A 3 in 1 fan for a 3D printer's print head typically consists of three separate fans mounted together or three blades on a single fan. The purpose of these fans is to cool the printed object and prevent warping during the printing process.
One of the fans is usually directed at the hot end of the print head to cool the nozzle and prevent heat from building up and melting the plastic filament. The other two fans are usually directed at the printed object to cool it quickly and prevent it from warping.
Having a 3 in 1 fan can help simplify the design of the 3D printer and save space, as multiple fans can take up a lot of room. Additionally, having a dedicated fan for the hot end of the print head can help to prolong the life of the print head by preventing it from overheating.
If you're looking to upgrade your 3D printer with a 3 in 1 fan, make sure to check the compatibility with your printer's make and model, and ensure that the fan provides sufficient cooling for the type of filament you plan to print with.