What is the reason for the blur of portable printers?

What is the cause of blurring, black lines, etc. when printing on a portable printer?

Question 1. Some words cannot be printed. Cause: The print head is dirty and the typesetting is incorrect.

Method: Clean the print head, and see if the printed words are overlapped and re-typed.

Problem 2: Unclear when printed and black line appears Cause: The print head is dirty or the print head is broken.

Method: Clean the print head. If not, replace the print head.

Question 3: The font is clear when printing, and the barcode is not clear. Reason: The barcode content is too much and the density is too small.

Method: shorten the bar code content or increase the bar code density. For 200dpi and 300dpi machines, the bar code density is generally above 7mils, that is, the scale factor should be 2 or more, and the bar code printed by the micro printer is clear.