How to clean a Thermal Head receipt printer
After printing, the thermal head can be very hot. Be careful not to touch it and to let it cool before you clean it. Do not damage the thermal head by touching it with your fingers or any hard object.
Turn off the printer, open the printer cover, and clean the thermal elements of the thermal head with a cotton swab moistened with an alcohol solvent (ethanol, methanol, or IPA).
Epson recommends cleaning the thermal head periodically (generally every 3 months) to maintain receipt print quality.
Below is a YouTube video on how its done
Print head is a slightly green tinted piece of metal below the cutter head.