Vase Mode and Thin Walls

What vase mode does

In normal printing, each layer's outer wall starts and stops at a point, and those points stack up into a seam (see Seam Placement). Vase mode removes the stops. Prusa describes it as a continuous single outline that gradually increases the Z height. After the solid bottom layers, the nozzle never lifts or jumps; it spirals upward in one unbroken line. Bambu Lab notes that apart from the bottom layers there is no start or end point, so there is no seam scar on the surface.

Where to find it: PrusaSlicer has Spiral vase under Layers and perimeters; Bambu Studio and OrcaSlicer have it under Others, Special mode. Other slicers have their own name for it; check their documentation.

What it switches off

When you turn it on, the slicer forces the settings that a single spiral needs:

Setting	In vase mode
Walls (perimeters)	1
Infill	0 percent
Top layers	0
Supports	Off (PrusaSlicer)
Bottom layers	Still adjustable

Prusa adds that copying these settings by hand without enabling vase mode is not the same thing: the object will still print in separate layers with a seam.

Which models suit it

• Model it solid. Prusa says the model should be defined as a solid. If you design a hollow vase with its own inner wall, the slicer cannot make one spiral out of it. Model only the outside shape and let the slicer hollow it.
• One closed outline per layer. Bambu Lab warns that because there is only one wall with no infill or top, the mode only works for relatively simple structures. Handles, branches or anything that splits into two outlines at some height leave parts that cannot be reached by the single spiral, and they print floating in mid-air.
• No supports. Supports are off in vase mode, so every overhang has to print unsupported from a single line. Test any shape that flares out steeply.
• Good candidates: vases, planters, lampshades, cups for dry items, cylindrical covers and test pieces for flow, where a single wall is easy to measure.

More than one object

A single spiral cannot hop between objects. Prusa states only one object at a time can print in vase mode, and that you can get around this by enabling sequential printing. Bambu Lab says the same: choose the By object print sequence. Sequential printing has its own clearance rules; see Batch Printing and Repeatability.

Thickness, strength and watertightness

A vase-mode wall is exactly one line wide, so the line width sets the wall thickness. Prusa suggests increasing the external perimeter extrusion width for a thicker, stronger or watertight vase; its example goes from 0.45 to 0.6 mm Starting point. A wider line needs more plastic per second, so check it against your hotend's flow limit (see High-Speed Printing and Its Limits). A larger nozzle allows a wider line.

Whether a single wall holds water depends on how well that one line fused all the way up. If a vase must hold water, fill-test it before trusting it Measure it.

Smoothing and flow at the ends

• Smooth spiral. Bambu Studio and OrcaSlicer can also smooth the X and Y moves so the joins between loops disappear even on walls that are not vertical. A maximum XY smoothing value limits how far points can move; Bambu gives the example that 200 percent on a 0.4 mm nozzle allows 0.8 mm. Bambu warns it can leave small bumps and suits smooth, round shapes more than vases with sharp edges.
• Starting and finishing flow. OrcaSlicer explains that flow ramps up over the first spiral loop and down over the last, which can under-extrude at the start and end, and offers starting and finishing flow ratios to adjust it (with relative E distances enabled).

Thin walls outside vase mode

Many models have thin fins, ribs or lettering that are not vases. Normally every wall is made of an outer and inner perimeter with infill between, so a wall thinner than two lines is a problem.

• Prusa's design guide says walls thinner than one nozzle perimeter cannot be printed. For a 0.4 mm nozzle with 0.45 mm lines it lists about 0.45 mm for one perimeter, 0.9 mm for two, 1.35 mm for three and 1.8 mm for four Rule of thumb, and marks thicknesses between one and two perimeters as a problem area.
• PrusaSlicer's Detect thin walls option can print a single perimeter that serves as both the inside and outside of a thin wall. Walls thinner than one line will likely still be ignored, and the option is turned off automatically when the Arachne perimeter generator is active, because Arachne already varies line width for thin walls.
• The simplest fix is in the model: make thin features a whole multiple of your line width. See Wall Thickness and Minimum Feature Size.