3D Printing Z Seam & How to Eliminate It From Your Prints

One of the most common 3D printing imperfections is a very visible seam.

The Z seam is a verticle line along the Z-axis with an unusual appearance of a raised line or verticle stacking of blobs. The Z seam is the location where each layer of the print starts and stops.

Slicing software like Ultimaker’s Cura does a good job of hiding the Z seam by placing them in a sharp corner or a very tight radius. Additionally, you can hide the Z seam by adjusting retraction settings, reducing nozzle settings, enabling coasting, enabling linear advance, and lowering the print speed.

What Causes Z Seam in 3D Prints

A Z seam in 3D printing refers to the point where each layer of the print starts and ends as the printer builds the object layer by layer. Imagine 3D printing as stacking layers of material, like drawing circles on top of each other. It get’s its name as the seam follows the Z-axis.

The Z seam is where the end of one circle meets the beginning of the next one. A Z seam is formed as the printer stops extruding to move to the next layer. The stop-and-start creates a visible line or small imperfection on the surface of the printed object.

This seam along the Z axis is noticeable because the material slightly builds up on either side of a small gap that forms as the printer transitions between layers.

Z seams don’t have much impact on your prints’ mechanical ability. But, if you’re printing display models where aesthetics are important, a visible Z seam ruins the look of a finished print.

Even if you plan to post-process your finished prints, it makes sense to eliminate the Z seam as the raised Z seam requires more sanding to create a smooth surface.

Fortunately, there are several easy ways to eliminate the Z seam.

How to Eliminate Z Seams

There are several ways to reduce the presence of Z seams in your prints. You can fine tune slicer settings to reduce the visibility of layer transitions and enable slicing software settings to alter where your layers start and stop.

1. Adjust the Z Seam Alignment

Slicing software like Cura allow you to control the alignment of the Z seam. The Z Seam Alignment controls how the bumps are aligned on your 3D print.

The Z Seam Alignment setting doesn’t reduce the impact of layer transitions. Instead, you can hide the seam or reduce its visibility by strategically placing layer transitions in less noticeable areas of your 3D model.

The setting essentially allows you to choose the starting point for each new layer.

Cura offers four options for Z Seam Alignment:

• User Specified: Allows you to manually control where you want the z seam to be located. This could be useful if you have a specific side of the object that won’t be seen. The setting allows you to select a preset location. It’s best to set a coordinate on the inside of your model so you can bury the seam within the print.
• Random: Gives the software total control of where to place the seam. A random Z seam alignment selects random starting points on each layer. The setting eliminates the verticle seam by ensuring that two consecutive layers don’t have the same overlapping layer transition. Moving the layer transitions to different points of the print lessens the overall negative visual impact of the seam. However, it’s not a perfect solution. You may still see ugly-looking blobs or zits scattered around the part, but they will be less noticeable. This setting is best saved for perfectly calibrated 3D printers with minimal Z seam to start.
• Shortest: Sets the layer start point closest to where the previous layer finished. Using the shortest setting speeds up print time but does nothing to hide the Z seam. Do not choose this setting if you want to disguise the Z seam.
• Sharpest Corner: If you have a part with a sharp corner, like a cube, it places the Z seam at the sharpest corner. Essentially, this option hides the z seam in a corner, making it less noticeable as it blends into the vertex. Flat surfaces will not be visually impacted by the seam.

2. Change the Z Seam Corner Preference

The Z seam corner preference setting in slicing software like Cura allows you to select the starting point and location of the Z seam in your 3D print. This setting is crucial in determining how visible or hidden the seam is on the final print. Here’s a breakdown of the different options available for Z seam corner preference and their effects:

1. None: This setting indicates no specific preference for where each layer should start. It leaves the decision to the slicer’s default behavior, which might not be optimal for hiding the Z seam.
2. Hide Seam: This option aligns the Z seam with the innermost corners of the model. Placing the seam in less visible sections of the print makes it less noticeable, though it doesn’t remove it entirely.
3. Expose Seam: Contrary to hiding the seam, this setting places the seam on the outward corner. While often more noticeable than the “hide seam” option, this placement might be less obtrusive in some prints, depending on the model’s geometry.
4. Hide or Expose Seam: This more flexible setting allows the printer to choose either the innermost or outermost corner for placing the Z seam. It gives the slicer some discretion based on the model’s design.
5. Smart Hiding: Similar to the previous setting, this option allows the slicer software (like Cura) to decide the placement of the Z seam. It primarily tries to pick the innermost corners but can also select the outermost corner when necessary. This setting aims to balance seam visibility with print aesthetics intelligently.

