Hi guys, I'd like more information if anyone has experience with these spindles, the ones you find in aliexpress with built in motor, they have multiple air connections, the information I got is following:

-Air in ( for tool changing)
-Air/Gas seal (as they call it )
-Dust clearing line
-Air return

from what I understand the air seal prevents any contaminants from entering the spindle, the dust clearing just blows air if opened, however why is there air return line? its connected to which one of the 3? to the air in? what am I supposed to do with that line?


thanks!