Brother QL 570 - P-Touch B/W Direct Thermal Printer, Service Manual

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II- 1
CHAPTER II THEORY OF OPERATION
2.1 OUTLINE OF MECHANISMS
2.1.1 Print Mechanism
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Structure of Thermal Head
This machine adopts direct thermal printing system. The thermal head consists of 720 pieces of
heating elements arrayed in vertical single row as shown in the Fig.2.1-1. The dimension of
each heating element is vertical length 0.0847 (0.0847mm pitch) x horizontal width 0.13mm.
Fig. 2.1-1 Heating Elements of Thermal Head
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Printing Process
A thermal tape is pressed again the thermal head in the printing process by the force comes from
a nip between the cylindrical rubber platen and the thermal head. At this timing, voltage is
applied selectively to 720 pieces of heating elements arrayed on the thermal head. By this
voltage application, the heating elements generate heat and the thermal tape develops dots by
itself at heat sensing points. After application of voltage the thermal tape is fed to the next
printing position by the platen (0.0847mm). This printing cycle is repeated and characters and
geometries are printed on the tape.
One time travel distance (0.0847mm) is shorter than the width of a heating element (0.13mm), so
that continuous printing cycle can print characters and geometries on a tape by developing dots
with no gap.