Chapter Ii Theory Of Operation; Outline Of Mechanisms; Print Mechanism - Brother PT-D600 Service Manual

CHAPTER II THEORY OF OPERATION

2.1 Outline of Mechanisms

2.1.1

Print Mechanism

 Structure of Thermal Head
This machine uses direct thermal printing. The thermal print head has a heat
generator consisting of 128 heating elements which are vertically aligned in 180 dpi
as shown in Figure 2.1-1. Each heating element is 0.18 mm wide by 0.141 mm high.
 Printing Process
When the cylindrical rubber platen is pressed against the thermal print head with the
tape and ink ribbon sandwiched inbetween, the CPU applies current to the selected
ones of those 128 heating elements.
If the selected heating element(s) generates heat, the ink on the sandwiched ribbon
will be melted and transferred to the tape, producing a dot(s) on the tape. The ink
ribbon and the tape are advanced and then the next heating cycle is repeated, thus
forming a graphic pattern on the tape.
For laminate tape cassettes, the CPU processes the print data to generate a mirror
image so that the printed pattern can be seen normally when viewed from the other
side of the printed face of the tape.
 Graphic Pattern Formation
While the tape feed motor (stepping motor) feeds the tape and ink ribbon (tape only
when using non-laminate thermal film tape cassettes) by 0.141 mm for 14.1 ms, the
thermal head generates heat once. The feed amount of 0.141 mm is smaller than the
width (0.18 mm) of the heating elements so that the heat generated at one heating
cycle will overlap with the next heating cycle. This forms a graphic pattern having no
gap between adjacent printed dots.
18.048 mm
(128 elements)
Figure 2.1-1 Heat Generator of Thermal Head
II - 1
0.141 mm (1/180")
0.18 mm