© 2002-2008 Sanford, L.P.
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About the LabelWriter 400 Series Printers
The LabelWriter 400 series printers (LabelWriter 400, 400 Turbo, Twin Turbo, and Duo) are
high-performance, low-cost printers used for printing mailing labels, postage, file folder labels,
bar code labels, and more. The printers have a 57 mm wide, 300-dpi print head and a 63 mm
wide paper path. The LabelWriter Twin Turbo printer has two side-by-side label printing
mechanisms in a single printer. The LabelWriter Duo printer has a label printing mechanism as
well as a tape-printing mechanism that can print continuous-length labels in several different
widths (6 mm, 9 mm, 12 mm, 19 mm, or 24 mm), using a 96-dot or 128-dot, 180-dpi print
head
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The 57 mm wide thermal print head uses 672 individually addressable dots to form individual
raster lines of data at 300 dpi. Because they use specially treated, heat-activated paper, the
printers require no ink, toner, or other refills.
All 400 series printer models connect to a host computer through a standard full-speed USB
2.0-compatible interface. When used as raster-only printers, there are no built-in fonts. The host
computer is responsible for sending commands and data to the printer to form each individual
raster line of data. This is generally performed by printer drivers in the host computer that
convert the image of the label into the proper command and data stream required by the printers.
The Print Head
The print head prints the image onto the label by heating a row of resistive elements; this
blackens the thermally sensitive label material. These 672 resistive elements are .085 mm
square and are spaced at 300 per inch on the print head. To print a line, the control electronics
load the desired data into a serial shift register. This shift register has one register for each print
element. A "1" in a register causes the corresponding dot to be printed; a "0" leaves the dot
blank.
The darkness or density of the image depends upon the amount of heat applied to the label
material. The heat depends upon both the temperature of the print head and the amount of
energy applied to the resistive elements. The energy applied to the resistive elements depends
upon the voltage applied and the length of time that the voltage is applied. In order to maintain a
constant density, the control electronics measure the print voltage and the head temperature
before each print cycle, and then calculate the required print strobe time.
The power supply is designed to handle printing an average of 37% of the total dots per line at
full speed. If the voltage drops below 19.3 volts at the print head, printing is suspended until the
power supply recovers to 21 volts.
In order to protect the print head from excessive heat, the control electronics halt printing if the
print head temperature exceeds 80° C. Printing resumes when the print head cools to 55° C.
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The DYMO LabelWriter Duo printer initially shipped with a 96-dot print head for the tape-printing mechanism.
This has been replaced with a 128-dot print head.