3. Retraction Settings

Retraction settings tell your 3D printer to pull back the filament in the hot end (or nozzle) when it stops printing and moves to another location. Retraction reduces the Z seam by preventing filament from oozing or leaking of filament during these non-print movements, such as layer changes.

There are two retraction settings you need to know: retraction distance and retraction speed. Both settings are used together to minimize stringing and the Z seam.

1. Retraction Distance: This setting determines how much filament is pulled back into the nozzle. If the distance is too short, it might not effectively prevent oozing. Conversely, setting it too long could lead to filament grinding or clogs in the extruder. The exact distance varies depending on the printer and filament type, but we use a retraction distance of 6 mm on Bowden tube 3D printers and 0.8mm on direct drive machines.
2. Retraction Speed: The filament’s retraction speed is also important. A faster retraction speed can be more effective in preventing oozing, but if it’s too fast, it might cause issues like filament stripping or excessive wear on the extruder. We use a retraction speed of 50 mm/s on Bowden Tube and direct drive 3D Printers.

We’ve found adjustments to the retraction distance by as little as 1 mm can make a noticeable difference in the Z seam appearance.

Tip: Adjusting your retraction settings too high can create jams or blockages in the printer nozzle.

4. Reduce Nozzle Temperature

Nozzle temperature directly impacts both the 3D printer flow rate and the viscosity of the plastic. Higher nozzle temperatures create more viscous plastic leading to higher extrusion rates and more plastic flowing through the nozzle.

Reducing your nozzle temperature prevents over-extrusion, making the Z seam less pronounced.

You can fine-tune your nozzle temperature with the help of the temperature calibration tower on Thingiverse.

5. Lower the Print Speed

Slower printing, especially of the outer wall, gives the extruder more time to retract filament between printing movements. With more time to extrude filament, there’s less pressure in the 3D printer nozzle between layer transitions reducing Z seam visibility.

Setting an outer wall speed as low as 15 mm/s greatly reduces Z seams in your 3D prints.

6. Enable Coasting

Coasting tells your printer to stop feeding filament into the printer nozzle a bit before the print head finishes each layer.

When coasting is enabled, it relieves pressure inside the heat block. The residual pressure extrudes filament on the last portion of the layer, but eliminates over-extrusion once the print head reaches the end of the layer.

It is important to play around with this setting and try to find a balance, as setting the coasting too high can result in tiny gaps when the printer runs out of material before the end of the layer.

If the coasting value is set too low, it won’t prevent unwanted extrusion at the end of the layer, producing a Z seam.

7. Adjust the Outer Wall Wipe Distance 

Wiping relieves pressure inside the hot end by using a quick side-to-side movement at the end of each layer. Wiping stops melted plastic from dripping before starting the next layer.

8. Enable Linear Advance

Linear advance is a firmware feature adjusts the heat block pressure to keep extrusion constant in relation to printer speed.

When your nozzle makes sudden stops and starts or drastically reduces speed, the pressure inside the extruder produces extra filament. Linear advance lowers the pressure in the nozzle by adjusting retractions based on the nozzle speed. The result is minimal excess material at the layer seam.

Unlike the other options, linear advance is set in the firmware settings of the printer and not in the slicing software. Enabling linear advance is easy enough and significantly improves print quality.

You’ll have to calibrate the K factors for your filament’s material properties and print temperature. But a setting of 0.5 works well for most PLA printing.

9. Use Cura’s Vase Mode

The final way to completely hide Z seams is by using Cura’s Vase Mode, or “spiralize outer contour” in PrusaSlicer. Vase Mode completely eliminates layer transitions as each new layer continues with a smooth transition to build upon the previous layer.

In other words, there’s no stopping and starting between each layer change when Vase Mode is enabled.

The 3D prints don’t have a Z seam because there’s no stopping between layer changes. For that reason, it also produces quicker print times.

Enabling vase mode is most people’s immediate solution to hiding the Z seam.

So why did we put it last on our list?

It’s not that we don’t like the setting, but we believe properly calibrating your 3D printer is a better approach to preventing the Z seam. Though calibrating a printer is tedious, it teaches you valuable skills and makes you a better creator.

But if all else fails, don’t be afraid to give vase mode a try.