Vase mode is one of the most misunderstood settings in FDM printing. Most makers either never touch it or try it once on a model it wasn’t designed for and give up on it entirely. Used on the right geometry, vase mode produces single-wall prints with no layer changes, no infill lines, and a surface quality that standard printing can’t match. Used on the wrong geometry, it fails in ways that aren’t always obvious until 80% of the way through a long print. This guide covers exactly when to use it, when to avoid it, and the design rules that make vase mode work reliably.
What Vase Mode Actually Does
Vase mode (called Spiral Vase or Spiralize Outer Contour in Bambu Studio and PrusaSlicer) changes how the slicer generates toolpaths in a fundamental way.
In standard printing, each layer is a closed loop. The nozzle traces the layer’s perimeter, completes the loop, moves up in Z, and starts the next layer. This creates a seam: a small visible mark on the surface where the Z-hop occurs between layers.
In vase mode, there are no discrete layers. The nozzle spirals continuously upward, always moving in XY while simultaneously and continuously increasing in Z. The entire print is one continuous extrusion path with no seam, no Z-hop, and no layer changes.
What this produces:
- No visible seam line on the exterior surface
- Noticeably smoother exterior than standard printing
- Single-wall thickness only (one nozzle width thick)
- No infill of any kind
- Very fast prints despite the quality (less material, fewer moves)
- Watertight-ish prints depending on layer quality
What it requires: The model must have a single continuous outer contour at every height. No internal walls, no overhangs, no enclosed holes or cavities. The model must taper or remain consistent without splitting into multiple separate contours.
Where Vase Mode Excels
Decorative vases and vessels. The original use case, still the best one. A smoothly curving vase shape with a single outer wall produces a print that looks noticeably more finished than the same model printed in standard mode. No seam, smooth surface, translucency in thin-walled versions with lighter filaments.
Lampshades and light diffusers. A 0.4-0.6mm wall in translucent or white PLA diffuses LED light beautifully. Vase mode on a geometric lampshade shape produces clean even diffusion with no infill shadows.
Pots and planters. Decorative plant pots, seed starters, succulent holders. Fast, light, and the smooth exterior looks better than infilled versions at equivalent settings.
Architectural hollow structures. Column caps, pillar sections, decorative hollow forms for dollhouse and scale modeling applications where the wall itself is the aesthetic.
Prototype shells. When you need to quickly print the outer surface of an enclosure or housing to check form and fit without committing to a full solid print, vase mode gives you the exterior geometry fast and cheap.
Where Vase Mode Fails
Models with overhangs. Vase mode cannot place supports. Any overhang in the outer contour will sag or fail. Models must be fully self-supporting at every Z height.
Models with multiple contours at any height. If the model’s cross-section splits into two separate shapes at any height (a handle that loops away from the main body and rejoins), vase mode fails at that transition. The slicer attempts to print both contours with one continuous path and the result is wrong.
Models with flat tops. Vase mode only prints the outer contour continuously. There’s no infill and no top surface layers. A model with a flat top simply has no material at the top. Workaround: add a base of standard layers (the “vase mode bottom layers” setting in Bambu Studio) but accept that the top is open.
Functional parts requiring strength. A single nozzle-width wall is weak. Snap fits, load-bearing elements, and anything requiring structural rigidity are wrong for vase mode.
Thick-wall requirements. Standard vase mode is always one wall thick. Bambu Studio and recent PrusaSlicer versions support a “thick vase” mode that prints multiple wall passes per spiral, trading the seamless surface quality for more thickness. Worth knowing it exists.
Vase Mode Settings in Bambu Studio
Enable under Process > Quality > Spiral vase (Spiralize outer contour).
Bottom solid layers: The number of standard-mode layers at the base of the print before the spiral begins. These form the bottom of the vessel. Default is usually 3-4 layers. Increase for stronger bases on heavier objects.
Smooth threshold angle: Controls how the spiral transitions around sharp corners in the model’s cross-section. Higher values smooth the spiral more aggressively. Reduces surface quality issues at sharp transitions.
Layer height in vase mode: 0.2-0.3mm are the most common settings. Higher layer height means faster printing and slightly coarser surface. For maximum surface quality on display pieces, 0.12-0.15mm is worth the extra time.
Print speed: Vase mode benefits from slightly slower outer wall speeds (80-120mm/s) to allow consistent extrusion. The model geometry is entirely outer wall, so outer wall speed applies to the entire print.
Line width: Using a slightly wider line width (0.5-0.6mm on a 0.4mm nozzle) produces thicker walls and more translucency on display pieces, and reduces the risk of under-extrusion gaps on complex geometry.
Designing Models for Vase Mode
The best vase mode prints come from models specifically designed for the technique.
Single continuous outer contour at every Z height. No exceptions. If your model has a handle, it must stay connected to the main body at every height or rejoin before the contour splits.
No overhangs. Every face of the outer contour should be within 45-50 degrees of vertical. Curved organic shapes work well. Sharp horizontal lips do not.
Consistent or gradually changing cross-section. Abrupt cross-section changes (from round to square, for example) produce visible artifacts in the spiral where the slicer transitions between geometries. Gradual transitions produce smooth results.
Base diameter larger than top diameter. Models that taper upward are inherently vase-mode friendly. Models that are wider at the top than the bottom have outward-leaning walls that approach overhang territory.
Testing in the slicer preview: After enabling Spiralize in Bambu Studio, look at the layer preview. The entire print should show as a continuous single outer-wall path with no infill. Any layer that shows infill, multiple contours, or standard-mode toolpaths is a geometry issue that will cause print problems.
Frequently Asked Questions: Vase Mode and Spiralize
Is vase mode watertight?
Yes and no. The continuous spiral extrusion produces a technically solid wall, but layer adhesion quality determines whether it holds water. A well-tuned print with consistent extrusion at optimal temperature holds water reliably. A print with under-extrusion gaps won’t. For decorative water features or planting containers, apply a coat of spray lacquer or silicone sealant inside for a reliable watertight finish.
Can I print any model in vase mode?
No. Only models with a single continuous outer contour, no overhangs, and no internal geometry. The slicer will attempt to convert any model to vase mode regardless of whether the geometry is compatible, and incompatible geometry produces failed or incorrect prints.
How is vase mode different from printing with 1 wall?
Printing with 1 wall still uses standard discrete layer mode with Z-hops between layers, producing a seam. Vase mode spirals continuously with no Z-hop and no seam. The surface quality of vase mode is noticeably better than 1-wall standard mode on curved surfaces.
Can I use vase mode for the outer shell of a model and standard mode for the interior?
Not directly within a single slicer setup. Some advanced workflows use multi-material printing with the outer shell in vase mode and an infill printed separately, but for most applications this is impractical.