LINEAR THERMAL EXPANSION OF PLA, ABS AND PETG PARTS PRODUCED BY FDM 3D PRINTING MEASURED WITH A LOW-COST DEVICE, AND ITS IMPLICATIONS FOR PLA/ABS BILAYER THERMAL ACTUATORS

Parts produced by fused deposition modeling (FDM) often work under varying temperature, but the coefficient of linear thermal expansion (CTE) of printed parts is rarely measured, and the CTE mismatch between polymers is what makes multi-material parts warp or, conversely, act as thermal actuators. This work aimed to measure the CTE of FDM-printed PLA, ABS and PETG with a low-cost device and to use the measured values to predict the bending of a PLA/ABS bilayer strip. Five specimens of each material (100 × 5 × 3 mm, 100% infill, 0° raster) were heated stepwise on a Peltier-controlled aluminum plate from about 15 °C to 55 °C; elongation was read with a dial gauge and temperature with a thermal camera, and the CTE was obtained by linear regression. Mean CTE values were 79.0 ± 16.2, 96.0 ± 6.9 and 79.8 ± 2.1 × 10−6 °C−1 for PLA, ABS and PETG, respectively, within the range reported for printed parts; ABS differed significantly from PETG, whereas the PLA scatter prevented its distinction from ABS. Timoshenko’s bilayer model, fed with the measured values, predicts a radius of curvature of about 470 mm and a bending angle of about 12° for a 0.6 mm PLA/ABS strip heated by 50 °C. The device is a viable low-cost option for CTE screening, and actuator design must rely on CTE values measured on the filaments actually used.