Residual stress measurement in Fused Deposition Modelling parts

Fused Deposition Modelling (FDM) has become one of the most employed technologies to build complex 3D prototypes directly from a computerized solid model. In this process, the model is built as a layer-by-layer deposition of a feedstock wire. One of the most important issues in the FDM process is the distortion of the part during the printing. This issue is due to the rapid heating and cooling cycles of the feedstock material that could produce accumulation of residual stress during part building up. The aim of this work is to measure the residual stress in FDM parts made of ABS employing the hole-drilling method. In order to avoid the local reinforcement of the strain gage, an optical technique, i.e. ESPI (electronic speckle pattern interferometry), is employed to measure the displacement of the surface due to the stress relaxation. Furthermore, the effect of the stacking sequence and the residual stress distribution on each side of the specimen have been investigated.