How to Fix Z Seam Problem in 3D Prints

Z seam is a common print quality issue found in almost every 3D print. Although it is generally present, its prominence can vary depending on several factors. This issue arises from the way a 3D printer extrudes material and transitions between layers, especially when the printhead moves to the next layer. Let's break down the causes of the Z seam, along with effective methods for minimizing or even preventing it.

What Is a Z Seam?

A Z seam manifests as a vertical line of raised marks, blobs, or bumps on the surface of a 3D print. It typically forms when the nozzle moves from the end of one layer to the starting point of the next. During this transition, even though the printer stops extruding material, pressure builds up in the hot end, leading to a slight, unintended extrusion. This causes the filament to ooze out and deposit excess material on the surface of the print, resulting in the visible Z seam.

The problem becomes more prominent if the printer’s extrusion is not properly calibrated or if there are issues like over-extrusion or under-extrusion. Additionally, the design of the model, especially when it has smooth or curved surfaces, can make the Z seam more noticeable.

Causes of Z Seam Issues in 3D Prints

The Z seam is primarily caused by two main factors: the extrusion process and the behavior of the slicing software.

1. Pause and pressure release: When the printhead finishes a layer, it halts extrusion and pauses for a split second to transition to the next layer. During this pause, the nozzle remains pressurized, and the built-up pressure causes a small amount of filament to ooze out. This excess material is then deposited at the transition point, creating a bump.
2. Slicer settings: Most slicers, such as Cura or PrusaSlicer, automatically align the starting point of the new layer directly above the ending point of the previous layer. This alignment results in a vertical line of bumps—the Z seam. While it may seem like the slicer could simply shift the starting point to a different location, doing so might increase print time and introduce new issues like stringing.
3. Model geometry: Certain designs exacerbate the appearance of Z seams, especially models with smooth or curved surfaces. The seam becomes more noticeable when there are no sharp corners or edges to hide it.

Cura 5.3: Notable Issue with Z Seam

Some users of Cura 5.3 reported encountering artifacts, such as random Z seam blobs, especially on curved surfaces. These artifacts were attributed to an issue in the slicing algorithm. Fortunately, this problem appears to have been resolved in later versions, such as Cura 5.7. However, if you notice similar artifacts, reverting to an earlier version like Cura 5.2 may be a temporary solution.

How to Minimize and Prevent Z Seam

While eliminating Z seam may be impossible, there are various methods to reduce its visibility or impact. These solutions range from adjusting print settings to utilizing specific features in the slicing software.

1. Enable Linear Advance

Linear advance is a feature that helps regulate pressure in the nozzle based on the print speed, preventing excess filament from oozing out at the end of a layer. This can significantly reduce the occurrence of Z seam bumps, especially when printing at higher speeds.

• How It works: Linear advance adjusts the extrusion in real-time, ensuring the pressure inside the nozzle remains constant regardless of changes in print speed or direction.
• Implementation: To use linear advance, you may need to update your printer’s firmware or invest in a high-speed 3D printer equipped with this feature, such as the Anycubic Kobra 2 Neo. This printer, with a speed of 250mm/s, supports the linear advance feature and can deliver better print quality.

2. Lower Hotend Temperature and Reduce Printing Speed

If your printer lacks the linear advance feature, another effective way to reduce Z seam issues is to adjust the temperature and speed settings.

• Lowering temperature: Reducing the nozzle temperature helps minimize the flow rate of the filament, making it less likely to ooze out between layers.
• Slowing down print speed: Printing at slower speeds allows more time for the extruder to retract the filament properly, reducing the chance of leaving unwanted blobs at the transition point.

3. Optimize Retraction Settings

Retraction is a feature available in most slicing software that pulls filament back into the nozzle when the printhead moves between layers. Proper retraction can significantly reduce Z seams by minimizing the excess material extruded at the start of the next layer.

