This bulletin covers the preventive measures to guard against premature fuser wear and/or failure. These items are all combined into one document because of the interrelated issues.

WARNING!
Allow the fuser to cool first! Do not touch any of the fuser components while the fuser is still hot!

PROBLEM/SYMPTOM:

1. Early wear on the fuser. Nonremovable toner buildup and galling (scratching) of parts such as the fuser roller, thermostat, and thermistor.

2. Print quality (graying, streaking, ghosting). Print quality problems are created when the form exits the fuser.

3. Message "Fuser failure"on the display. Unrecoverable error that will usually persists, even after cycling power.

4. Discoloring of the form. A light brown band occurring horizontally across the form is created when the fuser roller initially contacts the form but the form is not yet moving (start up).

CAUSE:

Excessive toner residue on the upper fuser roller is the indirect cause of most fuser problems. Toner residue is toner that did not fuse or melt into the form. This residue will clog the felt cleaning pad, become permanently attached to the upper fuser roller, buildup on the thermistor and thermostat, and cause galling (scratching) of the upper fuser roller. The following information describes the causes of toner residue and what types of problems may result from the residue:

A higher fuser mode (temperature) will fuse more toner into the pores of the form and create less residue for the felt pad to pick up. A lower temperature will do the opposite and create more toner residue.

Setting the print density control (green dial) above "3"may transfer excessive amounts of toner to the form. An excessive amount of toner will not fully fuse into the form. Higher print density settings can result in excess toner residue and therefore excessive wear. Low print density settings should lower operating costs by reducing both toner consumption and maintenance costs.

Print media with low surface porosity such as synthetics (vinyl), will not absorb toner and therefore increase fuser wear due to the high degree of toner residue.

Extensive use of dense print images (high dot densities), such as barcodes, can contribute to higher toner residue on the fuser roller. All unnecessary or dense images should be avoided wherever possible.

Once caked with toner, the felt cleaning pad cannot effectively remove toner residue from, or apply protective silicone to the upper fuser roller. Furthermore, toner has a high iron content which is very abrasive. A cleaning pad caked with toner will actually scratch the upper fuser roller. The felt pad requires frequent change intervals when any of the aforementioned conditions exist. The fuser cleaning pad is the primary defense against problems caused by toner residue.

Correct installation of the felt cleaning pad is equally critical to the life of the fuser assembly. The pad is only effective when it is positioned properly under both spring clips of the upper frame assembly. The spring clips that rest on top of the pad are visible when the pad is properly installed. If the springs are bent backwards and not riding on top of the pad, remove the pad and bend the springs forward slightly then try to re-insert the pad. Incorrect pad installation may be the single biggest cause of premature "Fuser Failure". Do not use a pad in which the felt is not evenly centered inside the plastic wand. The height of the pad should be even around its perimeter. Check the pad frequently during operation to make sure it is wearing evenly and not clogged at any one point along its length.

Streaking, graying and ghosting are caused by a film of toner residue on the upper fuser roller caused by a defective, improperly installed or clogged felt pad. A ghost is a faint repeat of an image that occurs about 3"following the original. However, a ghost that occurs at approximately 4.5"is probably coming from the OPC drum.

Smudging that occurs once the form passes through the fuser can be caused by lumps of toner permanently adhered to the upper fuser roller, these lumps are caused by excessive toner residue buildup. In severe cases the lumps will deform the paper at those points.

The aforementioned print quality problems can be caused by other issues unrelated to the fuser. To verify that the problem is created by the fuser, open the cover on the printer and check to see if the problem can be seen on the unfused toner image inside the printer, if so, the problem is not associated with the fuser.

"Fuser Failure"error can be caused by excess toner buildup between the thermistor and the fuser roller. This causes the thermistor to detect a temperature that is lower than the actual temperature of the upper fuser roller. In turn, the fuser is heated excessively in an attempt to warm the thermistor to the temperature defined by the fuser mode setting. The excessive actual temperature of the upper fuser roller can cause the thermostat's safety thermoswitch to trip, resulting in a "Fuser Failure"message on the display.

Discoloration of the form can be caused by toner buildup between the either the thermistor (as mentioned above) or on the thermostat. Toner buildup can occur on the thermostat (although less likely) which will raise the effective trip temperature of the thermostat. Therefore, if the thermistor and the thermostat both have a buildup of toner, the upper roller may get excessively hot and the thermostat may not trip unless the fuser gets even hotter. The result could be slight discoloration of the form on start-up. This condition is usually caused by insufficient felt cleaning pad replacement intervals.

SOLUTION/PROCEDURE:

Preventative maintenance is the key to extending the life of the fuser. Take the following measures before physical damage to the fuser occurs.

Always use genuine Output Technology toner, other brands may not have the proper release characteristics for the fuser. Non-Output toner has been known to cause a host of problems ranging from waste toner bottle overflows, poor life expectancy and damage to the fuser and consumables.

If an application requires card stock, labels, or anything other than standard computer paper, consult technical bulletin 93-LM1000-161 for recommended form specifications. Whenever these types of forms are used, it is best to lower the print density setting, avoid lowering the fuser mode temperature, and change the felt cleaning pad frequently. Even recommended media can be less than ideal, therefore always follow these guidelines when printing card stock and labels.

CHANGE FELT PADS FREQUENTLY! This is the best line of defense for fuser wear. Make sure the pad is seated properly, the cleaning pad must be fully seated on top of the upper fuser roller with both pressure springs properly positioned on the top of the pad. When installing a new pad, check to see that the thickness of the felt extending above the cleaning body is uniform. Do not use pads that are not uniform in height.

