The fuser of a laser printer consists of a rubber roller
(often called a press-roller) that is pushed(by springs) against
a metal cylinder. This cylinder is called a heating roller.
Inside the heating roller is a halogen lamp(heating lamp) that
heats the roller(usualy to over 200 degrees celsius). The
roller has a outer coating of teflon to prevent the paper
or excess toner from sticking to the roller. The excess toner
is usualy cleaned off by a cleaning pad(a felt rod soaked in silicon oil)
or a rubber blade(cleaning blade).
To regulate the temperature in the fuser there is a termosensor
placed against the heating roller, this is then connected to the logic bord of the printer
when the fuser reaches the correct temperature the lamp is turned off.
if the temperature drops to low the lamp is turned on again.
If the logic-boards electronic should fail and the lamp is not turned of
a thermofuse/thermostat cuts it off to prevent fire.
When the printer is printing the paper passes through the fuser
, between the press-roller and the heating roller, were
the heat and pressure melts and is fused to the paper.
Without the fuser the toner would just fall off.