If you’ve ever printed a great-looking model only to spot an unsightly line or blob running vertically along its side, you’re dealing with a Z seam. This seam is the point where your printer transitions between layers, leaving behind small imperfection that almost looks like a zipper.
Thankfully, you don’t have to settle for visible seams. In this guide, you’ll learn exactly why Z seams appear, and I’ll give you practical tips on how to hide or eliminate them.
Causes Of Z Seam
If you’ve ever noticed a vertical line or bump running up the side of your 3D print, you’re dealing with a Z seam. It’s one of those frustrating imperfections that can take an otherwise perfect print and make it look… less perfect.
The Z seam is where your 3D printer stops and starts each layer. The Z seam forms where your slicer instructs the nozzle to extrude at a specific point on each new layer. Because the printer has to stop, reposition, and then resume printing, the transition point between layers appears as a zipper or tiny zits spread throughout your model.
Now that you know what causes Z seams, let’s look at how to minimize their appearance with the right slicer settings.
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.
Hiding the Z Seam (Slicer Techniques)
Now that we know why Z seams happen, let’s talk about how to hide them using slicer settings. Modern slicers, like Cura, PrusaSlicer, and Bambu Studio let you control where the seam appears, helping you tuck it away where it’s less noticeable.
Instead of letting the slicer randomly place the seam, you can take control and position it strategically. Each slicer offers slightly different options:
Cura Z Seam Alignment Options:
- Sharpest Corner – Places the seam along the sharpest edge of the model, making it less noticeable. This works well for objects with sharp geometry and well defined corners.
- User Specified – Let’s you manually set the seam location by choosing coordinates or selecting a model face. This is the best option for complete control.
- Random – Scatters the seam across different layers, making it less visible on curved surfaces. One downside is that you’ll often find zits and blobs scattered throughout the print where the layer transitions occur.
- Shortest – Positions the seam where the nozzle has to move the least between layers. This setting reduces print times but doesn’t choose the cleanest seam placement.
PrusaSlicer Seam Position Options:
- Nearest (Edge): Attempts to place the seam on the nearest edge of the current layer. This is effective for models with sharp corners where the seam blends into the geometry.
- Aligned: Aligns the seam consistently throughout the object by placing it nearest to the start point of the previous layer. This creates a uniform seam line, which is easier to manage during post-processing.
- Random: Chooses a different point for each layer’s seam, dispersing the seam’s visibility but potentially resulting in a less smooth surface due to minor imperfections scattered across the model.
- Rear: Positions the seam towards the rear side of the print bed (maximum Y direction), attempting to place it in less visible areas. It also tries to avoid overhangs and prefers corners for seam placement.
- Seam Painting: Starting with PrusaSlicer 2.3, the Seam Painting tool allows detailed control over seam placement. Users can manually paint ‘Seam enforcers’ or ‘Seam blockers’ directly on the model, specifying exactly where seams should or shouldn’t be placed, giving you more control over seam visibility.
Bambu Studio Z Seam Settings:
- Seam Position Settings:
- Random: Distributes the seam across different locations to prevent a continuous vertical line, useful for minimizing seam visibility on curved surfaces.
- Aligned: Stacks the seam in a straight line, making it easier to locate and potentially post-process, suitable for models where the seam can be placed on a less visible side.
- Back Left/Right, Front Left/Right: Allows positioning of the seam in a specific quadrant of the model, enabling strategic placement on less noticeable areas.
- Seam Hiding Mode: Automatically adjusts seam placement based on the model’s geometry to minimize visibility, simplifying the process for users seeking optimal seam positions without manual adjustments.
- Seam Painting: Similar to PrusaSlicer’s feature, this tool enables manual definition of seam placement by painting directly on the model, offering precise control over seam location.
- Seam Gap Filling: Slightly over-extrudes at the seam to create a smoother transition, effectively blending the seam into the surrounding surface and reducing its visibility.
Minimizing the Appearance of Z Seams With Slicer Settings
Even if you can’t eliminate Z seams, you can minimize their appearance by adjusting key slicer settings. Here are some of the most effective changes you can make to reduce seam visibility before your print even begins:
Retraction and Coasting
Retraction settings control filament moving in and out of your nozzle to prevent blobs and stringing. Filament can ooze slightly when the nozzle moves between layers, creating bumps at the seam.
Proper retraction settings prevent filament from oozing out of the nozzle at layer transitions. Here are my recommendations:
- Retraction Distance: This determines how far filament is pulled back into the nozzle between moves. Start around 5–7 mm for Bowden-style extruders or 0.5–1 mm for direct-drive extruders.
- Retraction Speed: Controls how quickly filament is retracted. Start with 35–50 mm/s and adjust as needed.
- Coasting: This setting stops extrusion slightly before the end of a layer line, allowing built-up pressure in the nozzle to dissipate, preventing oozing. Set a coasting distance of around 0.2–0.5 mm and adjust gradually if blobs still appear.
Outer Wall Wipe Distance
Outer wall wipe adds a short overlapping move at the end of each layer, which helps blend filament at layer transitions, reducing gaps or bulges. Start with a setting around 0.2–0.4 mm.
Pressure Advance or Linear Advance
Pressure builds up inside the nozzle when printing. The pressure can cause inconsistent extrusion at layer starts and stops. Some printer firmwares compensate for the nozzle pressure with a Linear Advance or Pressure Advance feature.
Start with recommended Linear Advance settings provided by your printer’s manufacturer and make slight adjustments (increments of 0.05–0.1) to improve results. A well-calibrated setting ensures uniform extrusion and reduces visible bumps or gaps at seams.
Temperature Settings
High nozzle temperatures increase filament flow, creating blobs at layer transitions. Lowering your nozzle temperature by 5–10°C reduces filament ooze, helping minimize seam visibility. Experiment carefully to find the lowest practical temperature for your filament.
Your goal should be to print with the lowest temperature without gaps. Most PLA filaments work well at 190-210°C.
Print Speed
Reducing print speed gives filament more time to adhere cleanly at layer transitions, smoothing out seams. Lower your outer wall speed by approximately 10–20% compared to standard printing speeds to achieve cleaner transitions at seams. You can set your outer wall speeds as low as 25–35 mm/s to balance print quality and efficiency.
Post-Processing to Eliminate Z Seams Completely
It’s not always possible to eliminate or hide the Z seam, even with careful slicing adjustments and a perfectly calibrated 3D printer. Post processing your 3D print is a great way to eliminate seams and create a smooth finish on your prints.
The following steps will eliminate seams from your prints.
Step 1: Sanding and Polishing
Start gently with low-grit sandpaper (around 200–400 grit) and carefully sand along the seam line. Gradually move to higher grits (600–1200) for a smoother finish.
When using higher grit sandpaper of 600 grit or more, it’s a good idea to try wet sanding. Add a small amount of water to the sandpaper or model and sand as usual. The water helps keep down dust, and prevents the sandpaper from scratching your model’s surface.
Step 2: Filling and Priming
For deeper or stubborn seams, use filler to fill the gap. Products like automotive spot putty or wood fillers work great and can be sanded for a seamless finish. Apply a small amount along the seam, let it dry, then sand until smooth.
Step 3: Prime and Paint
After filling and sanding, I like to apply a coat of automotive filler primer. The primer is designed to fill small gap,s so in addition to eliminating the z seam, it also works to fill layer lines. You’ll need to be careful on miniatures as the primer can hide small, intricate details in your print.
After priming your model, you can paint away. Acrylic paints and spray paints work great for 3D printing. With just a bit of post-processing, you can achieve professional-quality finishes and eliminate Z seams from your final prints.
