Print Quality

Z-Seam & Scarf Seam Guide

Everything you need to know about seam types, scarf joints, and slicer settings to get rid of that line running down your prints.

What Is a Z-Seam?

Every perimeter loop on every layer has to start somewhere and end somewhere. Where those two points meet is the seam.

When your printer finishes one perimeter and moves to the next layer, the nozzle has to stop extruding, retract, travel up, and start extruding again. That stop-start transition leaves a small bump, zit, or line on the surface of the print. On parts with flat faces or sharp corners, you can often hide this transition in geometry. On cylinders and organic curved shapes, there is nowhere to hide it — and it shows.

The Z-seam gets its name because the nozzle moves in the Z direction (up) between layers. Every FDM print has one, and on most prints it is the single most visible surface imperfection. Glossy and silk filaments make it worse because they reflect light off the bump. Transparent filaments are even more unforgiving — you can see the internal overlap through the wall.

Your slicer controls where the seam lands and, in more recent slicers, how the extrusion starts and stops at the seam point. Understanding the options is the first step to dealing with it.

Seam Types Compared

Every slicer offers multiple seam placement strategies. Each has tradeoffs — there is no single best option for all parts.

Aligned
All seams stacked on a single vertical line. Predictable and easy to sand or post-process. Creates one visible line on the surface — very obvious on cylinders but easy to orient toward the back of a part. Best when you can control part orientation on the build plate.
Random
Seam position randomized every layer. Eliminates the single vertical line but scatters small zits across the entire surface. Generally the worst option for surface quality. Each random point is a tiny blob that catches light differently. Avoid unless you are sanding the entire part anyway.
Sharpest Corner
Slicer tucks the seam into the sharpest available corner on each layer. Hides the seam in geometry where it is least visible. Best automatic option for parts with corners and edges. Struggles on cylinders and organic shapes that have no sharp corners to hide in.
Nearest
Minimizes nozzle travel by placing the seam at the closest point. Slightly faster print times but unpredictable placement with poor cosmetic results. Rarely a good choice for visible parts. Useful for internal structures or functional prints where speed matters more than appearance.
Scarf Joint
Instead of a blunt start and stop, the slicer gradually ramps extrusion up and down to create a smooth tapered overlap. Eliminates the blob entirely. The biggest recent innovation in seam handling. Covered in detail in the next section.
Default recommendation: Use sharpest corner as your everyday default. Switch to scarf joint for cosmetic prints with curved surfaces. Use aligned when you plan to sand or hide the seam against a wall.

Scarf Seams Explained

The scarf joint is the most effective seam treatment available in modern slicers. Here is how it works and where it came from.

A traditional seam works like this: the nozzle starts extruding at full width, prints the entire perimeter, then stops extruding and retracts. Where the start meets the end, you get a double-thickness overlap — a visible bump. No amount of retraction tuning fully eliminates it because the fundamental problem is geometric: two blunt ends overlapping.

A scarf joint seam takes a different approach. Instead of starting at full extrusion width, the slicer gradually ramps up extrusion volume over the first few millimeters of the perimeter. At the end, it gradually ramps down. Where the tapered start overlaps the tapered end, the combined extrusion volume equals exactly one normal wall width. No excess material, no blob, no gap. The result is a perimeter that looks continuous, as if the seam does not exist.[2]

The name comes from woodworking. A scarf joint connects two boards by cutting matching angled faces, so they overlap into a flush joint instead of butting end-to-end. The same principle applies here — a gradual taper instead of an abrupt transition.

History & Slicer Support

Scarf joint seams were first implemented in OrcaSlicer around 2024, building on earlier community experiments with flow ramping. The feature proved so effective that BambuStudio adopted it quickly (the two slicers share a codebase forked from PrusaSlicer). PrusaSlicer 2.8 added its own scarf seam implementation in late 2024.[1]

Cura does not have scarf seam support as of early 2025. Cura users can partially mitigate seam visibility with coasting and wipe settings, but cannot achieve the same result. If seam quality is a priority, OrcaSlicer is free and worth trying even if Cura is your main slicer.

How the Flow Ramp Works
Start of Perimeter
Extrusion width begins near zero and linearly ramps up to full width over a configurable distance (typically 10-15mm). The nozzle is moving at print speed the entire time — only the flow rate changes.
End of Perimeter
Extrusion width ramps down from full to near zero over the same distance. The taper zone at the end overlaps the taper zone at the start. Combined, they equal one normal extrusion width.
Why It Works
Traditional seams fail because full width + full width = double width at the overlap. Scarf seams succeed because half width + half width = normal width. The transition is smooth enough that the surface looks continuous.

