The Need to Clean Laser Printers

Laser printer problems are quite often caused by a buildup of toner and dust in the print mechanism, particularly on the metal contacts and electrodes that supply voltages to the developer, drum and transfer roller. Although it's possible to own a laser printer for years and never need to clean it, printers in urban environments and factories need more attention. Every printer is likely to need cleaning eventually. It's a good idea to check cleanliness briefly whenever you change a cartridge, particularly if you are using recycled cartridges.

The first place to look for advice on cleaning might be the user manual. Some recent printers have a special cleaning mode, where printers tend to part company with their documentation and it isn't always much help, so here are some general guides:

Cleaning Laser Printers.

Laser printer manufacturers have done their level best to make their product office friendly. Cartridges hold the parts that might leak toner or be vulnerable to contamination from a finger print. Making the machine simple and reliable is one of the justifications for using print cartridges rather than simply selling toner in bottles or bags.

Most cartridges contain toner, developer photoconductive drum and waste container all in one box. The delicate photoconductor and developer are amongst the parts most likely to fail, so being able to change them with the print cartridge is handy. People do wince at the price of new cartridges but the answer to most faults is to try changing the cartridge.

Most cartridges are all-in-one, a technique developed by Canon. An alternative design has each as a separate component: toner, developer and drum. Having separate components should give lower running costs because the developer and photoconductor last longer than the toner. It does make fault diagnosis a bit more difficult because each part has to be considered.

When changing the cartridge doesn't help then cleaning the printer might help with faults such as:

  • Faded Print often caused by a poor contact or by transfer voltages leaking away. Dirty optics are another cause of bad print helped by cleaning
  • Dirty leading edges or corners of pages are often toner leaks near the transfer roller.
  • White Pages likely to be a bad connection causing a voltage to drop
  • Dark pages again likely to be a bad voltage. Most of the things that will make a page "look wrong" are likely to be fixed by cleaning.
  • Misfeeds Paper jams and pickup failures could be caused by scraps of paper caught in the paper path. Cleaning helps spot the obstruction. It is also an opportunity to look for worn rollers and at the fuser which are the other two main causes of faults.

Cleaning a printer can be a five minute job once you are used to the model and its quirks. This page might take a bit longer to read, partly because we have to give warnings such as keeping water and static electricity out of the machine.

Inspect the Cartridge(s)

The first step in cleaning is to take the cartridge out and examine it closely. Look particularly at the metal contacts on the side. A typical cartridge has three or four electrical contacts from the machine (ground, precharge, developer and toner feed). If it's a colour machine there will be four cartridges, one each of cyan, magenta, yellow and black. All the contacts need to be clean and making contact with springs on the machine body. The contact springs are often rather unimpressive to look at but they are vital to performance.

It is worth looking briefly inside the cartridge shutter or doors. The OPC drum itself is usually blue or green, sometimes bright but sometimes opalescent. You can find mixtures of quite different looking cartridges in the same colour printer.

The OPC surface should be even - a scoremark or blemish is bad news. Don't touch the drum surface because finger marks cause blemishes.

A common sign of trouble is that the catridge has a lot of toner sputtered over the inside of the shutter. It often suggests a failing seal or bad voltage.

The cartridge itself needs to be clean, otherwise it is just going to transfer loose toner back into the printer.

If there seems to be anything questionable about the cartridge then it has to be changed, despite the cost. Cartridges are deliberately made as sealed units, so whilst they can be recycled or refurbished by specialists they aren't readily repairable.

Clean Machine

If changing the cartridge doesn't solve a problem the next step is to clean the printer. Leave the cartridge out of the machine but if the job will take a while, put the cartridge in a dark place such as the bag and box it came in. The drum OPC material gradually loses its abilities when exposed to light.

Laser printers use high voltages to attract a special dust called toner. Printers naturally attract other dust and toner to the wrong places as well as the right ones and this can make them malfunction.

Toner is a fine powder and when it is exposed to air some will escape. There is also dust in the atmosphere shed by the people and clothing round about. Pollen, micro-organisms, windblown sand; we live in a dirty world.

What we are concerned with here is the inside of laser printers. The outside doesn't matter much except that a dirty printer might imply no-one cares. The inside surfaces matter to the process because laser printers are electrostatic, they work by attracting little particles of toner. If toner is in the wrong place or if surfaces that should be clean gather dust that carry charges the printer won't work properly.

However you shouldn't just take a wet cloth or the office vacuum cleaner to the printer innards.

