Seam Position: Aligned, Nearest, Random and Rear

Every non-continuous wall in a 3D print has to start and stop somewhere, and that start/stop point — the seam — always leaves a small visible mark. Seam position controls where that mark ends up, and Bambu Studio's default is a genuine compromise rather than the best choice for every model.

The options and what they actually do

• Aligned (Bambu's stock default: aligned) stacks seams roughly on top of each other up the Z axis, creating one visible vertical line instead of scattering marks randomly. It's a genuine compromise: consistent and predictable, but that one line is the most visible artifact on an otherwise clean model if it lands somewhere prominent.
• Nearest minimizes travel distance by starting each layer's wall wherever the nozzle already is — fastest printing, but the seam wanders unpredictably across the surface layer to layer, which can look worse than a consistent line in the wrong place.
• Random deliberately scatters the seam so no single point on the model shows a concentrated mark — the best choice when the whole surface needs to look uniformly clean and no single seam line is acceptable.
• Rear forces every seam to the back of the model relative to its build orientation — the right choice when you control the model's final orientation and can guarantee the "back" is the side nobody looks at.

Strength implications, not just looks

A seam is a real discontinuity in the wall, not just a cosmetic one — the wall loop physically stops and restarts there, which is a small, localized weak point. With Bambu's stock 2 wall loops, that means two separate restart points stacked at the same spot on every layer by default (one per loop) when seam position is Aligned — for a purely decorative print that never matters. For a mechanically loaded part, seam position choice becomes a strength decision, not just an appearance one: pointing every seam toward the side that will experience the least stress (or scattering them with Random so no single Z-height carries a concentrated stack of weak points) can matter more than infill density for parts that fail along one visible line.

Choosing per print, not once globally

• Display models where one hidden side exists: Rear, oriented so the seam faces away from the display angle.
• Display models with no hidden side (e.g. a figurine seen from all angles): Random — no single viewing angle catches a concentrated mark.
• Functional parts under directional load: Rear or a manually-placed seam, pointed toward the lowest-stress face — treat it as a strength decision.
• Fast prototyping where looks don't matter at all: Nearest, for the small print-time win.

If a seam is showing up as more than a thin line — a bulge, a gap, or a consistent blob — that's usually an over-/under-extrusion or retraction problem riding along the seam, not a seam-position problem; see the over-extrusion and retraction guides.