Slicer Settings

Exact setting names and locations for each slicer. These change between versions — locations listed are accurate as of early 2026.

Slicer Setting Name Location Key Options
OrcaSlicer Scarf joint seam Quality → Seam Toggle on/off. Separate scarf joint speed setting, scarf joint flow rate, option to apply to inner walls. Most configurable implementation.
BambuStudio Scarf joint seam Quality → Seam Same settings as OrcaSlicer (shared codebase). Speed and flow options available. Scarf angle configurable.
PrusaSlicer 2.8+ Scarf joint seam Print Settings → Seam Toggle under seam options. Fewer tuning knobs than OrcaSlicer — PrusaSlicer handles the taper length automatically.
Cura Not available — No scarf seam support. Use coasting (try 0.064mm³) + wipe distance as partial workaround. Reduces but does not eliminate the seam bump.
OrcaSlicer scarf speed: If you set a dedicated scarf joint speed, keep it at or below your outer wall speed. Faster scarf speeds make the flow ramp less precise because the extruder has less time to respond to volume changes.
Inner walls: OrcaSlicer lets you apply scarf to inner walls too. This can help on thin-walled parts but adds processing overhead. Start with outer walls only and enable inner if you still see artifacts.
Cura workaround: Enable coasting at 0.064mm³ (stops extruding slightly before the end of the perimeter to relieve pressure) and set a wipe distance of 1-2mm. Not as good as scarf, but noticeably better than nothing.

When to Use Scarf Seams

Scarf seams help most on materials and geometries where seams are most visible. Not every print needs them.

Biggest Benefit
Silk & Glossy PLA
Glossy surfaces reflect light directly off the seam bump, making it the most obvious imperfection on the part. Scarf seams make the biggest visible difference here. See all material types →
PETG
PETG is prone to blobbing and stringing at seam points due to its higher melt viscosity. The gradual flow ramp of scarf seams avoids the pressure spike that causes PETG seam blobs.
Transparent Filament
Translucent and clear filaments show internal overlap through the wall. A scarf seam's flush overlap is far less visible than the double-wall bump of a traditional seam.
Cylinders & Organic Shapes
No corners to hide the seam in. On a smooth cylinder, every seam type except scarf leaves a visible mark. This is where scarf seams earn their keep.
Moderate Benefit
Standard PLA
Seams are visible but less glaring than on glossy variants. Scarf helps, especially on curved surfaces, but the improvement is less dramatic.
ABS / ASA
These materials handle retractions reasonably well, and their matte finish helps hide seams naturally. Scarf still improves curved parts but the baseline is already decent.
Least Benefit
Matte PLA / Textured Filaments
Matte surfaces scatter light and naturally hide seam bumps. Wood-fill, carbon fiber fill, and other textured filaments do the same. Scarf still works but the visual improvement is marginal.
Skip For These
Vase / spiral mode: There is no layer seam in spiral mode — scarf does not apply. Very small perimeters: If the perimeter is shorter than the taper distance, the ramp cannot develop properly and may cause artifacts instead of fixing them.

Scarf Seam Gotchas

Scarf seams work well when the conditions are right. Here is what can go wrong and how to avoid it.

Short perimeters cause artifacts. The taper zone needs space to ramp up and down (typically 10-15mm). On small holes, thin pins, or tiny features, the taper cannot develop fully and you may get under-extrusion or gaps instead of a clean join. Some slicers auto-disable scarf on short perimeters; check your slicer's behavior.
Pressure advance must be calibrated first. Scarf seams rely on your extruder responding predictably to flow changes. If pressure advance (Klipper) or linear advance (Marlin) is uncalibrated, the actual flow will lag behind what the slicer expects, and the taper will not be smooth. Calibrate pressure advance before enabling scarf →
Taper zone landing on sharp corners. If the scarf taper happens to overlap a sharp corner, the reduced extrusion width at that corner can cause a visible gap or under-extrusion. Use the seam position setting (e.g., aligned to a flat area) to steer the taper zone away from corners.
High print speeds reduce precision. At very high speeds (>200mm/s), the extruder has less time to respond to the gradual flow ramp, making the taper less smooth. If your slicer offers a separate scarf speed setting, keep it moderate — 50-80% of your outer wall speed is a good starting point.
Not retroactive. Changing the seam setting in your slicer does not fix already-sliced G-code. You need to reslice the model and send the new file to your printer. Sounds obvious, but it catches people who change settings mid-queue.
Bowden extruders are harder to tune. Direct drive extruders respond faster to flow changes, which makes scarf tapers more precise. Bowden setups have inherent delay from the tube length. It still works, but you may need a slightly longer taper distance and lower scarf speed.

