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.
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 is created when the print head begins and ends each layer. As the printer nozzle moves to begin the next layer, it leaves behind a little extra material. When the printer head begins each level at the same starting points, the blobs stack, forming a very visible Z seam.
Z seams don’t have much impact on your prints’ mechanical ability. But, if you’re printing display models where aesthetics are important, a very visible Z seam can ruin the look of a finished print.
Even if you plan to post-process your finished prints, it makes sense to eliminate the Z seam.
Z seams are the result of extra filament during layer transitions. 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. Some extrusion settings prevent the seam, while other settings work to hide it in the print.
To prevent Z seams, you must fine-tune your slicer settings to stop excess material from extruding during layer transitions.
There are several dozen factors that influence print quality. Calibrating a printer to perfection is a time-consuming process.
And even the most finely-tuned printers can still show seam imperfections, which is why it’s often easier to hide the seam.
Here are several slicer and calibration techniques to prevent Z seam:
- Adjust the Z Seam Alignment in Cura
- Change the Z Seam Corner Preference
- Retraction Settings
- Reducing Nozzle Temperature
- Lowering the Print Speed
- Enabling Coasting
- Adjusting the Outer Wall Wipe Distance
- Enabling Linear Advance
- E-Steps and Flow Rate
Adjust the Z Seam Alignment in Cura:
Cura gives you the ability to control the alignment of the Z seam. The setting helps hide the Z seam reducing its overall impact on the print.
It 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. You can use this setting to hide the Z seam by moving it to a side that won’t be visible. The setting allows you to select a preset location, or you may opt to set a coordinate 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 may be your best method if your slicer settings are properly calibrated.
- Shortest: Sets the layer start point in the closest location 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 will align the seam to the corner of the part, which means that the flat surfaces will not be visually impacted by the seam. And the Z seam is relatively unnoticeable as it blends into the vertex.
Change the Z Seam Corner Preference
The Z seam corner preference allows you to select the starting point and location of the Z seam:
- None: This setting tells the slicer you don’t have a preference for where each layer should start.
- Hide Seam: Moves the Z seam alignment to the innermost corners of the model, which should make it less noticeable. Moving the seam position to a less visible section of the print makes it less noticeable but doesn’t remove it entirely.
- Expose Seam: Places the seam in the outward corner. The seam is often more noticeable than choosing “hide seam.” However, there are some prints where the seam will be less noticeable. You’ll just have to experiment.
- Hide or Expose Seam: This setting allows your printer to choose either the innermost or outermost corner.
- Smart Hiding: This setting is similar to the previous one and allows Cura to decide the placement of the Z seam. Smart hiding attempts to pick the innermost corners as much as possible but still allows the outermost corner to be selected.
Retraction Settings
Retracting settings is a Cura slicing setting that uses the extruder stepper motor to pull the filament out of the heat block when the print head finishes its path.
Pulling the filament away from the nozzle will help reduce nozzle pressure. Enabling retraction prevents over-extrusion, which is a cause of the visible z seam.
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.
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.
Reduce Nozzle Temperature
Nozzle temperature directly impacts both the flow rate and the viscosity of the plastic. Naturally, the higher the nozzle temperature, the lower the plastic’s viscosity will be. This will lead to higher extrusion rates and more plastic flowing through the nozzle.
The over-extrusion and a more noticeable blob along the seam.
You can fine-tune your nozzle temperature with the help of the temperature calibration tower on Thingiverse.
Lower the Print Speed
Another trick to reduce the effect of Z seams is to lower the print speed. When you print at a speed that’s too fast, it doesn’t give the extruder enough time to retract the filament between printing movements.
Lowering the print speed allows for more consistent extrusion by giving the hot end the time it needs to retract the filament properly.
If you want to fix issues with the Z seam, you’ll want to adjust your Outer Wall Speed. Cura sets the Outer Wall Speed to 25 mm/s by default. And it should work well for most prints.
Reducing the Outer Wall Speed to 15 mm/s leads to less pressure inside the print head and a reduced Z seam.
Enable Coasting
Coasting tells your printer to stop feeding filament into the printer nozzle as the print head finishes each layer.
When coasting is enabled, it relies on the pressure inside the heat block to continue to extrude filament on the last portion of the layer but limits the over-extrusion seen on the seam.
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.
To reduce Z seams further, it sometimes helps reduce the Travel Speed in addition to coasting.
Adjust the Outer Wall Wipe Distance
The outer wall wipe distance relieves pressure on the print head by traveling side to side for a short time after each layer.
Outer Wall Wipe Distance is a setting specifically created to reduce Z seams in Cura.
The wipe setting allows the nozzle to travel further at the end of each layer without extruding the filament. The setting works similarly to retraction, but instead of reversing the extrusion, it “wipes” the contour closed.
Adding a wipe to your print won’t eliminate the Z seam. But it makes the seam more manageable for post-processing.
Enable Linear Advance
Linear advance simply 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.
Tip: Don’t enable coasting if you have enabled linear advance. The two settings don’t work well when combined.
Use Cura’s Vase Mode
The final way to completely hide Z seams is by using Cura’s Vase Mode, or “spiralize outer contour.” The setting tells your 3D printer to print in an endless “spiral.” In other words, there’s no stopping and starting between each layer change.
Layer transitions are not as abrupt with vase mode enabled as regular printing. Each new layer continues with a smooth transition to build upon the previous layer.
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.
Tip: Prusa has a similar setting called Spiral Vase Mode.