Printer Faults - Intermittent Paper Error

Intermittent paper jams are probably the commonest laser printer fault.

Intermittent faults are more difficult to trace and fix than continual faults. It is in the nature of an intermittent fault to be elusive. For a fault to be intermittent the machine must be working almost properly and some small alteration creates the fault. An intermittent fault with paper feed might be a bad batch of paper, a few bad sheets or bad handling. A service engineer visits and the fault disappears.

For that reason we suggest:

• asking the user questions about precisely what is happening. Users are sometimes gruff in response, but since many things can cause an intermittent problem the answer might emerge in conversation rather than in the form of a worn roller.
• in the absence of any clear diagnosis give the printer a "general service" - take the consumables out, inspect and clean those parts, clean the paper path and and if there is any sign of wear on rollers and pads replace them. Intermittent faults tend to waste money on time and repeat calls and a new set of rollers eliminates one of the most likely causes.

We would suggest changing the rollers - we sell feed roller replacement kits. A new set of rollers is often the answer to intermittent feed problems. We suggest other possibilities below.

The problem can be:

• Paper Quality - most paper is made correctly but then gets damp or is mistreated.
• Worn or aged rollers - rollers have a typical life of about 100,000 pages or 4 years.
• Something lurking in the printer - usually a bit of torn paper or a sticky label.

Printers detect paper feed faults when one of the paper path detectors doesn't operate at the expected time. If the paper flag never operates then there will be a continual jam.Intermittent jams show the paper flags can move at the correct time, that paper can feed normally and suggest the main issue is elsewhere.

Paper Problems.

Paper quality is the most common source of printing problems.

Office copier paper is a highly standardised product. Most of it is produced by a few big paper mills and then marketed under different names including those of printer manufacturers, paper merchants and stationers. The paper industry has been undergoing "consolidation" for 50 years or more, meaning that production tends to come from massive mills. Ordinary office copier paper shouldn't vary much.

Most business users are small businesses and home offices. There was once considerable competition to have quality stationery but that has been eroded by the ubiquity of copiers and laser printers that don't always cope well with anything unusual like thicker paper, and embossing. Unfortunately that standardisation has driven some of the knowledge and quality control out of the market. Supermarkets and low cost deals probably aren't the best way to get paper that has been well treated.

Check any unusual paper such as 60gsm or 120 gsm against the specification in the user guide for the tray.

Laser printer designs tend to assume the use of 80gsm copier paper as a basis. They may handle 70gsm through to 150gsm in some cases - but standard copier paper is at the heart of design expectations. Hundreds of pages of this kind of material should feed without an error. When problems do occur they tend to happen in clusters, often just after the paper source changed.

Paper that is damp and / or has been guillotine cut and is not breaking away from the stack well will cause feed problems. Has the paper pack got an "up" arrow. Try turning the paper the other way up and then the other way round in the tray. Examine the paper closely, is their a dent in the stack at one point. Try gently bending and fanning the paper to make sure it all breaks lose. Re-stack the paper. Try another ream of paper. Try paper from a different source.

Paper Trays.

A common cause of problems is the paper trays themselves.

People get fed up with the printer running out of paper so they put too much paper into a tray. The paper feed ability for small printers is a balance between the upward pressure of a spring and the pressure from a roller. Overloading the tray causes problems.

If you need a greater paper capacity then you need a "workgroup" printer with a motorised tray that can handle 500 sheets - or multiple trays.

Are the paper guides set correctly. User guide recommendations should be followed. Experience suggests most printers need the guides setting to just about touching the paper stack - but not gripping it.

Multipurpose Tray.

Most mid-range office printers have two trays.

Does the fault still occur if you use the multipurpose tray. The MP tray (often tray 1) has several benefits:

• tray 1 is normally less used so if this works well but tray 2 gives frequent misfeeds that might suggest the rollers for tray 2 are worn out.
• tray 1 can often work with a wider variety of media because it has a straighter path, particularly to the rear face-up tray.
• Its easier to observe what happens with the multi-purpose tray because the pickup and feed action is visible. Did the printer simply fail to pick up the page or did it succeed and feed an inch of paper - then fail when the first paper sensor didn't act in time?

Worn Rollers.

