While effects associated with distortion are already understood quite well in keyhole laser welding in the macro range, this is not yet the case for welding in the micro range. In special, the effect of sheet thickness on distortion in micro welding of aluminium sheets with single-mode fibre laser is of interest. To investigate this effect, linear bead-on-plate welds were carried out, whilst total nominal heat input was scaled with sheet thickness by scaling laser power. Distortion (out-of-plane) was measured using a laser triangulation sensor. To improve understanding of the effect of heat input and sheet thickness, a straightforward analytical model from thermal bending was modified and applied.
It was found that average (out-of-plane) distortion will increase with decreasing sheet thickness, leading to a displacement out of plane of up to approximately double the sheet thickness. A simplistic model for buckling in thermal forming was applied and found to be in good correlation with the experimental data, giving a dependence of distortion on sheet thickness s0 according to approximately 1/s02/3.