5-12
Phaser 440 Color Printer
5
Theory of Operation
Printing
After checking the transfer roll's position (through the transfer roll mark
sensors) the thermal head lift motor rotates an eccentric cam to push the thermal
head down from its standby position to its print position, sandwiching the
transfer roll and paper together between the thermal head and the drum.
Printing begins as the drum slowly rotates forward (clockwise) drawing the
paper and the transfer roll past the thermal head where dye is vaporized from
the transfer roll onto the paper to form a printed image. Contact friction
between the moving paper and the transfer roll moves the transfer roll past the
thermal head at the same rate as the paper.
The sheet of paper is drawn past the thermal head three times to form a
complete image. When the first pass (yellow printing) is completed, the thermal
head lift motor raises the thermal head to its standby position allowing the
paper clamp to pass underneath. When the paper reaches the print-start
position, the thermal head lift motor rotates to bring the thermal head back to
the print position, and printing continues with magenta printing. This process
repeats again for cyan printing and black and then the print is ready to be
unloaded to the printer's output tray. (During forward rotation, the drum stops
are simply pushed out of the way. The drum stops can only open the clamp
during reverse drum rotation.)
Figure 5-7 Printing on the paper
8699-14A
Thermal head
Transfer
roll
Paper
Drum and
transfer roll
move at
same rate
Drum stops at
each end of the drum
pivot out of the way
Transfer roll
mark sensors
