen during the print action.

Since it's entirely a matter of firmware and software support it would be impossible to give any worthwhile details here except to say that it tends to be a feature of the larger, better thought out sorts of printer.

This is clearly a developing field. The Service Manual is definitely needed if you want to experiment with the test modes on a printer and it may need support software that could prove to be "dealer only".

Desperate Measures

If the printer just won't feed and is needed there are several ways out.

Sometimes rollers have a build-up of material on their surface from the paper coating, so washing them will restore their action, at least for a while.

AF PCL100

Platen cleaner is an old product that keeps finding new uses. A typewriter platen was the hard rubber roller that carried the paper under the print position, and it tended to dry out and get contaminated with ink so that the paper slid about - hence the "funny name". Platen cleaner is effective at restoring rollers in inkjet and laser printers. It is a mixture of alkanes (waxy liquids) in an alcohol

One way to apply platen cleaner to an inkjet is to wet some paper with it and then pass it back and forth through the printer using the page feed button. DONT do this with a laser printer as the effects on drum, transfer roller and fuser are uncertain. The product will evaporate in the fuser anyway (The MSDS says it is non flammable but boiling point is 170 centigrade). Platen cleaner doesn't generally do any damage, but given the variety of rubbers it won't always work.

If there are two or three identical rollers try swapping them round. If the printer has more than one cassette then the rollers in subsequent tray-units are sometimes identical.

The following steps could make things better or worse.

Some roller materials lose their softness with age. The too-hard surface will crack away with washing and a bit of vigorous rubbing.

"D" rollers have a portion of the rubber tyre that never contacts the page. With a bit of effort the tyre can be rotated on the core.

If the tyre will slide off the core will it work inside-out?

How about scoring the surface with a kraft knife to give it some texture?

Some of these measures are a bit desperate, if they don't work the roller will be ruined. Its a bit like a failed inkjet printhead or formatter board - what have you got to lose? The old roller is scrap anyway!