How do you stop 3D print corners lifting off the raft?
The raft stayed flat. The part didn’t. Its corners curled up off the raft halfway through the print. A plain modeled raft holds the part down only through that one-layer gap, and you’ve tuned the spacing for days. Slant 3D skips the tuning. They tie the part to the raft with little 1 mm struts that snap off afterwards.
Applies to
- Process
- FDM / filament
- When
- Part corners lift or peel off a modeled raft
- Materials
- Warp-prone plastics; very high-warp ones may need the hemisphere option
- Pairs with
- A modeled raft plate (see designed rafts)
Why it matters
Spacing alone is fussy. Too big a gap and the part lifts. Too small and it won’t come off. You end up tuning a number that changes with every machine.
Struts take the guessing out. The part is physically connected to the raft, so the raft holds it down and adds grip right where warping starts. At 1 mm, they’re easy to snip or break off by hand. Slant 3D calls it a simple zipper.
For very high-warp material, they go one step further. Thicken the raft so it’s stiff enough not to warp itself; a thick raft can even have its own infill. Then join it to the part with a row of hemispheres, with each contact point only about 0.4 mm across, up to 0.5 mm. That row acts like velcro. It holds hard and still tears away cleanly, like a perforation.
What good looks like
- Struts sit under the edges and corners where the part tends to lift
- Corners stay down through the whole print
- The part snaps or snips off the raft by hand
- Strut stubs are small enough to clean up in seconds
How to apply it
- Start from a modeled raft plate one layer height below the part.
- Add small 1 mm struts from the raft up into the underside of the part, along the edges.
- Put them at the corners first. That’s where the part peels.
- Print, then snip or snap the part off. The struts are the planned break line.
- Still lifting in a very high-warp material? Thicken the raft and use a row of hemispheres along the joint, with contact points about 0.4–0.5 mm wide.
Test it on your setup
- Print a 40 mm square block in your warp-prone material on a modeled raft, once with no struts and once with 1 mm struts at the four corners. Check the corners with a feeler gauge or a sheet of paper after printing.
Exceptions & tradeoffs
Mind you, the hemisphere interface is advanced. Slant 3D says it takes real teamwork between the designer and whoever’s printing it, so the interface slices and breaks the way you intended.
Keep hemisphere contact points at about 0.4 mm or more. Go too thin and the slicer may skip them as a too-thin wall, and then there’s no connection at all.
Common mistakes
- Fighting corner lift by shrinking the raft gap a hair at a timeAdd 1 mm struts and stop tuning the gap
- Making the struts chunky so they ‘definitely hold’Keep them small; 1 mm holds the part and still breaks off
- Hemisphere contact points so thin the slicer drops themSize them around 0.4–0.5 mm so they actually print
Frequently asked questions
- Why are my print’s corners lifting off the raft?The part is shrinking as it cools and the raft gap alone isn’t holding it. Tie the corners down with small 1 mm struts to a modeled raft.
- How thick should raft struts be?Slant 3D uses 1 mm struts. That’s enough to hold the part down and still easy to snip or break off.
- How do you attach a part to a raft in very high-warp material?Thicken the raft so it resists warping, then join it to the part with a row of hemispheres whose contact points are about 0.4–0.5 mm. It holds firmly and breaks away like a perforation.
A plain raft doesn’t hold the part down; corners can warp off; 1 mm struts tie the part to the raft and break or snip off like a zipper — Design Rafts in CAD | Stop Using Slicer Settings ↗ at 03:38.
Advanced option: a thick raft plus a row of hemispheres with thin (about 0.4–0.5 mm) contact points for high-warp material — Design Rafts in CAD | Stop Using Slicer Settings ↗ at 06:03.
The 1 mm strut zipper and the thick-raft hemisphere interface are Slant 3D’s. The 0.4–0.5 mm contact size is their number too. The corner-lift test block is my addition.