Replacing Fuser Film Heaters

The fuser in a laser printer uses a combination of heat and pressure to adhere toner powder to the page. Toner is a plastic material, typically styrene with some resin and wax to limit adhesion to the fuser roller. This is adhered to the page by heating it to the point where it is sticky. The print surface of the paper has to get a temperature of around 150 Centigrade. The heat is applied indirectly through a roller or film, so the actual heater temperature is somewhat higher.

Older fusers use an aluminium roller coated in teflon with an incandescent lamp down the centre. The core temperature of the lamp might be 2000 Centigrade, they run a bit cooler than halogen lamps but are otherwise similar. Rays hit the anodised inner surface of the fuser roller which might rise to about 200 Centigrade, sufficient to raise the surface of a fast moving paper sheet momentarily to 150 Centigrade. Problems with this design are that the lamp has a limited life and sometimes falls off its mount. Teflon being a non-stick plastic ultimately wears and when it does the material quickly strips away from the roller. A significant problem these days is that the roller needs to be kept warm if the printer is to respond quickly - but heating the roller in an idle printer is a waste of power.

Instant On Film Sleeve Fusers

Canon and HP developed the idea of doing away with the roller and replacing it with a film or foil of telflon. The film is in contact with a powerful heater which raises its temperature and that of the page. This has a big advatage, the fuser comes to temperature very quickly so it need not be kept warm when the printer isn't in use. Printers tend to be used in a ‘ bursty ’ fashion - the user suddenly prints two or three pages then nothing more for several hours. Turning the fuser on only when it is needed saves power, they are advertised as an instant on ’ device

Instant-on fusers use a heater made from a ceramic rod with a conductive track printed on the surface. The track looks like carbon, but might be tantalum-aluminium or suchlike material. The end of the track is metalic - possibly silver - it needs to bond to the heated track and make good contact with a connector. Sometimes the mating between the heater and connector goes badly and the metalisation burns out.

Film-fuser heaters last quite well, It may be reasonable to replace a fuser-film without replacing the heater providing the heater shows no signs of damage if this is your own printer. With commercially refurbished fusers we would prefer the heater to have been changed. Ultimately the heater will fail. Typically there will be a burnt-out distorted bit in the track and measurements with a multimeter will show it open-circuit instead of the expected 5 to 15 Ohms.

For some models of printer replacement heaters are avilable. Heaters do tend to be model specific and come in 110 Volt and 220 Volt versions. Using the wrong heater is unlikely to work and quite likely to damage the other parts of the fuser.

Heaters are glued onto the heating core and can usually be removed by levering up with a knife blade or pushing through access holes from inside the heater core. Before removing the old heater carefully observe its orientation - which side the wires emerge and whether the heater tracks face up or down. Clean any residual glue until the heater core is completely clean and smooth.

New heaters are fragile and will break easily. The new heater is glued into place. Glues used usually have some flexibility and designed to work at a very high temperature. The glue will need about 10 minutes at room temperature to set. Ordinary household glues wont do the job properly.

If the heater has been changed it is normal to change the teflon sleeve as well .