3D printing supports: tree vs normal, interfaces and painting

Use tree (organic) supports for figurines and curved shapes, and normal supports for big flat overhangs on mechanical parts. Then set the top Z distance to about one layer and add a few interface layers, and most supports will peel off cleanly.

When do you actually need supports?

Each layer must rest at least partly on the one below. The classic rule is that overhangs up to about 45° from vertical print fine without help. With good part cooling, many printers manage 50–60° in PLA, though the underside gets rougher as the angle grows.

• Bridges (flat spans between two supported edges) often print unsupported for 10–20 mm, and further on well-tuned printers.
• Small horizontal holes usually print fine up to roughly 10 mm across; teardrop-shaped holes print cleanly at any size.
• Flat ceilings with no edge to bridge from and steep overhangs past about 60° nearly always need support.

Hotter, less-cooled materials such as ABS and ASA sag sooner than PLA, so expect to support them a little earlier. If overhangs curl upward, see warping and curling.

Support types and angle settings in each slicer

Every major slicer offers a grid-like "normal" support and a branching "tree" support, but the names, styles and threshold conventions differ. Mixing them up is the number one reason people end up with too many or too few supports.

Bambu Studio switches the default tree style to Tree Hybrid when you use a dedicated support filament or adaptive layer height. Snug normal supports follow the model's outline closely and save material; Grid is the more robust default.

Normal supports: when and how

Normal supports build straight columns from the bed (or a lower surface) up to the overhang. They're predictable and give flat, even surfaces to print onto.

• Use them for mechanical parts with large flat overhangs, faces that must stay flat, and overhangs close to the bed.
• Skip them for figurines and curvy shapes, where columns touch far more of the surface than needed.

Tree (organic) supports: when and how

Tree supports grow branches from a few points on the bed up to the overhang. They touch the model only where needed, use less filament, and leave smaller marks, which makes them the usual choice for figurines, miniatures and organic shapes.

• Tree Organic / Organic (Bambu Studio, OrcaSlicer, PrusaSlicer) builds smooth, rounded branches. It is the default in Bambu Studio and OrcaSlicer.
• Tree Slim uses thinner branches and less material; Tree Strong uses thicker ones for tall or heavy overhangs.
• Tree Hybrid mixes tree branches with normal-style support under large flat areas.
• Cura's Tree exposes branch diameter, branch angle and tip diameter directly; 2–3 mm branches are a common start.

Tree supports take longer to slice than grid supports, especially on detailed models. That's normal: the slicer is routing every branch around the part.

Support interfaces and Z distance: the secret to clean undersides

The interface is a dense layer (or several) at the very top of the support, right under the model. Without one, the model's underside has to bridge across a loose support pattern and comes out scarred.

• Top Z distance about one layer. 0.2 mm at 0.2 mm layers is the standard for same-material supports. Increase it by a layer if supports weld on; decrease it if undersides droop.
• 2–3 top interface layers. Bambu Lab notes that three interface layers form a flat platform for the model to land on.
• Interface density 70–90%. Denser gives a smoother underside but is harder to peel.
• Bottom interface optional. It only matters when supports stand on the model rather than the bed.
• Match the material. PETG bonds to itself very strongly, so give it an extra layer of Z distance or a PLA interface.

Soluble and breakaway support materials

With a multi-material printer (an AMS, MMU, toolchanger or IDEX), the interface can be printed in a material that doesn't stick to the part. You can then drop the top Z distance to 0 for a near-perfect underside. Print only the interface in the support material to save time and purge; see the multicolor printing guide for how material changes work.

Dry soluble filaments before use and store them sealed; see the filament drying guide.

Paint-on supports, blockers and enforcers

Automatic supports are generous: they'll fill a small cavity you don't care about and miss nothing. To support only what matters, tell the slicer where.

• Bambu Studio and OrcaSlicer: the support painting tool paints enforcers and blockers directly on the model. Add a support enforcer or blocker modifier for box-shaped regions.
• PrusaSlicer: the paint-on supports tool (shortcut L) paints enforcers and blockers; set supports to For support enforcers only to use only painted areas.
• Cura: use the Support Blocker tool to place blocker shapes, or a per-model setting to turn a mesh into a support mesh. Support painting arrives in the Cura 5.14 beta.
• Every slicer: "on build plate only" or "touching build plate" stops supports from starting on the model itself, which avoids most scars on figurines.

1. Slice once with automatic supports to see what the slicer thinks needs help.
2. Switch to enforcers only (or keep automatic and add blockers) depending on which is less painting.
3. Paint the surfaces that truly overhang and block cavities, text and cosmetic faces.
4. Slice and scrub the preview layer by layer to confirm every island has something under it.

How to design parts that need no supports

The best support is the one you never print. A few design moves remove most of them:

• Chamfer instead of overhang. A 45° chamfer under a ledge prints cleanly where a flat ledge needs support.
• Teardrop horizontal holes. Add a 45° point to the top of round holes that print sideways.
• Reorient. Rotating a part so its largest flat face sits on the bed often removes nearly all supports. Weigh this against layer strength, since layers are the weak direction.
• Split the part. Cut it along a flat plane, print both halves flat, then glue or bolt them together.

For more rules on overhangs, bridges and holes, see the 3D printing design guide.

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