Table of Contents
Advertisement
Page: 14
Service Guide ML172/ML182 Series
Chapter 2 Principles of Operation
2.2 MECHANICAL PRINCIPLES OF OPERATION : Printhead
The Printhead used by the ML172, ML182, ML182-PLUS and ML182-TURBO is a highly efficient Stored
Energy type. Power is not consumed until a printwire is activated, thereby extending the printhead life to
approximately 200 million characters.
The printhead is designed with nine (9) vertically aligned wires. Each wire is welded to an armature ring.
Behind this armature ring is a spacer ring.
Each of the nine print wire armatures on the ring has a permanent magnet behind it. The magnets attract
the armatures, keeping the print wires inside the printhead. Because of the spacer ring behind the
armature ring, the armature is attracted toward the permanent magnet at a cocked angle. There is also a
coiled wire, wrapped around each of the nine permanent magnets.
When a dot is to be printed, current passes through the coiled wire, creating a magnetic field which
counters the magnetic field of the permanent magnet. This causes the armature and print wire to spring
forward and imprint a dot onto the paper.
When the current is removed from the coiled wire, the magnetic field of the permanent magnet attracts the
armature, causing the print wire to retract into the printhead.
This printhead contains a built-in thermistor (rated at 100 degrees Celsius) to monitor the head
temperature. When the printhead temperature exceeds the 100 degree setting, the thermistor generates
an output signal to the Control PCB.
The printer then stops printing and sends a BUSY signal to the host computer. Data remains in the print
buffer until the printhead temperature is below 100 degrees Celsius. At this time, the BUSY signal to the
host computer becomes inactive and printing is resumed.
Advertisement
Table of Contents
