Metrology for production aerospace applications
3D optical metrology can report form
deviation, thickness, parallelism, roughness,
leak paths, edge radii, defects, etc. all
in the matter of a few seconds, with one
instrument, in one set-up. This single
instrument can replace two to three
alternative gauges that may not necessarily
report the same required functional
information.
Clark continues, “Manufacturing is slow
to change, and despite the inherent
advantages of 3D optical metrology, there
is still some resistance to replace legacy
solutions. 2D metrology — especially
profilometry and CMM — is the standard
throughout manufacturing, and the ISO and
ASME GD&T and surface standards were
developed around the 2D measurement
methods of the day. However, times have
changed, and now there are 3D and areal
standards to control those measurements
and allow designers to put 3D callouts on
drawings.”
“Effectively, manufacturing’s resistance to
this paradigm shift is because of not being
familiar with the tremendous advantages of
3D metrology, and a lack of understanding
of the ‘function’ of the components they
produce and what must be measured to
ensure functional parts and assemblies.
Therefore, adapting to new manufacturing
methods and metrology is sluggish.
Engineers and scientists in companies are
ZYGO has been and will
continue to be a strategic
partner in Woodward’s
quest to be an example of
the best use of advanced
metrology.
not being allowed to ‘get out there’ and
see the new world that has evolved and is
passing them by”, states Clark.
Today, integration of 3D optical metrology
is well established in research laboratories,
shop floor metrology cells, fully-automated
manufacturing and assembly lines. Optical
metrology is fast, repeatable, and requires
little maintenance — allowing it to be used
in all phases of manufacturing metrology
and process control. There are many
aspects of the manufacturing process for
which 2D contact gauging may not be
the best option. For example, an artifact
that occurs randomly would likely be
missed by a single line trace but would
easily be detected by a 3D instrument that
characterizes the entire ROI.
Knowing for sure that the manufacturing
process as a whole has been
characterized is vital. Not only for
adherence to drawing specifications, for
example, but detecting manufacturing
process issues such as machine tool
vibration due to a “bad bearing,” poor tool
set-up, or worn cutting inserts. All these
can be characterized with 3D optical
metrology, and subsequently controlled by
the manufacturing team.
METROLOGY AT WOODWARD
At Woodward, Clark specifies the use of
ZYGO 3D optical metrology instruments in
particular. “The criteria for the choice of
any metrology instrument is extensive. In
terms of reliability and uncertainty, ZYGO
instruments are proven to produce less
noisy data and are faster in data acquisition
and analysis. (Data collection and analysis
time is critical in automated applications.)
On ZYGO instruments, long-term
instrument reliability is outstanding, which
results in consistent long-term results. Plus,
the software is designed specifically for
manufacturing applications and conforms
to international standards. ZYGO is also
adept at providing ‘special equipment and
function’ to accommodate demanding
metrological applications, part handling,
and varying surfaces that can cause
uncertainties in optical measurement.
Issue 45 PECM 7