Service manual

5-2 DECcolorwriter 1000
5 Theory of Operation
Print engine
Wax transfer — the engine's printing technology
To make colored prints, the print engine uses a color printing method called sequential
surface thermal transfer printing. Simply said, the print engine prints by melting dots of
colored wax from a Mylar ribbon onto a piece of paper. The benefits of this method are
high-resolution printing, easy maintenance, and fast printing.
The print process
Figure 5-1 illustrates the printing process employed by the print engine. In the printing
process, a single piece of clay-coated paper (or transparency film) is drawn past a thin
Mylar ribbon, called a transfer roll, which is coated with sequential bands of colored
wax: yellow, magenta and cyan. A heating device, called a thermal head, melts the
colored wax from the transfer roll onto the paper. The wax melts at approximately 68
o
to
70
o
C (154
o
to 158
o
F). The thermal head is an electrical device containing over 2400
individually controlled heating elements aligned parallel to the short axis of the paper it
prints upon. And because the row of thermal elements span the width of the page, the
print engine prints an entire line at one time; this accounts for the print engine's fast print
time. The printer uses a special clay-coated paper which presents a smooth, flat surface
for the wax to adhere to.