Lawrence Livermore National Laboratory researchers have developed a new and more efficient approach to a challenging problem in additive manufacturing -- using selective laser melting, namely, the selection of appropriate process parameters that result in parts with desired properties.
Selective laser melting (SLM) is a powder-based, additive manufacturing process where a 3D part is produced, layer by layer, using a high-energy laser beam to fuse the metal powder particles. Some SLM applications require parts that are very dense, with less than 1 percent porosity, as the pores or voids are the weakest part of the material and most likely would result in failure.
But building functional parts and components to specific standards and performance specifications can be challenging because a large number of parameters must be set appropriately. Some of the key parameters include laser power, laser speed, distance between laser scan lines, scanning strategy and powder layer thickness.As a result, there is a need for a reliable and cost-effective approach to determine the right parameters to develop parts with such desired properties as high density.
LLNL researchers have developed an efficient approach, based on simple simulations and experiments, to identify optimal parameters to print 3D high-density metal parts. Their work, titled "Density of additively-manufactured, 316L SS parts using laser powder-bed fusion at powers up to 400W" was recently published in the International Journal of Advanced Manufacturing Technology.
The paper explains how parameters for higher-power SLM machines can be selected by using simple, computational simulations to explore the process parameter space. These simulations are used to compute the dimensions of the melt pool, which is the pool of liquid formed when the laser melts the metal powder particles.
"We mine the simulation output to identify important SLM parameters and their values such that the resulting melt pools are just deep enough to melt through the powder into the substrate below," said Chandrika Kamath, an LLNL researcher who is the lead author of the article. "By using the simulations to guide a small number of single-track experiments, we can quickly arrive at parameter values that will likely result in high-density parts."
Kamath and her colleagues, who are part of LLNL's Accelerated Certification of Additively Manufactured Metals (ACAMM) Strategic Initiative (acamm.llnl.gov), are using simulations at various scales to gain insight into the SLM process.
"We found that the metal density reduces if the speed is too low, due to voids created as a result of keyhole mode laser melting, where the laser drills into the material," Kamath wrote. "At the same time, too high a speed results in insufficient melting. The key is to find the right parameters where the melting is just enough."
The LLNL team found that the use of different powders affected densities at lower power, but not at higher power.
"Furthermore, for 316L stainless steel, at higher powers, the density is high over a wider range of scan speeds, unlike at lower powers," the article states. "This would indicate that higher powers could provide greater flexibility in choosing process parameters that optimize various properties of a manufactured part."
Although 316L stainless steel was used in this experiment, Kamath said the team's approach can be applied to other metal powders as well.
LLNL's findings will eventually be used to help certify properties of metal parts built using SLM. The paper is the first step in understanding how we can exploit computer simulations and a small number of carefully chosen experiments to efficiently determine the process parameters, Kamath said.
"Density of additively-manufactured, 316L SS parts using laser powder-bed fusion at powers up to 400W," International Journal of Advanced Manufacturing Technology
LLNL Additive Manufacturing
Ken Ma | Eurek Alert!
Serendipity uncovers borophene's potential
23.02.2017 | Northwestern University
20.02.2017 | Arizona State University
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
24.02.2017 | Life Sciences
24.02.2017 | Life Sciences
24.02.2017 | Trade Fair News