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| Claudio Bartali (left) has seen impeller
inspection time reduced by a factor of four |
Every year, GE Oil and Gas invites customers to an open house at
its factory in Florence, Italy. This year 800 customers saw the
results of a GE Oil and Gas New Technology Introduction project - a
DEA Global coordinate measuring machine (CMM), retrofitted with a
Renishaw REVO system and
measuring impeller parts at a dramatic speed.
As Claudio Bartali (Manufacturing Technology Project Leader)
explains "The demonstration was spectacular - inspection time on a
typical impeller reduced by 4 times. However, that is not the main
reason we started the project and employed Renishaw to retrofit the
CMM with REVO. The exciting part will start soon when we use the
massive amount of accurate REVO-measured data to compare the form
of inspected surfaces with the 3D CAD models."
The retrofit, performed directly by Renishaw with its own
experienced engineers, replaced the previous head, touch trigger
probe, DEA controller and PC-DMIS software with the Renishaw
Renscan5 system - REVO 5-axis scanning head, UCC2 controller and
MODUS software
Saverio Chiari (Manufacturing Technology Leader) is delighted
with how smoothly it went, "The Renishaw service is very good -
they are very focused on customer support and have been very
supportive in the changeover to REVO."
With a requirement for 100% inspection, there is a high demand
on the CMMs and programming systems, which need to adapt
constantly. At the GE plant in Florence, the DEA Global is used to
perform dimensional inspections on components varying in size and
geometry up to 1000 mm diameter.
The new REVO measurement method
REVO is a contact scanning probe with 2 integral measuring axes,
which can work in a true 5-axis measuring mode when using the 3
axes of the CMM, allowing a completely different method of checking
impeller dimensions. The top face, for example, is measured with
what Renishaw calls a' gasket scan', a rapid sweep of the top
machined face in about 2 seconds, gathering thousands of points.
This compares to the previous method involving four touch trigger
points and taking close to 30 seconds. A best-fit calculation of
this data allows the software to plot a plane through all the
points, confirming the position of the face and its relation to
other surfaces. In the near future it is intended to use this large
amount of data to calculate if the surface is deformed in any way,
and exactly which parts of the face deviate from the ideal CAD
model of the component.
Transforming inspection without a new machine
Paolo Trallori (Calibration and Metrology Leader) explains why they
chose to retrofit REVO. "We needed a change in inspection
capability but not the expense of a new machine. The lightweight
REVO head is extremely fast when measuring, with the speed of the
machine's axes movement no longer the limiting factor - the machine
is often acting just as a 'carrier' for the REVO. In most
circumstances this means inspection moves can be 50 or 100 times
faster than before."
Mr Trallori continues, "Some moves, like scanning the outside
diameter of the impeller, are limited by the machine speed, but in
this case REVO still reduces overall inspection time. By
maintaining constant contact with the surface in one smooth rapid
move, rather than moving on and off to take single points, time is
still much reduced. And we have gathered thousands of points in
that move. Just wait until we start to analyse that data for
deviation of the measured surface from the CAD model. We will be
able to certify the quality of components in terms of form
tolerances as well as simple dimensional tolerances."
GE Oil and Gas decided to test the accuracy of the new system
itself, and performed a direct comparison between the touch trigger
method and REVO. "The accuracy of measured points was at least as
good, but at considerably higher speeds and while gathering so many
more points", concluded Mr Trallori.
Integration into a highly flexible production system
As Mr. Chiari comments "You could say we have gone beyond a 'design
for manufacture' system to a 'design for inspection' system here."
The Renscan5 system has been integrated fully into GE Oil and Gas'
production systems, with the Renishaw MODUS software executing
inspection moves generated by a Unigraphics CAD/CAM system.
The compatibility of MODUS with DMIS is very important here. The
3D CAD model generated in the design of the component originally is
used for everything, including machining the component in the first
place, then verifying its quality. Each component is tracked
throughout the process by its serial number, with a full record of
every stage in its production. Now GE Oil and Gas will be going one
step further and will add extra quality data to that record, with
the ability to further improve machining operations.
The next stages
The team at GE Oil and Gas are quite clear how they intend to
continue the project - by using the scanned data to compare form
and by retrofitting more CMMs. A second machine, a DEA Scirocco
with less volume for smaller impellers, is currently being
retrofitted with a REVO system. Another larger gantry machine, for
the very large impeller parts, is also being considered for
retrofit. These machines are inspecting other parts from the GE Oil
and Gas range, so they will be using the full range of REVO
inspection routines.
As Mr Bartali concludes, "REVO has brought us a far better and
more comprehensive method of inspection in a shorter time, now we
will be implementing quality standards for form measurement,
something we could never do before."
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