①If you are printing from PDF file, it is suggested to use Adobe acrobat software to open PDF file for printing.

②For other printing, please confirm the settings on the driver, set “None” on “Halftone” or “Color option”.

③You can set your "Darkness" and "Speed". By default SP410 Printers are set to print at an average speed of "8". Slowing this speed will result in a higher resolution. Note: Increasing the number for your density / darkness will result in a darker print. Setting the density too high will result in unwanted dark lines and / or label getting too hot and sticking mid-way to the Printer head. Decreasing this number will result in a lighter print. 

Below pictures show you how to set on driver:

iDPRT Window driver

Mac version

Seagull driver in windows