Geometrical defect analysis of overhang geometry produced by electron beam melting: experimental and statistical investigations

While electron beam melting is used to produce near net shape parts, it is still important to study geometrical defects since the final parts may include a serious change of geometry or considerable distortions and thus cannot match the desired geometry even after machining. For example, overhang geometries are very challenging to manufacture, because of the defects they present, such as warping, side loss, and raised edges. The objective of the present paper is to identify relations between the typical geometrical defects found in parts that include overhang volumes, especially side loss and warping defects. The originality of this study lies in the manufacture of a large number of Ti-6Al-4 V parts in order to carry out a statistical analysis of the results. Correlations are studied between the characteristic parameters of the defects and as a function of the manufacturing conditions. In addition, a principal component analysis is proposed to identify families of defects (modes). Finally, future prospects are discussed for designing parts with the aim of improving geometric quality and for simulating defects.