Consider starting a log for felt cleaning pad replacement intervals. Such a log should have a foot count and description of the condition of the used cleaning pads. This will help determine how often the pad must be replaced in an application. (The felt pads are available separately, part number LM1000C106. )

The felt pad should be changed when any part of it becomes caked with toner residue. Once this happens, the pad is not effective at cleaning the roller or applying silicone. Furthermore, toner residue is very abrasive due to its high iron content, making the dirty pad even more detrimental to the fuser. The exact pattern of toner buildup across the felt pad depends on the location and levels of dot densities on the form. The pad section with the greatest buildup should not exceed the maximum recommended level.

The main purpose of the adjustable fusing temperatures of the LaserMatrix Models 5 & 6 is to compensate for media width. Without compensation, the ends of the upper fuser roller will become excessively hot when printing narrow forms, lowering the fuser mode slightly will prevent "Fuser Failure"in those cases. However, lower fuser temperatures are not as effective in melting toner into the form and will increase toner residue. Ironically, a lower fuser temperature may eventually cause the fuser to overheat and cause a "Fuser Failure".

Use a fuser mode of "4"if the edge-to-edge form width is between 4"and 5". Use a fuser mode of "5"if the width is between 5"to 6". For forms between 6"to full width, use the factory default fuser mode setting of "6". For full width heavy forms, such as wide card stock, a setting of "7"may be used. A "Fuser Failure"may occur if the fuser mode "7"is used with standard 18-20 pound (wide) paper.

A lower fuser mode setting will have a minimal affect on forms stacking and curling problems. Avoid making fuser mode adjustments for that purpose. Lowering the fuser mode to reduce melting of synthetic media should be done only on a temporary basis. High volumes of synthetic forms ran at a low temperature will lead to premature fuser problems. Turn down the print density dial and change the felt fuser pads more frequently whenever the fuser temperature is reduced.

The thermistor should be occasionally removed, inspected and cleaned when operating in demanding applications. To do this unplug the printer, remove the black felt cover, locate the thermistor located at the center of the fuser roller and remove the screw that secures it to the upper fuser frame assembly. Carefully scrape the face of the thermistor to remove toner residue. Care should be taken when cleaning the sensor as it is somewhat fragile. It is normal for trace amounts of toner to be permanently embedded into the sensor.

In most cases, it is possible to modify fusers to relocate the thermistor to the alternate right-hand location on the fuser frame assembly. This positions the thermistor outside of the printable area and therefore out of the path of toner residue. This design virtually eliminates toner build-up on the thermistor. This modification is beneficial when printing on synthetic media such as vinyl, where it is especially difficult to prevent toner buildup on the thermistor.

This modification also avoids the negative effects of the temperature gradient which forms in the upper fuser roller. The temperature gradient is where the ends of the roller become hotter than the center. This effect is more exaggerated when printing narrow forms because there is no media located at the ends of the fuser roller to "sink"heat away. If the ends of the upper fuser roller become too hot, the thermostat (a thermal safety device) will trip because it is located at the left end of the upper fuser roller. Because the right-hand thermistor location regulates the temperature of both ends of the upper fuser roller, the thermostat is not likely to trip and cause a "Fuser Failure". The trade-off with this modification is that the form temperature may fluctuate widely initially when printing narrow forms. See the P/N rework instruction "Fuser Repair, Rebuild and Modification"document part # 025-00102-00 for details on this modification.

The thermostat should also be periodically checked for toner buildup or wear. To inspect, unplug the power cord to the printer and remove the black felt fuser cover. The thermostat is located inside a black plastic housing at the left side of fuser frame assembly. Remove the two screws holding the housing to the fuser frame and carefully cut the tie wrap to the left of the housing. Carefully scrape the toner buildup from the face of the thermostat. Replace the thermostat if its face cover is worn through. Re-install a new tie wrap and secure the white lamp wires so they cannot become pinched in the fuser frame when the fuser opens and closes. The fuser must be completely rebuilt if the Teflon fuser roller coating is worn away at the point of contact with the thermostat, new thermostat will not last long when running on bare metal.

A tripped thermostat will cause a "Fuser Failure"and the printer will not print under any circumstance. To resume operation, the thermostat must be replaced or reset. The thermostat is closed in normal operation, and opens if tripped. To reset the thermostat, the device must be cooled to below 0 degrees Celsius for several seconds. It is possible to reset this device with "Circuit Cooler", a CO2 aerosol commonly used in component-level troubleshooting. The performance of this device will usually degrade after being tripped then reset using the above procedure. It is always best to replace this device with a new unit when possible.

If the fuser roller becomes permanently contaminated with toner it will affect print quality and require the fuser roller to be replaced. There are no solvents or cleaning solutions that can remove the contamination. A small amount of contamination can be removed using reagent-grade alcohol or by installing a new felt pad. Avoid oily cleaners such as "AVON Skin So Soft". These solutions may burn or evaporate which can create an oily film inside of the printer. The Laser Scan Unit cover glass may become fogged with this contamination. This may result in print quality problems in the form of a blurred or fuzzy image, smudging, or "dirty"background.

If a fuser roller becomes damaged it can only be replaced by an authorized service center, they are not user replaceable.

SUMMARY:

• Change the fuser cleaning pad frequently.
• Avoid toner buildup on the pad, less than 50% buildup is recommended.
• Use forms that fall within the paper & label specifications. See Technical Bulletin #93-LM1000-161.
• Use the lowest print density setting possible.
• Use the highest fuser mode possible for the width of form used (see text for suggested settings).
• Periodically check thermistor and thermostat for toner build-up.
• Consider a thermistor modification when printing on synthetic media.
• See Rework Instruction 025-00102-00 for details on this modification.