Warping and first-layer adhesion

Theory

As material cools after deposition it contracts. Lower layers are already solid and resist contraction; the thermal gradient across the part cross-section creates a bending moment that lifts corners. Large, flat cross-sections close to the platform maximise this effect. ABS, ASA, and Nylon are most susceptible due to high thermal contraction coefficients. PLA and PETG are less prone. In DMLS rapid solidification of metal produces the same effect at much higher magnitudes: hence mandatory stress relief.

Application

Orient parts to minimise the footprint base area and split large flat bases into ribbed structures or break them with chamfers. Use mouse ears (small circular discs at corners) for FDM to increase local adhesion. Warm the bed to 60–110 °C depending on material. Design the base layer with a slight brim allowance in critical cases. For DMLS, orient the largest flat face perpendicular to the build plate when possible.

Common mistakes

Mouse ears left attached to functional parts interfere with assembly. Over-heated beds can cause 'elephant foot': first layer squish wider than nominal. Thin flat parts (< 2 mm) warping cannot be fixed by settings alone: add ribs or print vertically and accept Z-weakness.

Related terms: Build orientation decision, Self-supporting design (minimising supports), Anisotropy / Layer adhesion (XY vs Z), Residual stress and stress relief (DMLS)