Electricity and water should never mix. Anything driven by high voltages is potentially dangerous and that includes notebook computers and TV sets. Laser printers are often full of high voltage circuits.

Ordinary office vacuum cleaners create static charges. Static might destroy circuits in the printer. Ordinary vacuum cleaners are also likely to blow toner straight through the filter bag because the toner particles are smaller than the filter holes. An ordinary cleaner may just spread toner in a thin layer around the office.

So if the ordinary ways to clean something cause problems what shall we do?

Cleaning Products

There are a whole range of cleaning products for IT equipment.

  • Vacuum cleaners with sub-micron filters suitable for handling toner and anti static plastic parts that avoid damaging the printer electrics or causing an explosion.
  • Cleaning cloths with magnet- impregnated fibres to pick up toner dust. These are good on the HP/Canon toners which have a magnetic component.
  • Lint free cloths ordinary tissues leave bits of fiber behind and this can disrupt the electric fields and attract more dust and toner
  • Isopropyl alcohol is a solvent that evaporates quickly and is relatively non-toxic. It is particularly good at dissolving greasy contamination. Stubborn toner concentrations break down in "iso".
  • Special brushes ideally with anti-static properties to get into the recesses that often contain the high voltage contacts.
  • Spray duster spray duster is compressed gas in a can so it's often called "canned air".
  • Spray soaps for the outside surfaces of printers. After cleaning the inside it might as well look good on the outside.

Professional technicians carry these tools. There are specialist companies who do nothing but cleaning IT equipment. If you have a large population of printers and fairly frequent issues to deal with these things are tools of the trade, as are a set of screwdrivers.

Alternatives

For the ordinary office or IT manager the special tools might seem unnecessarily expensive, so here are some suggestions.

Damp Cloth

Water inside anything electric is normally to be avoided, as already mentioned. Don't take even the dryest damp cloth to the insides of a TV, there are stored charges that can kill and no need for the components to be clean.

Printers aren't designed to get wet but there shouldn't be any stored charges when the printer is off. They do need cleaning for the reasons mentioned - dirty printer innards will tend to give bad print.

The safety interlock switches cut the high voltages when the lid is open. Most modern electronic devices are never truly off until the plug is pulled so for safety unplug the printer.

Experience suggests a tissue soaked in water then wrung out hard so that no drips escape from it is an acceptable alternative to a proper wipes. The tissue picks up toner because water discharges the static that makes toner cling and once the mechanical action of the tissue breaks down the repellent action of surface tension it picks up toner. A dot of mild detergent might help, particularly if the innards of the machine are greasy. Laser printers get used in kitchens and factories as well as in offices. Don't squeeze water into the recesses and contacts - use a brush to get at them. The tissue does leave tiny drops of water so make sure they are dry before using it.

Keep detergent to a minimum and make sure it is removed. If grease is a problem it may be better to use isopropyl alcohol. Don't use foam cleaners or window cleaner inside a printer. Detergent residues may damage the static fields. Ammonium cleaner will destroy the photoconductive drum.

Antiseptic handwipes might be acceptable, they are usually a mix of water and alcohol but the antiseptic and detergent residues might be questionable.

The printer innards then need wiping over with a dry cloth. A clean dry cloth that doesn't leave bits behind is preferred, poor quality tissue paper tends to leave lint. Some supermarkets sell good quality kitchen roll that doesn't tear easily. Make sure all surfaces inside the printer are dry before turning it back on. If there are places that are difficult to clean this is one reason to prefer isopropyl alcohol to water as a solvent. it will dry away relatively quickly.

The special magnetic cloths that pick up HP/Canon type black toners relatively easily are not expensive and might be useful.

Brush

Toner caught in crevasses and contact areas might need moving with a brush. The contacts tend to be in recesses to make sure they slide together with the cartridge well. A brush is also handy for getting into the transfer roller well in mono printers and for all the little spring contacts that connect the transfer belt on colour printers. A paintbrush will do. Technicians tend to have a 1 inch paintbrush and an old toothbrush in their kit

Air Duster.

Spray cans of air duster are useful when a printer has dust in a deep recess. It is appropriate where dust is causing a problem, mechanical brushing is difficult and both water and isopropyl water would be a nuisance. With some precaution you can use an air compressor as well, if you have access to one. The main precaution is that there shouldn't be any oil or water coming out of the air line (garage compressors tend to do this). Also keep the pressure quite low and don't use the compressor to spin fans - using them as turbine generators causes overvoltages. There is a possible issue with static in the air flow from compressors as well. Cans of air duster are possibly better for the circuitry.

