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THEORY OF OPERATION
3. Printer Mechanism
3-1. Thermal Head
The TSP400 printers employ thermal line printing. The thermal head consists of a horizontal line of 640 heat elements.
These elements print one line of dots at a time as the paper passes over the head. The head is fixed in position; only the
paper moves.
The printer prints a dot by heating the corresponding heat element. The heated element causes a chemical reaction in the
coloring layer of the thermal paper, resulting in the formation of a visible dot.
Fig. 2-13 Principle of Thermal Printing
3-2. Paper-Feed Mechanism
The paper-feed mechanism is comprised of the paper-feed motor, gear train, platen, and thermal head. The paper-feed
motor drives the gear train, which in turn rotates the platen. The platen carries the thermal paper past the thermal head.
The paper-feed motor is a PM (permanent magnet) type, 4-phase 48-pole step motor. A single step feeds the paper
approximately 0.125mm.
Fig. 2-14 Paper-Feed Mechanism
Thermal head
Heat element
Coloring layer
Platen
Printed point
Thermal paper
Thermal paper
Platen
Paper-feed motor
Thermal head
Gear train