On the influence of building position on dimensional accuracy and surface quality of aluminum blocks manufactured by L-PBF

The precision of the objects fabricated by laser powder bed fusion (LPBF) and their overall quality is currently commonly increased by process optimization, however the relatively complicated process-structure–property relationship may represent a significant obstacle to its efficiency. This study aims to determine the effects of the position of L-PBF manufactured blocks on the building plate on their geometrical dimensions, tolerances (GD&T) and surface roughness. Within the study, 9 cubical specimens were manufactured from AlSi10Mg powder via LPBF using optimized process parameters, consistent for all the samples, and their GD&T and surface roughness were subsequently analyzed by CMM and perthometer. The system utilized to manufacture the samples was supplied with 200 W Yb-laser with the 90 µm diameter of the laser spot. The fabrication of the blocks and their subsequent GD&T analysis were simulated numerically to further explain the mechanisms of distortion creation. Numerical results were validated by experiments, where the maximal relative error reached 6.88 %. Statistical significance of position on GD&T was demonstrated for dimensional deviations, bottom faces planarity, parallelism of top and bottom faces and perpendicularity of top and x-oriented faces and the regression equations were assessed (with R2 96.30 %, 93.09 % and 99.79 %, 94.54 %, 98.47 %, 99.65 %, and 99.28 %, respectively). The lowest dimensional errors (0.0738 mm in x-, 0.1048 mm in y-, and −0.3844 mm in z-direction) were detected in the block located in the middle of the building plate, which can be reasoned by favorable thermal fields as the specimens are surrounded from all sides by other blocks cumulating heat. Similarly as with dimensional errors, the errors of planarity, parallelism and perpendicularity correlated with the thermal fields over the building platform, resulting in the least distorted cube located in the middle of the base plate.