On the Job: Nissan's UK Plant Uses Reverse Engineering to Repair Press Tools15 Jan, 2005 By: Cadalyst Staff Cadalyst
Delcam software facilitates in-house fixes so new car models roll off the line sooner
Over the past few years, Nissan's site in Sunderland, United Kingdom, has become renowned internationally as the most productive car plant in Europe. Steve Easter from Nissan's 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 (numerical control) facility was set up in Sunderland developed around an Okuma MCR B II five-axis machine with a 5X2-meter bed using Delcam software. Despite its size, the Okuma gives an incredible 2-micron accuracy across the length of the bed.
Nissan justified the initial investment in the Okuma unit for its ability to reduce new model introduction time by completing detailed tool changes in the United Kingdom 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," comments Easter. "This makes it much easier to maintain the accuracy we require."
Now a profile is digitized 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 modeler to recreate the trimming edges of that tool. A model of the trim edges is then passed to the PowerMILL CAM system to generate machining data to recreate them on the Okuma NC machine (figures 1 and 2).
Figure 1. Press tool inserts made using Delcam's Power Solution CAD/CAM software.
Figure 2. A complete repaired press tool.
Initially with trim tools, the new process was used simply to duplicate the manual operation of 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," claims 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. These areas wear more quickly because of the effects of the laser weld, so engineers must replace them with harder material to extend the overall lifetime of the tool. Again, surface data from the affected area is collected using the Renishaw probe. The replacement section is modeled with CopyCAD and PowerSHAPE and then machined on the Okuma machine using tool paths generated in PowerMILL.
Technicians have developed a new database containing PowerSHAPE models of the various press tools as they are repaired, which has led to 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, allowing technicians to quickly and easily determine whether the problem is with the die surface or from another cause.
When asked about his choice of software, Easter replies, "The main reason for choosing Delcam was that I could get all three elements of the system -- reverse engineering, modeling 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 adds. "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."
The vehicles that roll off the line at the Sunderland plant -- including the award-winning Nissan Micra (figure 3) -- are proof of those excellent results.
Figure 3. Body panels for Nissan's Micra are manufactured with tooling maintained using Delcam software.