Warping arises from thermal stress during cool-down, especially with large solid volumes or strong wall-thickness variations. Prevent it via uniform wall thickness (1.5-2 mm), shelling solid volumes into cavities with walls, orientation optimisation (long parts flat), and internal ribs for stiffness instead of mass. Our engineers flag risk zones in the DfAM check.
Why SLS parts can warp
SLS powder is held at ~170 °C during printing, just below the melting point. Your part gets built layer by layer with this heat inside the material. After the print the bed cools slowly (12-24 hours).
Strongly different wall thicknesses (e.g. 5 mm solid next to 1 mm wall) shrink differently. The solid zone shrinks more than the thin zone. Result: internal stress, warping or cracking. Fibre-reinforced materials (Carbon LW, PA802CF) are more sensitive than standard PA12.
Four design tricks against warping
Standardise wall thickness. Aim for one wall (1.5-2 mm) through the whole part. Need more material? Ribs instead of mass.
Shell solid volumes. Anything above ~5-10 cm³ as solid carries warp risk. Hollow to 2 mm walls with outflow >=5 mm so powder gets out.
Avoid long thin spans. A 300 mm long thin panel warps guaranteed. Add cross ribs or split the part.
Mind orientation. Long parts lie better than stand. Our slicing software optimises that, deliberate design helps.
What we do if it happens anyway
On prototypes: warping in the first iteration is useful feedback. We adjust orientation or design in the next version.
On production series: our QC runs sample dimensional checks. Structurally problematic? DfAM consult to rethink the design fundamentally.
Sometimes annealing (controlled reheat and slow cool) removes residual stress. We look at that case by case. For very dimensionally stable parts: Carbon LW, high stiffness makes small residual stress less noticeable.