Fraunhofer
IFF develops complex measuring arrangements as well as methods and algorithms
to evaluate measurement data for innovative and individual metrology and
testing systems for its customers. For example, a geometric 100% component test
can be carried out using sensors with "OptoInspect 3D", a technology
developed by the institute. Dr. Dirk Berndt is Head of the Measuring and Testing Technology Business Unit.
1. The requirements
for material surfaces are constantly increasing in the industry. In addition,
many production processes take place in the micro or even nano ranges. Does
this also lead to an increased demand for optical 3D measurement technologies?
Dr. Dirk Berndt: This is correct,
and it is also reflected in the growing number of device providers. Consider,
for example, the established optical measurement methods of focus variation,
white light interferometry, or conoscopic holography. But future requirements
will also be the integration of these optical measurement technologies into the
production flow to record surface features quickly and reliably for every
component and to allow one to intervene and adapt the process controls. Only
then will we come a lot closer to the vision of zero fault production.
2. Does the increasing complexity and
variety of products not also mean that many different measuring methods are
needed? Or to put it another way: do you need many different "measurement
devices" within one production line or are there devices that perform
several functions?
Dr. Dirk Berndt: Very demanding
functional components have very complex geometric features, which have
extremely different tolerances due to their future use. At the same time,
features with wide tolerances generally have a larger lateral expansion of
several centimeters while narrow-tolerance features have a lateral expansion of
a few millimeters.
Multi-sensor solutions are needed to fulfill complex measuring requirements
from a state of the art aspect. For macro to micro features, we can use, for
example, triangulation-based measuring methods and for micro to nano features
white light interferometry is a suitable method. Geometric features within cast
components are also becoming increasingly interesting; computer tomography can
be used in the area. All the methods have to determine the respective features
within a defined component coordinate system, which requires the methods to be
linked (known as registration) as well as data fusion. A lot of research still
has to be carried out in this area.
3. What types of features are measured in
production processes?
Dr. Dirk Berndt: A lot of different
features. In current production processes optical coordinate measurement
machines are used to carry out random measurements. In addition,
triangulation-based methods, such as laser light sectioning, stripe projection,
and photogrammetry offer a lot of application potential for process and
machine-integrated solutions. These are used to test car and railcar wheels,
railcar wheel sets, profiles, car body components in automotive production,
stressed-skin fuselages in the aviation industry etc. for dimensional, shape
and geometric tolerances.
4. The software issue usually also raises
the question about standardized interfaces.
Dr. Dirk Berndt: Although it may not
seem obvious to users, standardization has come a long way. Almost all optical
and digital measuring devices use modern camera systems with standardized
interfaces for connection with PC systems. More relevant for users is the issue
as to how the measuring systems can access default values and in which way the
measurement results are documented and archived.
For the standardized provision of default values, the developments in CAD
systems from being a pure 2-D drawing program to a 3-D volume modeler are a
real benefit for us. Increasingly, industrial end users are able to provide 3-D
models from which the automated default values can be derived. But even here,
there is a lot of work to do before we have a standardized measurement program
that understands all the measuring devices from different manufacturers.
The situation regarding documentation and archiving of the measurement results
looks a lot rosier. Here, we have standardized data interfaces to statistical
quality analysis programs, archiving in databases and export to spreadsheets.
5
. Shorter lead times and cost savings
are the most commonly used buzz words in production technology. Both
inconceivable without automation. How "automated" is optical
measurement technology?
Dr. Dirk Berndt: In principle, the
technologies of optical, dimensional 3-D metrology offer the advantage that
they can operate a fully automatic measuring system and can be integrated into
the production flow, thus allowing every single component in the production
cycle to be measured. Even complex sensor solutions integrated into milling
centers are possible. However, this inline metrology requires specific
solutions – adapted to suit the individual task – that cannot be configured
from standard sensors. To manage these challenges, the Fraunhofer IFF in Magdeburg has developed tools that allow the
development, implementation and start-up of sensor systems adapted to suit
specific tasks. Many of these systems have already been implemented.
6. What are the latest trends in
industrial optical measuring technology? What direction is it taking?
Dr. Dirk Berndt: It must be possible
to integrate optical 3-D measuring systems inline so that process
irregularities can be detected at an early stage. This needs interdisciplinary
cooperation between machine and system manufacturers and optical production
metrology experts. For robust and reliable practical use, the 3-D measuring
systems must be able to adapt to changes in ambient conditions – such as
temperature, vibration or the optical features of the objects to be measured.
It must be possible to reconfigure solutions in optical, dimensional 3D
production metrology that use optical 3D sensors easily so that they can be
adapted to suit more flexible production systems in the future – as lot sizes
in production become smaller. This will need suitable, user friendly processes
and tools to be developed that guarantee measuring capability at all times.
Future-oriented solutions will require the geometric data that is recorded to
be processed fully automatically and very quickly.
Thank you for the interview. 
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