Medical Design Briefs - June 2022 - 18

ADDITIVE MANUFACTURING
Measurements of AM parts post-process serve to provide clues into fabrication problems left by surface signatures.
measurements on specifi c instruments to
new feature-based analysis and machine
learning to interpret results. Of particular
interest is IPM for evaluating the quality
during manufacture, following each
additive line and layer in real time. This
information can be used to inform control
strategies and later in-process metrology
developments. An important part
of IPM development is correlating to reference
metrology, including benchtop
surface metrology instruments.
Another example of leading-edge research
is at the University of North Carolina
at Charlotte, where Prof. Christopher
Evans and coworkers have been using
interferometry and electron microscopy
to study AM materials in collaboration
with the U.S. National Institute of Standards
and Technology (NIST), and Carl
Zeiss GmbH at Oak Ridge National Laboratory
(ORNL). These researchers have
been studying Inconel 625 - a hightemperature
Ni superalloy for AM that
exhibits an intriguing variety of surface
signatures. These surfaces have areas rich
in oxide fi lms that are visible in true-color,
3D surface topography maps obtained
with ZYGO's interference microscopes.
These instruments also serve as excellent
workhorses for examining large areas
with high detail, such as distorted weld
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MDB Zygo Additive Feature 0622_CC_1.indd 18
pools, by assembling or stitching together
multiple high-lateral resolution images
each with millions of data points.
While the challenges of quality control
of AM parts are a great concern for
those who make these parts, these same
challenges present an attractive opportunity
for new solutions and spinoff businesses.
Founded in 2018 in the UK,
Taraz Metrology is an example of a
spinoff enterprise that combines university
research, practical engineering, and
commercial experience into a unique
product development capability customized
to the needs of AM. Taraz currently
offers freestanding fi nal inspection solutions
for all types of AM parts and leverages
proprietary software for advanced
fringe projection and photogrammetry
of topography.
Standardization and Traceability
The ability of AM to produce geometrically
complex parts, its role as an enabler
of mass customization, and the potential
time and cost savings associate with its use
are all important for the future of industry.
However, when compared to more familiar
and established manufacturing
methods, AM technology is dynamic and
rapidly evolving, and technology innovators
are working to overcome the barriers
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5/25/22 2:48 PM
to adoption of AM for production applications,
including those related to quality
control standards.
ZYGO is actively researching calibration,
traceability, characterization, and verifi
cation for surface topography measurements,
with 16 papers published in the last
fi ve years alone on these topics, and a further
seven specifi cally focused on physical
modeling of optical measurements of surface
structures - including complex,
steeply sloped surfaces characteristic of
AM parts - and fi ve more papers on the
measurement of AM parts per se.
ZYGO is also a partner in the €2.2M
EMPIR 20IND07 TracOptic project, with
the title, " Traceable industrial 3D roughness
and dimensional measurement using
optical 3D microscopy and optical
distance sensors " - of obvious value to
the AM sector.
National and international standards
are critical both to industry adoption and
to ensuring quality control across multiple,
developing manufacturing technologies.
The company is an active member
of ISO TC213 WG16 for the development
of the ISO 25178 surface texture
standards, working in collaboration with
international experts on the ISO 25178603
and 25178-604 standards for interference
microscopy, and the 25178-700
Medical Design Briefs, June 2022
Credit: Zygo
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Medical Design Briefs - June 2022

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