LLNL is able to reduce metal powder spatter during fabrication

At the Lawrence Livermore National Laboratory (LLNL), a team of researchers has developed a technique to reduce the defects that can occur during the metal 3D printing process, particularly during laser powder bed fusion. Using a computer model, they were able to carry out various construction experiments on a microscopic scale, simulations which led to the definition of a stability criterion and a power map. This could help to reduce printing defects caused by powder particles ejected from the laser trajectory that fall back onto the workpiece – these are called spatters or projections.

Laser powder bed fusion (LPBF) is a metal additive fabrication process that uses a laser to solidify the powder layer by layer until the desired part is achieved. During the printing process, a number of parameters must be taken into account to avoid errors – laser power, part orientation, temperature management, etc. – and to ensure that the laser is always in the right position. Despite this, it is not uncommon to obtain a part with large cavities and pores – the laser can sometimes dig a hole in the metal due to too much energy being focused on a particular point.

Metal powder spatter could increase defects

Reducing metal powder spatters

Researchers at the LLNL have pinpointed another type of problem: the LPBF process can cause powder spatters. The powder is deflected from its original trajectory and deposited on the workpiece without being fused. Pores and defects appear, reducing the quality of the final part. Saad Khairallah, lead author of the study and computer physicist at LLNL, explains: “Spatter is the enemy of beautiful parts; it is not just small particles that fly, it can create powder aggregates that can then affect the print in various ways and under different scenarios.”