Preventing Overheating Of The Printhead - CognitiveTPG A798 User Manual

Preventing overheating of the printhead

There are restrictions on the duty cycle because of the heat generated by the thermal printhead when printing solid blocks
(regardless of the length of the block in relation to the print line). The restrictions are ambient temperature, the percentage
of time (measured against one minute) of continuous solid printing, and the amount of coverage.
Keep in mind that the ambient temperature may be affected by factors such as direct exposure to sun or close proximity to
heating elements.
Caution: When the duty cycle exceeds the limits shown in the table, the receipt printhead will heat up and shut down. This
may damage the printhead.
To avoid this problem, do one or a combination of the following:
1 Reduce the amount of coverage.
2 Reduce the time of continuous solid printing.
3 Reduce the ambient temperature.
Allowable duty cycle (measured over one minute of continuous printing)
Amount of solid coverage
20%
40%
100%
For reference:
• A typical receipt with text (contains some blank spaces) is approximately 12% dot coverage.
• A full line of text characters (every cell on the line has a character in it) is approximately 25% dot coverage.
• Graphics are approximately 40% dot coverage.
• Barcodes are approximately 50% dot coverage.
• A solid black line is 100% dot coverage.
10/07 10/07
Ambient temperature
25°C 35° C
100% 50%
50% 25%
20% 10%
A798-UG00001 Rev. A A798-UG00001 Rev. A
Chapter 4: Using the Printer
Duty cycle
50° C
Percentage of time that the speci ed
20%
"Amount of solid coverage" can be printed
10%
during a one minute period of time.
4%
Example: at 20% solid coverage,
35° C temperature, a 50% duty
cycle is to be used, resulting in
30 seconds of printing and
30 seconds without printing.
A798 Thermal Receipt Printer: User Guide A798 Thermal Receipt Printer: User Guide
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