• Adjust Retraction Distance and Speed: Insufficient retraction distance or slow retraction speed can lead to over extrusion.  However, be careful not to over-adjust these settings, as too much retraction can cause filament clogs or gaps between layers.

4. Enable Coasting

Coasting is a feature that stops filament extrusion just before the end of a layer. This helps release internal pressure in the nozzle, reducing the chances of unwanted blobs or stringing.

• Setting coasting parameters: You can adjust coasting volume, speed, and other related parameters in slicers like Cura or Simplify3D. While this feature can be effective, it may require careful calibration, especially for novice users.

5. Calibrate Extrusion Settings

Properly calibrating your printer’s extrusion settings is crucial for reducing Z seam and other print quality issues. There are several factors to consider when optimizing extrusion:

• E-Steps calibration: Calibrating the extruder’s steps (E-steps) ensures that the printer extrudes the correct amount of filament. When properly calibrated, the printer will consistently extrude the required amount of material, reducing over-extrusion and the likelihood of Z seam bumps.
• Flow rate: Adjusting the flow rate (extrusion multiplier) controls how much material is pushed through the nozzle. Fine-tuning this setting after calibrating the E-steps can help improve extrusion consistency.
• Nozzle temperature: Higher nozzle temperatures can lead to over-extrusion, making the Z seam more pronounced. Finding the ideal temperature for your filament can minimize the issue.

6. Use Slicer Features to Hide the Z Seam

If minimizing the Z seam through extrusion and temperature settings is not sufficient, you can also use slicer settings to hide the seam. Most slicers offer options for controlling where the Z seam appears on the model.

• Z Seam alignment: In Cura, for example, there are several options for aligning the Z seam:

-User Specified: This option allows you to manually choose where the Z seam will appear. You can set it to a less visible area, such as the back of the model.

-Shortest: This setting aligns the Z seam along the shortest path, resulting in a straight line of bumps. While efficient, it may not be ideal for aesthetics.

-Random: The random setting places the seam at different points on each layer, dispersing the bumps. This can make the seam less noticeable but may still leave visible artifacts.

-Sharpest corner: For models with sharp angles, placing the Z seam on the sharpest corner helps hide it, blending the seam into the model’s geometry.

-Seam corner preference: Some slicers allow you to further refine where the seam is placed:

-Hide seam: This setting places the Z seam on the innermost corners of the model, making it less visible.

-Expose seam: In contrast, exposing the seam places it on the outermost corners, which could be preferable depending on the model’s design.

7. Spiralize Outer Contour (Vase Mode)

For models that have simple, continuous contours, activating "Spiralize Outer Contour" or "Vase Mode" can effectively eliminate the Z seam. This mode removes layer transitions entirely by keeping the nozzle in constant motion while printing a single continuous layer.

• Smooth spiralized contours: When using vase mode, enabling this setting ensures the nozzle movement is smooth, further reducing the visibility of any potential Z seam.

Best 3D Printing Software 

Having looked at 3D print Z seam, it’s also important to have a look at the best 3D printing software that you can use to create your files and even prepare them for 3D printing. There are many 3D printing software that are available, but we recommend using SelfCAD. SelfCAD is an easy-to-use 3D design that comes with all the tools that you need to create your files from scratch or even edit the existing ones. Get to know the overview of SelfCAD in the video below.

In addition to 3D modeling tools, SelfCAD also comes with an in-built online slicer that you can use to slice your files and generate the G-code to send to your 3D printer. Learn how to slice STL files in SelfCAD in the video below.

Z Seam Fix: Simple Tweaks for Seamless Prints

The Z seam is an unavoidable issue in 3D printing, but with the right adjustments, its impact can be significantly minimized. Whether through enabling advanced features like linear advance or optimizing retraction and extrusion settings, there are numerous ways to improve print quality. 

---

Enjoy powerful modeling, rendering, and 3D printing tools without the steep learning curve.

Need to learn 3D modeling? Get started with interactive tutorials.