How to Fix Z Seam or Vertical Seam in 3D Printing

Unlike resin 3D printing, the limitations of FDM 3D printing make it unable to create highly detailed objects and difficult to avoid certain imperfections, such as the Z seam. Fully eliminating the Z seam mark can be impossible, but we can reduce the visibility of the Z seam by calibrating the printer and adjusting the print settings. Today, we will discuss how to fix and reduce the 3D print Z seam.

What Causes 3D Printer Z Seam?

3D Print Z Seam

A Z seam is a vertical line of raised marks or blobs on the outer wall of a 3D print. After one layer is printed, the nozzle will have an empty travel to the starting point of the next layer. Within this distance, due to the high pressure inside the nozzle, even if the printer has stopped extruding, a small amount of filament can still leak out uncontrollably and deposit, forming an invisible Z seam on the model's surface.

The geometry of the model you're printing can significantly affect the visibility of the Z seam, especially for ones that are exceptionally smooth and have no sharp corners to hide the seam. When your printer experiences under-extrusion or over-extrusion issues, the seam will be more noticeable.

You can make it less noticeable by adjusting your print settings in slicing software. Many slicers, such as Cura and PrusaSlicer, now have tools designed to resolve how to hide the Z seam issue, but these tools are not the main focus here. Additionally, post-processing can truly help get rid of the Z seam. Below, we list the reasons why the Z seam occurs in your 3D prints.

  • Not using Linear Advance.
  • Hotend temperature is too high.
  • Printing speed is too fast.
  • Incorrect retraction settings.

How to Reduce 3D Printing Z Seam

1. Enabling Linear Advance

Linear Advance

Due to the increased printing speed, when the nozzle changes its print direction, excess plastic drops on the model's corners, causing a rough surface and Z seam. Linear advance ensures that the nozzle generates the correct pressure based on the print speed, almost eliminating the rough quality and reducing Z seam marks.

You can obtain this feature by upgrading the printer firmware or by directly investing in a high-speed 3D printer with Linear Advance, such as Anycubic Kobra 2 Neo, available for under $200. With a maximum speed of 250mm/s and an average speed of 150mm/s, it is equipped with popular Marlin firmware, and even beginners can easily get better print quality.

2. Lowering Temperature and Slowing Down Speed

FDM 3D Printing

If your printer firmware lacks the Linear Advance feature, the most direct way to reduce the Z seam defect is to simply lower the nozzle temperature and slow down the printer speed. Print temperature affects the flow rate of the plastic material, making it easier to ooze out of the nozzle. Printing too fast can also result in 3D printing seams, as the extruder doesn't have enough time to retract material during nozzle travel.

3. Adjusting Retraction Settings

Z Seam Test Model

(Perfect result for the test model.)

Retraction settings are available in many slicers. When the nozzle completes a layer and travels without extruding, the extruder gear pulls the filament back to reduce the deposition of excess material into the Z-seam. Insufficient retraction distance and slow retraction speed can lead to over-extrusion issues, so you need to optimize them. Do not over-adjust them, as it may lead to filament clogs and gaps in your layers. Different extruders may require different values for retraction, and you can refer to another guide on how to adjust retraction settings.

4. Enable Coasting

Enable Coasting

(Image source: Ultimaker)

Coasting is a feature that comes from slicers, and you can find it in Cura and Simplify3D. It involves stopping the filament extrusion in advance just before the end of a layer. The nozzle then performs a travel move to release internal pressure, reducing issues such as stringing, blobs and zits, and Z-seam on the surface. To make the most of this feature, you need to properly adjust many parameters like coasting volume, minimum volume before coasting, coasting speed, and bridge wall coasting; otherwise, other problems may arise. This can be a challenging task for a 3D printing novice. In such cases, directly lowering the print speed or using a 3D printer that supports the Linear Advance feature can reduce costs and errors.

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