3D printing Z-seam: causes and methods to hide marks

In FDM 3D printing, the Z-seam is a common visual artifact appearing as a vertical line of small bumps, reliefs, or flaws on the external wall of a printed object. This occurs because the printer nozzle must start and end the deposition of each perimeter, creating a meeting point between the plastic extremities. When these points align across successive layers, they form a visible seam.

The seam is particularly noticeable on cylindrical objects and smooth surfaces. It is typically not a result of mechanical misalignment of the Z-axis, but rather a consequence of extrusion path planning and material behavior during the opening and closing of perimeters.

Software tools like PrusaSlicer offer various settings to manage this, including Aligned, Rear, Random, and Nearest options, as well as a Seam Painting tool to manually orient the seam. Additionally, techniques such as Scarf Seams are being utilized to smooth the transition between perimeters.