If a narrow vertical row of marks runs up an otherwise smooth print, compare it with the seam positions in the slicer preview. Where a closed perimeter starts and ends, it can leave a small surface mark. Moving that start point can hide a line on the front of a part. It does little for a defect that continues around an entire layer.
Put the seam where the part can afford it
| Shape | First choice to preview | What could go wrong |
|---|---|---|
| A box with a sharp rear corner | Align the seam at the corner or paint a narrow preferred strip there | Rounded corners can move the chosen start onto the visible face. |
| A cylinder with a defined front | Put the seam down the back and check the part’s orientation on the plate | The printer’s rear and the finished object’s rear can be different. |
| A cylinder viewed from every side | Compare one aligned line with random placement or a scarf seam if your profile offers it | Random placement spreads small marks around the surface. A scarf adds toolpath length. |
| A sleeve that fits over another part | Check inner and outer perimeters in preview | A cosmetic improvement on the outside may leave a raised start on a mating surface. |
PrusaSlicer’s seam-position options choose start locations. Its seam-painting tool lets you mark preferred or discouraged areas. These are regions the slicer evaluates, so inspect the sliced result rather than relying on what you painted in the model view. Seam position · Seam painting
Try it on a nameplate holder
Orient the holder as it will sit on the desk. Identify the visible front, the back, and the slot that grips the card. Paint a narrow strip along the back corner. Slice, turn on the seam markers in preview and step through the layers where the slot begins. Look closely at the curved ends where the corner disappears. If the marker wraps onto the front at that height, extend the preferred region onto a less visible face and compare again.
A spiral-vase profile can remove the usual perimeter start above the base on a suitable open vessel. It changes how the object is built, including its wall and top geometry. A closed enclosure, threaded lid or multi-wall sleeve needs a different solution. Prusa’s spiral-vase constraints
Keep the original filament profile while making this comparison. If the physical marks stay in place after the previewed seam moves, reassess the diagnosis before tuning flow. Changing to matte filament may make marks less conspicuous, but leaves their position unchanged. Matte and basic PLA surface finishes