Seam in 3D printing: the vertical line on the surface of a part

Why a seam forms

The outline of each layer is a closed loop. The nozzle has to start it somewhere and finish it somewhere, and at that spot the plastic builds up a little or, on the contrary, is missing. Across all the layers stacked on top of each other this makes a line running up the height of the part. The options a slicer has for dealing with it are described in the OrcaSlicer wiki.

The seam is a property of FDM technology, not a fault in the printer. When printing in a spiral there is no seam, which is why vase mode does not have one either.

How a seam is hidden

• In a corner. A sharp edge hides the seam best, which is why a slicer likes to place it in an outer corner.
• In one line. Even a visible seam looks better when it is all in one row than when it is scattered around the outline.
• With a scarf joint. Newer slicers blend the start and end of the outline smoothly, leaving a barely noticeable mark.
• On the back. The seam can be sent where it is not seen at a normal glance.

What you can do in the design

On a cylinder, a vase or a ball the seam cannot be hidden because there is nowhere to hide it, and it looks like a fine vertical groove. A relief, lettering or a fuzzy skin surface will cover it. On a cube or a small box, a sharp outer corner is enough. If one side of the part matters more, turn the model so the seam is on the opposite side, see model orientation.

Seam and mechanical strength. The seam is mostly just a cosmetic issue. For a part that will be stressed, though, a seam on the outer wall is a place where it can crack, especially if it is aligned in one line. For parts under load it helps to turn the model so the seam lies away from the main stress, or so the load is spread over a larger area.

The seam in your order

We choose the position of the seam according to the shape of the part, and you do not set it in the calculator. We choose these settings ourselves according to the model and material. In the calculator you choose the material, infill strength, scale and number of pieces, and the rest is in the price. A seam is a normal property of FDM printing and we do not regard it as a defect. If a particular surface matters to you, write to us at jakub.novak@boostello.com, but we cannot promise to hide it completely.