Isopropyl.

Isopropyl alcohol is fairly readily available - as well as being sold under the names isopropanol, 2-propanol and "IPA" and also as things like whiteboard cleaner. It's good at breaking up grease, oil, ink and many adhesives and is relatively non-toxic. It also dries very quickly which means it is preferred over water for cleaning electrical items.

Vacuum

An ordinary vacuum cleaner might blow toner dust all over the place. Toner particles include some sub-micron components that could blow through an ordinary vacuum cleaner bag.

If the voltages in the printer aren't fatal to an unwary user the static voltages made by a vacuum cleaner could damage the printer (and can damage computers - don't take an ordinary vacuum cleaner to the computer innards either).

If there is a lot of toner then the static made by a vacuum cleaner could cause an explosion just as coal dust can. The problem is that the small explosion that damages the vacuum cleaner causes a dust cloud and a secondary explosion which is much worse. There have been fatalities from this kind of accident.

Ideally you need a proper toner vacuum cleaner but because these are technician tools they are fairly expensive - generally about £150. There are also explosion-proof industrial vacuum cleaners including models with pneumatic rather than electrical motors - they are really expensive but if you run a cartridge recycling business that might be what you need.

If there isn't very much toner to move and the vacuum cleaner is one with a known good HEPA filter then it should be OK - but remember the warning about static and the printer contacts.

Parts to Clean

The user cleanable parts are the accessible bits of the print path with the cartridge out. A lot of the paper path is occupied by registration rollers (foreground in the picture) and by the paper transport path (background). In the middle of a mono printer directly under the cartridge drum is the transfer roller - usually grey-black in colour and made of conductive material.

Contacts

Print cartridge contacts take all sorts of forms with little metal plates, wire springs and axle ends being favourites. The illustration here shows two contacts being made by ball bearings, two by springy metal contacts and a big spring contact that engages the drum axle.

Electrical contacts are often on the left of a printer. If the control panel is on the right then the formatter tends to be on that side as well, so it makes sense to put the High Voltage PSU (HVPS) on the left.

Large Spills

Large spills of toner tempt people to solve the problem with a vacuum cleaner. That is unwise because of the risks:

  • as already suggested fine powder can explode. This may seem unlikely because toner is just a plastic or wax but it has a big surface area and is meant to generate big static fields - so a spark in a swirling filter-bag could set it off.
  • more insidiously fine powders can leak through the filter of an ordinary vacuum cleaner so the machine is effectively blowing the dust around.

First remove most of the toner by shovelling it up with pieces of paper and putting the waste in a bag or envelope.

Never use warm or hot water on toner. Toner is designed to melt at quite a low temperature and even warm water will soften it making it more likely to cling to fabrics and surfaces. Cold water with a small amount of soap or detergent in it to loosen static bonds should help.

Don't rub at a spill. Rubbing causes both static fields and friction heat so the toner will bond more strongly.

Rather than rubbing take fabric outside and tap or beat the material from behind the spill. Carpet beaters are no longer typical domestic items but a stick will serve the same purpose, the idea is to make toner particles jump off. Outside and away from other people is the best place for this because its best to avoid breathing toner in or afflicting the dust on others.

Material Safety Data Sheet

If a big spill has happened and people have been exposed to dust then it might be advisable to get the "Material Safety Data Sheet". The easiest way to get these is to put a phrase such as the cartridge type and filetype:pdf into a search engine. For instance

C4127A "Material Safety Data Sheet" filetype:pdf

Gets the relevant material for the LaserJet 4000 cartridge as a pdf.

Reading through the 6 page document you will see that the bulk of the toner is:

  • Styrene Acrylate Copolymer - 40-50%
  • and Iron Oxide - also 40-50%

Hazards are:

  • Inhalation: Minimal respiratory tract irritation may occur with exposure to large amount of toner dust.
  • Ingestion: Ingestion is not applicable route of entry for intended use.
  • Skin: Unlikely to cause skin irritation
  • Eyes: May cause eye irritation.

On chronic health issues they say:

  • Prolonged inhalation of excessive amounts of any dust may cause lung damage.

On hazards:

  • Use of this product as intended does not result in inhalation of excessive amounts of dust.

And on Carcinogenicity:

  • Not a known or suspected carcinogen according to any IARC Monograph, NTP, OSHA Regulations (USA), EU Directive, or Proposition 65 (California)