| Over the past few years, Nissan’s site
in Sunderland, UK, has become renowned internationally as the most productive
car plant in Europe. Steve Easter from Press Engineering and technicians
in the Press Die Maintenance section use Delcam’s Power Solution
software as part of their contribution to this proud record.
Currently all press tools used in Sunderland are supplied from Japan.
It would clearly be too expensive to return them to Japan for design modifications
so an NC facility was set up in Sunderland based around an Okuma MCR B
II, five-axis machine with a 5 metres by 2 metres bed using Delcam software.
Despite its size, the Okuma gives an incredible 2 micron accuracy across
the length of the bed.
The original investment justification, when the unit was first established,
was to reduce new model introduction time by completing detailed tool
changes in the UK rather than Japan and to allow more efficient repair
of trimming tools. Previously, design changes and damaged cutting surfaces
on the tools were built up with weld and then ground into shape by hand.
“Now we have the technology to fully complete reverse engineering
applications,” commented Easter. “This makes it much easier
to maintain the necessary accuracy we require.”
Now a profile is digitised from the trim line on the press tool by fitting
a Renishaw probe onto the Okuma machine. The captured data is then used
in a combination of Delcam’s CopyCAD reverse engineering software
and the PowerSHAPE hybrid modeller to recreate the trimming edges of that
tool. A model of the trim edges is then passed to the PowerMILL CAM system
for machining data to be generated for their recreation on the Okuma NC
machine.
Initially with trim tools, the new process was used simply to duplicate
the manual operation in carrying out local repairs to each damaged area.
More recently, it has been expanded to cover machining of all the welded
sections and replacing the complete trimming edge. “Replacing the
whole edge doesn’t take that much more time,” claimed Easter.
“Plus it gives a much better result with a longer time between subsequent
repairs.”
The next application to be developed was to replace sections in draw tools,
especially where laser welding is used to join sheets of different grades
of metal together. These areas wear more quickly because of the effects
of the laser weld so there is a need to replace them with harder material
to extend the overall lifetime of the tool. Again, surface data from the
affected area is collected with the Renishaw probe. The replacement section
is modelled with CopyCAD and PowerSHAPE and then machined on the Okuma
machine with toolpaths generated in PowerMILL.
The establishment of a new database developed by technicians, containing
PowerSHAPE models of the various press tools as they are repaired, has
given extra benefits in Nissan’s quality control process. If any
inaccuracies are found in panels from a particular die set, the tool can
be scanned and the results checked against the database. It is then both
quick and easy to see if the problem is with the die surface or whether
it is from another cause.
When asked about his choice of software, Easter said, “The main
reason for choosing Delcam was that I could get all three elements of
the system – reverse engineering, modelling and machining –
from a single source. Other potential suppliers were offering a mixture
of programs from different developers, which I thought could cause compatibility
problems.”
“As well as being better integrated, the Delcam systems were also
user friendly,” he added. “The layout seemed to be very logical
and this has proved to be the case. Even though we are only part-time
users, we still get the excellent results we need.” |
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