were consistently inferior. The team found that most of this porosity can be eliminated by adjusting the printer's process parameters, but methods must include enough information to properly characterize it. The center's method, which does, gave a minimum feature resolution of 1.5 microns.
Researchers at Lawrence Livermore National Laboratory discovered interactions that can lead to porosity in parts produced by laser powder bed fusion metal processes, contributing to future better part performance. (Source: Julie Russell/Lawrence Livermore National Laboratory)
Researchers at Lawrence Livermore National Laboratory also looked at porosity issues. They discovered what interactions can lead to porosity in parts produced by laser powder bed fusion metal processes. Due to evaporation that occurs when the laser irradiates the metal powder during a build, vapor flux clears away powder near the laser's path. This reduces how much powder is available when the laser makes its next pass, and that causes gaps and defects in the finished part.
The team used a vacuum chamber, an ultra high-speed camera, and a custom-built microscope setup to observe ejection of metal powder away from the laser during the melting process. Through computer simulation and fluid dynamics, the researchers also built models to help explain the particle movement. The effect has important implications for part quality and build speed, so it must be captured and used to update simulation models, which will help optimize the process. Next steps will be investigating how porosity develops in real time and exploring advanced diagnostics and modifications to the process for improving build quality, using the new information.
But Metals aren't the Only Materials that Count
Metals, of course, aren't the only materials that count in 3D printing. Photopolymers still represent the biggest part of AM materials at 59.8% in 2015, according to a recent report from BCC Research . But it's also the slowest growing segment, and expected to decline to 47% by 2021. During that time, the report predicts that thermoplastics will remain the second-largest group at 25% to 26% of the market. Ceramic, metals, and other materials comprise the remaining categories.
One of the latest entries into engineering-grade polymers for 3D printing is Evonik's recently announced VESTOSINT 3D Z2773 . This material is its first new plastic powder developed with HP for use with HP's Multi Jet Fusion 3D printers, and the first certified material in HP's Open Platform program, announced last May, which will support this line of printers.
The new PA-12 powder has superior mechanical properties and is FDA (Food and Drug Administration) compliant, so components printed with it can be approved by the FDA for food contact. For several years, Evonik has produced plastics for the industrial production of high-performance components using 3D printing technologies. These include other PA 12-based VESTOSINT powders with high quality and processing capabilities, and with properties profiles for each powder matched to a specific 3D printing technology.
BASF, an HP materials partner in the same program, also said recently it's beginning development of 3D printing materials with HP, leveraging its broad portfolio of engineering thermoplastics, polyurethanes, photopolymers, and other polymers, as well as metal