The dynamic arch bending mechanism of flat bridge structure of AlSi10Mg during SLM process

Abstract SLM (selective laser melting) is a very promising manufacturing method for complicated precision parts of metals and alloys. However, deformation of the bridge structure during fabrication process and post treatment is still a typical problem. In this paper, the deformation of aluminum alloy AlSi10Mg flat bridge structure with various span lengths was investigated by numerical simulation and experiment. The longer the span is, the greater arch bending deformation is. A mechanism of deformation of bridge was discussed. During selective laser melting process, the first layer of bridge bends upward because of no constraint. Then the arch bending results less or no powder on it after powder sweeping for next layer. The bridge bends up further during the formation of the following layer. These alternative phenomena cause the evolution of deformation. However, as the bridge becomes thicker and thicker, its stiffness increases, which leads to the difficulty of its further bending. Therefore, after some layers, there is even no further bending during the forming of following layers with the arch shape kept in the initial layers. Decreasing the laser energy density for the bridge area and using supports are helpful for the reduction of the arch bending deformation.