The paper pickup and feed rollers break the paper away from the supply stack and push it the first couple of inches towards the registration rollers.

Paper feed rollers usually have a tyre of soft synthetic rubber. A plain tyre by itself would need some pressure against the paper to give it grip. Rollers usually have a tread or texture that grips the flock of the paper sufficiently to move it.

Pickup needs to be quite vigorous in fast printers - there is under a second to get the paper out of the tray to the registration station ready for the next print. Roller action is usually a bit vicious partly to ensure paper arrives quickly and partly because roller drive is simply hung off the main motor drive chain with a solenoid actuator. Rather than accelerate together the roller will spin momentarily on the paper. Vigorous action will wear out the roller tread.

Wear of the tread will inevitably limit the life of paper feed rollers. This might not really be a problem because the roller would probably age anyway. There is obviously some volatile component in most feed rollers, hence they have an odour when taken out of the packet. The surface would age and stiffen. Many older designs of printers had harder black rollers and they tended to pick up a shine - presumably a combination of plasticiser with kaolin dust from the paper. One thing to be said for the old black hard rubber rollers was that the polished surface often came off with a bit of rubbing so you could temporarily get the printer going and at least prove the nature of the fault.

With "D" shaped rollers the rubber sleeve can be rotated half a turn to get a bit more life out of it whilst ordering a relacement.

Manufacturer manuals generally recommend not handling the rubber of the rollers. The problem is that grease from handling may de-nature the rubber. Don't use isopropyl alcohol to clean soft rubber rollers as it will remove any volatile plasticiser and this may make the roller more inclined to slip on the page.

You can't get the surface texture back onto modern soft rollers. However if the roller is fairly clearly the problem and the printer hardly ever works because of it you might try scoring the roller surface with a kraft knife - its a temporary fix but might give enough grip to get the printer going.

If misfeeds have worsened over time examine the pickup and feed rollers. If the rollers have lost their texture they cannot feed properly and need replacing. It is normal to replace the separation pads at the same time as the roller. The pads probably do wear at a similar rate. It is also rather difficult to spot a worn pad so it's better to replace them than chase needless faults.

Roller Life.

Maintenance kits include a fuser and a paper feed repair kit - a set of rollers and pads. Rollers tend to last somewhere between 20,000 and 200,000 pages depending on their design and the paper in use. Rollers don't cost much compared with diagnostic effort.

Bigger printers tend to have bigger rollers that will last longer. The more surface area there is on the roller the longer it will tend to last.

Printer manufacturers don't always state an expected life for rollers. That may just be an omission, it may also be because the number will prove a bit variable with paper types and some user actions. Overfilling the tray for instance will overload the rollers.

Fitting Rollers

In many modern printers the rollers just clip into place. It isn't always evident how its done - with the RM1-0037 illustrated above the little plastic clip is visible on the lower roller.

Obstructions.

Examine the printer for obstructions. Most modern printers have an "S" shaped paper feed path from a cassette sliding into the printer base to the print station. Swarf from an old paper jam or sticky labels can get stuck in the throat just above the tray. Take the cartridge and tray out and turn the printer upside down or on it's back to look. This needs a bit of care:

• Any lose toner will fall towards the laser scanner so make sure the mechanism is generally clean.
• The rear or top plastics on the printer are likely to be delicate - don't turn the printer onto something that can't support it's weight.

Sometimes it will be easier to lie on your back looking into the printer than to turn the printer over. Some obstructions are only visible with a torch.

Other Causes of Intermittent Misfeeds.

It isn't completely unknown to have a clean printer with a new set of pickup rollers and pads, no obstructions, perfectly ordinary 80gsm paper - an a persistent intermittent feed fault.

If this happens look closely at the top and bottom margins of the page - do these drift more than a millimetre or so? That would suggest a fault in the paper feed clutch or solenoid.

Replacing a clutch varies in the amount of trouble it causes. For some printers you can get the whole pickup assembly as a replacement part.

Another sometimes overlooked cause of misfeeds is uneven surfaces. If the printer is heavy and stands on a lightly made desk it will distort the desk to some extent. In turn the printer chassis might give a bit, changing the shape just enough to cause problems. the fault disappears in a workshop because the shape is now correct. Older printers were built like tanks so this fault was rare but the modern trend to light plastics might increase it.