Additive Manufacturing Special Report - November 2023 - 20

TECH BRIEFS
The team also manufactured 3D
circuit boards with complex metal
topologies, like an LED stereo
circuit with nickel and a doublesided
3D circuit with copper.
" Using the MM-DLP3DP process,
arbitrarily complex metal-plastic 3D
parts having specific metal patterns
can be fabricated. Furthermore,
selectively inducing metal deposition
using active precursors can provide
higher quality metal coatings. Together,
these factors can contribute to the
development of highly integrated and
customizable 3D microelectronics, "
Umezu, Song, and Sato said.
The new manufacturing
process promises to be a
breakthrough technology for
the manufacturing of circuits,
with applications in a diverse
variety of technologies, including
3D electronics, metamaterials,
flexible wearable devices, and
metal hollow electrodes.
For more information, contact
Umezu Lab at umeshin@waseda.jp.
Detecting Porosity Defects in 3D-Printed Metal Parts
Research addresses the issue of detecting the formation of keyhole pores, a major defect
in laser powder bed fusion.
University of Virginia, Charlottesville, VA
A
research team led by Tao Sun,
Associate Professor, University of
Virginia, has made new discoveries that
can expand additive manufacturing
in industries that rely on strong metal
parts, including aerospace. The research
addresses the issue of detecting the
formation of keyhole pores, a major
defect in laser powder bed fusion (LPBF),
a common additive manufacturing
technique introduced in the 1990s.
LPBF uses metal powder and
lasers to 3D-print metal parts, but
porosity defects remain a challenge
for fatigue-sensitive applications
like aircraft wings. Some porosity is
associated with deep and narrow vapor
depressions, which are the keyholes.
The formation and size of the
keyhole is a function of laser power
and scanning velocity, as well as the
materials' capacity to absorb laser
energy. If the keyhole walls are stable,
it enhances the surrounding material's
laser absorption and improves laser
manufacturing efficiency. If not, however,
the material solidifies around the
keyhole, trapping the air pocket inside
the newly formed layer of material.
This makes the material more brittle.
The team developed an approach
to detect the exact moment
when a keyhole pore forms
during the printing process.
" By integrating operando synchrotron
X-ray imaging, near-infrared imaging,
and machine learning, our approach
can capture the unique thermal
signature associated with keyhole
pore generation with sub-millisecond
temporal resolution and 100 percent
prediction rate, " Sun said.
In developing the keyhole-detection
method, the researchers also advanced
the way operando synchrotron
x-ray imaging can be used.
" Our findings not only advance
UVA materials science and engineering postdoctoral fellow Zhongshu Ren (left) and Tao Sun display
the results of their research. (Image: Tom Cogill for UVA Engineering)
20 NOVEMBER 2023
additive manufacturing research, but they
can also practically serve to expand the
commercial use of LPBF for metal parts
manufacturing, " said Anthony Rollett,
Professor, Carnegie Mellon University.
" Porosity in metal parts remains
a major hurdle for wider adoption
of the LPBF technique in some
industries. Keyhole porosity is the
most challenging defect type when
it comes to real-time detection using
lab-scale sensors because it occurs
stochastically beneath the surface, " Sun
said. " Our approach provides a viable
solution for high-fidelity, high-resolution
detection of keyhole pore generation
that can be readily applied in many
additive manufacturing scenarios. "
For more information, contact
the Office of Communications
at bmoriarty@virginia.
edu; 434-924-1713.
ADDITIVE MANUFACTURING SPECIAL REPORT

Additive Manufacturing Special Report - November 2023

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