Print Process In Operation - Tektronix Phaser 360 Service Manual

5
Theory of Operation

Print process in operation

5-16 Phaser 360 Color Printer
Once a PostScript image has been processed and a printing bitmap created, a
print cycle begins. The printhead and drum are brought up to their operating
temperatures and the ink levels in the ink reservoir are checked and ink is added
from the ink loader, if necessary. Next, the printhead is driven horizontally to its
home position and the drum is rotated to its home position.
Warning Keep your fingers away from the process gear drive system; it uses
a closed-loop drive system. A closed-loop servo drive system is
inherently dangerous. Since the motor speeds up if it senses the
process gears drive system slowing down, fingers caught in the
process belts and gears can be severely injured.
Printhead tilt
The printhead is tilted forward into its print position. The process motor is
activated, which drives the process drive belt. The belt, in turn, drives a
compound gear. Through a pair of follower gears, the compound gear drives
the head tilt cam gear clockwise. A cam follower, mounted on the lower end of
the head tilt arm, follows a groove in the rotating cam gear, which tilts the
printhead. The cam gear rotates until a set of missing teeth in the cam gear
"disengages" it from the cam drive gear. The head tilt solenoid latches the head
tilt cam gear in this position. At this point, the printhead is in its upright print
position (home position). (The head tilt cam gear is principally rotated in a
clockwise direction to tilt the printhead forward and back. It only rotates
counterclockwise during some printhead cleaning operations.)
Tilted forward, the missing teeth of the head tilt cam gear allow the process
motor and gear train to perform other print functions without affecting the
printhead's tilt position. The head tilt solenoid must be energized to allow the
head tilt cam gear (with a slight spring assist) to advance forward enough to
engage its drive gear and tilt the printhead back.