What causes this vertical line?

Exactly as the title states, it’s a tube that intakes air, so no holes nor gaps are acceptable, I’ve printed the same model 3 times, and it makes the same line, but any other prints come out fine

This seems to a result of the seam position setting in your slicer. Here it is shown how to hide it in Cura: https://3dprinting.stackexchange.com/questions/20029/how-where-do-i-hide-the-seam


That’s called z seam. It can be very hard to hide them in circular models.

As others have mentioned, that’s the Z seam - the point where the nozzle changes layers on your print. Other than it being ugly, it’s not an issue with the finished print that I’ve seen - and I print a lot of pipe-type shapes.

EDIT - with my SV06, I’ve seen a huge reduction in the Z seam by setting my Retraction amount to 1mm on PLA and .7mm on PETG and lowering the extruder temperature to between 2C and 5C from the manufacturer’s recommended minimum print settings.