How do you stop a 3D printing raft from warping?
Now the part is stuck to the raft just fine. But the raft is peeling off the bed. 3D printing raft warping usually comes down to long, unbroken lines of plastic in the base layer, each one shrinking as it cools. Slant 3D breaks those lines up with cuts in the model.
Applies to
- Process
- FDM / filament
- When
- A modeled raft lifts or warps off the bed
- Materials
- High-warp plastics like ABS
- Pairs with
- A modeled raft plate with rounded edges
Why it matters
The base layer of a raft is usually printed as straight rastered lines. A long streak of plastic shrinks a lot along its length, and all that pull lands on the raft’s edges. That’s what lifts it.
Cut a shallow circle out of the middle of the base and only the outer edge touches the bed. The grip stays where the force is highest. The middle peels off easily.
Slant 3D notes a production bonus: parts release more reliably, which helps automatic part ejection on a print farm.
Line length also varies by corner. Where the raster runs the long way, the streaks are longer than at the corner turned 90°. An X cut through the raft breaks those runs up too.
What good looks like
- The raft base has a shallow center relief; only the rim touches the bed
- The raft is still one solid piece above that first layer
- Long lines are broken by an X cut or similar pattern
- The raft stays flat through the print and pops off the bed cleanly
How to apply it
- Start from a modeled raft with rounded edges.
- Subtract a large circle from the bottom of the raft, one layer deep (0.2 mm at a 0.2 mm layer).
- Leave a solid rim around the outside. That rim is what holds the raft down.
- Cut an X through the raft to break the longest continuous lines.
- Slice and confirm the first layer prints only the rim, with no long uninterrupted lines.
Test it on your setup
- Print a long raft in ABS twice, once plain and once with the center relief and X cut. Check the corners with a sheet of paper during the print and after it cools.
Exceptions & tradeoffs
Mind you, the relief only works because the raft is still solid above that first layer. Don’t cut it deeper than one layer or the raft loses its strength.
Slant 3D says there’s more to try here, like zigzag patterns. The X is the simple starting point, not the only one.
Common mistakes
- Making the raft thicker and thicker to stop it warping off the bedBreak up the base layer instead: center relief plus an X cut
- Cutting the relief several layers deepOne layer is enough; keep the raft sound
- A square raft with sharp cornersRound the outline; corners are where warping starts
Frequently asked questions
- Why does my raft warp off the bed?Long continuous lines in the raft’s base layer shrink as they cool and pull the edges up, especially in ABS. Break those lines up with a center relief and cuts.
- How deep should the raft relief cut be?One layer, so 0.2 mm at a 0.2 mm layer height. The raft stays solid above it while only the rim grips the bed.
- Does a raft help with ABS warping?It can, but a plain raft can warp too. A modeled raft with rounded edges, a center relief and an X cut holds down better and still releases cleanly.
Linear rastering creates long streaks that shrink and warp the raft — Design Rafts in CAD | Stop Using Slicer Settings ↗ at 04:22.
Remove a circle one layer deep from the raft base so only the outer edges stick; helps auto-ejection — Design Rafts in CAD | Stop Using Slicer Settings ↗ at 04:48.
Cut an X through the raft to break up continuous lines; other patterns like zigzags are possible — Design Rafts in CAD | Stop Using Slicer Settings ↗ at 05:19.
The center relief, the X cut and the auto-ejection point are Slant 3D’s. The ABS comparison print is my addition.