Seam Optimization Tips

These apply to all seam types, not just scarf. Get these right first — they make every seam strategy work better.

Calibrate pressure advance / linear advance first. This is the single most impactful tuning step for seam quality. Pressure advance compensates for the delay between extruder motor commands and actual filament flow. Without it calibrated, every seam type will blob at the start and gap at the end. Speed & pressure advance guide →
Enable coasting for non-scarf seams. Coasting stops extrusion slightly before the perimeter ends, using residual pressure to finish the line. In Cura, start with 0.064mm³ coasting volume. OrcaSlicer and PrusaSlicer handle this differently — check your slicer's documentation.
Align the seam to the back of the part. If you are using aligned seam positioning, rotate the model on the build plate so the seam line faces a wall, the back of a display piece, or any surface that will not be seen. This costs nothing and hides the seam for free.
Use sharpest corner as your default. For everyday prints with mixed geometry, sharpest corner gives the best automatic results without any manual positioning. Switch to scarf for cosmetic curved parts, aligned for parts you plan to sand.
Clean your nozzle tip. Residual filament on the nozzle tip gets dragged to the seam start point, adding extra material to an already-sensitive area. A quick wipe with a brass brush before starting a cosmetic print makes a noticeable difference.
Tune retraction before blaming the seam type. Under-retraction causes oozing at the seam. Over-retraction causes gaps. If every seam type looks bad, the problem is likely retraction distance or speed, not the seam positioning itself. Troubleshooting guide →
Reduce outer wall speed for cosmetic parts. Slower outer walls give the extruder more time to respond to flow changes, especially at the seam. If scarf seams look good but not perfect, try dropping outer wall speed by 20-30% and see if the taper smooths out.
Browse Filament on SpoolHound Filament Materials Guide →

Frequently Asked Questions

What is a scarf seam in 3D printing?
A scarf seam (or scarf joint seam) gradually tapers extrusion volume up at the start of a perimeter and down at the end, so the overlap zone has the same combined volume as a normal extrusion width. This eliminates the blob or bump that traditional seams leave behind. The name comes from woodworking's scarf joint, where two pieces are cut at matching angles for a flush join.
Which slicers support scarf seams?
OrcaSlicer introduced scarf joint seams around 2024 and remains the most configurable implementation. BambuStudio shares OrcaSlicer's codebase and has the same feature. PrusaSlicer added scarf seam support in version 2.8. Cura does not support scarf seams as of 2025 — the closest workaround is coasting at 0.064mm³ combined with wipe distance.
Does scarf seam work with all filament materials?
Scarf seams work with most materials but benefit some more than others. Silk and glossy PLA, PETG, and transparent filaments see the biggest improvement because seams are most visible on shiny and clear surfaces. Matte PLA, wood-fill, and carbon fiber filaments already hide seams through surface texture, so the visual improvement is smaller. Very fast-oozing materials may not respond well to the gradual flow ramp.
Should I use scarf seam for every print?
Not necessarily. Scarf seams are best for cosmetic parts, especially curved or cylindrical shapes where traditional seams create a visible line. For functional parts, parts with sharp corners that naturally hide seams, or very small perimeters where the taper cannot develop properly, sharpest corner positioning is often a better default. Use scarf when appearance matters; use sharpest corner for everything else.
Can I combine scarf seam with aligned seam positioning?
Yes. In OrcaSlicer and BambuStudio you can enable scarf joint seam and still set the seam position to aligned or sharpest corner. The scarf taper applies at whatever position the slicer chooses. Combining scarf with aligned positioning puts the tapered overlap in the same spot each layer, which can further reduce visibility compared to scarf with random placement.
Do scarf seams affect print strength?
Scarf seams generally have no negative effect on part strength and may slightly improve it. Traditional seams create a stress concentration point where the perimeter starts and stops abruptly. The gradual taper of a scarf seam distributes that transition over a longer distance, reducing the weak point. For structural parts, the difference is minimal either way — layer adhesion and infill matter far more.

References

  1. Prusa Knowledge Base — "Seam Position." help.prusa3d.com/article/seam-position_151069
  2. OrcaSlicer GitHub Wiki — Scarf Joint Seam documentation and implementation details. github.com/SoftFever/OrcaSlicer/wiki
  3. Ellis' Print Tuning Guide — Pressure advance calibration and seam tuning. ellis3dp.com/Print-Tuning-Guide