Supports fused to the part surface and won’t break away cleanly. Removing them damages the surface underneath, requires aggressive tools, or the support material literally tears off with chunks of the part attached.
The Z-Distance Setting Is the Most Important Control
Z-distance (also called “support Z gap” or “top/bottom separation”) is the vertical gap between the top of the support and the bottom of the part surface. At 0mm, the support contacts the part — guaranteed fusion. At 0.3mm (typical target), there’s enough separation for the support to snap off without bonding.
Set Z-distance to 0.2–0.3mm (or 1–2 layer heights, whichever is larger). If your slicer shows “Z contact distance” and it’s set to 0 or 0.1mm, this is why supports are fusing.
Some slicers have separate “top distance” and “bottom distance” settings — the top distance (gap between support and the overhanging surface above) is the one that matters most for clean removal.
Support Density
At 20%+ density, support lines are close enough that they start to fuse into a mesh that bonds to the part. For breakaway supports, 10–15% density is usually sufficient to hold up the overhanging surface while remaining removable. Denser support wastes material and makes removal harder.
Interface Layers
Interface layers (1–3 solid layers at the top and bottom of the support) create a smoother mating surface, which counterintuitively makes supports easier to remove — the interface layer separates cleanly instead of individual support lines sticking irregularly. Use 1–2 interface layers at 50% density with 0mm gap between interface and part (but with the main Z-distance gap below the interface, not below the part).
Some slicers let you set the interface layer gap separately. If yours does, use 0mm gap between interface and surface but 0.2mm gap at the interface/main-support junction.
Tree Supports vs. Normal Supports
Tree supports contact the part with very small contact points, making them significantly easier to remove on most geometries. They use less material and are the default in OrcaSlicer/Bambu Studio for good reason. Use tree supports whenever the geometry allows (they can’t always reach every overhang on complex models).
Temperature Matters
Supports printed at higher temperatures bond more aggressively. If you have a slicer that supports per-feature temperatures (OrcaSlicer does), drop the support print temperature 5°C below the main body temperature. This reduces fusion without affecting part strength.
Soluble Supports
For geometry where any bond is unacceptable — artistic pieces, medical models, complex channels — use a dual-extrusion printer with PVA (dissolves in water, works with PLA) or HIPS (dissolves in d-limonene, works with ABS). The supports disappear in a bath with no mechanical removal. The setup cost (dual extruder, soluble filament) is significant, but for complex parts it eliminates all support removal issues permanently.