In ‘Fluid and particle dynamics in laser powder bed fusion,’ authors P. Bidare, I. Bitharas, R.M. Ward, M.M. Attallah, and A.J. Moore examine laser bed and powder bed interaction. In this study, the team was able to study and create images of areas where powder was removed during single line and island scans.
Research gave the scientists further insight into the PBF process, making it obvious that it is more dynamic than previously realized, and includes substantial movement (driven by the laser-induced plume of metal vapor and plasma above the melt pool) between power and agglomerates both in and above the powder bed. Previously, images have been recorded through a Renishaw AM250 3D printer, but laser and powder particles ‘could not be resolved.’ Other image sequences, however, were used to discover powder areas overheating, and then defects.
The scientists used an open architecture PBF system for in situ measurements, offering automated build of fully dense components. The computer offers:
- Vertical movement of the build plate between layers
- Movement of the silicon cord powder spreader
- Laser illumination and scanning
- Flexibility is available for laser power and speed
The system offers high resolution imaging plus the ability to melt single tracks in the powder bed and during builds using multiple layers.
“Minor modifications were made to the top and end faces of the Perspex shielding chamber to incorporate viewing windows,” stated the researchers. “For top views of the powder bed, a window of diameter 50 mm made from infra-red absorbing KG glass was added.”
Direct imaging was allowed through the top viewing window, with an infra-red absorbing window offering the side views. The team inserted the camera onto a tilt stage, transforming the powder bed area, and meaning that several areas could be both scanned and imaged. They then moved forward in imitating gas and plasma dynamics during PBF thermal effects. For process thermodynamics, an energy balance was used to account for all types of heat transfer from conductive to convective to radiative.
Temperature increases build plasma density and powder agglomerates forming when scanning islands.
“Agglomerates can also be affected by the laser plume-induced flow: they can be drawn back into the melted track, presumably with an increased likelihood of producing porosity, or ejected into the atmosphere and produce large molten beads if they interact sufficiently with the laser beam, hot gas, or a combination of both.”
Laser plume was directed in a forward motion for the first time from the melt pool, and other studies have remarked on this happening because of droplet detachment. The team also believes the forward motion is specific to PBF.
“The combined results showed that the inert atmosphere and laser plume are integral to the heat, mass and momentum transfer of the process,” concluded the scientists. “Their inclusion in numerical models is critical to process optimization, to identify parameter sets which result in reduced denudation. Observation of plume and particle behavior under cross-flow emphasized the importance of uniform extraction streams above the bed, carrying enough momentum to prevent contamination of the bed from ejected particles. Taking hydrodynamic phenomena into account during process planning can improve the overall build quality and limit the adverse effects of ejected vapor and particles.”
What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source / Images: Fluid and particle dynamics in laser powder bed fusion]
Subscribe to Our Email Newsletter
Stay up-to-date on all the latest news from the 3D printing industry and receive information and offers from third party vendors.
You May Also Like
How to Win at 3D Printing Acquisitions: the Sandvik Example
As the 3D printing market continues a new phase of growth, this time fueled more likely by large, existing holders of capital, we will see more interesting plays by larger...
3D Printing Webinar and Event Roundup: January 22, 2023
For this weekend’s roundup, the TIPE 3D Printing Conference kicks things off with its third iteration on Tuesday, and ASTM International will hold an AM construction workshop. There will also...
3D Printing News Briefs, January 21, 2023: 3D Printing Camp for Kids, Medical Devices, & More
Let’s get kids 3D printing! Kicking off 3D Printing News Briefs today, Anycubic and Yale Funbotics held virtual camps to introduce children to 3D modeling and 3D printing. Moving on...
3D Printing News Briefs, January 19, 2023: Metal AM Standard, Inkjet 3D Printing, & More
We’re beginning with standards news in today’s 3D Printing News Briefs, before moving on to a business collaboration and a new facility. Risk management and quality assurance provider DNV released...